Marine Battery Banks & Over-Current Protection

A 300A (MRBF)Battery Terminal Mounted Fuse by Blue Sea Systems

In this article we will discuss fuse selection, fuse types, wire ampacity, Amperage Interrupt Capacity (AIC) and even potentially unsafe ABYC “exceptions to the rules”. In short, this article deals with why fusing your battery banks is a critical safety measure.

Bank Fusing Steps

1 – Know the amperage of the load you need to fuse

2 – Know the Ampacity of the wire you are trying to protect

3 – Determine the AIC of the bank you are trying to protect

The ABYC Standards – A bare Minimum not a Maximum

In regards to over-current protection of battery banks, owners should consider that the ABYC standards are a bare minimum requirement. In many cases, especially battery bank protection, certain aspects of ABYC E-11’s battery bank over-current protection should be considered as inadequate, potentially unsafe and below where a boat-owner should set their sights, if they want true safety. What the excerpt below is Saying is that any + conductor connected to a battery bank requires over current protection within 7 inches of the batteries positive terminal. This includes house banks, windlass banks, thruster & winch banks.

Your House Bank Requires over current protection!

Yes, I am an ABYC member, ABYC certified electrician and also part of the electrical sub-committee that helps develop these standards. Sometimes rational arguments made by the likes of Nigel Calder, myself and numerous others are over-shadowed in favor of taking a shortcut or to save boat-builders money. In many cases you can and should aim to exceed the ABYC standards. Specifically with regard battery bank fusing or sheathed/loomed or conduit protected wire.

Definitions Used:

Ampere Interrupting Capacity (AIC) – the maximum short-circuit current that an over-current protection device can safely interrupt under standard test conditions.

Source of Power – In regards to battery bank over-current protection the battery bank is the “source of power” that we are protecting the wires from.

Conduit – an enclosure that is part of a closed wiring system for insulated conductors and/or cables in electrical installations, allowing them to be drawn in and/or replaced. Conduit or sleeving also serves to protect from chafing and shorting.

Equipment Enclosure – the outside shell of equipment that provides personnel protection from electrical hazards, burns, rotating machinery, and sharp edges, and provides protection to the device from mechanical damage or weather.

Ignition Protection – the design and construction of a device such that under typical design operating condition, will not ignite a flammable hydrocarbon mixture surrounding the device when an ignition source causes an internal explosion, or it is incapable of releasing sufficient electrical or thermal energy to ignite a hydrocarbon mixture, or the source of ignition is hermetically sealed.

Loom – a flexible covering designed to protect conductors.

Main Over-current Protection Device – an over current protection device with no other over current protection between it and the source of power.

Pigtails – provided conductors integral to an electrical component or appliance for the purpose of connection to external circuits. eg; LED navigation lighting.

Self-limiting Device – a device whose maximum output is restricted to a specified value by its magnetic or electrical characteristics.

Sheath – a material used as a continuous protective covering, such as overlapping electrical tape, woven sleeving, molded rubber, molded plastic, loom, or flexible tubing, around one or more insulated conductors.

A battery bank fuse is there to protect the wire!

The ABYC Standards on Battery Bank Fusing:

Fuse Location:

The ABYC requirement is for a battery bank fuse is to be within 7 wire inches of the battery bank. The European ISO/RCD (which is law) requires the fuse be within 200mm. 200mm equates to about 7.9”. In this regard, the European ISO/RCD is essentially the same as the ABYC’s 7” requirement. The difference here is the ABYC standards are still voluntary. I only point this out because we hear time and again that the ABYC is not a law, and it is not, but the ISO/RCD (recreational Craft Directive) is a law.

These fuses, one for each bank, are in compliance with ABYC E-11. The one on the cranking battery exceeds and goes above and beyond the ABYC standards.

In the real world of boats and battery compartments meeting the 7” rule is not always as easy as it sounds. If you can’t get within 7″ then the next best thing is to be as close as possible but the wire should always be in a protective conduit or flexible loom, once the jumper to the fuse exceeds 7″.

If you’re having trouble meeting the 7″ rule, the Blue Sea battery terminal fuses shown in this photo are an excellent option for up to 300A. If trying to fuse a bank that may ever need to be used to start a bigger engine, you may need a Class T or ANL fuse and the correct fuse holder..

These fuses are excellent but they do add nearly 2″, in height, to a battery post, if vertically mounted so measure your battery compartment height carefully.

Exceptions to the 7” Rule:

While the standards do have an allowable exception for over current protection regarding cranking conductors. Nowhere in the ABYC standards does it suggests not fusing cranking conductors. In other words, the ABYC is not saying “don’t fuse a creaking conductor” they’re simply allowing you an exception to the rule if your engine is too big to be fused.

It is quite often repeated as fact on the Internet, by folks who don’t understand what they’re talking about, that the ABYC says “don’t fuse engine cranking conductors”. The standards say no such thing.

Other Exceptions to the 7” Rule:

Under ABYC E-11 the fuse does not always need to be within 7”. Depending upon the location & where the wire connects to, meaning the battery or other source of power, such as a battery switch, and when “contained throughout its entire distances in a sheath, or enclosure such as a conduit, junction box, control box, or enclosed panel” the fuse can be either at a maximum distance of 40” or 72”.

72” Exception to the 7” Rule:

40” Exception to the 7” Rule:

“Exceptions” to Bank Fusing – Do They Always Make Sense?

Remember above where we mentioned that the ABYC standards are a bare minimum and you can often do better? Well, exception #1 “cranking conductors is one area where the ABYC is simply leaving far too much room for dangerous installations.

In today’s day and age you can, and ideally should, strive to achieve better than the extremely low bar set by ABYC E-11 on bank fusing. Compass Marine inc. has been fusing cranking conductors since the mid 90’s and these circuits have likely undergone hundreds of thousands of engine-starts. I can count on two fingers the number of nuisance trips we’ve had.

#1 An engine that hydro-locked due to a scoop strainer installed with the scoop facing forward. (darn good thing the fuse tripped)

#2 A boat that tangled in lobster gear and the reversing gear was stuck in gear. The owner tried to start it anyway. (Again, it’s a darn good thing the fuse tripped.)

Sure, using the “cranking conductor” exception is an easy mark for a boat builder, as it saves them money, but many of us who do this for a living find this exception to be patently unsafe without also mandating the cranking conductors be located in a protective conduit/sleeve. Nigel Calder is one such individual who also believes this exception is not one to use (see excerpts below).

The argument a few of the members of the ABYC committees make is that starting motors draw too much current and are difficult to fuse. Ok, if this is the argument, why don’t we take a look at devices such as DC powered bow thrusters. A bow thruster is not a cranking conductor so by the ABYC standards that connection to the thruster bank must be fused.

This series wound thruster motor is exactly like a typical marine engine starter motor. The only difference is that it actually draws a lot more current, and for a lot longer, than you’ll find on the vast majority of marine engines.

The difference between a starter motor and a thruster are however huge. A typical engine starting duration ranges from about * 0.75 seconds to 1.5 seconds on average(*data Midtronics EXP 1000HD) . Bow thruster motors are rated for as much as 3-5 minutes and many owners use them for 30 seconds or more at a blast. The bottom line is this; a bow thruster is treating a fuse in a much more abusive manner than a starter motor ever will! The ABYC requires the bank feeding this bow thruster to be fused but not starter motors? This is about as nonsensical and hypocritical as your everyday politician( either side of the aisle, your pick)!

This particular bow thruster draws well over 1000A for in-rush, and physically maxes out our Fluke 376 which can measure to 1000A DC for in-rush. Under actual thrusting loads it typically pulls 330-365A, for as long as 30 seconds or more at a time. On land, with no load/water to move, it draws about 285A +/- which is pretty much spot-on for the motors 376A rating. Also keep in mind this is not the biggest 12V thruster we deal with.

“But, the motor says 3kW what about Ohm’s law?”

3 kW = 3000W If we take a typical no-load rating of the motor this is; 3000W/11.5V = 261A

11.5V is a perfectly acceptable voltage sag on a bow thruster bank under that type of load. However, as I mentioned, this is a “no-load” rating meaning no gears to turn, propeller to spin or water to move. This is how and why a 3kW motor can typically draw much more current than the face value 3kW rating.

“But, the rating plate says 376A, why does it disagree with the 3 kW rating?”

Yes, the rating plate may say 3kW and 376A but the motor wattage rating is a no-load rating. Put a load on any DC motor and it will draw more power than the no-load wattage rating indicates. See chart below.

One more example:

This is the current spec from an Anderson Electric Winch we installed. The ABYC requires these winch batteries to be fused. Notice how high the in-rush is (green square)?

And here is a chart showing the winch current draw based on winch load. As stated, apply a load to an electric motor and it will draw more than its face value rating.

The point in all this discussion on bow thrusters and electric winches is to examine why mandating over-current protection for DC bow thrusters/winches and then making “exceptions” for engine starting motors is actually pretty silly..

What would make a cranking conductor fuse exception ok?

A fuse exception would be OK if the ABYC actually mandated un-fused cranking conductors to be protected in a protective sheath, conduit, sleeve etc. like the 40” and 72” rules do, but the standards do not call for this. Unsleeved/unprotected wire is perfectly fine for a cranking conductor under ABYC E-11. Crazy? You Bet bet is!

What AWG do manufacturers suggest for cranking conductors?

Here are some minimum manufacturer suggestions for battery/starter cable from Westerbeke and Universal.

Universal / Westerbeke minimum wire size requirements (wire length round-trip)

2 AWG = 8′
1 AWG= 10′
1/0 AWG = 14′
2/0 AWG = 18′
3/0 AWG = 22′
4/0 AWG = 28′

Nigel Calder addresses the fusing of cranking conductors in his books;

Begin Quote – Nigel Calder:

End Quote:

and

Quote Nigel Calder:

End Quote:

A real-world example of why this exception can be dangerous.

Exceptions to the Rule vs. Common Sense

In August of 2010 a local yacht clubs junior sailing program had a chase boat returning to the dock with a few 8-10-year-old junior sailors, and their coach. They were aboard a well maintained 15’ Boston Whaler. As they tied up to the dock, the battery cables under the helm seat started to smoke. Within seconds the entire boat was engulfed in flames. The boat was a total loss. The kids barely made it off the boat before the fire fully engulfed the vessel.

Points to Consider:

• The ABYC standards do not even require a battery switch let alone a main bank fuse for this boat!
• This tiny Honda outboard is very, very easy to fuse with an MRBF battery terminal mounted fuse!
• This boat fire was driven by a single group 27 battery, into shorted 6 GA wire!

What if this happened when the kids & coach were out on the bay, not as they approached the dock? Safe? Hell no!

If a single G-27 battery can do this to the Honda outboards factory supplied wire, & this boat, what do you suppose two 8D cranking batteries will do to your wire & boat if the wire shorts?

A small MRBF fuse holder & fuse, that costs $30.00, would have 100% prevented this fire.

The bank below is capable of 18,000A of short circuit current!

The installer put the wires in protective loom and went above and beyond what the ABYC requires. Smart guy!

Fuses Work!

Below is an example where the owner’s boat was protected by a fuse. This owner had a 1/2/B switch and decided it would be a good idea to fuse both banks. A year after doing this DIY upgrade he had a plastic wire-tie fail and the large gauge battery cable came in contact with the engine.

The 300A fuse, that was protecting this wire, saved this owners boat from burning to the waterline.

Foolish to not protect all batteries with over-current protection or a protective conduit? You bet it is!

Bare Minimum Fuse Sizes

Let’s cut-to-the-chase on this. Below are the minimum bank fusing we prefer to see for any bank that could ever be called upon to start a motor. If your vessel has a 1/2/B switch both banks need to be capable of starting the engine.

Bare minimum fuse size for small diesel engines 8HP to 25HP = 250A

Bare minimum fuse size for medium diesel engines 25HP to 60HP = 300A

Above 60HP 75% of measured *inrush current as minimum fuse size.

*You will need a clamp meter such as a Fluke 376, or equivalent, to measure the inrush.

If you follow the above guidelines, you will not suffer “nuisance trips” if fusing your starting bank.

If your engine is too large for a fuse put the entire length of the cranking conductor in a protective conduit or protective loom! Unprotected battery cables are a fire waiting to happen!

Selecting the Proper Type of Fuse:

Battery banks larger than 255Ah should be protected with fuses not breakers. The following types of fuses are suitable for main bank protection:

ANL

CLASS T (preferred for Li-ion& large AGM Banks)

MRBF

These fuses are available from Blue Sea Systems and other reputable sellers. They should however be “Ignition Protected” fuses if installed on a gasoline boat and Blue Sea Systems is the only one I know of offering ANL fuses with ignition or spark protection for ANL’s. Class T fuses are not technically IP rated however they are fully encased in a metal body. Class T fuses have simply not been tested for IP rather than do not meet IP. In speaking with Blue Sea systems I was told they have no documented cases of an IP breach on any Class T fuses.

Remember, the main battery over current protection (OCP) or over current protection device (OCPD) is sized to protect the wire. The main bank fuse is not there to protect the down-stream equipment. Those fuses would be located after the main bank protection fuse. This is often misunderstood.

You can always go smaller with OCP than the wires ampacity rating, but ideally should not exceed the ampacity rating unless you are fusing the battery bank and the bank could potentially be called upon to crank a motor. The main bank fuses are there to prevent the wire from overheating, melting and starting a fire in a dead short situation. Generally speaking a fuse is sized to not exceed the maximum ampacity of the wire. In certain instances the ABYC allows for up to 150% of the chart below.

What if my engine draws more than the wiring is rated for?”

Nigel Calder clearly addressed this above and this is actually not uncommon at all. Many builders undersized starting wire for many years, and got away with it, due to the short-duration starting circuits are physically current-loaded for. Today, most builders have come up closer to where they should be for wire ampacity.

A good example of this is the original Universal M-25 as shipped on Catalina Yachts in the 80’s and most of the 90’s. Catalina used to ship the Universal M-25’s with 4GA battery wire. In the late 90’s they began shipping the same engine, a Universal M-25XPB, with 2/0 gauge wire. Going from 4 AWG to 2/0 AWG is a huge improvement. If you have small gauge wire, an upgrade to larger wire can be a very good investment. Your engine will also start quicker and the starter will see a lot less voltage-drop. Larger wire means you’ll be able to develop more cranking current for faster starts. Nearly every sailboat I went aboard during the last boat show, including a tailerable 28 footer, was using 1/0 or larger wire with 1/0 and 2/0 being the most popular in boats over 30′.

Won’t the starters in-rush current blow my fuse?

First, let’s identify what in-rush current really is? In-rush current is the very brief spike in current that the starter undergoes to get the motor to begin turning over from a stopped state. The in-rush duration is usually about 100ms to 300ms long, and is not long enough to blow a properly sized fuse. ANL, MRBF or Class T fuses are not sized for the inrush, they are sized so they don’t nuisance trip when cranking an engine.

Compare the in-rush duration to a fuse rated for main bank protection and it becomes clear as to hoe this is so.

ANL FUSE- TRIP DELAY CURVE

CLASS-T FUSE -TRIP DELAY CURVE

MRBF TRIP-DELAY CURVE

Contrary to popular misconception fuses don’t always trip at their face value rating. You also need a long enough duration at high current. As can be seen above, each fuse has a trip-delay curve. These curves are from Blue Sea Systems.

If you look closely, a 300A Blue Sea Systems ANL fuse can support 600% of its rating, or nearly 1800A, for approximately 0.5 Seconds. The inrush duration is not this long.

If we look at the trip-delay curves above it becomes quite clear that ANL, Class-T or MRBF do not trip at face value unless the duration of high-current is long enough.

For example, a 300A Blue Sea Systems ANL fuse can handle 300% of its rating for an entire second or 900A. Peak cranking currents just don’t last this long. If we look to the far right of the trip-delay graph you can see that it would take nearly 500 seconds or 8.3 minutes at 150% of the ANL fuses rating to actually trip. For a 300A fuse this is 450A for as long eight minutes or so. This is the reason why fusing cranking circuits is not the problematic concern some make it out to be. You just need to size the fuse correctly.

300 AMP ANL Seconds vs. Trip-Amperage

.7 Seconds =1800A
1 Second = 900A
5 Seconds = 500A
500 Seconds =450A

AIC & Why It’s Critically Important!

AIC stand for Amperage Interrupt Capacity. The AIC is sometimes called “interrupt capacity”too. AIC is the short circuit amperage capacity the fuse or breaker can “interrupt safely” without welding shut, blowing up and losing “ignition protection” or jumping the gap and failing to provide protection..

The ABYC Standard

The green arrow is pointing to a specification that can only be met by a Class T fuse!

Table 3B below.

Not All Fuses/breakers are Created equal!

Not all fuses/breakers are created equal. Always Stick with fuses by Blue Sea Systems, Cooper Bussmann or Littlelfuse.

When ordering from less than reputable sellers make sure the products can meet the following;

Avoid purchasing fuses/breakers off of Scamazon! The customer below learned a very hard lesson. The pictured breaker came from Amazon and the customer certainly got scammed! The 200A breaker was consistently tripping every time his alternator output got to 85A! Amazon refused to publish his review on the product! The alternator load dumps caused his alternator to fail and also took out his brand new B&G plotter!

And here’s a guy who’s budget breaker welded itself shut! This is why AIC Matters!

*Images below courtesy Attainable Adventure Cruising

The welded & melted breaker

Below is another example of why AIC maters. The fuse below was attached directly to the battery + terminal and when it tripped it failed in a manner that it kept allowing current to pass. The owner noticed a fumy smell and it was his bilge pump starting to melt.!

The meter is still showing continuity even though the fuse clearly tried to blow! The AIC rating of the fuse maters!

The above ATC Fuse only had an AIC of 1000A yet was directly connected to a bank of AGM batteries that could deliver 20,000A of short-circuit current

ATC Fuse AIC

What Fuses have an AIC that is suitable for a cruising boat bank?

Class T, ANL and MRBF fuses all have an AIC that can be suitable for house banks. If you have a large bank of AGM or Lithium batteries then a Class T fuse is the best fuse to meet the AIC requirements. For LiFePO4you really want to use class T. ABYC E-13 specifically calls this out.. The AIC rating of Class T fuses is 20,000 amps at 125V. It is significantly higher at 12V but Blue Sea Systems has not run the AIC tests at 12V. A 20,000A rating at 125V is a very, very impressive AIC rating. The Class-T fuse is the most robust fuse we use in the marine environment because it is fully metal encased.

ANL fuses have AIC of 6000A at 32V and MRBF fuses are 10,000A at 14V.

What about Breakers & AIC?

The concern with AIC & breakers is that breakers can literally weld shut before tripping, if the bank has enough short-circuit current behind it. For smallish house battery banks, you ideally want an AIC rated fuse or breaker of 5000A AIC or greater. Even Blue Seas Best class of breaker, the 187 series is only rated at 5000A AIC.

Just one group31 Odyssey TPPL AGM is capable of 5000A of short circuit current! Please understand that AIC is not just for large AGM banks or LiFePO4 batteries. A single 100Ah Group 31 Odyssey AGM battery can deliver 5000A of short circuit current into a dead short. A 200Ah bank of Group 31 Odyssey AGM batteries is 10,000A into a dead short. This is why the AIC rating of the over-current device is critically important.

The actual ABYC requirement for batteries is that any bank over 255Ah needs 5000A AIC rated protection or greater.

Cheap Fuses have no place on your boat

For the ABYC Li-Ion Battery sub-committee I spent A full day blowing all types of fuses and one thing that was seen very early on is that all fuses are not at all created equally. When a fuse trips it needs to trip in a safe manner. Knock of fuses, often found on the internet for car stereos, etc. are not built to the same standards as fuses from the likes of Blue Sea Systems, Littelfuse or Cooper Bussman. With a quick phone call any of these three companies you can quickly get all the testing data for any products they sell. Go ahead and try that with off-brandfuses/breakers you find on Amazon I know what the answer will be, we tried to do it for one of our customers who had a Scamazon breaker blow up one of his alternators. It tripped at just 110 A and was rated 250A! Sorry, no, this is not covered under warranty!

Blue Sea Systems ANL fuses have an IP rating “ignition protection” which is important on boats as the fuse must fail/trip safely so as not to ignite any on-board fumes. In the image below we have a bunch of cheap Amazon ANL fuses. A Blue Sea Systems ANL is built with G10 fiberglass sheet, features four rivets holding it together and uses a very durable Mica window. The cheap ANL fuses are a plastic body, two rivets and they use thin plastic windows that are prone to blow out when the fuse trips. We tripped 22 of these cheap fuses and the windows failed unsafely 20 out of 22 times. You can see the blown-out window in this image. When in doubt stick with fuses and fuse holders from Blue Sea Systems, Littelfuse or Cooper Bussman.

The photo below is a prime example of what can happen to a cheap ANL fuse. These claimed to be “ignition protected” (IP) and AIC rated fuses. After multiple emails to the vendor, they failed to provide any documentation to back any of these claims up? When buying fuses on Amazon it is certainly buyer beware! A few weeks later I noticed the specifications had magically changed and they no longer claimed IP or an AIC rating. Sadly, the only data I was able to find on the fuses was “Made in China“.

The fuses below were connected directly to a LiFePO4 lithium battery bank and then the circuit was shorted. The fuse trip was so violent, it literally blew the windows out of the fuses. This is an UNSAFE failure mode for a fuse. It failed for both AIC and ignition protection safety.

What About Victron Lynx Distribution Buses?

Victron has a beautiful line of distribution busses called the Lynx series. The Problem with these busses is they employ MEGA fuses that only have a AIC of 2000A. The solution is quite simple. You simply feed the distribution bus with a fuse that has the correct AIC Rating for the battery bank.Once the mega fuses  are behind the main distribution fuse, a fuse that has the correct AIC rating, the MEGA fuses are now fine.

The Solution:

Pro Tips:

If you lack battery compartment height, and your batteries have lead posts, a military post can get you horizontal with an MRBF.

MRBF fuses work really well mounted to busbars

ANL or class T fuses/holders can be bussed together using copper bar stock from McMaster-Carr

Fuse Safely!!

Lead is Dead (almost)

You may be wondering why I am saying lead is dead ?The answer to that is simple; lead acid battery makers dug their own graves by grossly misleading the general public. They know damn well none of these batteries will never meet the cycle-life claims out in the real world whwere PSoC use is a reality. Why? Because the real-world is not a white coat white glove laboratory and in the real world “sulfation-happens”.

Claims of 1000 cycles or 1200 cycles or 1600 cycles is as laughable as Jim Gaffigan beating Usain Bolt in the 100 meter dash. In a battery use survey conducted on sailboatowners.com, the largest ever of its kind with 1480 users surveyed, the vast majority of boat owners reported they rarely if ever get more than 150 cycles out of their lead acid batteries. 150 cycles!!!!! Many of these are batteries that have claims of 100 to 1200 cycles or more. Laughable is about the best way to describe it. Lead is dead because the manufacturers dug their own graves by misleading their customers. Perhaps if they had been more honest in setting reasonable cycle-life expectations the mass exodus from lead to LiFePo4 would not be quite as rampant?

The image below is but one example of why I can say lead acid battery cycle-life claims are laughable. I don’t and will never make a claim like this without data. We have been conducting capacity test on lead acid batteries for close to 20 years. While the equipment for capacity testing batteries has gotten significantly better, the quality of the lead acid batteries has not. This poor customer purchased a brand-new bank of Trojan SCS-225’s in the spring. His boat is on a mooring and he did not have solar. I explained to him the batteries may only last 1 to 2 seasons. He was very surprised that based on Trojan’s claim of 600 cycles to 50% depth or discharge. The results below are not atypical. The battery is at 63.4% state of health in just one season. By industry standards a lead acid battery is considered end-of-life when it can only deliver 80% of rated capacity. 20+/- years of testing marine use batteries to BCI Testing standards has taught us that claims of 1000+ cycles from lead acid are about as fairy tale as Tinker Bell..

These days LifePo4 has come down in-price enough to be at near parity with AGM & Gel in a $$ to usable Ah Comparison. When we add in $$$$ to Ah & include cycle-life, LFP is wiping the tears of the lead acid battery makers off the floor..All that said.. Let’s take a loot at current prices;

Lifeline GPL-31XT– AGM- 125Ah X 3 for a 375 AHBank=$1596.96- 187.5 USABLE Ah @50%DoD(at best *300 hundred cycles(real world usage)) =**8.52/Ah
*20+ years of read world experience including many hundreds of capacity tests..

KILOVAULT HLX+ 2400X  2 400Ah BANK= $3090.00 for 320 USABLE Ah @ 80%DOD-5000+/- cycles=$9.65./Ah

KILOVAULT HLX+ 2400  X 2 for a 400AH BANK= $3090.00 for 400 USABLE Ah @ 100%DOD 2000 cycles=$7.73/Ah

A t 100% DoD the cost per Ah is only a little more than AGM

What About Cost per cycle?

HLX2400 Cost per cycle@ 80%DoD=0.62

HLX2400Cost per cycle@ 100% DoD=$1.55

LiFeLineAGM Cost per cycle@ 50% DoD=$5.32.

Drop-In Pluses& MinusesPreface:

This article discusses 12V (nominal) LiFePo4 Drop-in batteries for use on boats.

This is the first article I’ve written since I suffered a major stroke on September 1 (nearly died). It took me six+ months of recovery to get to this point. I am writing this with new speech to text software(Dragon) which is not easy to master and I only have one finger to type with(my left arm/hand are still paralyzed.. My vision was also affected by the stroke so working at the computer for more than about 30-40 minutes a day is exhausting(though with hard work my endurance is slowly getting better). My brain is pretty worn out after 30-40 minutes, so an article like this has taken me more than120 hours to author. I’m getting it done but everything is just taking a lot longer. I am committed to MarineHowTo.com and this article is just the beginning of my recovery. I had started the outline of this article back in August before I had the stroke..

 

What do we recommend for drop in Batteries?

For the highest quality; Lithionics

We also love the KiloVault HLX+ batteries

Good Product assembled in the USA; Battleborn

A Tremendous value are the batteries by *SunfunKits.com

(*use coupon code; marineht for an additional 5% off at sunfunkits.com)

Discuss what you read about in this article in the groups below:

LiFePo4 Drop-In Batteries For Boats

For general Marine electrical systems discussions; Boat Electrical Systems

I Actually Use LiFePo4

It’s important to know that I’ve been using lithium iron phosphate batteries on my own vessel since early 2010 I built my battery bank back in 2009 well before any of these drop-in batteries even existed. My LFP bank will be 13 years old on May 10 of 2022. The bank has in excess of 2200 cycles on it & most every single cycle has been to at least 80% depth of discharge with many many, many cycles (at least 100+ cycles) going to 0%. That battery bank can still deliver 100% of its 400Ah rated capacity so LFP batteries can last, where lead acid don’t.

Having been using LFP since 2010, you could not pay me to go back to lead acid..

Important:This article is not intended to pick on any manufacturer at all. It is intended only to make you a more educated buyer. Where it was possible brand names have been obscured..(I do call out one manufacturer but that is rare for me).

Drop-In LiFePO4 Batteries, don’t you just drop them in?

No you don’t! Any consideration of LFP batteries on a cruising boat must be treated as a system wide approach.Don’t just take my word for it. Boat US is one of the largest insurers in the US.

But, But, they say “drop-in replacement for lead acid?”

“Do Not Connect to analternator”?WOW!I’ve never seen a lead acid battery disallow connection to a non-smart alternator??Drop-in? Apparently not so much?

Terminology Used:

• LiFePO4= Lithium Iron Phosphate also called, LiFe & LFP
• BMS= Battery Management System
• C-Rate- “C “= Capacity and the rate is usually depicted as 1C, .5C.,.33C, .02C etc. A 100Ah battery with a charge rate of .5C would be 50A charge current or 100Ah ÷.5 = 50A
• Load Dump- A BMS Disconnect during charging which disconnects the battery.
  
• VPC- Volts per cell
• Pack voltage- voltage of the entire battery measured at the packs positive & negative terminals

What is a “drop-in battery?

A drop-in lithium iron phosphate battery is a self contained battery that comes in a standard lead acid case size e.g; group 24,27,31 group 4D, group  8D etc..These batteries are self contained and should always have a BMS built in.. Batteries that use an external BMS such as Vicron or some of the Mastervolt or Lithionics batteries are not considered drop-in batteries.

Ignore The Trolls & Safety

Internet trolls pollute the Internet like cigarette butts pollute city sidewalks and gutters. You know who I’m talking about, the undereducated know-it-all who enters any conversation regarding lithium iron phosphate batteries in a Facebook group or boating forum and   starts with; “The only people looking at lithium iron phosphate batteries are the ones who want their boat to blow up”. A great example of this can be found in the “parting shot” of the April /May 2022 issue of Professional Boat Builder Magazine.. Even though the parting shot is editorial in nature,Pro-Boat should be embarrassed by that piece and the complete lack of research on the authors part. Pro-Boat normally works with authors who are actually experts in their field such as Steve D’antonio or Nigel Calder but the author failed to do any research on this topic and put out a grossly under researched apiece..

Let’ cut out the BS right now. LiFePo4 and LiCoO2 (Boeing) are about as different as water and gasoline in terms of resistance to burning/exploding. While LiCoO2 and LifePo4 are both Li-Ion batteries, the chemistries are vastly different in terms of safety. Let’s not forget Flat-Earthers still exist too…

When you see these trolls politely ignore them &, as the internet goes, “don’t feed the trolls“..

Li-Ion= Rechargeable Li
Lithium = non-Rechargeable Li

Don’t just take my word for it here is the FAA

A Reader Challenge

Reader Challenge:I will continue to offer a challenge that I have been offering now for 10+ years on the Internet and that is; the first person to bring me an image of a lithium iron phosphate cell, properly installed, that erupted into flames or resulted in an explosion due to overcharging, I will pay them$50 cash for that image! In 10+ years not one person has been able to bring me such an image…This is because LiFePo4 is an extremely safe chemistry.

A Dramatic example of LiFepo4 Safety

The image below is but one example of the safety of lithium iron phosphate batteries. The cells below came out of a drop in battery where the solar controller failed & the 100V+/- array started feeding hundred+/- volts to the batteries. The BMS tried to protect the batteries but once the BMS shut off. in the solar array was still feeding 100V+/- to the chip in the BMS. Once the chip failed the 100V made it to the FET’s and they too failed allowing the full array voltage to get to the LFP Cells.

No fire, no explosion just swollen ruined cells & cell venting.

The Cells were overcharged so violently that it blew apart the metal case!

HOW IS A DROP IN BATTERY MADE?

A 12 V (nominal) lithium iron phosphate battery is made from four 3.2 V cells wired in series. This is referred to as “4S”. This makes the battery a 12.8 V rated battery. The difference between lead acid and lithium iron phosphate is that each cell in a lead acid battery is a nominal 2 V cell but in a lithium iron phosphate battery each cell is 3.2 V. So, a 12 V lead acid battery requires six 2V cells and an LFP battery only requires four  3.2 V cells.

START WITH THE CELLS & BMS

There are currently three different cell form factors being used in drop-in batteries. the first is called prismatic these are square blocks that nest together and most often require what is called cell compression,the Chinese call this a “fixture” . The “fixture” is used to prevent cell swelling / bulging during charging .

The second type of cell that is commonly used in drop-in batteries is called a cylindrical cell this can be anywhere from the size of a AA battery up to approximately the size of a D battery. Cylindrical cells are quite robust because they don’t need cell compression as the cylindrical form factor prevents swelling. The drawback to cylindrical cell batteries is that they typically require lots of spot welds to connect the cells in parallel cell blocks before they be are put into series series.

the third type of cell for drop-in batteries is called a pouch-cell we typically do not advise pouch cells for use on boats where vibration can be high. pouch cells can be easily ripped and often times they are just dropped into an and aluminum housing that can sometimes have sharp edges. pouch cell drop-ins are getting better and these days have less chance of ripping but prismatic or cylindrical is typically better for use in high vibration environments.

PRISMATIC CELLS & BMS

CYLINDRICAL CELLS & BMS

Pouch Cells

ADD A  BATTERY CASE

Clearly I’ve left out a lot of the important details of the manufacturing of a drop-in battery. In order to build a battery properly the cells must be impeccably matched before the the cell block is assembled. By impeccably matched I am talking about cell to cell Ah capacity and cell to cell internal resistance. If the cells are not carefully matched the BMS inside the battery may never be able to keep up with balancing.We have seen this in numerous instances with drop-in batteries.

What is a BMS?

BMS stands for battery management system. A battery management system is used to protect the individual cells inside the battery. Each 12.8 V (nominal 12 V) drop-in battery must use a battery management system. You could also call a BMS a cell protection system as it actually serves to protect the battery cells inside the drop-in battery. The BMS will protect the battery cells from such things as temperature voltage and current. The BMS also serves to balance the cells should they get out of balance. The BMS protects the battery by disconnecting the battery from the charge sources in the loads. Lead acid batteries do not do this.

Insane Market Growth  of Drop-In Batteries

In the last two years the proliferation of lithium ion phosphate(LFP) drop-in batteries has literally gone berserk. Drop-in technology has finally advanced far enough that I believe it’s now worth discussing in an article. I had previously avoided this topic because many of thethe early drop-in products were pretty poorly engineered, BMS’s had weak power handling etc..

Disclaimer: MarineHowto.com does not currently sell any lithium iron phosphate batteries. Health issues (a near deadly hemorrhagic stroke forced what is perhaps the permanent closure of my local electrical & on-line businesses.We are also not involved in any affiliate programs that could potentially sway our opinions! This site, like always, is for your education only. We want to ensure that you do not get ripped off in the field LFP drop-in batteries. What you get here is an expert opinion that is based on many years of experience in this field(since 2007). With no money potentially swaying these opinions, you’ get an unvarnished view.

While the internet is full of folks claiming to know what they are talking about sometimes it is easiest to just use a photo. The image below shows the ABYC marine safety standards that I work on. I have been involved with the lithium-ion subcommittee since it was first formed back in late 2013. I was personally invited onto this committee by the committee chair.

Beyond being a Marine electrician/engineer, I have been using lithium iron phosphate batteries on my own vessel since Spring 2010. And yes, that  bank (built well before drop-in LFP batteries even existed) is still going strong and it still delivers 100% of its original capacity when capacity tested.

I am also a voracious reader & research junkie;

As can be seen from the image below I have a massive collection of technical documents,research papers&white papers. Everything below is in regards to lithium ion phosphate batteries. I run a 32 inch monitor and I can’t even come close to fitting everything onto one page for a screen grab. This LiFePO4 folder alone has 377 PDF documents on lithium iron phosphate batteries. Yes, I have read them all…

LFP drop-in batteries have come a very, very long way in the last few years but this does not mean there are no sleazy manufacturers left out there. How do you avoid 98% of the poor LFP products? Easy, don’t buy directly from China on your own. If you don’t know what I mean by this I would urge you to spend some time on Will Prowse’s YouTube channel but, please don’t focus on his reviews(in a marine application sense), instead focus on how many failures he’s had cutting open & examining drop-in lithium iron phosphate batteries! Please remember that a manufacturer who is sending Will Prowse a battery often knows darn well who he is.. They still fail to send him well-built / well executed batteries many of them lacking cold-weather protection (You can’t charge LFP below freezing) even though they frequently lie and tell him the battery has it.. If guys like Will Prowse can’t pick quality batteries out of China how can you expect the average Joe to wade through all the murky information and get good LFP drop-in batteries directly from China? Hey, I’m not complaining, Will has indirectly sent us a lot of paying customers! These customers have had a number of issues with batteries,cells or BMS’ he’d reviewed. We’ve made a lot of money testing these batteries in our lab, only to tell the customer they had  been sent “B-grade or reject cells etc… This sort of stuff, has been sold as  “A”grade” but, the customer got “B” grade or reject products. This scammery runs rampant on Aliexpress, Alibababa, eBay, Bangood Amazon etc. etc. so be very careful when ordering direct from China because you’re on your own once you do..!

Purchasing- Rule#1

Rule number one for purchasing  lithium iron phosphate drop-in batteries is that you always want to buy from a well established US or North American company!(This site is read world wide but is still a US based company. (Insert Germany UK, Norway, Sweeden etc. for USA), even if that company is having the batteries manufactured in China. Hint: All lithium iron phosphate cells are manufactured in China. Some US manufacturers such as Battleborn choose to import the components from China and assemble them here in the US. This allows them to better control assembly quality. You want, and need a presence here on North American soil (insert your country here)  to ensure that the company can stand behind the product and you are protected by US (your country) consumer laws..

Most of the “bad” images you will see below are what happens when aDIY attempts to become the importer of LFP batteries.These sorts of issues are almost non-existent  where a decent US company is behind the importation design & manufacturer selection process.

Disreputable sellers will lie and think nothing of it. This LFP cell is 100% made in China……

Always Check with your Insurer First!

The image below is from Markel, one of the largest insurers of boats in the USA.

And here’s an insurance questionnaire/form. Lie on this document and guess what ? You’re not covered!

Important:This insurer wants to see a US company, on US soil so they  have someone to go after should an accident occur. This is why they demand a company based in the US.

Batteries such as Kilovault (MA), Lithionics (FL, Battleborn (NV), Dakota (ND), Relion (SC), Mastervolt (WI), Victron (ME), Trojan (CA), Lifeline (CA) etc. would meet this criteria.

Batteries that come directly from China such as SOK, AmpereTime, Chins, AO Lithium etc. Would not meet this criteria.

There are still many insurers who allow LFP but please check with them first!

What About the ABYC:

If your Drop-in battery cannot meet the underlined criteria (Insert “Strong-Opinion”) you  may want to keep looking:

ABYC TE-13

What About the ISO/ European Safety Standards:

ISO/TS 23625
ISO is Pretty Similar to the ABYC only this standard is active now (ABYC E-13 coming very soon)…

“Rod, isn’t the ABYC is a “voluntary” standard?

Absolutely, but here’s the rub. Every Marina in the United States, and most in Canada, require insurance. If you’re vessel is insured the insurance company has standards they expect. In North America those standards are the ABYC standards. They use Marine surveyors to ensure the boat is safe and up to their underwriting standards. Marine surveyors are currently using ABYC TE-13  as a guide for LFP installations and are actively calling out installations that don’t meet the nature of the TE-13 document.We get emails about this routinely.Our answer is, as always, do as your insurer requests as finding another policy especially if your boat is older can prove to be very difficult..

ABYC TE-13 is currently a technical edition (TE)meaning a technical white-paper defining safe installations. TE-13 will be converting to a full-blown standard called E-13 perhaps as soon as July 2022(could be earlier too). I cannot speak to any of the specifics at this point because I am under an NDA (non-disclosure agreement). Throughout this article I will give some “strong opinions“on what is safe and what is not. You can take from those opinions what you what you want. My opinions will be based on what the final document may look like.

Be Very Careful With the Marketing!

“Marine Grade”

I’m not intending to pick on this manufacturer but it is a good example of where marketing and standards can clash..  Recently a customer emailed us about the new XXX Brand “Marine” batteries, a brand we had never worked with. He is insured by Markel. A couple of days later he sent us this email:

One would think a battery marketed heavily as “Marine Grade” would actually meet the Marine standards?

  YouTube Reviews

I really do like like Will Prowse and I think he’s doing the general public a tremendous service in cutting open all these drop-in batteries and exposing all the dirty little secrets. We too have cut open a slew of these batteries I just don’t do video or video editing well..  The problem I have with Will is that he does not operate in the marine environment and the marine environment is a different set of circumstances & standards than it is for RV or off-grid cabins. For example, I don’t know a single RV that has a 12V bow thruster that can pull over 600A(no load rating) at 12 V and 1600A+for in-rush LRA/FLA rating. An in-rush like this is capable of ruining some FET BMS boards especially after repeated thrusts.

We have had too high a number of readers & a few customers(who self installed) destroy or damage drop-in batteries with their bow thrusters and windlass motors! The good news is that FET BMS’s are getting bigger and more robust all the time so these issues (wimpy FET BMS’s) may soon be behind us…As you can imagine, it gets very, very expensive when you ruin a battery by applying too much in-rush current.. Be careful taking Wills advice at face value for a Marine application is all I’m saying.

Having been asked over and over what “Drop-In” batteries Compass Marine Inc. prefers, likes or That we believe are well designed, the following two brands are where we stand today.

Lithioncs $$$$$$$-Amazing quality drop-in batteries. Built like no other LiFePo4 batteries!

KiloVault $$– These 100Ah, 150Ah and 300Ah 12V batteries are very, very well built for the price point and include one of the most robust BMS’s of any drop-in product we know of. They also use extremely high quality aluminum prismatic cells and each battery has Bluetooth built in for external communication & “visual” TE-13 compliance. Even the busbars inside these batteries are made of Nickel plated copper. Having torn piles of LiFePO4 batteries apart I can say without a doubt these represent one of the best values there is in a 12V drop-in battery.

Is Your Vessel a Good Match for Drop-In Batteries?

Use this flow chart to find out

An upgrade to lithium iron phosphate batteries can always be done in stages. We typically advise starting with the charging system first, as your on-board items become antiquated or become failure prone. We suggest upgrading any sort of charge equipment eg; solar controllers, alternators or alternator regulators with devices that can be fully programmed for lithium iron phosphate batteries in the future.Doing this as the items begin to become failure-prone means that in the future when you’re ready to upgrade to lithium iron phosphate batteries your system will be ready for it.

Let’s Look at Drop-In Battery Specifics:

The popularity of drop-in LFP has literally exploded in the last 2 years. This is good for LFP batteries as a whole, but can also potentially be bad, if the right drop-in’s are not chosen to properly match your vessel.. There are things that need to be considered beyond just “dropping them in“. The term “drop-in replacement” is a very misleading moniker, as these batteries are far from a “drop-in” replacement for lead acid.

Drop-In batteries are most often sold in standard lead acid case sizes eg: Group 27, 31, 4D, 8D etc.. One of the drawbacks to a drop-in battery is that most of them lack any external communication between the internal sealed BMS and the vessel. Currently the 320Ah Lithionics GTX12V320A is the only drop-in marketed battery that offers external communication between charge sources and the battery.

Most of the drop-in batteries have been Chinese in origin, and this is not necessarily a bad thing, if you’re buying from a reputable manufacturer. A large number of the US available brands eg; Trojan, Lifeline, Relion, Kilovault etc. are buying from a hand-full of premium Chinese factories. The difference between straight up US sticker applicators & Trojan, Lifeline Relion, Kilovault and pure US based sticker applicators is that Trojan, Lifeline Relion  & Kilovault designed the batteries and have them built to their specs just like Apple computer does.

Where drop-in LFP batteries often fail the purchaser is in marine specific engineering. To understand why, we simply need to look at the reason these batteries were originally created. Drop-in form factor LFP batteries were originally designed for telephone pole mounting where light weight and “drop-in” replacements for lead acid were critically necessary for the solar powered street lighting & cell repeater industry. The demand for this type of battery, especially in third world countries, is absolutely staggering.

Drop-in batteries were not invented for the use  you think they were

I know many boat owners tend to assume we are a large market, but we are not, and no, many of these drop-in manufacturers are not specifically building marine batteries for us, though they certainly are marketing to us. The application of a “marine” sticker, and perhaps even a well marketed brand name on the plastic box, does not always denote a product that is well engineered or specifically engineered for use on a cruising boat.

Unfortunately, for our industry, many of the “A” graded LFP cells used in the plethora of Chinese drop-ins, are sold into the street lighting or EV market industries. Please understand that the term”A” grade is really a meaningless-term in China. “A”grade really means EV grade but the Chinese have figured out that people think “A”grade actually means something…It may actually mean “A”bhorrent grade” depending on who you buy from

For boaters buying drop-in batteries direct from China this can mean the low-grade “orphaned” or “rejected” cells wind up in batteries that may look exactly the same but are sold on Ali-xxxx, , eBay or through other less reputable sources.. Once the cells are sealed in its glued together plastic case you the buyer have no way to know what quality cells you got.Below is an example;

Direct from China FAIL! This battery came directly from Aliexpress:

You may ask yourself why I say take Will Prowse reviews with a grain of salt? This image explains exactly why I say that. I have yet to see Will’s reviews include a discharge capacity test of each individual cell in the battery. I know darn well why he does not do this …. Time.. We use the exact same computerized capacity tester Will does, plus a few others, but this stuff takes time, lots of time. The problem with this Aliexpress battery is that the cells had a 8.3% variance in their Ah capacity! This battery tested at 100% capacity on cycle #1. On the recharge is where the problems showed up. As a result there was no way this particular BMS could ever keep the cells in balance. The bottom line is this battery was built from reject /grade B cells that never should have been in a battery that was marked or sold as “A” grade! We’ve done lots of testing for viewers of Will’s that confirmed the cells or battery they got from Aliexpress were not actually A grade or EV grade cells.There are not many companies capable of doing this testing, so this has meant quite an in-flux for us in the last few years.

Sadly Ali-xxxxx has literally become the numero-uno dumping ground for reject LFP cells and batteries from the Chinese factories. They get away with this because they know the vast majority of buyers have no way properly to test them once the battery case is glued together. Frustrating? You bet it is! Always buy your LFP batteries from reputable companies not directly from China unless you love to gamble.

The internal BMS in this battery was completely incapable of balancing the cells & one high cell kept tripping the BMS on high voltage. 3.65V is the maximum safe cell voltage for a LiFePo4 cell (the image above has two cells in the danger zone). We spent about two hours reprogramming the BMS after multiple emails back & forth with the manufacturer who refused to give us the BMS passcode so we could custom program it to make it work better for poorly matched cells. We then tried to charge it and to get the cells balanced for three straight days. Nothing we did could balance the cells so this battery would not trip the BMS on cell high-voltage.Please note the recommended charge voltage was 14.6V and even at 14.2V we have two cells well into the danger zone.

The customer finally gave us the okay, after emailing with the manufacturer,  to open the battery and test each cell individually. This required the complete destruction of the battery case because it had been glued together with what appeared to be superglue. The only way to get open was to cut it open. When we finally capacity tested the cells it was discovered that there was an 8.3% variance in cell to cell  Ah capacity on these four 100 ah cells.There was no way this BMS was going to keep up with that variance, balancing wise.

Once the manufacturer had the testing data they then backpedaled on the warranty and refused to take battery back because the battery had been cut-open(which they had said was ok). The customer was out all the money he spent on shipping plus the battery costs direct from China(His take was that as an Aliexpress buyer you have no rights and no recourse). He was also-out  about $380 in labor for our shops testing costs. In the end he wound up buying two KiloVault batteries and has had zero issues since..

Drop-In LiFePo4 – Important Points to Consider:

 BMS Current Handling 

The current rating of the internal switch that protects the battery is quite often too small for the task on many cruising boats. Drop-in LFP batteries routinely use multiple tiny little MOSFET switches as the batteries BMS protection ON/OFF switching. Unfortunately these FET’s often can’t handle the typical loads imparted by many cruising boats. On board devices such as bow thrusters (400A +), windlass’ (100A to 300A+, large inverters 150A to 300A +, electric winches 75A to 300A +, electric cook tops, massive alternators, chargers or large inverter-chargers are very very common on-board cruising boats these days. These are exactly the devices many boat owners are hoping to see a gain in performance from when switching to LiFePO4.

This is what a 120A rated FET based BMS looks like it is pretty for a typical 100Ah drop in battery. This is what an internal FET based BMS boards typically looks like with the heat sinks removed. The blue wires connect to the neg end of the cell string and the black wires are connected to the external negative battery post.fet bms’S DISCONNECT ON THE NEG SIDE OF THE BATTERY This one uses two 10GA wires for its 120A continuous rating. All 120A has to pass through those two 10AWG wires, the printed circuit board and the FET’s. The hotter FET’s run the shorter the MTBF (mean time between failure) is. This Particular BMS ,a JiaBaida, uses 32 FETS(the board has double sided FET’s.  We have cut open drop-in batteries with 100A rated BMS’s ( that use only 10 FET’s.(see image below this one)..

What a FET BMS Looks Like

The Miniscule BMS below came out of a customers AliExpress  drop-in that was sold as a 100A continuous BMS. It was also sold as Hot and cold temp protection. As can be seen the temp sense port(only one port not two.) is not even soldered to the BMS’s PCB. Hard to have hot and cold BMS protection when the sensor ports are not even installed. These are the “Lies” we talk about when flying solo and ordering directly from China..Oh and this was wired to the batteries neg terminal with 12AWG wire…! 12AWG/100A!

Do You know the quality of the FET’s ?

What if I have High-Current DC Devices?

If you own a vessel with high load devices, do yourself a favor and look at the contactor ratings (the BMS protection switch) that “marine specific” companies such as Lithionics/OPE-Li3, & Mastervolt use for their”marine specific” LFP batteries. What you’ll often see is a 500A continuous rated Gigavac, Blue Sea ML-RBS, Tyco EV-200, or in the case of Lithionics, military grade 500A contactor/relays are being used as BMS protection switches.

Compare that to some of the drop-in batteries being sold out there which can have relatively low-current handling capability due to the use of often under-designed( for a cruising boat)FET based switches. The manufacturers building “marine specific” batteries eg; LFP Mastervolt OPE-Li3, &Victron know what a typical cruising boat needs in terms of current handling and they engineer this into the product. Does this mean you need to use a “marine specific battery? No, it does not it just means you need to choose your drop-ins very carefully for your vessel.…

A Dead FET BMS (windlass in-rush)

Below is the BMS “switch” used by Mastervolt on their MLI series LiFePO4 batteries. It can handle bow thrusters, large windlass motors, massive inverter-chargers, massive alternators. etc.. The ML-RBS  switch is rated for 500A continuous, 700A for 5 full minutes and 1450A for as long as 30 seconds. While many smaller boats can often get by with a FET based BMS, not all boats will, so please consider the max continuous discharge and recommended charge ratings of the battery you are purchasing. This rating is not usually limited by the cells but rather the internal BMS’s current handling capabilities.

Let’s take a look at the BMS switch Mastervolt  uses. (Lithionics uses a similar switch on their external BMS batteries.

You read that correctly; 500A continuous or 1450A for as long as 30 seconds!!!

Sadly, when buying direct from China,you can still find diminutive 50A continuous rated FET switching BMS’s installed inside a 300Ah LFP battery. As a comparison a 150Ah KiloVault can handle 150A continuously or 200A for as long as 30 minutes. While a 50A rated BMS may be fine for small boats,  if you have large on-board DC loads, or want to charge a 300Ah battery quickly, then a battery like this is going to be a less than ideal battery for marine use. So, you still really need to do your homework to make sure the batteries & the internal BMS are a fit for your vessel.

Building a Drop-In Bank to handle Large DC Loads

When it comes to FET based BMS batteries we typically advise smaller individual batteries, wired  in parallel. This is done to share the load across the FET based BMS’s. For example three 100Ah / 1C rated LFP drop-ins can theoretically handle a 300A discharge, if the parallel wiring is perfect and all batteries share the load equally(rarely happens that way.) A 300Ah 8D format drop-in, like the one addressed below, can really only handle a 100A (0.33C) discharge. When in doubt with FET based BMS systems smaller batteries in parallel are usually a better solution than one large battery with a low current rated BMS.

You Need to Read The Specs Carefully!

Purchase FAIL!

Sometimes one just has to laugh when reading the specification sheets on some of these direct from China drop-in batteries.

This drop-in LiFePO4 (LFP) battery is rated at 12V-300Ah with a maximum charge current of just 50A!

A 50A max charge current on a 300Ah battery is a charge rate of 0.16C

0.16C IS A LOWER CHARGE RATE THAN A FLOODED LEAD ACID BATTERY CAN HANDLE

The specification also claims 2000 100% SOC to 0% SOC cycles, not too dis-believable for LFP. However they then claim 20,000 cycles at the end of the spec! This is at least double what any reputable LFP maker claims! It then claims “fully charged in 60 minutes“.

“Fully charged in 60 minutes” Holy $hite, that’s fast, but just to be safe, lets do the math..

300Ah battery at 0% SOC – 300Ah / 50A = 6 hours –Fail

300Ah battery at 20% SOC – 240Ah / 50A = 4.8 hours –Fail

300 Ah Battery at 83.4 SOC – 50Ah / 50A = 1 hour –Winner

You read that math correctly. The only way we you can get this battery to charge in 60 minutes is if you only discharge to 83.4% SOC……. So much for those deep-cycling &  “fast charging” LiFePo4 batteries? My point here is to help you learn to dig deeper into the specs so you can learn to spot bogus claims.

If you’re less than educated on a subject, drop-in battery makers will try to sell you anything you want to believe. Educate yourself and do the research

Another Purchase FAIL!

The image below is a prime example of how boat owners, without enough knowledge, can get burned buying LiFePO4 batteries. We were consulted by an owner who purchased a 300A drop-in battery from what he thought was a “reputable manufacturer“. During the transaction, he had no consultation with the manufacturer and no questions were asked by the re-seller. He just ordered it based on it’s “8D drop-in” format, the claim that it was an exact drop-in replacement for his lead acid Lifeline 8D battery, and the 300Ah capacity rating.

He felt comfortable because it was, what he considered, a “reputable manufacturer” and they are based here in the USA. He quickly destroyed three alternators and the BMS kept disconnecting when he was inverting with his large 3kW inverter/charger. The BMS disconnecting while charging also damaged his inverter/charger. When I pulled up the spec sheet on the 300Ah drop-in battery he’d purchased, the problem became crystal clear. It is highlighted in yellow below….

You are reading that correctly, this massive 8D form factor LiFePO4 battery was only capable of a 100A discharge and a max short duration charge of 100A. To keep the BMS cool, and the cells balanced, the manufacturer has a “recommended” charge rate of just 15A to 50A for a 300Ah battery. This 15-50Ais not a limitation of the cells inside the battery it is a limitation due to the FET based BMS that is used to protect this battery.

PURCHASE FAIL! For this particular application this drop-in was a horrible fit. A fault of the battery? No, not at all. This was a shared failure in the marketing, the retail chain, and of the owner. I partly blame the owner here because he failed to do the research and fully comprehend the specifications of what he was actually buying. Of course who can blame him when these batteries are boisterously marked as “drop-in replacements“. As can be seen from this example these are ABSOLUTELY NOT drop-in replacements for a lead acid 8D battery as his Lifeline 8D’s never once disconnected themselves from the alternator or the inverter…

What EVERY Drop-In Battery Spec sheet SHOULD Look Like

*Highlighted specifications are the critically important ones.

High Voltage Disconnect (HVD) Cut-Off Protection: This is critical to know because it is the voltage at which the BMS will disconnect the battery from the vessel.This is usually specified on a per cell basis. So a 3.65V disconnect on a 12V battery would be 3.65V X 4 cells=  14.6V BMS Disconnect Minimum Absorption Voltage (to Initiate Cell Balancing): This is important because you need/want to activate balancing with each charge cycle. You also want to avoid pushing to the maximum charge voltage every cycle if you wish to maximize cycle life. Maximum Absorption Time: Again, This one is critical to cell longevity. If it suggests a maximum absorpyion duration of 30 minutes you had better make sure all your chargers can be programmed not to exceed this.. High Internal BMS Temperature Charge Cut-Off- This is one you have little control over other than to not push your BMS near the charge-current limits. It is always best to charge at no more than the “recomended charge-current. 95% of the load-dump damage we’ve seen is not due to high voltage cut-offs but rather from a BMS disconnecting due to BMS Temp. Be Sure your manufacturer specifies This!

High Internal BMS Temperature Discharge Cut-Off:  same as above but for discharging. Delay until Peak Discharge Overcurrent Protection Cut-Off: This spec, from a reputable manufacturer ,will almost always be followed by the millisecond rating (ms)before disconnect eg:320A 8ms This would mean the BMS will disconnect if it sees 320A for 0.008 seconds or more. This is why knowing the in-rush draw of all DC Motors is critical before installing LiFePo4 drop-ins. Recommended Continuous Charge Current: Always follow this guidance not the “max charge current.The reason for this lower number is to keep BMS temp down and to allow balancing to keep up. Many of these BMs’s only have 20-390mA of balance current to work with! If the celllsget out of balance & you are fast charging the BMS may never be able to keep up!! Maximum Parallel Configuration : (Identical Model Batteries): Do not exceed this number! Maximum Series Configuration:(Identical Model Batteries):Do not exceed this number!

If you are unfamiliar with what the specifications mean or why they are critical you may want to reconsider drop-in batteries until you have completed the research phase.

Vibration

Many of the very cheaply sourced drop-ins are using 18650, 26650 or 32650 cylindrical cells inside the battery case. In a worst case, a 100Ah LFP battery, built from 18650 cells, would need a grand total of 364 cells with two connections per cell.

Hows that math work?

18650 Cell = 1.1Ah (typical Ah rating for an 18650 LFP cell)

91 Cells Make Up Each 3.2V cell

Four 3.2V Cells Make Up a 12.8V 100Ah Battery

91 X 4 = 364  18650 Cells

Positive & Negative Connections Inside The Battery = 728

If the manufacturer uses 5Ah 32650 cells, and some do, we then only need 80 cells total, and 160 spot welds or bolted connections to potentially fail or work loose. (32650 cells are available in bolted or spot weld versions)

The connections, with 18650s’s, are almost always spot welded to end boards that make up the individual cells.  So, in a single 100Ah battery, made of 18650’s, just to connect the cells, we have as many as 768 spot welds to rely on. Beyond that we have all the internal wiring and BMS connections. These spot welded assemblies are often just dropped into the polypropylene case with no other support or vibration dampening material.  To be safe, always be sure to ask the battery supplier to furnish third party vibration testing results or testing to UL or IEC vibration standards.

A Look at the BAD of LFP:(most of these images are “direct fromChina” purchases).

Do you suppose this Rube Goldberg level Ali-xxxx LiFePO4 drop-in battery manufacturer, and I use the term "manufacturer" sarcastically here, has paid to have this battery vibration tested?
                                 Image courtesy MHT Reader

No  Not Kidding!

                                                     Image courtesy MHT Reader

Heck the guy assembling these cells, most likely in his mom’s spare bedroom, can’t even solder well or use a spot welder with any level of quality or precision. Vibration testing? Only if they are flat out lying about it. Purchasing LFP anything on Ali-xxxx is a very strong buyer beware!

This LFP”starting battery” has NO BMS Protection!! Balancing only!!

                                                                     Image courtesy MHT Reader

Starting a 44HP Westerkeke takes…….640A!!!!

What’s Wrong here?

OK, I’ll Help Out.. Look closely at the series connection below!!!!

An 18650 cylindrical-cell battery failure

How did we discover the spot weld failures? The zipper like discharge graph was a dead giveaway..After a discussion with the manufacturer we had to tell the customer to stop using his bank immediately…It had also lost significant capacity from over charging.His lead-acid charger that held 14.6V way too long. We were testing them for capacity when we discovered the spot weld failures (brand purposely obscured). In the screen grabs below you can see how varied the voltage was on discharge.We had wanted to run the discharge at 40A but the zippered graph was even  worse at 40A so we ran the capacity test at 10A..

Data point =12.582V

Data point = 12.702V

What happens when you cram multiple small wires into one terminal and ask them to carry 100A +/-Hint: You get terminal melt down..

And here’s what they look like when you hit them with thermal imaging.

This is the level of “quality” you may find inside that beautiful plastic case

Because you can always trust the sticker on the outside of the battery

More Direct from China misleading BS

 

A FET  BMS has aluminum heat sinks because it needs cooling. Stuffing it in-between foam blocks is well…… not a wise solution.

But, some dude on the Internet said LiFePO4 is 100% safe…..

No battery chemistry is 100% safe, especially when you over charge it.(However no-fire , no-flames & no explosion just cell swelling and heating… FWIW this “starting battery” has zero BMS Protection!!

                                                                        Image courtesy MHT Reader

Do you know what horrors are hiding in that”direct from China” plastic box?

The Battery Below(image5) is typical of the Quality you’ll often find on Amazon or Aliexpress. So, what happened?

1-BMS is Catastrophic protection only. If a BMS allows cells to charge beyond 14.6/3.65VPCWalk away!!

2- BMS Allowed cells to hit 15.6V /3.9VPCbefore disconnecting!max safe cell voltage is 14.6V//3.65VPC

3- Cells were not in a case that provides cell compression to limit cell swelling

4-Cells balooned and split the battery case open- Battery ruined.

Aluminum Prismatic Cell ruined by over-charging

*image5– Cells ballooned/swelled  due to over charging. This BMS was catastrophic protection only and allows the cells to hit 15.6V before the BMS disconnects (this is enough to ruin the cells and totally brick the battery)

This what proper cell compression for prismatic cells looks like looks like! Has your chosen manufacturer included this?

The “Bad”images above are a reality of what you can often find buying your batteries directly from China without a reputable company insulating you from these horrors…

One last warning about buying direct from China

What Better Quality Looks Like

Compare the above cell block from Ali-xxxx to the photo below of a Lithionics g-31 drop-in battery. This battery uses impeccably matched aluminum encased 5c LiFePO4 cells. The cells are fixed in place by an injection molded jig that protects them from movement and vibration failures. The busbars are high grade nickel plated copper and self locking flange/wizz nuts are used to hold the cells to the busbars. The BMS used in this battery is certainly FET based but it is made here in the USA, of Mil-Spec components, and is designed to handle starting engines. There is a huge variance in the quality of LiFePO4 drop-in batteries. Yes, this battery is more expensive than a 100% Chinese made drop-in, and they are only sold after a consult to ensure they are the correct fit for the vessel. Bare minimum alternatives to the Lithionics would be the KiloVault HLX Series. A lot of folks swear by Battleborn but the Battleborn batteries to not yet meet ABYC requirements for E-13.E-13 will be official in about 60 days from this article being published.

Internal Wiring 

It is not uncommon to open a 100Ah drop-in battery, rated at 1C, and find a single 10GA or 12GA wire feeding the main positive and negative terminals. When someone finds a 10GA or 12GA wire rated for 100A, under any safety standard, please let me know?

This is how Lithionics does it on their 4D 320Ah drop-in.

BMS Shortcomings -Lack of low or high-temp Protection

Some of the drop-in batteries may lack  BMS temp protection altogether . Drop-in batteries should have both low and high temperature protection (a requirement for both ABYC and ISO) but many don’t. Far too many drop-in batteries lack low temp protection and a large number of manufacturers who claim it has low temp protection are actually lying about it. If  You live up North,buyer beware!

Non-Communicable BMS 

This one is perhaps the most frustrating aspect on-board a cruising boat. For a trolling motor, who cares? It’s not powering anything critical. For a house battery, on a cruising boat that ventures off-shore, and is powering critical navigation and safety equipment, this can create a dangerous situation. A non-communicable BMS is one that can not communicate externally with the vessels charge and load systems, or even you the owner. It has no means of externally communicating or sending/sounding warning alarms or activating relays/triggers to properly and safely disconnect charge sources or give ample warning of an impending BMS disconnect. Some batteries are now featuring Bluetooth monitoring but this still requires you the owner to be watching it.

Let’s take a look at one of the worlds most respected marine standards for shipping etc., Bureau Veritas.

As can be seen, under Bureau Veritas standards external communication between the battery and the rest of the systems such as charging is a requirement. For why see below.

WHAT ABOUT CHARGING?

LFP batteries are charged using a CC/CV profile. This means constant-current/constant-voltage

Bulk = Constant-Current(charge source working flat out  or as hard as it can)
• Absorption = Constant voltage( voltage is held steady for a short time or until current declines to the manufacturers spec.
• Absorption Duration = Once the batteries have achieved the absorption voltage the time the batteries spend  at this voltage must be limited. Many lead acid charge sources spend far too long in absorption and this is not healthy for LFP

BMS LOAD DUMPS

DON’T FORGET YOUR ALTERNATOR

Email from MHT Reader:

“RC,

The alternator for the Volvo MD2030 with 300 Amps LiFePo4 14.6 max lasted a few hours. I believe BMS was switching on to off  I to keep theLiFePo4 voltage to safe measure? Boat service replace alternator and it happens the second time? I now read your story on lfp and it explain to me why.”

Unfortunately the reader above learned the hard way. Ask yourself what happens when your alternator is in bulk charge, supplying all the current it can, and the internal BMS decides to “open circuit” or disconnect the battery from the boat? I’ll help out a bit here.

BMS load dump illustration
What a voltage transient looks like:

The load dump transient captured in the above image is from an ISO test of a 12 V automotive alternator. Of important note is how quickly this transient surpasses 90V. The transient surpasses 90V in just 0.01 seconds!

   A) The alternator diodes, unless avalanche style, (rare in many existing marine alternators) but all Balmar alternators now use them, can be blown and the alternator can be rendered non-operable. Two years ago we  did exactly this. Using the alternator test bench here at CMI the 90A  alternator was running at full bore charging an LFP battery. The “system” I set up had a .3A dummy load on, light bulb, to simulate a depth sounder. With the alternator running at full bore I disconnected the battery, just as an internal sealed BMS can do for BMS temp, cell diff-voltage or cell high voltage. Poof went the alternator diodes and the light bulb was burned out instantaneously! Worse yet the voltage transient I recorded on the “load bus” (think your navigation electronics) using a Fluke 289 was 87.2V. Ouch. Even if your alternator uses avalanche diodes, like Balmar’s do, the voltage at which they begin to protect the alternator is far too high for the vessels load bus equipment so you still need a way to protect against a load dump.

   B) If the boat is wired, as is typical with drop in batteries, the voltage transient caused by the open circuited alternator will now directly feed the DC mains and potentially destroy your navigation equipment.

TIP: At a bare minimum, every drop-in LFP battery bank, that can be charged via an alternator, should be installed with an Alternator Protection Module!

The Balmar Alternator Protection Module is an inexpensive insurance policy against a BMS load dump destroying your alternator. If you can afford to purchase drop-in LFP batteries you can also afford to protect your alternator from a BMS load dump.

A well designed marine specific BMS would open a relay that can de-power your charging sources on the input side, thus shutting the charge sources down correctly and safely with no risk of a damaging voltage transient. For a large inverter/charger it would de-power the AC input side, for an alternator it would de-power the field wire or regulator B+, for solar it would open a relay in the PV feed etc. etc.. With a drop-in battery, that features a sealed BMS, you have no way to do any of this. Only Lithionics Drop-In Batteries have this Capability.

But Rod, I plan to program all my sources below the BMS disconnect voltage.

Sounds like a good plan right? Well, lets examine the reasons a BMS can disconnect

This image sums up why programming a lower charge voltage cannot always protect against a BMS disconnect.

Are  BMS Load Dumps Real?

I’ll  let Balmar Explain this;

How about a fairly knowledgeable owner who bought a very beefy alternator and still killed it due to BMS load dumps.

Drop in batteries with the exception of Lithionics do not have a way to properly shut down the alternator before the battery disconnects. For this reason we need work arounds..

The number one reason we see batteries shut down(when everything is programmed correctly) is almost always due to BMS temp related issues not necessarily  high cell voltage..

A good technique to mitigate load dumps is to keep a buffer “load” on the charge bus at all times (Buffer load = lead acid battery on the systems charge bus see FET Isolator wiring below). With FET isolators we like to see them at least double the rating of the alternator eg; a 200A ARGOFET for a 100A alternator. The cooler FETs run the longer they last.   And yes, we have seen FET isolators fail…

Load Dump Work-Around’s

Using Low Volt-drop FET Isolators

Using Low Volt drop FET Isolators

USING DC to DC CHARGERS

There are many benefits to using DC to DC chargers. One of those benefits is that the charge profiles can be custom configured to charge lithium iron phosphate batteries where your factory alternator or legacy lead-acid charge equipment cannot be programmed for this. The Victron and Sterling power DC to DC chargers can also absorb a load-dump from a BMS disconnect where your factory alternator cannot.

However, caution needs to be used when sizing DC to DC chargers. A DC to DC charger should be sized at a maximum of 50% of the factory alternators rated output. This means if you have 100 amp factory alternator the maximum DC to DC charger you should use is 50A. This will help keep the alternator cool and keep it from burning itself up. Currently there are only two DC to DC chargers we recommend and those are Sterling Power and Victron.

The only drawback to using DC to DC chargers is that you give up charging your lithium ion phosphate batteries quickly. Seeing as that is one of the major benefits of  LFP batteries we would strongly advise considering an externally regulated alternator with an external regulator  such as the BamaMC-618 or Wakespeed WS-500these regulators can be programmed for LFP and have an alternator temperature sensor to protect the alternator from heat damage. This will also result in considerably faster charging!

Caution:I don’t often do this as I hate to ever advise against any manufacturer but there is one manufacturer that we would urge a very strong caution on and that is Renogy. We’ve not seen a manufacturer with this many failure prone products in 30+ years in this market. Their failure rate is far too high for us to even consider making a recommendation. Consider yourself warned about buying Renogy.

You can read about  DC to DC Chargers HERE.

WARNING:Do not size a DC to Dc charger at any more than 50% of your stock alternators rated output!

The drawback to using DC to DC chargers is that it results in SLOW LFP charging

Using a Victron Orion TR Smart DC TO DC Charger (Be sure it is not the Orion TR- it must be the TR SMART)

CAN I USE MY STOCK ALTERNATOR?

The short answer is we do not advise this for charging lithium iron phosphate batteries directly.You can however use your stock alternator if i it is behind a DC to DC charger that serves to protect it and that provides the proper charge profile for the lithium iron phosphate batteries.

WHY?

1-A stock alternator rarely has the correct charging voltages for lithium iron phosphate batteries.
2-They can over absorb the batteries resulting in over-charge damage
3-The absorption voltage is very often too high (see below)which  can lead to BMS load-dumps
4-Stock alternators do not FLOAT, they only do bulk and absorption.
5-Alternator heat damage

Do You know the voltage set point of your stock alternator?

Please understand that we have been an alternator manufacturer for more than 15 years so we understand internal vs. external regulators and how these alternators are built. We also have access to data, such as you’ll see below.This is data the average DIY would never have access to.

The max charge voltage for any drop in LFP battery is 14.6V(some are much lower). Below is a sampling of common internal voltage regulators. Pay attention the voltage set points!

 IF your BMS Disconnects at 14.6V / 3.65VPC a reg with a 14.6V set-point is likely to cause you BMS disconnect issues.

These are the most common regulators found in the very popular Delco 10/12Si series Alternators

There is also the Potential for Alternator heat damage!

LFP batteries have a tendency to enjoy eating alternators for lunch. The internal resistance of LFP batteries is extremely low resulting  in very long bulk-charging times. As a result alternators can burn themselves up trying to charge these batteries. I’ve said this many times before on the site and I will say it once again, there is no such thing as a small frame alternator that is continuous duty, I don’t care who built it!  Because Compass Marine inc. is a manufacturer of marine alternators so we get to see these failures regularly. We are not an n=1 data point like the “dude on the internet” who says your stock alt will be fine charging LFP. We have seen far too many alternators completely melted down by LFP batteries to ignore this information..

If you insist on using your stock alternator we would strongly recommend that you put it behind a DC to DC charger (50% smaller than your alternator amperage rating. This will help limit the amount of work the alternator is doing and protect it from a meltdown.Doing this means you can continue to use your stock alternator.

If you expect to charge lithium iron phosphate directly from the stock alternator without a DC to DC Charger in-between, we advise not changing a thing. Do not increase the wire size  to the battery bank ,do not move the volt sense a wire do not touch the factory wiring .zDoing so can result in an alternator meltdown. The typicalfactory wiring on these alternators is horrible and results in a lot of voltage drop. That in and of itself can help protect your alternator from melting down.

Why does LFP cause heat damage?

It is very simple your alternator never catches a break!

Our assembly bench on a typical day..

Don’t be this guy!

ImageCourtesy MHT reader

This stock Yanmar/Hitachi alternator was destroyed in a matter of weeks with just three 100 amp hour drop-in batteries.

Another burned up stator from charging LFP

Oh crap another one!

Jesus H…..! Another LFP Cooked alternator

But Ample built good alternators? Yes, they did but during this vintage Ample Power did not believe in using an alt temp sensor on their regulators.. When LifePO4 came around…Toast!

Series Wired Systems ?

In a parallel wired bank one battery BMS dropping out only creates problems when it re-engages into a different SOC than the rest of the bank by causing a large in-rush. With a series bank (for 24 V 36v or 48V a single BMS taking itself off-line spells disaster at sea and takes out the entire bank. I know a Drop-in owner who hit a granite bridge abutment in his electric boat using a 48V series bank of drop-in batteries. It did a few thousand in damage to the boat, and his pride, but it could have been much worse. The owner had zero warning the battery was about to disconnect itself before he lost all propulsion power. This failure occurred going under a drawbridge in a very strong tidal current. This is but one reason why the ABYC & ISO European standards make sense. Kilovault will soon be out with a communication system for series wired batteries so they stay in balance.We do not advise series wired drop-in batteries unless the BMS’s can communicate with one another. Parallel batteries stand a much better chance of remaining in-balance, series batteries do not unless the BMS boards can communicate with one another.

CATASTROPHIC PROTECTION BMS VS. CELL HEALTH PROTECTION BMS

Please don’t assume every drop-in battery BMS will manage your battery for maximizing cycle life, it may not do that! The BMS in far too many drop-in batteries is designed for catastrophic level protection only. Catastrophic protection means the BMS is only there to protect the cells from thermal run-away conditions. They can have BMS disconnect voltages exceeding 15V for a 12V nominal battery. The max safe cell voltage for an LFP cell is 3.65V X4 cells = 14.6V max. It is up to you, the owner, to ensure the battery never exceeds a safe operating envelope  even if the BMS allows for this. Well built drop-in batteries use an internal BMS that actually protects the battery from a maximizing cycle life perspective. Batteries built to maximize cycle life will have much more conservative HVC and LVC voltage levels.

TheBMS on this battery is built to maximize cycle life:

Never purchase a drop in battery that allows the cells to exceed 14.6V/3.65VPC or that disconnects below 10.0V/ 2.5VPC

#9 Understanding Cycle Life Claims – When an LFP cell manufacturer rates a cell at 2000 100% DoD cycles this is; charge to target voltage, stop immediately once you hit that voltage, discharge to the low voltage threshold, repeat, repeat, repeat. If this target voltage for cycle life testing is 14.6V they charge to 14.6V, stop immediately and discharge. These cells, at this rating, are not held at a the target voltage for cycle-life testing. In other-words you may not get the claimed cycles using a lead acid charger that holds an absorption cycle timer orcharges differently than the way the cells were tested.

WHAT ABOUT CHARGING LFP WITH OTHER SOURCES?

LFP batteries are charged using a CC/CV profile. This means constant-current/constant-voltage

Bulk = Constant-Current(charge source working as hard as it can see burned up alternators above)
• Absorption = Constant voltage( voltage is held steady for a short time or until current declines to the manufacturers spec.
• Absorption Duration = Once the batteries have achieved the absorption voltage the time the batteries spend  at this voltage must be limited. Many lead acid charge sources spend far too long in absorption and this is not healthy for LFP.

Do you know what this means?

max charge voltage 14.6V

max charge current 20% of installed Ah Capacity

When at 14.6V all charging must stop when accepted charge current has dropped to 0.02C or 2% of installed Ah capacity

Can Your existing charge system do this?

Pay attention to the details!

When installing these LFP batteries in parallel the max charge voltage is just 13.8V-14.2V   (it’s 14.6V for a single battery”details”)
Max charge current is 50% of installed Ah capacity or .5C.
When at 13.8V – 14.2V and charge current has fallen to 5% of installed Ah Capacity all charging MUST STOP

Can Your chargers do this?
Can Your charge sources be programmed for these parameters?

*Drop-In Charge Voltages – Follow the manufacturers guidance!

Some drop-in batteries are not using cells that are impeccably matched. Lithionics would be an exception to this rule but they are obviously a lot more costly.

Unfortunately, with most “drop-in” batteries you don’t really know what is inside, or how well matched the cells or cell blocks are. You’re essentially shooting darts with a blind fold on. Lithionics and Kilovault are in a very small group of manufacturers that take quality & cell matching to the level it should be. Lithionics can actually supply a performance test sheet for every cell in their drop-in batteries.  Battheborn matches individual cell modules(they use cylindrical cells) but not each cell in a module.

Series Solar Warning!

Over the last few years on boats one of the trends that can be a little terrifying has been that solar panel array voltages have been creeping up and up.. Many boat owners want to install their solar panels in series and then run them through an MPPT controller to maximize the energy capture of the array.

This is all well and good until there is an issue and the MPPT controller fails. Imagine what happens if you’re MPPT controller fails and starts passing PV voltage through to the batteries? If your array is over 60V & these are lead acid batteries they will eventually explode. If they are lithium iron phosphate drop-in batteries you will toast your BMS! Once the BMS is been fried by the solar array voltage you have no BMS protection & the solar array will continue feeding dangerous voltage to the batteries until they are destroyed. You can imagine what will happen if this continues to go on after in an MPPT failure. In case you’re wondering yes, these failures have happened and lithium iron phosphate batteries have been destroyed due to this. These failures almost never occur in tier-top tier supplier MPPT’s.

How do you avoid this?

#1-observe the maximum number of series batteries you can wire for. With most brands limit this is 24 V or 48 V. This voltage is typically the maximum SAFE voltage the battery bank BMS CAN handle. So, your PV array should not exceed this voltage.

#2 if you wish if you wish to use series-solar on your vessel you will be safer to split the array into smaller series strings that remain below the batteries maximum series allowable voltage and give them each their own MPPT solar controller.

#3 Use only top tier MPPT suppliers (eg; VICTRON, OUTBACK, MIDNITE, MORNINGSTAR ). These controllers use isolated input/output and  are designed not to fault in a manner that passes full PV voltage through to the batteries..

*Pack Voltage vs. Cell Voltage:

Pack voltage tells you nothing about cell voltage as can be seen below!

Know your loads before you buy!

The critical load data you need to know is the in-rush current for all DC Motors .This includes a windlass, electric winches or a bow thruster. You also want know your inverters Pre-charge in-rush.  Unfortunately most DC Clamp meters cannot properly capture DC in-rush current. We own three DC clamp meters that claim to do in-rush but all except the Fluke meters fail miserably. The image below is one of our Fluke 376 meters capturing the in-rush current for a Lewmar V2 Windlass. This customer ruined his FET BMS (seen in an image above in this article) byusing his “direct from China” drop-in battery to power his windlass. Warranty? Ha-ha now that’s funny….

The image above is a prime example of how drop-in battery bank went wrong for this customer. he wanted to lighten the load in the bow of his sailboat so he installed a single drop-in battery to power his windlass.What he failed to understand was the BMS’s current handling rating . In just a few short weeks he destroyed his drop-in battery with his windlass when he failed to account for what the peak in-rush current handling of the BMS., Warranty? Not covered!

1) Balance current-The sealed internal BMS’s in most drop-in batteries don’t have a lot of balance current to work with, usually mA level currents for balancing. We have even seen some BMS specs suggesting they can only balance the cells at a maximum 10 – 30mA or just 0.010A to 0.03A.If you’re running a 200 or 300Ah @12V battery the cells had better be well matched or the BMS may not be able to keep up….Again, Only buy from reputable Vendors!

2) Ballancing –Ballancing Does not usually start until the cells are exceeding 14.4V or 3.6V per cell. Some are slightly higher and some slightly lower, just depends upon what you bought. Where the cells begin balancing MUST always be specified!If you don’t see this spec ask the manufacturer.. This means that in order to ensure the cells stay in balance they need to get to a balance level at each 100% SoC charge cycle. The reason drop-in makers suggest such high voltages is because balancing is typically done at the top-of charge with a FET based BMS.  KiloVault batteries begin to balance at 14.0V(pack) or 3.5VPC.This is is excellent for cell longevity and iswhy Kilovault can claim 5000 cycles @ 80% DoD….

3) Absorption Duration –The manufacturers, for obvious reasons, want a short absorption voltage duration, some as short as just 2 minutes but many demand less than 30 minutes. With mA level balancing current, two minutes is not a lot of time to re-balance cells so they depend upon the battery getting to the balance voltage with each excursion to 100% SoC. If it does not get to a balancing voltage, the battery cells can become out of balance and the FET BMS may never be able to catch up with out of balance cells..

WHAT YOU WANT TO LOOK FOR IN A DROP-IN?

#1 Externally communicable BMS; at a bare minimum Bluetooth FOR ABYC  “VISUAL”COMPLIANCE.

#2 BMS current handling(in-rush data): You’ll need an internal BMS  capable of handling the amperage’s found on your  boat. If you’re vessel has large DC loads such as electric motors powering winches a windlass or a bow thruster you need to carefully confirm that the drop-in batteries you’re buying can handle these loads. The proper measurement of these motors is not the wattage rating it is the in-rush-current.

 #3 UL Testing -Bare Minimum=Individual cells that have passed UL testing

#4 Third party vibration testing data – UL, IEC or equivalent vibration testing for the entire battery, not just the bare cells

#5 Verification of internal cell matching. Currently Lithionics is the only drop-in battery manufacturer I know of that can physically send you the cell matching testing data for each cell in a battery. With only the batteries serial number, Lithionics can print this report and send it to you. This is the type of data that every drop-in battery maker should be able to provide.

#7 Internal wiring gauge & temp rating specifications

#8 External BMS alerts that can externally warn of a trend towards a disconnect.(Both an ABYC and ISO Requirement)

#9 BMS low voltage, high voltage and over & under temp protection for each of the four 3.2V cells in the battery

 

 

Legitimizing LFP

It’s not just the Chinese who realize they can grab market-share with LFP. After having their “deep cycle“clocks cleaned by LFP, both Trojan and Lifeline battery, two major lead acid players, have entered the LFP market. Having actual lead acid battery manufacturers in this marketplace actually lends credibility to LFP. These manufacturers can no longer ignore it as they have dug their own graves by misleading customers about cycle-life. The manufacturers lifeline and Trojan have partnered with in China are two of the finest drop-in battery manufacturers there are, these are, not elcheapo’s. In the end this is good for the market! Xantrex also now has a battery. Xantrex is no slouch as their parent company is Schneider Electric..

Victron is Also in the Drop-in Market

LFP WARRANTIES ARE Nothing more than lawyer Speak!!

LiFePo4 Marketing:

“Each XXXXX brand Battery is Protected from over-heating, over charging…”

Warranty exclusion reality:

CONSIDER YOURSELF CONFUSED!!

Exclusion: “Damage due to over-charging”

vs. the Marketing ; 

“Each XXXXX brand Battery is Protected from over-heating, over charging…”If you’re wondering how a battery that has a BMS that “protects from over-charging Can be “over-charged” it is pretty simple.”OVER CHARGING CAN BE FROM “OVER ABSORBING”! Lead acid chargers are notorious for over-absorbing !

Of the price-point drop-in batteries, Battleborn is quasi putting their money where their mouth is. They back the battery with a 10 year “manufacturing defect” warranty. (KiloVault is 7.5 years) Please understand that Battleborn is not a 10 year warranty that covers any sort of cycle life. This warranty only covers manufacturing defects. We see it repeated over and over that Battleborn(10 year) or Dakota(11 year) have the best warranty in the industry but that warranty only covers a defect in manufacturing! Defects in manufacturing typically show up pretty quickly. Lithionics for example actually puts a cycle-life warranty on their batteries(currently the only manufacturer we know of that does this-Let us know if you find others).

That said, kudo’s to Battleborn,Dakota, KiloVault and others who put a decent “manufacturing defects” warranty on their batteries. The internal build quality of the Battleborn, is  decent compared to many batteries at this price level,but the Kilovault we believe is better and is less money. We have/cut open a slew of Chinese LFP imports and what’s inside can be HORRIFYING! The only reasonably priced non USA assembled battery we have cut into that we find to be extremely well built are the KiloVault batteries.

Will Your Manufacturer even be around to honor a 5+ year warranty?

The two brands below no longer exist…..

Have you done enough research on a manufacturer?

Could this be a reason why one of the brands from above disappeared?

WHAT ABOUT FLOAT CHARGING & STORAGE?

Float Charging

Float charging is a relic that’s left over from lead acid battery charging. Lead acid batteries directly benefit from being held at 100% SoC. LFP do not benefit from this.. Float charging is not necessary for lithium iron phosphate batteries. The only reason any lithium ion phosphate battery manufacturer even suggest a float voltage is to satisfy end users who want to continue  using legacy/antiquated lead-acid charging equipment . In no way does float charging benefit your LFP batteries. The act of holding LFP batteries at or near 100% SOC can only serve to slowly harm them and eat away at cycle-life. An LFP cell can achieve 100% SOC at just a bit over 3.4 VPC (13.6Vpack  voltage) if you’re battery manufacture suggests anything over 13.6V for float you may want to reconsider that and set it below 13.6V .You can always set it lower but should not go higher.

There are charger manufacturers out there who actually understand charging LFP batteries.Victron  is about the best known. Victron has a specific setting in their custom menu that allows you to set a “storage” voltage this is a voltage the charger drops to after a short float has been done. It can be custom programmed to allow the batteries to self discharge down to about 50% SoC before the charger kicks back in and maintains the “storage voltage.”the only chargers or inverter/chargers we currently recommend for lithium iron phosphate batteries are Victron.

Don’t take my word for it, here is Battleborn….

What About Storage?

As mentioned above lithium ion phosphate batteries do not prefer to be sitting at or near 100% state of charge for long periods of time. This is why you will see, from nearly every single legitimate drop-in battery manufacturer, a recommendation for storing the batteries at or near 50% state of charge or less

Below are snapshots from lithium ion phosphate drop-in battery manuals or specification sheets .

What about “Hybrid ” Systems (Lead & LFP in parallel)?

In one word NO!Sure you can find someone on YouTube to tell you what you want to hear, but this is not always what you should hear…

Reader Challenge:The First reader to bring us (in writing) a US based LiFePo4 Manufacturer/reseller that allows you to place lead and LiFePo4 in Parallel wins $25.00!!Here is where the Eoropean IzSO standards land

ISO/TS 23625

Even Direct from China  Manufacturers disallow it.

From LFP Manuals/spec Sheets

What About Over-Current Protection?

Lithium iron phosphate batteries can throw a ton of current into a dead short but the fuse protecting the wire must have a suitable AIC rating. AIC stands for amperage interrupt current. AIC is different than the fuses trip rating. AIC is the maximum safe-current the fuse or breaker can trip under without having an unsafe-failure. For example if a battery has too much amperage, in a dead short ,Circuit breakers can actually weld-shut before they can trip. This is why AIC matters. The bottom line is that class T fuses are what should typically be used when protecting lithium iron phosphate batteries.

ABYC TE-13

The UL image below depicts a drop-in battery with a FET BMS that is “short circuit protected”. As can be seen this single drop-in battery can stilldeliver over 5500A into a dead short! Now imagine if you have two or three of these batteries in parallel or four+. The short circuit current of a FET BMS is always considerably higher than one would assume it is When in doubt use Class T fuses for LFP.

The reason I’m showing an image of the mega or AMG fuse below is because of the growing popularity of the Victron Lynx distribution systems. These are excellent systems, we love them,however, caution must be used when connecting them directly to a battery bank. In North America over-current protection  needs to  follow the ABYC’s AIC guidance. Mega/AMG fuses are fine so long as they are downstream of A fuse or breaker that is properly AIC rated to handle the batteries short-circuit current. In other words, MEGA/AMG fuses should not be used to directly connect to a lithium iron phosphate as the primary over-current protection as the can only interrupt up to 2000A safely..

Below are the specifications for a blue Sea systems Cass T fuse. Notice the fully encased metal body and the 20,000 A interrupt capacity. Also note that these fuses are rated at 20,000A at 125 V. Tthe higher the voltage the tougher it is to meet in AIC rating. Compare this to a typical ANL fuse which only has a 6000 amp AIC rating at 32V. a class T fuse would have a significantly higher AIC rating@12 V if it was tested at this point because it meets 20,000 AIC it 125 V there was no sense in spending the money to tested at a lower voltage.

I would be sloppy if I failed to mention that any installed fuse should not be sized to carry more than 80% of its rating. This also goes for circuit breakers. This is especially true when installing inverters & charge equipment and especially alternators. For alternators a fuse of at least 140% of the alternators rating should be used. Thankfully , Blue Sea Systems is finally addressing this and putting it in their literature.

In summary, do your homework, purchase carefully, avoid direct from China imports when you can,install your system safely, use good quality charge equipment and you will be happy for many, many years and thousands of cycles.

Good luck and happy boating!

How we Tested the New Balmar SG200 Self Learning Battery Monitor

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The Balmar SG200 is a revolutionary new battery monitor in that its feature set, capabilities and algorithms are a brand new concept in battery monitoring.

The Balmar SG200 is a self-learning battery monitor which was 100% developed in-house by CDI/Balmar. Compass Marine Inc. / MarineHowTo.com worked quite closely with CDI/Balmar, along with other Balmar dealers, to identify what we wanted to see in a fresh new battery monitor. One thing we have grown to appreciate about CDI/Balmar is their willingness to identify what their dealers see as credible needs before pursuing a project.

While every feature we wanted to see, in a battery monitor, did not make it into the SG200, what we do have is a revolutionary new self-learning battery monitor that is flexible, remarkably accurate and incorporates a brand new SoH or State of Health calculation. SoH allows you to know where your bank stands in relation to the programmed or rated Ah capacity and has been previously non-existent in traditional Ah counters.

What is SoH?

SoH is a new feature in the SG200 that compares your banks current state of health to its “as new” factory 20-hour Ah capacity rating.

By industry standards batteries are considered dead when they can no longer deliver at least 80% of their factory rated Ah capacity. While 80% or lower does not mean they are “actually dead” it is where the battery industry sets the low safe level for continued use of deep-cycling batteries.

For setting up the SG200, let’s assume you have a 100Ah rated battery. You would simply program 100Ah into the SG200, regardless of the batteries age or current condition. Over time the *SoH will hone in and find your “percentage of new” state of health of the battery or bank. If the screen reads 77% SoH, after it has had ample time to learn the bank, then this would be an indication that the batteries are nearing end of life and replacements should be on the horizon.

*SoH is a function that only works with banks that are actively deep-cycled. In other words if you purchase an extra shunt for a bow or start bank don’t expect an SoH indication as the SoH feature is specifically engineered for banks that are cycled eg; house banks.

If you’re a coastal cruiser then this number may not be all that alarming but if you venture across the ponds you’ll want to give your bank much more serious replacement consideration when you start getting into the 70’s as a percentage of new.

Development

Like all good things the SG200 did not just happen over-night. All told, it took nearly 4 years to get from ideas on paper to an Alpha level product for testing. Here at Compass Marine Inc. we’ve conducted nearly an entire years worth of testing the SG200. It’s actually still on-going every time we come up with a new way to possibly trip it up or we come across a battery we believe can trip it up. Like most products the SG200 did not come out of the lab “prime-time” ready and a number of software tweaks were made along the way before the finished product began shipping. The engineers at Balmar were tremendous to work with and they responded quickly. While lab testing can’t always predict every single real-wold situation it can be used to develop a platform to start from.  Add in a learning algorithm, and the ability to update firmware for future proofing, and you’ve got a very simple to use product.

SoC, SoH, Amperage & Minutes Left (at current load)

Recently, while up in Maine for a boat show, Chris Witzgall, Balmar’s Product Manager, stopped by our shop to get an idea of how we tested the SG200. Knowing Chris is far better than us with a video camera, we decided to take a different approach to our normal long diatribe of words and photos. We hope this video sums up & conveys how we tested the SG200 and why we were so interested to see yet another battery monitor hit the market.

What we like about the Balmar SG200:

• Multiple shunts can be used with one display to monitor multiple on-board battery banks
• The smarts or computer chip of the SG200 are housed inside the newly designed “Smart Shunt“
• SoH (State of Health) calculation lets you know when your bank is no-longer in a healthy state
• SoC accuracy is quite good within half a dozen deep cycles and continues to get more accurate as time goes on
• Self-Learning means no more cumbersome programming
• Displays – SoC, SoH, Charge/Discharge Current, History, Faults & Alerts
• Supports battery banks up to 1300Ah
• Bluetooth capability via optional Bluetooth gateway
• Firmware changes can be updated via Bluetooth
• Supports Flooded Lead Acid, AGM, TPPL AGM, Carbon Foam AGM, GEL & *LiFePO4
• Supports banks of 12V to 48V
• SoC accuracy as good as 97% in just a few cycles
• Auto-Calibrating
• Remains accurate even as a battery ages
• Less money than the SoC only Smartgauge
• Our customers want simple, not complex, and the SG200 is simple, easy and accurate

*LiFePO4 – The SG200 may not work with certain “drop-in” Chinese LiFePO4 batteries. The SG200 has been tested with Lithionics, Battle Born, Relion, Mastervolt and numerous DIY built batteries with BMS protection operating on the positive bus.

What about Installation?

While the SG200 is a shunt based device, once you understand where the shunt needs to be, as close to battery negative as possible, and that wires that by-pass the shunt (sneaker wires) are not allowed, the installation is very straightforward.

The general installation is simple:

#1 Create a short negative jumper wire to go between the bank negative terminal and the battery side of the SmartShunt

#2 Wire all negative wires on the vessel to the “Cable” or “Load” side of the SmartShunt. Adding a heavy duty busbar can help with this

#3 Mount the display. It fits into a 2 1/16″ hole

#4 Run the SmartLink Cable then install the Deutsch terminal on the end and plug it into the display & SmartShunt

#5 Connect the orange wires to their respective banks (if applicable) and fuse within 7″ of battery positive.

#6 Double check that you have NO DC NEGATIVE WIRES ON THE BATTERY SIDE OF THE SHUNT!

#7 Pull the fuse from the red power + wire and connect it to the banks positive terminal.

#8 Reinstall the fuse and when the SG200 boots up program it with your banks information.

When wiring the Balmar SG200’s SmartShunt you may want to purchase a heavy duty busbar, as shown below, to collect all the vessels DC negatives.

Patience is a Virtue:

TIP: Once your SG200 is installed & programmed please be patient. The SG200 requires your bank to be deeply-cycled quite a few times in order for SoC and SoH to hone in. The deeper these cycles are, the faster the SG200 can learn the bank. Don’t be afraid to take your lead acid bank to 11.7V, if you want to speed up the learning process, just be sure you can recharge to 100% on the next cycle. Shallow cycling will just prolong the time it takes for the SG200 to “learn” bank behavior such as SoH.

Quote: “Rod, I have had my new SG200 connected for almost four weeks and am still getting three dashes for SoH? We have not been able to leave the dock yet but was hoping to know my banks condition before we do?”

***The SG200 can’t learn SoH while tied to a dock charging 24/7***

The SG200 also cannot determine SoH while not charging and resting. To test this, we connected a lead acid battery to the SG200 and let it sit for two and a half months, with no charging or discharging, other than the SG200’s connection to the battery. At the end of 2.5 months the SG200 was still showing three dashes — for SoH. Bottom line? The SG200 is smart enough to know whether you’re cycling or not. The good news is that the SoC prediction, at the end of 2.5 months, was accurate to within 3%, while just sitting there.

SoH Behavior:

At first the SG200 will show three dashes – – – for SoH. It will continue to do this until enough cycles have been completed, and they are deep enough cycles. You’ll want to discharge to at least 50% SoC. Once the three dashes disappear it will start to show a preliminary SoH. If your boat is dockside for a while SoH won’t begin to display until the bank starts being actively cycled. Unlike SoC, which responds more rapidly, SoH is not intended for rapid updating and really needs to learn your banks behavior. Expect upwards of a dozen or more deep-cycles for SoH to be accurate. Be patient!

Insider Guidance:

Please do not make the mistake of comparing the SG200 to a traditional Ah counter. They are not the same at all and not even close to being the in the same category ease of use wise. The SG200 is using multiple technologies to track the bank and doing so in a multiple cross-check fashion. The SG200 can measure and cross-check; battery impedance, internally stored battery behavioral models, voltage – measured many thousands of times per second, coulomb-counting, amperage/load, time *etc. and a self-learning algorithm to bring it all together.

*Etc. – There are other measurements & trade secrets going on inside the SG200 that we cannot publish.

The unique aspect of the SG200 is that each of these data measurements is cross-checked and is compared to the others so that no single measurement can control or skew the data. The SG200 can track both SoH and SoC and to do so very accurately without any cumbersome programming or manual re-sync being necessary.

The SG200 is the most accurate battery monitor for SoC & SoH we’ve tested here at Compass Marine Inc..

As I sit here typing this we have a Trojan SCS-225 130Ah flooded deep cycle battery on the test bench. It recently tested at 99.4Ah or 76.4% SoH. As can be seen the SG200 is reading 76% SoH. It honed in this accurately in just 10 deep cycles. This is about as perfect a prediction of SoH and you can get without an expensive or time consuming 20 hour test. This is rather amazing performance.

SG200 Do’s & Don’ts:

• Do mount the Smartshunt as close to battery banks negative terminal as possible – less than 12″ is preferred
• Do use the largest gauge wire you can between the Smartshunt and battery negative terminal
• Do coat the shunt bolts or nuts with an anti-thread galling compound such as Tef-Gel. They are SS.
• Do use crimping tools that result in the lowest resistance for any wire terminations
• Do aim for the lowest possible voltage drop in your bank & shunt wiring.
• Do connect the red fused wire directly to the battery banks positive terminal *only.
• Do install the fuse for the red wire as the absolute last item installed.
• Do wire parallel or series/parallel bank for optimal intrabank balance.
• Do be patient. The Sg200 can’t work miracles, it needs to learn your bank during deep-cycling use.
• Do cycle deeply on the first few cycles. The deeper you go the faster the SG200 will learn your bank
• Do set it and forget it.
• Do not keep changing settings hoping for it to speed the learning process, all you’re doing is slowing it down.
• Do not depower or disconnect the SG200 from the battery, unless during winter storage.

*For LiFePO4 this decision will need to be weighed by the owner as to place it on the load side of a BMS switch or not. Drop-In LFP you have no choice in this matter. The SG200 will perform best with a direct red fused wire connection to the battery banks positive terminal.

Before you consider an Ah counting battery monitor, one that requires copious amount of human interaction/programming, to keep them accurately tracking the battery, consider the Balmar SG200 and let it do the work for you.

Good luck and happy boating!

Making Sense of the ACR

WARNING: The ACR’s in this article are not for use with LiFePO4 Batteries!

What is an ACR?

An ACR is nothing more than a fully automatic, voltage triggered, BOTH/PARALLEL switch that closes when charging voltage is present and opens when charge voltage is no longer present.

You read that correctly, in its simplest form, all an ACR really does is parallel batteries when charging is present and un-parallel batteries when there is no charging present. It does this automatically with no human forgetfulness.

In days of old a boat owner had to use the battery switch to route/direct charging to the bank or banks they desired to charge. The most ubiquitous of these methods was simply switching to the BOTH/ALL or 1+2 setting on a 1/BOTH/2 battery switch. This was all well and good, charging in parallel, so long as the motor was running. However, when the owner stopped the boat the switch was often forgotten about and left in the PARALLEL position thus draining both batteries while on the hook.

Many a boater has succumbed to two dead banks due to what we refer to as HEF (Human Error Factor). Back in the early 90’s the first of the voltage sensing relays were hitting the market, thus no longer requiring the owner to do anything to the battery switch in order to charge both battery banks. Unlike a diode type isolator, which causes an approximate 0.6V volt drop to the batteries being charged, the combiner/VSR’s were simple voltage triggered paralleling switches and both batteries could be charged without human intervention or the voltage drop associated with diode type isolators.

The Blue Sea Systems ACR’s (automatic charging relays) are one of the most common charge management devices in existence today. In a conversation with Wayne K. of Blue Sea Systems, a number of years ago, he suggested that over 500,000 ACR’s had been sold world wide. Wayne has been retired now, for at least a few years, and that number is now likely much larger. Blue Sea Systems is not the only manufacturer of “Combiner/VSR’s” and today the competition is actually quite wide spread including; Yandina, Sterling Power, Victron, BEP and many, more. Even Smartgauge makes a VSR and the Balmar Duo Charge can be wired to work as a simple VSR. This article deals specifically with the Blue Sea Systems ACR, because they are easily the number one seller in this class of CMD’s. Most VSR’s operate similarly but with varying voltage triggers or delays.

Definitions used in this article:

Charge Management Devices (CMD’s): Devices used to route or direct charging sources to a targeted battery or battery bank. They include ACR/VSR/Combiners, DC to DC buck or boots chargers, diode type battery isolators, DC to DC buck type chargers & DC to DC current limited voltage following devices.

Automatic Charging Relay (ACR): A Blue Sea Systems trade name for an electronic voltage triggered paralleling relay

Voltage Sensing Relay (VSR): A generic term for an electronic voltage triggered paralleling relay

Combiner: Another generic term for an electronic voltage triggered paralleling relay

The term ACR is a trademarked term by Blue Sea Systems for their version of a VSR or voltage sensing relay. The class as a whole is know by many names such as VSR’s, ACR’s, Combiners, Parallel Combiners etc. and they all do just about the same thing.

Despite the gross simplicity of the Blue Sea Systems ACR these little units are fraught with myth and lore. Let’s take a look at some of the myth & lore that are often incorrectly assumed;

ACR Myth & Lore:

1- “An ACR charges the start battery first then isolates it and charges the house” = FALSE

2- “An ACR gives priority charging to the start battery” = FALSE

3- “An ACR will over charge a start battery” = FALSE

4- “An ACR can’t be used with mixed chemistries” = PARTIALLY FALSE

5- “You can’t charge the house bank first or the start battery will never get charged” = FALSE

6- “Blue Sea says to wire charging to the start battery only.” = FALSE

7- “With a smart battery charger you must wire an ACR disable switch into the negative lead of the ACR” = MOSTLY FALSE

8- “When the ACR combines batteries the massive in-rush current can blow up a battery.“ = FALSE

9- “An ACR will allow the start battery to drain into the house battery and leave it depleted.” = FALSE

There are many, many more but, you get the point. Hopefully this article can show you why the above myth & lore are just that.

What is a Relay?

A relay is the control device used inside a combiner, VSR or ACR. It is nothing more than an electronic switch that is closed or opened using a relay coil. By energizing or de-energizing the coil the relay can change positions from OPEN to CLOSED or CLOSED to OPEN.

In this image we are looking at the guts of a combiner/VSR that was 7 years old. It had somewhere around 12,000 hours of parallel combined use on a world cruising boat with solar, wind, alternator and genset charging. As can be seen the contacts are still in perfect condition even after 7 straight years of 24/7/365 world cruiser live-aboard life. Despite these units not being sealed to anywhere near the level of the Blue Sea Systems ACR, the Blue Sea Systems ACR’s are fully epoxy potted, this relay is in superb condition.

What about VSR/ACR/Combiner reliability?

As a class these devices are one of the most reliable devices we’ve seen in the marine market. In fact I can’t recall a single Blue Sea Systems ACR, that we’ve seen, actually fail. This particular VSR, a Yandina, carries an unconditional lifetime guarantee. You can’t guarantee a product like this for life if they are not reliable. We actually see more manually operated battery switches go bad than we do Combiner/VSR/ACR’s. Some ACR’s, such as the Blue Sea Systems 7622 ML-ACR  can be used as a manually operated parallel battery switch and a fully automatic ACR.

Inside a VSR/Combiner:

Contacts: We can see the natural state of the VSR and that is with the contacts normally open or what is referred to as “NO”. A relay with a natural resting state of closed would be called an “NC” relay. If a NO relay loses power it isolates or un-parallels the batteries. When the contacts are closed the batteries are in parallel.

Batt 1 & Batt 2: These heavy duty plated copper buses are directly connected to the Battery 1 and Battery 2 Terminals outside the unit.

Voltage Control Logic Board: This is the smarts of the combiner/VSR. This logic board simply measures the voltage at both Batt 1 and Batt 2 terminals and then tells the coil when to energize or de-energize to close or open the relay. Good quality combiners/VSR/ACR’s also have combine/un-combine delay logic and over or under voltage lockouts built in.

Relay Coil: The relay coil is what causes the contacts to move from open to closed or from closed to open. It is controlled by the logic board. Energizing this coil closed the relay and places the batteries in parallel. De-energizing the coil allows the relay to open and un-parallel the batteries.

ACR Parameters for Combine/Closed/Parallel

First we need to understand where to place/install an ACR. Placement matters. This image is intentionally over-simplified to show relay closed parameters and relay installation wiring and location. If you notice there are no battery switches, chargers, alternators etc. shown in this drawing. This is done purposely. Despite Blue Sea Systems heavily marketing their Add A Battery Kit (7650) an ACR or other combiner/VSR is completely independent of any battery switches. You do not need to purchase an additional battery switch to make an ACR work!

Where You Should Not Install an ACR:
An ACR does not get wired between battery chargers, solar, alternators, wind  etc.. Don’t laugh, we have seen this done. As an example we had a customer wire the alternator output to one side of the ACR and the other side to the start battery and house battery with both house and start bank positive lugs stacked onto the “A” terminal. By placing the start and house battery positive wires on terminal “A” it meant the start and house banks were now hard wired in permanent parallel. This was oops #1.

For oops #2 the owner wound up blowing the diodes in his alternator twice before calling us. With the relay open the alternator output had nowhere to go and the voltage, almost instantaneously, surpassed the 16V over-voltage threshold and the ACR entered “over-voltage lock out“. With the ACR locked open alternator voltage kept climbing until the diodes in the alternator were blown. Bottom line? A Blue Sea Systems ACR is never installed directly into a charge devices positive output path.

Where You Should install an ACR:
As can be seen in the image above an ACR is wired between the positive terminals of each battery bank with the only thing in its path being the fuses located within 7″ of each positive battery terminal. These fuses are there to protect the ACR positive wiring from the battery bank should they short to ground.

TECH TIP: If you make the “A” & “B” terminal wires for the ACR the same gauge as the house and start bank wiring eg: 2/0 and 2/0 the ACR can share the house and start bank fuses, if so equipped.  Start banks are not required to have over-current protection but it never hurts.

The above image is how an ACR parallels:

13.0V for 90 Seconds: If either the B or A terminals of the ACR sense 13.0V for more than 90 seconds the ACR will close and parallel the batteries. The green arrow is pointing to the relay being closed and the banks are in parallel.

13.6V for 30 Seconds: If either the B or A terminals of the ACR sense 13.6V for more than 30 seconds the ACR will also close and parallel the batteries. The green arrow is pointing to the relay being closed and the banks are in parallel.

Question: “I thought the ACR only sensed the start battery?”

Answer: The Blue Sea Systems ACR is a bi-sensing relay meaning it can sense/monitor charging or non-charging voltages at both the “A” & “B” terminals in order to parallel the banks or to un-parallel the banks.

ACR Parameters for Un-Combine/Open/Un-Parallel

Just like the logic used for closing the relay Blue Sea Systems also has logic to control when the relay opens.

12.75V for 30 Seconds – If either the “A” or “B” terminal sense a voltage below 12.75V for more than 30 seconds the relay will open/un-parallel the batteries.

12.35V for 10 Seconds – If either the “A” or “B” terminal sense a voltage below 12.35V for more than 10 seconds the relay will open/un-parallel the batteries. IF voltage is trending upwards and attains 12.75V before 10 seconds has elapsed the relay will remain closed. This logic is here to enure a large load will not cause the relay to open when it creates a short duration voltage sag. It is also there to help minimize “relay cycling” which we will discuss later.

Start Isolation – The SI or “Start Isolation” feature is a unique to the Blue Sea Systems line of ACR’s. The start isolation feature momentarily opens or un-parallels both banks when the starter motor is engaged. The SI terminal of the ACR is wired to the momentary “start position” of the engine switch (see above image) or to the starter button. It is never wired to the “run” position. Doing this will keep the relay open indefinitely. Again, we’ve seen this done. When the starter motor is engaged the ACR’s relay opens so any voltage sag is not transferred to the house bank, where low voltage may cause electronics to shut down. For the SI feature to work as intended you need a dedicated starting battery and a dedicated house bank. The SI feature does not work with a 1/BOTH/2 switch where starting and house loads are shared by the same bank.

16.00V Over-Voltage Lockout – Over-voltage lockout is just what it implies. If the sensed voltage at either the “A” or “B” terminal is 16.00V or higher the ACR will lock out and open itself.

9.50V Under-Voltage Lockout – Under-voltage lockout is just what it implies. If the sensed voltage at either the “A” or “B” terminal is 9.50VV or lower the ACR will lock out and open itself. If you’ve drawn one battery too low don’t expect the ACR to combine until the battery gets back above 9.50V. In a case like this simply use your manual battery switch set to Both or your manual emergency parallel switch.

The above has covered myth & lore 1 & 2

#1 “An ACR charges the start battery first then isolates it and charges the house”.

As can be seen above the ACR does not in any way do this it is either in parallel or it is not in parallel. Very simple..

#2 “An ACR gives priority charging to the start battery”

Please understand that even if you feed charging to the start battery first, which is not advised on a cruising boat with disparately sized banks, 30 seconds of charging is not charging, even for a minimally depleted start battery. A battery at 99% SOC is in the worst range of charge efficiency. Despite being minimally depleted it still takes a good bit of time to reach an actual 100% SOC again. Each Ah we deliver to the battery, at a high SOC, is not being stored at 100% or even 50% due to the horrible Coulombic efficiencies at high SOC. The logic delays in the ACR are not there to create “priority charging” for a start battery or house battery they are there to eliminate relay-chatter and to help minimize relay-cycling or on/off/on/off/on/off behavior.

Q: “Why are there two different parallel voltages and delays?”

It is all about depth of discharge and when it is prudent to parallel the batteries. The lower combine voltage is there for a very good reason. It is there so that a deeply discharged bank does not take very long to attain the combine point. The higher combine voltage is there for a bank that’s not been deeply discharged and rises in voltage near instantly.

This all goes back to myth & lore #5 “You can’t charge the house bank first or the start battery will never get combined & charged” 

Let’s put this myth & lore to bed…..

To address the question of the house bank taking a long time to combine with the start battery, we first need to consider a start batteries actual energy usage.

Start battery Energy Use?
A battery used for starting an engine is using very little stored energy to do this job. It is a very short duration but also high amperage. Most engines will use considerably less than 0.5Ah to start. This is due to the cranking duration, loaded starter to unloaded starter, averaging 0.75 seconds to about 1.5 seconds (averages measured over 70+ marine diesel engines using the Midtronics EXP-1000HD). This means your previously full start battery will still be at about 99%+ SOC after you’ve started the engine. A 99% SOC battery does not really require immediate charging or priority charging and has many, many, many more starts left in it before any charging would even become necessary.

In the image above we have a 44HP diesels cranking diagnostics:

Averaged cranking voltage = 12.04V

Averaged cranking Amps = 286A

Loaded to Unloaded Cranking Duration = 0.765 Seconds

Even if we round up the cranking duration to 2 full seconds we are using just 0.17Ah. If we correct for Peukert, due to the high load on the battery, we are looking at a max fudge factor number of about 0.29Ah’s to start this engine.

Experimentation: For the sake of experimentation we cut power to an external voltage regulator then proceeded to start a Yanmar 4Jh forty-six times before finally getting bored.  The battery used was a single Trojan SCS-200 Group 27 “Deep-Cycle” 12V battery. Not once did this group 27 “deep cycle” battery even so much as wince at starting this motor forty-six times, in less than one hour, without any charging what so ever.

The experiment above was only done to illustrate to an employee why we charge house bank first, not the other way around, on cruising boats. When you run the actual numbers, and see how little energy is used to actually start a motor, it becomes much clearer.

Q: “But how long does it take to attain a combine/parallel voltage?”

From 50% DOD/SOC, the max depth of discharge recommended by most lead acid battery manufacturers, it takes a bit less than 2 minutes at a .2C charge rate to attain 13.0V and this experiment was done on a high acceptance AGM battery.

Q: What is .2C?

The term .2C simply means 20% of the battery banks Ah capacity in charge current. Blue Sea Systems knows how simple it is to attain 13.0V, even for a deeply discharged bank, and this is why their ACR’s feature two differing combine/parallel voltage points, one at 13.0V & 90 seconds and one at 13.6V & 30 seconds.

This battery began charging at 50% DOD/SOC when the clock read 12:00. The charge rate was .2C or the bare minimum recommended charge current for this Lifeline AGM battery. As can be seen, after just 2 minutes of charging at 21A, it is already at 13.1V and the ACR can now combine. If your start battery is going to suffer not being charged for two +/- minutes, you have other issues.

Rumor/myth & lore #5 goes something like this: By using a battery combiner, on “high acceptance” AGM batteries, and feeding the alternator or battery chargers charging current directly to the house battery bank first, “it will leave your start battery under charged“ because “it will never get to the combine voltage or will take too long to get there”.

If you are practicing good battery management, and have even the minimum suggested charge current for an AGM or flooded battery, this is really a non-issue. In 2 minutes of charging, at .2C or 20% of Ah capacity from 50% SOC, the AGM battery voltage is already at the parallel/combine level for the Blue Sea Systems ACR. Even at .1C or 10% of Ah capacity the time to attain 13.0V is not very long, just a few minutes more. To get from 13.0V to 14.4V+ does take quite a bit more time but the relay has already combined at 13.0V and both banks are now being charged.

Battery voltage will rise pretty slowly from the low 13’s on but, to get to an ACR’s combine level, is relatively quick and easy, especially if you have your system set up properly. When hearing this rumor we need to also consider that Echo Chargers, Duo Chargers and a number of other DC to DC chargers also turn on at similar voltages and those devices require all charge sources to be fed directly to the house bank. On cruising boats with disparate sized banks Blue Sea Systems recommends feeding charge current to house first, not start, but you have the option to choose start first if you really feel the desire and you don’t with other products such as the Echo Charger, Digital Duo Charger etc….

Correctly Wiring an ACR on a Cruising Boat

While a three wire device, four if you use the SI feature or five if you use the remote LED indicator, seems simple to install, there are some areas that can trip you up. One of the most common blunders we see on cruising boats is leaving the alternator wired to charge the starting battery first.  This is most often the result of the Blue Sea Systems instructions not being very clear. The majority of these are sold for use on boats where the battery banks are nearly identical in size. They are very, very popular on center-console and walk-around fishing boats where the start battery and house batter are nearly identical in size and the motor is started and stopped multiple times per day while fishing and owners don’t want the sounders and plotters to drop out during starting (SI). With both banks nearly the same size feeding the start battery first works pretty well. Because most builders sell boats wired this way, alternator feeding start battery, this is how they are typically wired. In an ideal world the charging would be fed directly to the bank that gets most depleted.

On a cruising boat, with a large house bank and small start or start/reserve bank, the best way to wire an ACR is to have the alternator charge the house bank directly.

“Why is it best to charge the house first?”

There are a number of reasons to do this but the best reason is to ensure the bank that needs the most charging is actually getting it and getting it as efficiently as possible.

#1 With large house banks wiring charging sources to the HOUSE bank means more efficient charging and more optimal voltage sensing for the alternator.

#2 With large house banks, wiring charging sources to the HOUSE bank means less chance of what is called relay-cycling. Please take the time to read the link below. Blue Sea Systems covers relay cycling very well so there is no sense in us repeating it.

Preventing Cycling in Battery Combiners, Voltage Sensitive Relays, and Automatic Charging Relays

#3 By wiring charge sources to the larger HOUSE bank the relay contacts need to pass just a few amps at best in order to charge the start battery. By feeding all charging to START means the relay must be able to handle the full rated current of the alternator and we are utilizing it at max duty cycle. We are also passing the charging current through multiple more terminations and fuses and there will be additional voltage drop.

One part of the instructions that most installers miss is this:

What About Fusing / Over Current Protection?

One topic that comes up rather routinely is ACR fusing/over-current protection. Because the ACR or VSR is connected directly to the battery banks + terminals, or their respective *close-by charge / always on distribution bus, the wires themselves need over current protection. There is some confusion regarding ACR fusing, even among some professionals, that the fuse is intended to protect the ACR, and it is not. The fuse is there to protect the wire as Blue Sea Systems clearly illustrates below. If we are following ABYC standards these fuses should be within 7″ of the banks positive terminals or their bus.

(*Within 7" of the banks + terminal)

Fuse Sizing

One mistake we see all too often is a 120A 7610SI ACR installed with a 120A alternator feeding directly to a start battery and the relay is protected by a 120A fuse. If the house bank is heavily depleted the relay can conceivably pass close to 120A across it for a short period of time or until the alternator heats up and can no longer produce its cold rating. Also keep in mind that many alternators can exceed the cold rating for short periods by as much as 15%. I think you can see why a 120A alternator with a 120A fuse would spell disaster for the fuse especially when fed to the start bank first.

The fusing is there to protect the wire not the ACR, so if you have a 120A alternator the minimum fuse & wire size should be 175A & 1 AWG minimum. Fuses should not be run at 100% of their rating or they will eventually nuisance trip. This is why Blue Sea Systems calls for a 175A fuse for a 120SI ACR when being used with a 120A rated alternator. Of course if you wire it correctly, for a cruising boat, and the alternator feeds the house bank first, the relay will never see 120A across it except during very brief inrush duration’s that are not long enough in duration to trip the fuse.

TECH TIP:

If your house and start banks already have over current protection you can simply use the same size wire for ACR “A” and “B” terminals as the bank is wired with. In other-words you can share those fuses for protecting the A & B ACR wires, provided you use the same size wire. If both banks are already fuse protected this can mean no additional fusing costs for the ACR installation. If you make use of an already fused charge/always on bus, as shown below,  you can just connect the ACR to that bus with the same size wire the banks are already using. In the example below the banks are wired with 2/0 wire and fused at 300A.

The use of a charge / always on bus is certainly a best practice and one more professionals and DIY’s should do more often. A charge/always on bus prevents messy bank wiring & incorrect lug stacking and makes for a neat and tidy installation anyone can easily troubleshoot.

Connecting Other Charging Sources

One of the major benefits of an ACR is that it works with any and ALL CHARGE SOURCES. Because an ACR is triggered by voltage changes it means that its an extremely valuable tool for charge management. Unlike a diode type isolator, that can really *only work with an alternator, the ACR can work with alternators, wind, solar, hydro, fuel cells, and AC chargers.

*Diode Isolators – Diode type isolators do not have a voltage reference on the input stud. By voltage reference I mean if you place your DVM on the input stud of a diode type isolator you will read 0V. This is one of the number one trouble shoot calls we get from folks trying to integrate solar or wind to multiple battery banks using a diode isolator. A diode isolator can’t be used with most charge sources that need to see a DC voltage before booting up. Today most voltage regulation charge sources have a feature that does not allow them to boot into no voltage where a typical “dumb alternator regulator” will. This is a safety feature so you’re not charging into a failed battery. Today there are very few good uses on a boat for a diode type isolator.

The question of other charge sources ,and an ACR, comes up a lot. Due to marketing it can be a bit murky wading through it all. The bottom line, for simplicity & operational sake on a cruising boat, is that you want to wire all your charging sources to the largest bank eg: the house bank. This would include, alternator, AC powered battery chargers, inverter/chargers, solar, wind, hydro or fuel cells. It is critically important to wire low-current charge sources such as solar, wind, hydro, fuel cells or small battery chargers directly to the house bank to prevent relay cycling.

In the image below we can see a cruising boats foundation wiring with a 500Ah AGM HOUSE bank and a 125Ah AGM START/RESERVE bank. As can be seen all charge sources feed the house bank and the ACR parallels in the start bank when 13.0V or 13.6V is attained.

What about twin engine boats?

On twin engine boats one alternator, usually the largest and most capable, can feed the house bank directly and one can directly feed the start bank directly. The addition of an ACR means that both alternators will contribute to the house bank charging during bulk. Without the ACR the start bank alternators full capability is just being wasted by feeding a few amps at best to the start battery. By adding an ACR we can make much more effective use of both alternators and charge the house bank faster.

Myth & Lore #10- “With a smart battery charger you must wire an ACR disable switch into the negative lead of the ACR”

This one can be a bit confusing but all boils down to what is actually inside a “smart-charger“. If your smart charger actually has multiple voltage regulators and multiple power supplies inside it, then a switch in the negative lead can allow the charger to charge each bank with its own fully independent charge profile. The catch here, and why this is MOSTLY FALSE, is because finding a smart charger with two or three fully independent chargers inside one box is about as likely as Hillary Clinton switching parties and becoming a Republican. Follow me for a moment..

What you think you’ve paid for:

What you actually have:

Another way to view most multi-output chargers would be like this:

With this image it becomes more clear how the single voltage regulation and single power supply can be connected to multiple batteries through “isolated outputs”. For this example I drew simple diodes, an electrical one-way check valve, but most chargers these days are using FET’s on the outputs to achieve the same effect. The only purpose of the FET or diodes on each output leg of the charger is to prevent the batteries from back-draining (in parallel with each other) into each other when the charger is turned off. You guessed it all batteries get the exact same charge profile just as they would if you fed charger output #1 to HOUSE and then used an ACR to charge the START battery.

Let’s discuss myth & lore #3: “An ACR will over-charge a start battery”

Please examine the above images and let them hit home. Now ask your self a simple question; How is a “smart charger”, a model that uses one voltage regulator and one power supply and two or three diode or Mosfet (FET) isolated outputs, any different than the BOTH setting on your battery switch or the combined mode of an ACR? If you landed on “its not any different” reach over your shoulder and pat yourself on the back. The diodes or FET’s on the single circuit of a multi-output charger are only there to prevent parallel back-drain when the charger is turned off. An ACR achieves the same exact outcome, preventing back-drain, by opening the relay when no charging is present.

The same guys who walk the docks and profess that an ACR will over-charge a start battery are quite often the same guys professing why you need a smart charger to charge your multiple on-board battery banks. I know this because one of these guys attempted to re–edumacate me on a dock one day, & he used this very argument. The charger on his own boats was a muti-output single power supply single voltage regulation unit. The funny part about this re-edumacation was the start battery on the boat I was working on was 8 years old and had been charged via a Blue Sea Systems ACR for the entire 8 years. It had been charged via multiple charge sources, including a shore charger, solar & alternator. According to the “dockspert” that start battery had been murdered 7 years ago by the ACR yet in the real world it was still going strong at year 8.

It was not worth trying to explain the concept to him, in a short period of time, and besides he’d already made up his mind on the subject. Little do folks realize there is usually no difference between using the multiple-outputs of a battery charger vs. using just one output of the charger and an ACR.. The ACR simply prevents back-drain by opening the relay when there is no charging & the smart charger uses diodes or FET’s to prevent back-drain. Whether you use the isolated outputs of the charger or one leg of it, and an ACR, there is really no difference.

The vast majority of multi-output smart chargers are one charger hiding behind two or three back-feed prevented (diodes or FET) outputs. If you want to charge multiple banks, and you already have an ACR, use the ACR, as it will work with all charge sources. This will save you charger to bank wiring and an extra fuse/s. To get around the multi-output charger and differing bank voltage profile conundrum, a situation where neither the multi-output charger nor the ACR would be a good choice, Sterling Power products offers their Battery Chemistry Module.

Ok back to our dockspert for a moment.

If your single power supply, single voltage regulation smart-charger is not over-charging your start battery, how is it that an ACR would?

Think about it…… Even Blue Sea Systems own “P-Series” chargers are one single voltage regulator and one single power supply. They market the product describing how it can float one bank while charging the other at absorption. While this is certainly a nice selling feature we still have millions of single VR/single power supply multi-output “smart chargers” out there that don’t do this, and yet we don’t have start batteries being routinely over-charged & murdered.

What Blue Sea Systems is actually doing in the P-Series is switching in an additional diode to the start battery output leg. Switching in an extra diode causes a 0.6V drop on the start battery output. It is not a truly independent smart charge profile but rather a 0.6V drop from the absorption voltage & a nice selling feature for sure. To do truly smart-charging, the type most boat owners assume they have, the charger would need multiple voltage regulators and multiple power supplies something very, very few chargers actually have.

Still, if you desire to allow your “smart-charger” to do it’s thing, or you use a Sterling Power Battery Chemistry Module or Blue Sea “P-Series” and feel it does a better job than the ACR, by all means insert a simple ON/OFF switch into the negative lead of the ACR, to disable it, or just flip the switch of the ML-ACR to OFF..

When to Use a VSR/ACR/Combiner

To keep this simple, when charging lead acid batteries, is that it’s all about the appropriate charging voltages. Also we can’t forget that GEL, AGM, TPPL AGM and Flooded Deep Cycle batteries are all lead acid chemistry.

With that in mind;

If both banks can be charged within 0.1V to 0.2V of each other, an ACR is a fine choice

Same Chemistry & Same Charging Voltages = √

Same Chemistry & Very Similar Charge Voltages =  √

*Mixed Chemistry & Same Charging Voltages = √

*Mixed Chemistry & Very Similar Charge Voltages =  √

*Excludes mixing lead acid and Li-Ion batteries

Most lead acid batteries will have a safe voltage range for absorption & float. If we compare a bank of Trojan golf car batteries and a Trojan Group 31 12V battery it’s clear to see they share the same charging voltage range and thus a VSR/ACR/Combiner is a good chocie for this application.

When Not to Use a VSR/ACR/Combiner

If we go back to Myth & Lore #4; “An ACR can’t be used with mixed chemistries”

We describe this as “partially false” and here’s why…

Let’s assume you have a GEL house bank, an excellent deep cycling battery, and a TPPL AGM windlass bank and excellent high current capable windlass or thruster bank. The GEL battery should not be charged at over 14.1V to 14.2V so the primary charging sources, solar, wind, alternator, chargers etc., would all be set up for a maximum of 14.1V to 14.2V. The problem here is that the ideal charging voltage for a TPPL AGM bank is closer to 14.7V. In this case, if charging is set up for 14.1V to 14.2V, we will wind up chronically undercharging the TPPL AGM bank via the ACR.

If we reverse this scenario, and the charging is tailored to the TPPL AGM bank, we will quickly destroy the gel battery by over-charging it.

Same Chemistry & *Differing Charging Voltages = X

Mixed Chemistry & *Differing Charging Voltages = X

*Differing by more than 0.3V

If specified charging voltages are the same or similar then an ACR/VSR/Combiner is a worthy choice. Once we get beyond about a 0.3V difference, it starts to make more sense to move to a DC to DC charger such as a Sterling Power Battery to Battery Charger where we can get a true fully independent smart charge profile.

“But an ACR will Discharge my Start Bank.”

This statement takes us directly to Myth & Lore #9 “An ACR will allow the start battery to drain into the house battery and leave it depleted.”

The fully charged resting voltage of a typical lead acid battery is about 12.72V. At any voltage above this point there is really no usable energy stored when discharging (see image below).

By now I know you are understanding it, but if not, this one is really quite simple. The ACR normally opens/un-parallels at just above or just at the 100% SOC point of a lead acid battery. If either battery bank dips below 12.8V the relay opens within 30 seconds. If it dips to 12.35V, the relay opens in just 10 seconds. The answer to this myth is that it is indeed false that an ACR will allow the start battery to discharge into the house bank. Your start battery cannot discharge into your house bank in 10 or 30 seconds.

The discharge graph below (voltage is the red line) was a typical marine battery undergoing a 20 hour capacity test. The battery was fully charged, equalized and had an open circuit voltage before the discharge test of 12.95V or what we refer to as a “surface charge“, despite having rested for a full 24 hours prior to the test. Because this was a 130Ah rated battery the discharge rate was 6.50A (130Ah / 20 hours = 6.5A discharge rate). At data point #1 the battery was at 12.95V and by data point 2 the battery was already below the open/isolated/un-parallel voltage of the ACR at 12.76V.

You are seeing that correctly, by the time this battery hit 12.76V a paltry 0.002Ah worth of energy had been removed. If the ACR opens at 12.8V how much can we discharge either bank by? This answer is nothing worth even really discussing…

If the relay opens at 12.8V it can’t remove any Ah quantifiable capacity from either bank before the banks are isolated.

This does bring us to another myth we have heard and that is when the banks are combined, in parallel, they can transfer energy between each other. This one is also a pretty simple explanation.

The ACR combines at well above the natural resting voltage of a lead acid battery. Due to this, charge current can only flow in one direction and that is into the battery. At 13.0V or higher current flows is into the battery from the charge source and the charge source would take up both the DC loads and the charging.

The combine point of 13.0V is a charging voltage and when a battery is charging it can not also be discharging. It can only be discharging when voltage is below charging level. Very, very simple.

The final point we should discuss is myth & lore #8;

“When the ACR combines batteries the massive in-rush current can blow up a battery.”

The easiest way to answer this question was to create a scenario on the test bench that could show these “massive” currents, currents so huge they can blow up a battery. (sigh)

The math could easily be calculated to show why this is not a concern but, it is often easiest to physically see it in action. In the video below we created and tested for the scenario that created the highest in-rush current we could create. The term in-rush, as related to this example, just means the absolute peak current measured over a very *brief time period,  between banks, at the widest voltage spread.

*The Fluke 376 captures current transients at 0.1 second or one tenth of one second.

The point where the banks are combined, and voltage spread is widest, is the point where the most current transfer is created. This in-rush lasts less than .2 seconds and current transfer, between banks, literally nose dives very rapidly as the bank voltages close in on each other and attain parity.

We created this scenario based on a very popular 315Ah AGM house bank (3 G-31’s) with an AGM starting battery. In order to try and capture the most in-rush we could, an Odyssey Thin Plate Pure Lead AGM, or TPPL AGM, was chosen as the start battery. The Odyssey PC2150M is a battery that can deliver over 5000A of current into a dead short, 2150A of cranking current at 77F and 1150A of cranking current at 0F. The 172A peak current it delivered to the house bank, for about .2 seconds, is literal child’s play. The test delivered the maximum recorded in-rush current at about 30% state of charge or a 70% depth of discharge. This is a depth of discharge you should not be routinely seeing with typical AGM batteries. Interestingly enough when we discharged the large house bank to 80% or 90% DOD the maximum in-rush was actually lower than it was at about 70% DOD. We chose to show the maximum in-rush we could create.

If we have 315Ah’s of AGM batteries, and we play pretend fairy-tale stories and assume the 172A in-rush could last for even 30 seconds (it can’t physically do this) this equals a charge rate of about 0.54C or just 54% of Ah capacity. In the Practical Sailor PSOC testing all the AGM batteries were actually charged, not an in-rush, at .46C (46% of Ah capacity) and the batteries barely even got warm to the touch. Of course this extremely short in-rush is not a “charging current” it’s a fraction of a second peak-transient current and is in no way dangerous to your battery bank. Yes, myth & lore #8 is indeed false and there are no “dangerous” in-rush currents created when the banks parallel with each other.

Another example of why this is not dangerous, Lifeline battery states their 100A AGM battery can handle 500A of in-rush charge current with ease. This equates to a charge rate of 5C or 5 times Ah capacity. As you’ll see below the ACR switching closed could only transfer 54% of Ah capacity in this test for a very brief 0.2 second transient.

In this video you will also see the effects of relay cycling and why hooking up a cruising bank incorrectly can create this phenomenon..

Choosing an ACR

Blue Sea Systems offers two distinct types of ACR models, the basic fully automated SI-ACR’s and the larger, manual or fully automated ML-ACR’s. Both charging relays feature fully potted electronics, heavy duty 3/8″ studs and the ability to charge two banks.

ML-ACR – The ML-ACR is a step up from the basic SI-ACR, and also costs a bit more. For a bit more money you get a lot more in features and current carrying capability and it can handle as much as 500A continuously. The ML-ACR also allows for manual paralleling of banks via a dash mounted toggle switch or the yellow knob on top of the ML-ACR. This means the ML-ACR could take the place of your emergency paralleling battery switch and do double duty as both an ACR and an emergency paralleling switch. The 500A continuous rating makes it the ideal product for boosting the available current to a bow bank used for a windlass or a bow thruster. With the flip of the toggle switch it can go from automated ACR charging, which would open on voltage sag, to manually locked in parallel. This means your bow bank, house bank & alternator can now all contribute to your windlass or bow thruster performance and you can rather drastically improve bow thruster or windlass performance. The ML-ACR also features SI or start isolation. Standby draw on the ML-ACR is a scant 13mA or just 0.013A.

SI-ACR – This is the basic fully automated model and is a relatively inexpensive upgrade. The 7610 SI-ACR can handle 120A continuously, has SI (start isolation), fully potted electronics and heavy duty 3/8″ studs. If you don’t need the high amperage or manual paralleling feature of the ML-ACR the SI-ACR is a great value. Standby draw on the SI-ACR is just 15mA or 0.015A.

Today there are lots of options for charging multiple banks, without suffering from voltage drop, and the ACR/VSR/Combiner is just one of them. We stock quite a few charge management devices in the MarineHowTo.com webs store.

MarineHowTo.com – Charge Management Devices

Good luck with your project & happy boating!

Preface

This article contains three separate videos that show how to physically program Balmar regulators. The videos are meant to be watched in conjunction with reading this article so the misconceptions and misunderstandings I have identified over the years, regarding these regulators, can be explained with a bit more depth.

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UPDATE: Since this article was written Balmar’s new MC-618 regulator has been launched. The new MC-618 allows programming via the screen on the Balmar SG-200 battery monitor or via the SG-200’s Bluetooth App. It can also be programmed the same way as this article describes.

The Magnetic Reed Switch

For years I’ve listened to customers express concerns about “how difficult it is to program the Balmar regulator“, and I don’t necessarily disagree with this, especially if you’re a DIY or one who does not do this on a regular basis. Even for myself I can find programming a customers, already installed, Balmar regulator a bit tedious.

This article will help:

• Give you higher a comfort level in programming these regulators
• Clear up some of the confusing language in the owners manual
• Provide you with a “Regulator Programming Cheat Sheet“
• Discuss best practices for programming & installing these regulators
• Provide tech tips that will make the process easier.

This article features the Balmar MC-614H but programming & features are similar for the Balmar ARS-5H.

IMAGE: Pictured here is the Balmar MC-614’s magnetic reed switch location, as identified by the red dot.

Definitions: The Balmar owners manuals covers what the LED screen codes mean such as A1C, FFL, AGL etc. etc.. There is no need for us to repeat what is already in the manual in terms of what the numbers/letters are telling you, unless we believe them to be confusing. We have addressed the most commonly confusing parts of the manual, based on years of supporting these regulators, in the article. Please familiarize yourself with the owners manual before reading this article. With the manual and this article it will make more sense.

MC-614 Owners Manual .pdf Download

Why Choose a Balmar Regulator?

Why do I prefer to use the Balmar regulators vs. the other external regulators that are out there? FEATURES! There is no other external voltage regulator, other than DIYing your own, that compares feature for feature with the Balmar regulator. Balmar also delivers excellent customer service and tech-support where humans, that actually know something, answer the phones.

Reliability:

Despite what you you may read on the internet, even by me, because I had an early failure of an ARS-4 & experienced a few others too, these regulators today are very reliable. Over the last 11+ years and many hundreds of regulators I’ve had one regulator with a bad reed-switch (replaced immediately) and one the customer claimed was faulty, but when sent back, was in perfect operational order. Due to changes made over the years to improve reliability, this regulator underwent a full suite of testing, and I got a report from CDI/Balmar. This level of testing was done because these failures are now so rare.

Early on there were some failures of ARS-4’s and some MC-612’s but changes were made to make them more reliable in the move to the current generation. Since CDI Electronics purchased Balmar they have been even further refined for the ultimate in reliability.  I’ve not experienced a single regulator failure under the new CDI/Balmar ownership.

Programming & Control:

In today’s day and age there is simply no excuse for any DC charging product that uses “dip-switch” type programming. By dip-switch I mean programming that utilizes a typical three setting;  AGM, FLOODED or GEL setting. DC charging products like this, in today’s day and age, are simply antiquated tube TV era products. They really have no place being sold in this century other than to pick your pocket. Please do your best to avoid “dip-switch” set battery chargers, solar charge controllers and external voltage regulators that do not allow you to have full-control over your charge settings.

There are no commercially available external regulators, at this price point, that allow you the same level of programming & control that a Balmar does.

• Base Battery Type
• Belt Load Manager (can also be used for current limiting an alternator)
• Display Mode
• Alternator Failure Advisory
• Regulator Field Start Delay
• High Voltage Limit
• Compensation Limit
• Bulk Voltage Limit
• Bulk Time/Duration
• Absorption Voltage Limit
• Absorption Time/Duration
• Float Voltage Limit
• Float Time/Duration
• Low Voltage Limit
• Field Threshold % Bulk to Absorption
• Field Threshold % Float to Re-Absorption
• Alternator Temperature Threshold Limit
• Battery Temperature Threshold Limit
• Battery Compensation Slope Voltage Correction

The majority of the programming features above are non-existent on other external regulators.

Regulator Installation Best Practices

Balmar regulators use an epoxy potting to keep the regulators printed-circuit-board clean, dry & free from corrosion. Placing it in high-heat areas can increase the risk of the epoxy potting to crack, as shown. I prefer to see a maximum working temp of below 140F, but Balmar claims the regulator can now handle 194F with the newest potting epoxy revision.

The regulator in the image above was installed by a boat yard, yet it was installed in the engine bay and only inches from the exhaust riser & manifold. The high heat and rapid temp changes caused the epoxy potting, which makes the regulator highly water resistant, to crack. The cracks in the epoxy likely causing one of the traces or components on the PC board to fail.

This regulator was also located near the engines siphon-break and had some corrosion starting on the terminals. This regulator was replaced and relocated outside the engine bay. After replacing it we ran the boat for other purposes and I noted a surface temp where the regulator used be of 208F. This failure is not a result of the regulator but rather a very poorly chosen installation location.

Regulator Installation Worst Practices:

• Avoid installing the regulator in the engine bay unless yours runs pretty cool
• Do not install the regulator in a hot compartment or against the inside of a dark colored hull
• *Do not wire regulator negative to the back of the alternator
• *Do not wire voltage sense to the back of the alternator
• Do not just set a battery type and walk away
• Do not forget proper over-current protection / fusing
• Do not clean the epoxy potting with any solvents
• Do not use Velcro to affix your regulator to the vessel, there are four screw holes for a reason

Regulator Installation Best Practices

• Install the regulator in a cool & dry location, quite often this will be outside the engine bay
• *Wire positive & negative voltage sensing directly to the battery being charged or as close as possible
• Always use the advanced programming menu to get an optimal set up
• Always program the alternator specifically for your batteries
• Program the regulator at home rather than once installed, it give you much better control
• Always use the optional battery temp and alternator temp sensors (MC-614H offers two battery temp sensors!)
• If you need to extend the wiring harness make one yourself rather than adding onto the factory harness with hidden splices
• Always program your regulator to avoid dropping to float too early. I call this “premature floatulation“
• Always use proper crimp tools & terminals
• Always use over-current protection on any positive feed to the regulator Reg B+/red, #9 / v-sense and Brown / ignition
• Try to mount the regulator in a vertical orientation
• Maintain a decent distance from RF noise emitters such as the alternator itself, inverters, chargers etc.
• Allow for adequate air flow around the regulator
• Use the Balmar supplied magnetic screwdriver, it has the correct magnet strength for the reed switch.

*Please read this sister article on proper voltage sensing for the best charging performance.

Alternators & Voltage Sensing – Why It Matters

Installation Location

Over the years Balmar has had some varying advice on where to best install the regulator. This particular manual for an MC-614 (see image) says to avoid engine bays due to high heat. I tend to agree with this particular manual, unless your engine bay runs cool and is well ventilated.

The MarineHowTo.com Regulator Programming Cheat Sheet

*Click on image to enlarge

In order to help make the job of programming a Balmar regulator easier, MHT created a programming cheat sheet just for this purpose. This .pdf file allows you to print it, then go through each setting before hand. You simply choose what you want to change/set and enter it into the cheat sheet before you start programming. The cheat sheet follows the MC-614’s scrolling menu.

TIP: When you’re all done programming the regulator, please save your programmed settings by inserting the “programming cheat sheet” into your on-board owners manual. Now any service tech that gets on board will know exactly how your regulator is programmed. They will really appreciate this information and it may just save you a lot of time and money.

IMPORTANT: Please purchase batteries from manufacturers who can provide you with all the parameters necessary for proper programming.

This is a free printable .pdf download:

Regulator Programming Cheat Sheet Download – Click Here

Custom Cheat Sheets:

If you would like us to create a custom cheat-sheet for you, the flat fee is $65.00. Before you contact us please read the following;

1- We only do custom cheat sheets for genuine branded batteries such as Lifeline, Trojan, US Battery, Northstar, Odyssey, Crown, Deka/East Penn, Rolls, Fullriver etc.. We do not make cheat sheets for batteries sold by “sticker application companies” such as auto-parts stores, West Marine, Costco, or cheaply made off-shore batteries such as Renogy or most any non USA made battery sold on Amazon. If the sticker on your battery is not an actual physical battery manufacturer, please do not contact us for a cheat sheet.

2- We DO NOT make custom cheat sheets for LiFePO4.

3- You must provide us with a complete description of how you use the boat, daily Ah consumption, all charging equipment including brand, make, model and amperage. Also, if you have an externally regulated alternator we will need to know what belt you are driving the alternator with and the amperage of the alternator.

Regulator Cheat Sheet Example

*Click on image to enlarge

In this image, and downloadable .pdf, we have an example of a regulator cheat sheet all filled out and ready to program the alternator for a GEL battery. This is simply an illustrative example of what a filled out programming cheat sheet might look like.

Regulator Programming Cheat Sheet Example Download

Why is Belt Load Manager a Tremendous Feature?

Belt Load Manager, formerly known as Amp Manager, is a feature unique to the Balmar family of regulators and is built into both the MC-614 and ARS-5. It is programmed using bEL in the regulator programming menu. I know of no other external regulator, other than Wakespeed, that offers any way to limit the alternators current output to accommodate a belt limit situation or to reduce the chances of the alternator from over-heating.

Lets use this alternator as an example:

This owner replaced his 80A factory alternator with a 110A Balmar, only his existing regulator was not a Balmar, but rather a an older Xantrex/Heart Interface. This was a very bad idea. The old Xantrex regulator, like most others out there, had no way to limit the alternators amperage output to better match the v-belts capabilities. The belt on this engine was a 1/2″ or 13MM single v-belt, the standard belt for this engine. Using the factory 80A alternator belt dust was tolerable but two factory alternators burned up trying to feed the massive bank of AGM batteries so the owner sought higher performance.

Once the owner switched to the 110A Balmar alternator he began chewing up alternator belts at a rate of one belt for every 16-22 hours of engine run time. Wow!!!! The belt dust was literally choking everything including the alternator. Alignment was spot on, pulleys were clean and rust/corrosion free and the belt wrap on the alternator pulley was actually quite decent too. The problem was simple, he was just overloading the belt and had no way to limit this issue other than dual v-belts $$$$, a serpentine pulley kit $$$$, or a better designed regulator $$. The owner chose a Balmar regulator and belt manager was set to level 5. Belt dust was nearly eliminated and he went three years on the next belt. Ideally this situation required dual v-pulleys, or a multi-rib / serpentine kit, but with the Balmar regulator and Belt Load Manager, he was able to make it work and at a much lower cost than a pulley conversion.

IMPORTANT: Just because you purchase a 100A alternator don’t be fooled into thinking this is its maximum output. When cold a typical performance based small case alt can pump out 5%-15% more than its face value cold rating or 105A to 115A +, for short duration’s, even with a 100A rated alternator. Some brands will deliver more than 20% over the rating when cold. This overage, even for short duration’s, wreaks havoc on belts. Only Balmar regulators offer the Belt Load Manager feature.

Belt Load Manager can be used to solve two important issues:

#1 Limit an alternators output to better match the v-belts HP drive capabilities.

#2 Limit an alternators output in high demand/long bulk situations to allow longer alternator life by running it at less than “full bore/full output”. Contrary to popular misconception I know of not a single small case alternator that can be run at full output for hours on end, unless;

1. The rectifier has been removed and the unit is rectified remotely
2. It uses liquid cooling
3. You are directly force feeding it ice cold air while also exhausting the hot air

For example, if your desire a hot alternator output of 85A – 100A then you would ideally want to purchase a 120A or larger small case alternator and use Belt Load Manager in order to limit the alternator output to your target amperage. Sizing this way keeps your alt running cooler and keeps it within its safe operating envelope, in regards to a safe working temperature.  Again, only Balmar regulators have the capability to limit the alternators field potential.

IMPORTANT: Small frame / small case alternators, even those sold as high performance, are NOT CONSTANT-DUTY RATED.

Don’t be fooled by less expensive regulators which lack features and lack the programming the Balmar regulators have.

Belt Load Manager Misunderstandings?

Below is a direct quote from the Balmar manual:

“The MC-614 provides the ability to manage regulator field potential, making it possible to govern the horsepower loads placed on the drive belt(s) by the alternator. The Belt Load Manager can also be used to protect the alternator from extraordinary load created by a battery load that’s too large for the alternator’s capacity.”

I have highlighted the words “field potential” for a reason and that reason is because Belt Load Manager (BLM), and how it actually works, is very often misunderstood.

Each step in BLM results in a 5% reduction off the maximum available field potential (click the image to enlarge it). It’s important to understand that BLM is not a 5% reduction in amperage output on a 100A alternator, or a 20% reduction in output for a 150A alternator making the 100A a 95A alternator and the 150A alternator a 120A alternator. This is not how it works, but it’s how many folks assume it works.

What is Often Assumed or Misunderstood

*100A Rated Alternator

BLM #1 = 95A Alternator

BLM #2 = 90A Alternator

BLM #3 = 85A Alternator

BLM #4 = 80A Alternator

BLM #5 = 75A Alternator

*100A alternator used as example only

The reality is this is not how BLM works. We have RPM, rotor core resistance, battery voltage, cold alternator windings and hot alternator windings etc. all playing a role in its overall output and field demand.

As an overly simplified example, consider BLM this way;

If your alternators field could pull max of 6A, at a given RPM, field voltage & stator/rotor temp, and you then set the regulator to BLM #1, the field potential (field voltage), the alternator could see, based on all the previous criteria, is reduced by 5%.  This 5% reduction, in avaible field voltage, would result in less than 6A driving the rotor.

What is “Field Potential”?

Field potential, for a Balmar regulator, is battery voltage (sensed voltage) minus about a 0.4V to 0.5V drop across the regulator FET’s. So a battery voltage of 13.5V, during bulk charging as voltage is climbing, results in a field potential of about 13.0V to 13.1V. If we follow Ohm’s law, voltage is what drives our current, and the same is true into a alternators rotor. BLM reduces the available field voltage, measured after the FET’s, by 5% for each step. If we reduce field voltage (field potential) we also reduce field current and alternator output *generally goes down.

*Generally - Occasionally a single BLM step will not reduce output because the regulator is slightly over-driving the rotor to begin with.

Keep in mind that if you set up belt manager, into a hot alternator,  it will still produce more current when it is cold. If you set it up at a low RPM it will be different than at a high RPM.

Bottom line is that BLM is a reduction in the avaible field potential (field voltage) not a reduction in alternator output based on it’s “rated output”.

There are a few ways you can program this:

•      Reduce BLM in steps, over a few week period, with good solid runs in-between that would be sufficient to generate belt dust. Reduce BLM until you no longer have belt dust or you are no longer bouncing in and out of alternator temp limiting.

•     Beg borrow or steal an inverter that can load your alternator to its maximum output and set your engine at cruise RPM. Now use a DC clamp meter or other ammeter to measure alternator output amperage. While the engine is running reduce BLM until you are at your desired maximum output at cruise RPM. It will still be higher when the alt is cold but not for very long. If concerned about cold start load, reduce BLM by one more step.

Belt Load Manager is just PWMing (pulse width modulating) the field output during periods that would otherwise result in 100% regulator field output.

Program The Regulator Off the Boat

One of the easiest ways to program a Balmar regulator is at home, with a 12V source. It is simple, and requires only 4 wires for the MC-614, or 3 wires for the ARS-5. You’ll also want a fuse or fuses to do so this safely. In this image I’m using a small 12V GEL battery. I use this battery for testing mast wiring during spring commissioning. I have added a fuse block and three fuses; Ignition, Regulator B+ and regulator Volt-Sense plus the yellow regulator B-/Negative lead.

Programming the regulator, in comfort, is much easier, less stressful and you can easily double or triple check your work all while not having a hose-clamp tail piercing your backside. I pre-program every single Balmar regulator I install, here in the shop, before I even get to the boat.

Required Connections for Bench Top Programming:

Regulator B-/Negative – Yellow or Black Wire Terminal #1

Regulator B+/Power – Red Wire Terminal #2

Ignition / Brown Wire Terminal #3

*Voltage Sensing – Terminal #9 (*MC-614 only ARS-5 does not have a terminal #9)

IMPORTANT: Battery or source voltage must be at a minimum of 12.5V in order to program the regulator & have the changes save.

TECH TIP: Please fuse all positive wires (+ volt-sense, B+ & Ignition). Hooking the regulator up backwards, without fuses, can destroy it.

Programming The Base Battery Type

It is best to tackle the programming in three distinct steps with battery type being first:

1- Program the base battery type; bA

2- Program the next three settings of the hierarchical menu; bEL, dSP & bDL

3- Program the Advanced Settings

In the first video the MC-614 is programmed for the base battery type or bA:

The reason for programming the base battery type first is to prevent confusion down the road.  Let’s assume you left the regulator programmed to UFP or “Universal Factory Program” but then went in and created a full custom charge profile, in the Advanced Settings menu for your GEL batteries. The first thing a tech will do, when there is an issue, is to look at the UFP setting, then look at your GEL bank, and change the battery type to GEL. They may do this despite the fact that you have proactively changed the GEL or AGM or FDC settings in Advanced Programming, to exactly match your brand & type of battery. Correctly setting the battery type just prevents confusion.

The Programming Hierarchical Menu

The menu you see in this image represents the top line menu items that you’ll scroll through to program the regulator. Each hierarchical menu item is a gateway to change what that top-line menu represents.

TECH TIP: You do not need to go through each step each time. For example, if you made a mistake setting Belt Load Manager or bEL, but everything else is correct, release the magnet after “PRO” appears, then re-touch at bEL to set or change Belt Load Manager. Once you’ve fixed bEL just let the display scroll three times until you see SAU, which means SAV or SAVE, you’re now all set.

Hierarchical Menu In Scroll Order

bA = Set Battery Type –  The gateway to set battery type eg; AGM, GEL, FLOODED etc.

bEL = Set Belt Load Manger Percentage – The gateway to set BLM eg: level 4 is a 20% reduction in field potential

dSP = Set Display Mode – Two choices, long display or short display

bDL = Alternator Failure Advisory – Two choices ON or OFF

 — = Advanced Programming – The gateway into advanced regulator Programming which features 15 customizable parameters

This second video examines the hierarchical menu of the MC-614 Regulator:

The third video show how to use Advanced Programming

TECH TIP: For batteries such as LiFePO4 you may find it necessary to reduce the bv setting below the default low of 14.1V. When using the regulators menu in scroll-order this is not possible because Av is set to 14.0V and each step must be 0.1V apart. There is however a work-around for this.

If  you wanted to set bv to  13.9V & Av to 13.8V you would need to reduce Fv first, then Av and then you can reduce bv. Each constant-voltage stage, bv, Av or Fv, needs to be programmed with a 0.1V spread. In other words bv can not be set lower than Av or Fv. The work-around is simple, just start backwards by reducing Fv first, then reduce Av then set bv last. Now you can drop the bv, Av & Fv target voltages lower than the factory defaults allow for.

bv = Bulk Target Voltage

Av = Absorption Voltage

Fv = Float Voltage

Confusion Creates Communication Issues

“RC I am fed up with this piece-o-crap alternator.It is in “bulk” and this damn thing is only putting out 20A. How can I send it in for repair?”

The above quote is a typical day in my world. Because the manual and charge lingo Balmar has chosen are confusing at best, trouble shooting time is burned up over perceived issues that are not real all due to semantics.

This all really boils down to two things.

1- Boaters generally understand that “bulk charging” means maximum output from the alternator.

2- Balmar calls a constant-voltage or voltage limited stage of charging “bulk voltage”.

Once voltage is maintained at a constant limit by the voltage regulator ACCEPTED CURRENT DECREASES. Once at constant voltage “bv – bulk voltage” the alternator is not at maximum output. The Balmar charging graph above, and on the right side, has been edited to show what really happens before we attain bv or “bulk voltage”.

Balmar only shows two things happening before constant voltage;

START DELAY

SOFT RAMP

In reality it’s really;

START DELAY – In this stage the regulator is applying 0% field to allow oil for circulation in the engine

SOFT RAMP – In this stage, a max of about 2 minutes, the field (regulator blue wire) is gradually ramped up to the maximum so as not to “slam” the engine with a huge load all at once.

*BULK CHARGING – During bulk charging the alternator is delivering everything it can, in current, to the battery bank. This can take as little as a few seconds for a bank already at high SOC or as long as multiple hours for a large bank deeply discharged.

*This is essentially an entire stage of charging (bulk stage) that Balmar left out of the graph. It is part of what leads to the confusion.

Understanding Battery Charging Lingo

The marine charging equipment industry apparently likes to keep customers “confused“, especially on topics surrounding battery charging. I suspect this is because it keeps the mystique of the “complex wizardry“, that goes on inside the product, a big secret?

In the marine industry almost all manufacturers use what is referred to as CC > CV charging, and this includes Balmar. The DIN standard designations for  charging would be I > Uo > U.

CC>CV charging simply means: Constant Current then Constant Voltage

Constant Current = The maximum current the charge source can deliver to the batteries

Constant Voltage = Voltage is held at a constant value by the regulation circuitry

In the rest of the world there’s actually a DIN standards that defines the charging process and it looks like this; I  Uo  U

I = Constant Current, CC, Bulk or sometimes called Boost Charging

Uo = CV/Constant Voltage, Constant Over Voltage, Absorption, Acceptance or sometimes Topping Charge

U = CV/Constant Voltage, Float, Finishing Charge or sometimes Maintenance Charge

It is important to note that under all definitions, whether DIN or the US terminology bulk charging is not governed by voltage being held steady, it is limited only by the charge sources output capability. During bulk charging, using real definitions, not made up definitions by a marketing department, voltage is always rising during bulk charging.

BULK = MAXIMUM CHARGE SOURCE OUTPUT WITH VOLTAGE RISING

“RC can an alternator really deliver a constant current?”

The answer to this is essentially no unless the alternator and RPM are held perfectly steady and the temp of the alternator stays the same. Despite myself and many others often referring to bulk charging, with an alternator, as “constant current” it’s probably better described as the alternators maximum current potential.

An alternator is affected by many things that a typical fixed-current battery charger is not. An alternator needs a maximum RPM to deliver it’s maximum current output. As an alternator heats up its winding’s lose efficiency and it’s current capabilities drop off a bit. This is why an alternator, or solar for that matter, is really better described as a maximum current potential charge source during bulk charging.

All maximum current potential means is that the alternator is being driven as hard as it can be, by the regulator, and it’s delivering its maximum current potential based on RPM and temperature. The alternators maximum current potential will vary up and down based on RPM, temp etc. however, it is still bulk charging and voltage will always be climbing towards the constant voltage limit. Because Balmar leaves bulk-charging off of their “stages” chart, and the description in the manual is a bit misleading, it can be quite confusing for the average DIY and even marine techs. Whether you choose to call it; bulk charging, maximum current potential, constant potential,  constant current or “I” it’s really just a matter of preference. In any of these scenarios voltage is ALWAYS RISING to the CONSTANT VOLTAGE limit. It’s far more simple to just call it bulk but some manufacturers have muddied those waters, including Balmar by calling a Constant-Voltage stage “Bulk Voltage”.  Perhaps a better and less confusing term for Balmar’s “Bulk Voltage” stage would be “Absorption 1”, but I digress….

Bottom Line? DURING BULK-CHARGING BATTERY VOLTAGE ALWAYS RISING!

IMAGE = BULK CHARGING: In this image we have a hot 110A small case alternator, held at a steady cruise RPM, and it’s delivering a steady 85A of output (red line). As we can see by looking at the blue line the battery voltage is steadily climbing from the 12.1V it started at (approx 50% SOC) and at the end of BULK-charging it has finally approached the regulators 14.7V Constant voltage limit or the Absorption or Uo stage where voltage will now be held steady by the voltage regulator.

Balmar regulators essentially have two absorption or Uo stages and they are called bV and Av. Balmar’s terminology for BULK CHARGING is “Soft Ramp“… Confused? You should be because it makes little sense based on industry accepted terminology.

Constant Voltage Charging

Now that we have gone over what bulk charging is, it’s also important to know what CV/Constant Voltage charging is.

Constant Voltage = Uo, U, Absorption, Acceptance, Float & Equalization

All of the above words are examples of voltage being held steady or a CV stage of charging. DIN separates Absorption from Float by designating absorption as Uo where the “U” means constant voltage and the  “o” means over voltage. The “o” in Uo just means that this CV stage (absorption) can not be held indefinitely or over-charging will result.

The Uo or absorption stage of charging (bv and Av for the Balmar regulators) is one of the most critical charge stages to battery cycle life. The job of the absorption stage is to bring the battery to full charge or very near and to reconvert the lead sulfate, created during discharge, back into active material. The DIN term “U” means Float and lacks the “o” because float can be held for longer periods with minimal risk of over charging.

US Lingo For Three Stage: CC/BULK > CV/ABSORPTION > CV/FLOAT

DIN Lingo for Three Stage: “I”/BULK > “Uo”/ABSORPTION > “U”/FLOAT

To simplify this even more try to consider a voltage regulator as  a VOLTAGE LIMITER. All a voltage regulator is really doing, during CV charging, is limiting to a preset voltage point, once the battery bank has attained the targeted voltage.

IMAGE = ABSORPTION CHARGING: This graph is just a continuation of the charge process started in the previous image. To the left we can see the current still steady at 85A (max alternator current output) but the voltage is climbing up to the pre-programmed voltage limit of 14.7V.

Once the battery bank has attained the voltage limit, in this case 14.7V, the regulator switches / transitions from bulk/max current potential to constant voltage charging where the voltage limit of 14.7V is now held steady by the VR. The voltage regulator is now doing it’s job as a “voltage limiter” instead of just driving the alternator to its maximum potential output.

In the graph you’ll notice that once voltage is held steady the current begins declining. This current decline is simply the result of the relationship between terminal voltage, current & SOC (state of charge). In order for the regulator to hold voltage steady, with a climbing SOC, the current being fed to the battery has to decline or the voltage set point would be over-shot. During absorption charging (bv or Av) the battery is dictating what the current can be so as not to “over-shoot” the 14.7V limit. As the SOC of the battery increases less and less current is needed to not over-shoot the voltage limit.

Key Points:

#1 During bulk charging the amount of current available to a the bank determines the bulk duration.

*High Charge Current = Shorter bulk duration and a CC to CV transition point at a lower state of charge

**Low Charge Current = Longer bulk duration and a CC to CV transition at a higher state of charge

*A Lifeline AGM Battery bank charged at 40% of Ah Capacity (160A for a 400Ah bank) will be bulk charging for around 20 minutes. This means the maximum bulk duration is pretty short, the alternator is only at max potential for about 20 minutes and the rest is CV charging where current is steadily declining.

**If we cut the above charge current in half, and charge the same bank at 20% of Ah capacity (80A for a 400Ah bank), the bulk charging duration lasts about an hour and fifteen minutes. Asking any small-frame/small-case alternator to produce its maximum output for 1:15 is pretty tough and it will develop tremendous heat. This is why Balmar offers Belt Load Manager and an alternator temp sensor. Please use them if you have a large or high acceptance bank.

#2 During absorption/CV charging it is the battery that determines the time it takes to get to 100% SOC. The only way to change this relationship would be to increase the target voltage but most batteries have a reasonable limit as to the maximum target absorption voltage.

Programming Tips to Maximize Your Investment

IMAGE: This image is from a reputable deep cycle battery manufacturer and shows their suggested charge voltages for a 12V battery. The 12V battery at 77F  is highlighted by the blue arrows. Also note the temp compensation they show in this grid. The temp compensation for this brand is all based on a 5mV compensation (per cell) for each 1°C change in battery temp. If your battery manufacturer can’t provide this information, walk away.

Are you charging your deep-cycle batteries at the optimal voltages for a long cycle-life?

The Balmar regulator is an excellent tool for battery charging but sadly far to many of these regulators are not programmed to work as effectively as they can. These tech-tips can help.

TECH TIPS:

1- Small-Frame Alternators are Not Constant Duty – If you have a small frame alternator and a large bank please use Belt Load Manager AND an alternator temp sensor. Your alternator will last much longer when not pushed to it’s maximum every time it is used.

2- Setting Only bA / Battery Type is Inadequate Programming – Setting a base battery type, and walking away, is about as useless as buying a Bugatti Veyron Super Sport and then installing some 1940’s bias-ply whitewall tires.  You’re simply not getting your money’s worth out of the regulator by doing this.

3-  Use Alternator & Battery Temp Sensors – These regulators are not complete until you install the alternator temp sensor MC-TS-A, and the MC-TS-B battery temp sensors. Unless you bank is very small, in relation to the alternator, then an MC-TS-A will be a necessary insurance policy. Every battery manufacturer on the planet prefers temperature compensated battery charging, and most reputable manufactures require it. A Trojan battery that charges at 14.8V at 77F – 80F can not charge at 14.8V at 95F. Without a battery temp sensor you run a much higher risk of cooking your battery and causing accelerated plate erosion.

Battery temp Compensation Slope Adjustments: The battery temp compensation feature on the Balmar regulators is adjusted using the SLP or SLOPE feature  in the advanced programming menu. This allows the regulator to be programmed for exactly the temp correction the battery maker specifies. One area where folks often get confused is in thinking it is only adjustable from 0-8.3 mV per battery. The 0-8.3 mV is per cell and for a 12V regulator this is 6 cells.

In other-words the regulator setting is adjusting temp compensation slope on a per cell basis, in degrees Celsius, not based on 6 cells or a whole battery. If a battery manufacturer wants 0.002 mV per-cell, per-degree C, this would be 0.012V per battery, per degree C change, but the regulator would be set to 0.002 for slope per cell and would compensate the battery at 0.012 mV per degree C change because it knows it is a 12V regulator and automatically multiplies your setting based on 6 cells.

4- Avoid Premature Float – Setting an adequate absorption/CV duration, (time spent at constant voltage), is critically important to battery health. The factory settings of 18 minutes for bv and 18 min Av plus any “calculated” additional time are not going to help you get the most from these regulators. In a perfect world the “calculations” that can extend or shorten the CV time calculations would work perfectly, unfortunately they rarely do, and this is why there is an advanced programming menu. B1C (bv duration) and A1C (Av duration) can be extended or shortened in the advanced programming, and should be in almost every installation other than LiFePO4.

The algorithm for bv and Av works like this: Programmed time completed/elapsed, regulator field percentage below 65% (or what ever you’ve set it too), voltage has been stable for 2 minutes. Once these three criteria have been met the regulator can now move to the next stage. Please bear in mind that the alternator has NO CLUE what percentage of the field is being used to power on-board loads or to charge the battery! This is exactly why you will need to custom program it so you are getting your money’s worth.

As noted above B1C and A1C time settings, % field and voltage stability (why correctly wired volt sensing is critical) must be achieved before the regulator can move to the next stage, and this is most often a good thing. The factory “base battery type” settings allows for the regulator to drop to float far too early, and I say this with nearly 30 years of experience with these regulators as well as using them as teh default regulator on our alternator testing machine here at Compass Marine Inc… Unless you routinely motor for 6+ hours, when out cruising, you should rarely, if ever, see your regulator drop to float. If it is doing this, you can fix this in the advanced settings menu by extending the minimums on the B1C or A1C time clocks and / or adjusting the field percentages that allow a transition. The only parameter that cannot be changed is the voltage stability the reg is also looking for.

I will often set bv at 0.1V over max factory recommended absorption voltage for 6-18 minutes, depending upon battery type, then set Av to the maximum allowable absorption voltage for anywhere from 2 hours to as much as 5+ hours depending upon the bank and available charge current.

On 3/21/18 I capacity tested a 2014 100Ah TPPL AGM battery that has been charged “properly“. Properly defined as a minimum of .4C in charge current (40A for a 100Ah battery) per manufacturer minimum current guidelines. Bulk-voltage bv is set to 14.8V bv for 12 minutes, then to 14.7V Av for 5 hours. This is 5:18 at constant voltage, temp compensated and an alternator float of 13.8V. The other charging equipment on the boat is solar, set similarly but a 2 hour absorption vs. 5 hours (due to the low current), and with float set to 13.4V.

The battery delivered 96.54Ah out of it’s 100Ah rating. A month earlier I tested a 2016 version of the identical battery. It had been charged only by a stock Hitachi alternator only. It delivered 56.83 Ah’s. The correct absorption voltage and a long enough absorption duration matter and can make big differences in bank longevity.

Yes, the Balmar regulators “try” to maximize and deliver a correct constant voltage duration but, in most cases, they fall short and drop to float far too early. The reason for this is simple, all the regulator knows is voltage and % of field drive. Voltage is simple, but the % of field drive actually being used to charge the batteries is nothing more than a crap-shoot guess for the regulator. What I mean by this is the regulator only knows a voltage, as sensed by regulator + sense and regulator B-, and the percentage of field output. What if 60% of that field output was being used for a water-maker, refrigeration, inverter, or other house loads? What if there were no house loads on at all? What if they turn on and off throughout the charge cycle? You can spend lots of time messing with field percentages but they change and you may not be happy with the results.. The easiest way around premature float is to extend the constant voltage time parameters in either b1c or A1c.

“So what’s the bottom line?”

If your regulator is dropping to float before the batteries are accepting less than 1% – 2% of Ah capacity, at ABSORPTION voltage (NOT float) then it is dropping to float too early. Most AGM’s are between 0.5% of Ah capacity (Lifeline) and 0.3% (Odyssey, East Penn/ Deka etc.) of Ah capacity to use tail current as when to drop to float.. Control this via b1C or A1c or field percentages, if you decide to experiment with field percentage. Extending the A1c duration is generally the easiest method.

Charging Batteries Correctly is Critical

5 – Set Yourself Up For PSOC Success – Using the highest absorption voltage the battery maker allows for will result in the least PSOC (Partial State of Charge) damage to the battery. Even the fastest charging AGM batteries require approximately 5.5+ hours to go from 50% DOD to 100% SOC, and this is in lab conditions with no chance of premature float and with 20% to 40% of Ah capacity in charging current. Flooded & GEL batteries charge even slower so absorption times will need to be adjusted to suit the batteries. The worst efficiencies for charging are from 85% SOC to 100% SOC and this duration alone, the last 15%, even with AGM batteries, often takes 3 – 6+ hours depending upon battery state of health. In the ideal set up your batteries don’t drop to float until they are 100% full. With voltage regulated charging this is tough but we can certainly do better because the MC-614 and ARS-5 regulators can be programmed eight ways from Sunday with ample opportunity to minimize premature-floatulation.

6 – Over Charging Concerns – If you’re concerned about “over-charging” when you leave the dock “fully charged“, which is really more of a personal problem rather than a real problem, simply install a dash switch that interrupts the regulators brown wire or ignition feed to shut it down. If you want to further complicate a relative non-issue you can use a resistor in the battery-temp compensation circuit to trick the regulator into a lower voltage by making it think the battery is hot. I call this trick “switch triggered float”..

I’ve autopsied piles and piles of batteries, both sealed and non-sealed, and the number of “dried-out” VRLA batteries (GEL or AGM) I have seen have been an n=2 banks. Both of these banks were ruined by controller-less solar systems (no charge controller at all) pushing 15+V every day. These batteries were not ruined by voltage regulated alternators leaving the dock at 100% SOC. By far and away the biggest concern with marine batteries is chronic under charging. The Balmar regulators can be programmed to help you avoid this.

7- Utilize Balmar’s Advanced Programming Menu – If you’re not taking advantage of the advanced programming features, ones you’ve actually paid for,  you’re really only seeing a marginal, if any, gain in actual charging performance.

8- Wire the Voltage Regulator Correctly – I hear lots of belly-aching over short bulk charging. In every single case of this I find the voltage sensing circuit wired INCORRECTLY. In regards to charging performance, even the Balmar manual is incorrect on how to properly wire voltage sensing. This article cannot be over-looked: Alternators and Voltage Sensing – Why it Matters

9- Field % Transition Thresholds – For a DIY, with not a lot of electrical experience, I generally advise extending b1c and A1c time clocks and leaving the Field Percent Transition Thresholds, FbA (Bulk to absorption) and FFL (from float back to absorption) alone. However, please don’t take this as a blanket statement and don’t be afraid to experiment with the field transition percentages. They are easy to re-set to the factory default, if what you changed does not work.

The difficulty with field percentage transition thresholds is the regulator has no idea what percentage of the field is being used for charging the batteries and what percent of field is being used to power on-board house loads. It is, after-all, a voltage regulator not a current regulator. If your house loads are very predictable, you can easily get the field transitions to work well, but it may take some experimenting and time to dial it in just right. If you run large inverters while under way or have unpredictable loads, while charging, it may be tougher, but please don’t be afraid to experiment with it.

10- It’s All About the Correct Voltages – For years the flooded deep cycle battery industry was stuck in the dark ages as to how to correctly charge lead acid batteries that were used in a PSOC environment. This is because industry and stationary systems require slightly different charge profiles than do PSOC use situations. Today, thanks to folks like Tom Hund (retired), of Sandia National Laboratories Photovoltaic Department, we now know that in order to correctly charge deep cycle flooded batteries we need significantly more terminal voltage during absorption than the antiquated 14.1V to 14.4V old-school guidance used to suggest.

Sadly no-one has keyed in the majority marine charge equipment manufacturer’s about this “breakthrough” information. In their defense, we’ve only known this for 20 or so years. (grin) With a Balmar regulator you can program to your hearts content and get it right.

If you’re not charging deep-cycle flooded batteries at 14.6V (bare minimum) to 15.0V, for PSoC use (boats, RV’s or off-grid solar), they’re simply not getting properly charged. Even many AGM batteries are capable of being charged as high as 14.7V and their health is vastly improved by doing so. With all that said, use your battery manufactures recommended voltages but stick to the maximum of the safe-range not the low side. For example if your battery maker suggests an absorption setting of 14.4V to 14.8V you’ll want to be at 14.8V end of the spectrum not at the 14.4V end.

Proper Programming, It’s Your Choice

IMAGE: Pictured here is a typical automotive voltage regulator the type found on most marine engines as they ship from the factory. I busted it open and extracted all the potting material so you could see the difference. With this image it is easy to understand why an external regulator, with all the features the Balmar’s offer, can lead to better and healthier charging for deeply cycle batteries and to better protection for the hard working alternator.

In the end it is your boat, and you’ll need to decide how you want to program your regulator, for your own piece of mind. All I can say, as a marine energy management specialist, is that I find far too many external regulators inadequately programmed & wired for the owners to be “getting their money’s worth”. Get your money’s worth and venture into the advanced settings!

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Happy boating!

Port to Starboard Orientation

This photo is simulating a sailboat heeling with flooded batteries.

For years I’ve wanted to write this article, but until my friend Dave let me shoot this polycarbonate cased UPS battery, it was going to be tough to explain. As they say “A picture is worth a thousand words”.

Here we can see the three individual cells of this 6V battery. A 12V battery would have 6 cells. Even heeled like this the positive and negative plates are not and have not “uncovered” and this is good. The vents are also not having electrolyte try to escape out the vent holes. In a port starboard orientation, like this, the cells are in their “thin” orientation compared to port or starboard tacks. Cells running port to starboard, not bow to stern, is the preferred method for installing flooded batteries on a sailing vessel to minimize plates uncovering.

Sorry for just telling you this now, if you have them running bow/stern, but I needed the pics before the article could happen.This is a problem I had discovered back in the late 80’s. I was on a friend’s boat that we’d put a “state of the art” charging system on due to chronic short battery life. At the time, we incorrectly assumed it was “overcharging”. Even after the new alternator and regulator he still had short battery life.

He went through the first bank in less than a season. One day, while helping him work on it, I noticed electrolyte spilled in the cases. The plastic cases for the batteries were black and so were the battery boxes making it tough to see or notice.I removed the batteries and discovered quite a bit of electrolyte. I cleaned it out, neutralized the acid, and we went for a sail with no charging. We put her up on ear, beating to weather, and sure enough electrolyte began to drain out of the batteries fill/vent ports. The cases were not cracked or leaking but it was spilling out when heeled. It then dawned on me that the orientation of flooded batteries on sailboats actually mattered.

I looked at the cell layout, and fill/vent ports, and simply rotated these batteries to port/starboard orientation. After that quick fix he never again had a single drop of spilled electrolyte. This may not be an easy fix on all boats as many builders really stuff you into a box, by using built in battery trays oriented incorrectly for flooded batteries. That bank lasted 5 or 6 years, after those first few days of spilling. After multiple years of replacing batteries almost annually the fix was actually pretty simple. I can’t say all the issues were related to the exposing of his battery plates, and chronically low electrolyte, but it certainly did not help any.

This problem gets compounded with batteries that have “off set” fill caps meaning they are closer to the edge of the battery than the center. Orient offset cap batteries, in a bow/stern orientation, and you’ll have some real leakage issues on one particular tack.

Exposing the plates, especially under charge or discharge, can lead to considerably shorter battery life. Is a failure immediate and catastrophic? No, but if the opportunity exists to orient them, more optimally, then it should be something you consider. Monohull sailboats should ideally have flooded batteries installed so as to minimize electrolyte spillage and to minimize or prevent the positive and negative plates from uncovering during normal sailing activities.

It is important to note that battery manufacturers such as Trojan, actually weigh in on this. Trojan suggests a maximum angle of just 22 degrees for flooded batteries. This is really not enough for a typical mono-hull sailboat, so by simply rotating the batteries you can gain a bit more heel angle. If you race or keep your boat on ear a lot then a GEL, AGM or LiFePO4 battery can be a better choice.

Bow To Stern Orientation

Here is the same battery, only now it is oriented with the cells running bow to stern.

In this orientation the positive and negative battery plates are exposed and uncovered from the electrolyte. On these particular batteries spilling is not an issue, due to the height and design, but on certain 12V & 6V groups GC2, 24, 27, 31 4D & 8D batteries etc. this can not only lead to exposed plates but also electrolyte leakage.

Exposing or uncovering of the positive and negative plates of a battery from the electrolyte, especially when under load or when being charged, is not good for the battery. Even if you are not spilling electrolyte you may be exposing the plates.

While sailing most sailors are using the batteries to power house loads, auto-pilots etc. so proper orientation of the cells could actually be that elusive piece of the puzzle that finally leads to longer battery life.

Many owners have invested thousands of dollars in solar, wind, regulators, alternators, desulfators, fancy chargers, new large gauge wire, bank fusing and more, but if your batteries are improperly installed you’re still missing that last piece of the puzzle.

 

Side Profile = Uncovered Plates

Here’s a close up side profile of what happens when the batteries are installed in a non-optimal orientation for the vessel type.

This battery was also at the low level for electrolyte. If it was full, to where it should be, then leakage possibilities could increase a bit. Either way the positive & negative plates are exposed and this is certainly sub optimal for battery life.

It’s not just battery manufacturers, & MarineHowTo.com, that advise on maximum installation angles & orientation of flooded batteries. ABYC E-10 Storage Batteries addresses the issue as well.

Fill Levels

There are some construction differences between 2V & 6V batteries and the typical 12V batteries often used in marine applications.

In this photo you can see the blue line representing low mark for electrolyte levels, and this battery needs topping up. The bottom line is the low mark and the top blue line is the full mark. Even at low, this battery still has sufficient electrolyte covering the plates to sustain typical heeling angles, if properly oriented.
A 2V or 6V deep cycle batteries are taller than typical “marine” 12V batteries in order to leave room in the bottom of the case to collect lead sulfate. Why? They are sold and used most widely into heavy deep cycling use such as industry or golf car applications, and the added height benefits these batteries in two important ways.

1- The added height sometimes, but not always, gives more electrolyte depth covering the plates when compared to typical 12V “deep cycle” batteries where the plates are considerably taller than a starting or dual purpose battery. Golf carts are often driven on hilly terrain, parked at steep angles and this type of movement is closer to what a monohull sailboat undergoes. Only off road jeeps and four-wheelers put flooded batteries through the same pains as a golf car or sailboat. This added case height, and centered fill caps, allow for less chance of the plates uncovering when the golf car moves about on hilly terrain.

2- In deep cycling applications, like golf cars or sailboats, sulfation of flooded batteries is just a fact of life. The bottoms of 6V battery cases are deeper thus allowing for the collection of more shed lead sulfate to collect. This battery shows very little sulfate in the bottom of the case but I have cut open / autopsied batteries with a depth of lead sulfate in the bottom of the case that is actually touching the bottoms of the cells in 12V form factor G-24, 27 & 31 batteries.. The typical marine 12V batteries can actually become shorted internally, due to the build-up of lead sulfate, which eventually can reach the plates. This same phenomenon is quite rare in quality deep-cycle batteries.

A Proper Orientation

While this picture shows the battery cells lined up port to starboard, this is not how they shipped from the factory.
This entire battery compartment was re-configured to allow for a larger house bank of two group 31 12V batteries, no height for GC2 6V batteries, plus a group 27 starting/reserve battery. The factory installation had the batteries oriented in a bow/stern configuration, and only had room for two group 27’s.

Unfortunately the physical height of this compartment would not allow for deep-cycle golf cart type batteries so a compromise was made to use 12V automotive-cased light-cycling batteries.

Port/Starboard

If you look closely at this photo you can see the cell dividers dimpled into the top of the plastic battery cases. Look at the faint lines and you can count all six cells on each battery.

This is an example of a good factory installation. This bank happens to be on an older Sabre 34 MK I. This past fall, at the Annapolis Boat Show, the Sabre I was on, one of the last ones built, still had properly oriented flooded batteries. Nice job Sabre!

While this battery compartment is small, at least by today’s standards, the batteries are properly oriented.

Builder Blunder

I will certainly give kudos to builders who do it right, but there is no need to slam an out of business builder by calling them out by name. Those who own this model will know this battery compartment well. Note the recessed battery wells that will only fit batteries one way.

This owner has actually tried to do the right thing by installing AGM batteries. Of course they lasted all of two years, on a mooring, because he lacked solar, but that is a topic for another article. It just goes to show that nearly everything on a boat is actually a compromise.

Unfortunately this builder left no possibility for a proper installation of flooded batteries short of cutting fiberglass and re-configuring the battery tray. There is no way, in this tray, to orient the batteries any way other than bow/stern. Doh’….!

On a boat like this GEL or AGM batteries will be the only good option, short of major battery box surgery.

Mounting

Any discussion involving battery installation would be incomplete without addressing securing the batteries into the vessel. For this task I often prefer a set of heavy duty pad eyes and heavy duty polypropylene canoe/kayak straps, not nylon.

The other pad eye in this photo is for the house bank which has not yet been installed into the battery tray. Containment of acid is critical so that any metal tie downs don’t get compromised by acid. For containment plastic battery boxes will suffice.

Also important is that the battery box not be able to move fore, aft or side to side. In this installation it is entrapped by a 1.5″ tall X 1.5″ wide mahogany frame on the battery platform. There are many ways to secure your batteries, just be sure you do. A good way to think about installing your batteries is to mentally visualize your boat in a knock down. So, take a moment to picture your vessel in a knock down.  Not very pretty is it!

Now, where are your batteries…? $hit happens so please install your batteries safely. A little spilled electrolyte, if you have flooded batteries, is arguably better than multiple 70 pound chunks of lead flying through your cabin.

I generally dislike the cheap battery hold down straps that come with plastic battery boxes. The AGM photo before this one is a prime example of sub-par hold down straps. Neither of them was still operable. These cheap straps, with their plastic buckles, are marginal to useless at best. Northwest River Supplies (NRS) sell the type of canoe/kayak straps we typically use. Just be sure the material the strap is made from is polypropylene  not nylon. Nylon is prone to acid attack and polypropylene is not. NRS straps work extremely well and are very, very strong. *TIP: Coat the metal buckle with Boeshield or similar.

Off Set Fill / Vent Caps

Here’s a prime example of a 12V group 31 battery (Deka/East Penn) that really needs to be installed properly. If not installed correctly, they will leak on one tack and this leakage can quickly ruin the batteries.

In this image the batteries are installed with the neg post facing PORT and the positive post facing STARBOARD to minimize plate uncovering and electrolyte leakage.

I can not stress enough how critical proper orientation is with batteries that have offset fill/vent caps as these do..

4D Orientation

With 4D and 8D batteries the placement and orientation of cells is different than a typical 6V GC2 or 12V G24, G27 or G31 batteries. Both 4D and 8D batteries are generally unsuitable for sailboat installations.

In a flooded 4D battery the cells are mostly rectangular, as shown here via the red lines.  While not ideal, a flooded 4D is better than an 8D for use on a sailboat. If you insist on using 4D’s the cells on 4D batteries are best mounted so the long length of the battery runs bow to stern. This puts the narrowest profile of each cell oriented to minimize positive and negative plate uncovering during sailing conditions. The red lines represent the cell dividers inside the battery box. Each rectangle/cell is sealed from the others.

8D = NOT OPTIMAL

In this image I have left the red lines off the cell divisions. If you click the picture, and blow it up, you can see the faint divisions of the cell dividers imprinted into the plastic cover.

When you look close at the cell layout of an 8D battery you can clearly see that these cells square.The 4D has rectangular cells, which can be better situated, the 8D has no optimal configuration for a heeling sailboat.

Because of the square cells on an 8D battery there is no orientation that is better than another. Any way you install a flooded 8D battery, on a monohull sailboat, can result in the plates uncovering when heeled. This is not great for the batteries.

Good luck and happy boating!

Baseline Discharge 49.3% SOC

PREFACE: This article looks at the *charging times & achieved state of charge of an AGM battery in multiple scenarios.

1- 50% SOC to 100% SOC at .2C
2- 50% SOC to 100% SOC at .4C
3- 50% SOC Charged at .2C For Exactly 1 Hour
4- 50% SOC Charged at .4C For Exactly 1 Hour
5- 50% SOC Charged at .2C For Exactly 2 Hours
6- 50% SOC Charged at .4C For Exactly 2 Hours

*DISCLAIMER: This test represents this slightly used AGM and may not be representative of a brand new AGM or a battery with more use and in a worse state of health.

DEFINITIONS:

“C” Rate – .2C & .4C – Also called Point Two C and Point 4C. This is just represents a percentage of Ah capacity in either charging or discharging current. For example .2C = 20% of Ah capacity or 20A for a 100Ah battery and .4C = 40% of Ah capacity or a 40A charge or discharge current for a 100Ah battery.

SOC = State of Charge – SOC is a percentage of charge based on battery Ah capacity.

DOD – Depth of Discharge – Is the depth to which the battery has been discharged. For example 80% DOD is also 20% SOC or 80Ah removed from a 100Ah battery.

Ah Capacity = Ampere Hour Capacity – The total ampere hours a battery can store and deliver at a discharge rate that yields a 20 hour discharge time at 77F before hitting a terminal voltage of 10.5V.

20 Hour Discharge Rate – Also the “20 hour rating”. The discharge current at 77F that will yield a 20 hour run time before hitting 10.5V

How long does it take to charge from 50% SOC to 100% SOC?

I have long known that a higher charge rate, with AGM batteries, does not necessarily translate to *significantly faster charge times from 50% SOC to 100% SOC and thought it would be good to test this and measure the actual differences. For the first part of this test, 50% SOC to 100% SOC, I compared a charge rate of .2C with a charge rate of .4C on the same Lifeline GPL-31T battery.

“*Significantly Faster” – Please understand, & take with a grain of salt, what I am comparing “significantly faster” to. I was once told by a quite vociferant expert on AGM batteries, “expert” defined here as a boat owner who had AGM batteries and whom had read only the glossy marketing materials, (grin) that with his 150A alternator he could recharge his 440Ah bank of AGM batteries from 50% to 100% in less than an hour and a half!  Apparently the marketing departments don’t have prerequisites of chemistry 101, Ohm’s law or physics 101?

While the owner was fully capable of basic math, and actually a nice guy to boot, 1.5 hours times 150A = 225Ah’s, he failed to take into consideration that his .34C 150A alternator could not put out 150A for 1.5 hours and his bank, at anywhere close to .34C, would hit absorption voltage rapidly and begin limiting alternator current. He also failed to include for a declining CAR or what is referred to as the charge acceptance rate. Even if his alternator could run at at a face value of 150A it is simply impossible to return 225Ah’s to that bank in 1.5 hours from 50% SOC. I will repeat this, IMPOSSIBLE!

One can’t really can’t blame this owner for his rather misguided expertise because he had been rather grossly mislead by nearly everyone in the industry on the expected charge times from 50% SOC to 100% SOC with AGM batteries. Suffice it to say it is physically impossible to recharge a 440Ah bank of AGM batteries at 50% SOC to 100% SOC in 1.5 hours with a .34C charge current.

Charge Rate Explained:

0.2C = 20% Charge Rate of the Ah Capacity
0.4C = 40% Charge Rate of the Ah Capacity

In this image we have removed 48.54Ah from the battery which tested at 95.69Ah’s of actual capacity. This leaves the battery at 49.3% SOC or just about 50% SOC.  Voltage was used as the cut-off and 12.100V at 5.25A was the stop point for the discharge testing. Voltage as a cut off , at a known constant load and battery temp, is actually extremely repeatable.

The Test Battery:

The battery used for this testing is a 2015 Lifeline Group 31 AGM Deep Cycle battery. It had been used for approx 5 months as part of a bank on a power boat (trawler type) that cruises Maine and resides on a mooring. Once here in my shop it was cycled to 80% DOD then back to 100% SOC twice. It was then equalized at 15.5V for 4 hours, (Lifeline calls this conditioning). The battery then underwent one 20 hour discharge capacity test and was then cycled to 50% SOC and back to 100% SOC, 3 times and another 20 hour capacity test was run. The average of the two 20 hour capacity tests was used as the baseline Ah capacity. The baseline Ah capacity of this battery was 95.69Ah. Throughout testing the ambient temp of the battery averaged about 75.2F. While not 77F, the 75F temp should not have negatively impacted the testing. The battery has a rated Ah capacity, at 20 hours, of 105Ah. For charge and discharge rates I kept them based on the “as new” capacity rating, just as many boaters would do, to keep the test a bit more “real world“.. The battery is rated at 105Ah so -5.25A was the discharge rate used. The test was set up to try and simulate real world use on cruising boats.

Testing Equipment:

Charging – BK Precision 60A Variable Power Supply W/Dedicated Voltage Sensing
Discharging – Array DC Programmable DC Electronic Load W/Dedicated Voltage Sensing
Temperature – Fluke Infrared
Data Logging – Bogart Engineering Pentametric
Images – iPad Air with intervalometer software taking 1 picture every 2 minutes

2 Minutes – 50% SOC to 100% SOC .4C Charge Test

For the .4C charging test the timer was reset to 12:00 and an image was snapped using an intervalometer at 2 minute increments. At 2 minutes the voltage at a .4C charge rate had already risen to 13.6V.

18 Minutes @ .4C Approaching Absorption Voltage

This image shows the charger almost ready to exit bulk charging and enter absorption charging. If you look closely, on this lab grade power supply, you can see a little red light next to the letters “CC”. This means constant-current or BULK charging.

Bulk Charging is the Most Efficient Charging:

Bulk charging is the most efficient part of the recharging process with efficiencies ranging close to 100% of energy delivered by the charger being usable and stored. For AGM’s I have seen this anywhere from 96% to over 99.5%. Once the charge process switches from constant-current/bulk to constant-voltage/absorption, the charge efficiency continues dropping. In the high 90% SOC range we are converting a lot less of the supplied energy into stored energy. Charge efficiency is not a simply single data point number such as 20% efficient or 10% efficient. The Coulombic efficiency varies through the charge curve and is why getting all lead acid batteries back to 100% SOC, including AGM & GEL, takes a long time.

Bulk & Absorption Terminology Confusion

If you read the highlighted part of the Lifeline Battery Technical Manual you will see that Lifeline correctly understands the difference between BULK and ABSORPTION charging. Many companies, including Balmar and some others, do not correctly understand using the word “BULK”. When a company tells you that “bulk” is a voltage limited stage of charging this is PURE MARKETING BOVINE DUNG. Simply put, bulk=constant-current charging not constant-voltage.

BULK – Bulk Charging is the constant current stage of charging where the charge source is limited only by what it can deliver in current. Bulk charging is not a voltage limited stage of charging despite many companies bastardizing the term bulk for apparent marketing purposes.

ABSORPTION – Absorption, float and equalization are all examples of constant voltage charging stages. Absorption or constant-voltage is where the charge source holds voltage steady, hence the term “constant-voltage”. Once voltage is held steady, or it becomes voltage limited, current begins to decline and the charge efficiency worsens as SOC increases. Float charging is a further reduction in the constant-voltage limit and an equalization voltage would be an increase in the constant-voltage limit of charging.

The charging devices we use on boats are all considered CC > CV charge sources, or constant-current (BULK) then to constant-voltage (ABSORPTION, FLOAT & EQ). Simple stuff really. Please understand that BULK is not a voltage limited stage of charging, despite the marketing guru’s vastly missing the mark on this one…

Kudo’s to the guys at Lifeline Battery for properly understanding the difference between BULK and ABSORPTION. Shame on companies who grossly mislead the consumer and use incorrect lingo to pretend they are getting more than they actually are.. Words mean certain things and when we blur the definitions to sell $hit, it CONFUSES PEOPLE. (grin)

Please remember that bulk is not a voltage limited stage of charging it is constant current.

20 Minutes @ .4C Absorption Voltage Attained

Based on this image, and the data logger, I know the battery attained 14.4V at around 19 minutes. Here at 20 minutes, with the voltage now held steady at 14.4V (green CV/constant-voltage light on) we can see that the charge current has already dropped from 42A to 41.5A or a .5A reduction in accepted charge current into the battery.

If we assume that bulk was 100% efficient, and we will for round numbers, the energy returned to the battery at .4C during bulk charging looks like this:

42A X .32 Hours = 13.44 Ah

If we know the battery had 47.15 Ah left in it, at 49.3% SOC then:

47.15Ah + 13.44Ah = 60.59 Ah stored in the battery

60.59 Ah as a % of 95.69 Ah (tested capacity) = 63.3% SOC

If you’re paying attention this battery, when charged at .4C from 49.3% SOC, stayed in BULK/CC for 19 minutes and entered ABSORPTION/CV charging, where current begins declining, at 63.3% SOC. If you’ve listened to net lore or dock lore for years, as I have, we all know AGM’s “don’t come up to absorption until 80-85%” right? Wrong…. The point at which any battery becomes voltage limited or attains the absorption voltage is entirely dependent upon the charge rate you are feeding it.

This clearly charge rate shows very clearly how charge current affects the SOC transition point from bulk to absorption charging.

1 Hour – .4C Recharge

By 1 hour in, our 42A or .4C charge current has already declined to 19.5A..

2 Hours -.4C Recharge

By two hours of charging, at .4C from 50% SOC, we are down to just 7.3A in current flowing into the battery…

3 Hours – .4C Recharge

Here we are at 3 hours and the accepted charge current is now down to 2.8A.. That last few % takes the longest due to declining CAR.

4 Hours – .4C Recharge

By 4 hours, at .4C, in we’re now down to 1.1A in charge acceptance…

50% SOC to 100% SOC at a .4C Recharge Took 5:30

100% SOC was deemed as 0.525A flowing into the battery at 14.4V per the Lifeline Battery Technical Manual.
At a .4C charge rate it took this fairly healthy, though not perfect, group 31 battery 5:30 to reach 100% SOC from 49.3% SOC.

2 Minutes – .2C Recharge

Beginning of .2C Recharge Test:

For this test 12.100V was also used as the cut off voltage after a full 100% recharge. After a full recharge at 14.4V battery then spent 32 hours at a float voltage of 13.4V. It then had a 24 hour resting period. The battery delivered -48.33Ah or just about where it had on the previous test which ended at -48.54Ah.

As we can see in this image, at 2 minutes, the .2C charge rate only has the battery to 13.1V vs. 13.6V at a .4C charge rate. The voltage is climbing slower in bulk at .2C than it did at .4C. This is to be expected.

1 Hour – .2C Recharge

At 1 hour the battery voltage has only risen to 13.8V at a .2C charge rate. The .4C charge rate had attained 14.4V within 19 minutes.

If this was your alternator it had better be robust enough to deliver its full output for at least 1 hour straight. In this case, as you see next, it is 1:16 minutes before your alterntor would even begin to catch a break. A charge rate of .2C on a 450Ah bank, a pretty typical bank on a coastal cruiser these days, is an alternator that can deliver 90A continuously, even when hot.

1 Hour & 16 Minutes – .2C Recharge Absorption Voltage Attained

At 1:16 the battery finally attained 14.4V and the current had begun dropping.

If we again assume that bulk was 100% efficient, and we will for round numbers, the energy returned to the battery at .2C during bulk charging looks like this:

21A X 1.27 Hours = 26.67 Ah

If we know the battery had 47.36 Ah left in it, at 49.5% SOC then:

47.36Ah + 26.67 Ah = 74.03 Ah stored in the battery

74.03 Ah as a % of 95.69 Ah (tested capacity) = 77.4% SOC

This battery, when charged at .2C from 49.5% SOC, stayed in BULK/CC for 1:16 minutes and entered ABSORPTION/CV charging, where current begins declining, at 77.4% SOC.

Once again this clearly shows how charge current affects the SOC transition point from bulk to absorption charging. At .4C the battery attained absorption voltage at approx 63.3% SOC and at a .2C charge rate it attained absorption voltage at approx 77.4% SOC.  See batteries don’t just automatically attain the absorption point at 80% SOC it all depends upon the available charge current..

2 Hours – .2C Recharge

At 2 hours the charge current is down to 11A..

3 Hours – .2C Recharge

At 3 hours the battery is now accepting just 4.2A.

4 Hours – .2C Recharge

At 4 hours the battery is accepting just 1.6A..

Determining 100% SOC

The key piece when charging your batteries is how to determine when you are at 100% SOC. Some battery manufacturers give “*tail-current” or “*return-amps” in their technical manuals, Lifeline battery is one of them..

*Return-Amps” / “Tail-Current” – This is the amount of current flowing into the battery at ABSORPTION VOLTAGE where one can pretty safely determine 100% SOC.

Using return amps, at absorption voltage, (not float voltage) is usually the easiest method to determine 100% SOC when out cruising. This image is a screen capture of the Lifeline Battery Tech Manual. I have highlighted the important part for net return amps determining 100% SOC.

It is saying; A voltage limit (absorption voltage setting) of 14.3V to 14.4V should be used when the battery temperature is at 77F, this battery was at about 75F. When voltage is steady at 14.3V to 14.4V the battery can be deemed 100% full when charging-current,/tail-current/return-amps declines to 0.5% of Ah capacity.

When 14.4V and 0.525A were attained is when I deemed this battery at 100% SOC. Technically, the battery was only at 95.69Ah so I should have used 0.48A but close enough for this experiment.

What Is Full?

It is important to note that some sources claim a tail-current of 2% @ absorption voltage will yield 100% SOC. Odyssey, Northstar and East Penn/Deka all wanted to see 0.3% @ absorption voltage for the Practical Sailor PSOC testing. Lifeline wanted 0.5% and for Firefly we stopped at 0.5% as well. Over many years of capacity testing hundreds and hundreds of batteries, flooded, GEL and AGM I have yet to see a lead acid battery that could delivers its full storage potential at anything less than 0.75% in tail current at absorption voltage. My best research of antiquated data and materials suggests that 2% @ Absorption voltage originated from the Ah counting industry not from batteries actually being “full”.

Tail-Current is always measured at ABSORPTION VOLTAGE…

Please don’t confuse FLOAT tail current with ABSORPTION tail current. Far too many marine charge sources drop to float prematurely. If you check your tail current at 13.4V and see a 0.5% tail-current, you’re not full…

100% SOC – .2C Recharge

Here we are at 100% SOC at the .2C charge rate and it took 5:42 minutes.

Yes, it took longer to attain 100% SOC (per Lifeline battery tech manual) but that time was only about 12 minutes different with double the charge rate.

Both charge rates on this pretty healthy AGM battery took 5.5+/- hours and I have repeated this test with AGM batteries is worse shape that exceeded 7 hours to attain 100% SOC, likely due to sulfation.

IMPORTANT: Please understand that you will never likely charge this fast with a typical smart charger. Take for example the .4C charge rate. At 19 minutes it hit absorption voltage. Many so called “smart chargers” begin a timer, I call it an egg-timer, once absorption voltage has been attained. If that egg-timer clock started at 19 minutes, and was 2 hours long, the charger would have dropped to a float voltage of 13.4V at 2:19! OUCH!!!! Smart? Hardly! Murderous to your marine batteries? You bet!

Considering it took 5:11 minutes of absorption charging at the .4C charge rate your batteries would likely end up grossly under absorbed, under charged and would not last very long. Once we reduce voltage, eg: dropping to float prematurely, I call this premature-floatulation, we dramatically EXTEND charging time to 100% SOC. In my shop I use adjustable power supplies to avoid dumb so called “smart chargers”. With a fully adjustable power supply I can control when the battery changes from absorption to float and not rely on an egg timer. If I desire a timer cut off I simply program a digital wall timer.

Is too much current bad for an AGM Battery?

For AGM batteries generally speaking the more charge current the better the longevity of the bank. It helps, not hinders, with overall longevity to charge at high rates. Higher charge rates in AGM batteries actually yields longer life not shorter life. Dave V. the lead engineer at Lifeline battery published a study supporting higher charge rates being good for AGM’s a long time ago but it still holds true today.. Odyssey battery, thin plate pure lead AGM batteries, wants to see a minimum of .4C in charge current and Lifeline wants to see a minimum of .2C as recommended charge current.

This is from the conclusion section of Dave V’s study:

“In order to achieve the maximum cycle life from sealed lead acid batteries, (AGM) not only should the DOD be kept as low as possible, but the charge current limit should be as high as possible.”

The study then goes on to suggest that a balance needs to be met between equipment and optimal cycle life. Today Dave suggests a minimum charge current of .2C for Lifeline AGM’s.

It is a pretty rare boat that can muster a .4C charge rate, but some do. On a 450Ah bank that would be an alternator or large inverter/chargers that could sustain 180A when hot. Unless the boat has a massive Electrodyne alternator or multiple stacked “Combis” (inverter/chargers) it is quite rate to see even a 200A continuous charge rate.

You as a boat owner will have to decide what it’s worth in terms of equipment costs to charge your AGM’s at high charge rates. The eternal question of “Do AGM’s charge faster with high charge rates applied?” seems to still be open for debate. This battery only saw an approx 12 minute difference in a 5.5hour charge period but yes it did charge “faster” at .4C than it did at .2C.  Double the charge current to shave 12 minutes? It may be worth it to some, but getting to 100% is not the whole story….

It Is Important To get Back to 100% SOC

The importance of getting back to 100% SOC, as often as possible, can not be over emphasized. Here Lifeline Battery is referring to the “walk down” effect of PSOC use (*partial state of charge cycling). By not recharging to 100%, as often as possible, your Ah capacity will gradually “walk down” as sulfation becomes permanent and ruins them.

SUMMARY: In this portion of the testing 50% to 100% SOC, on this AGM battery, the difference between a .4C and a .2C charge rate, netted a 12 minute total charge time difference.

*For more information on the effects of PSOC cycling AGM batteries please read the May 2015 and August 2015 issues of Practical Sailor Magazine.

BEGIN: .2C – 2 Hour Recharge Then Discharge Test

In this second part of the testing I am replicating a few typical scenarios for recharging on a cruising boat. No one wants to run the engine or generator for very long so I wanted to illustrate what kind of energy can be stored in the AGM battery at a 2 hour time interval at a .2C charge rate.

This test started with a discharge from 100% SOC to 50% SOC with the battery delivering 47.85Ah at a 5.25A constant current load. The battery was then recharged for exactly 2 hours at .2C and then discharged back to 50% SOC and the stored energy for that cycle was measured.

The charge rate for this test was 21A and the timer set for 2 hours. If the battery could stay in bulk for two hours our maximum potential energy into the battery would be 42A. Because the battery hit absorption voltage, before hitting the 2 hour mark, we simply can not get 42Ah of energy into the battery…

CHARGING – 2 Hour Charge Test .2C – The Two Minute Mark

At two minutes into the test at 21A the battery terminal voltage is at 13.1V.

MYTH BUSTING: Think about this snap shot if you use or are considering a battery combining relay for charge management and are concerned or have been scared off by one of the many myths surrounding these effective and highly reliable devices.

The myth goes something like this: By using a battery combiner, on AGM batteries, and feeding the alternator or battery chargers charging current directly to the house battery bank first, “it will leave your start battery under charged“.

If you are practicing good battery management, and have even the minimum suggested charge current for an AGM battery, this is a complete non-issue. In 2 minutes of charging, at .2C or 20% of Ah capacity from 50% SOC, the AGM battery voltage is already at the “combine level” for the amazingly popular Blue Sea ACR.

Battery voltage will rise pretty slowly from here on but to get to an ACR’s “combine level” is relatively quick and easy, especially if you have your system set up properly. The Echo Charger, Duo Charger and numerous other DC to DC chargers also turn on at similar voltages and those devices require all charge sources to be fed to the house bank.

CHARGING – 2 Hour Charge Test .2C – Two Hour Mark

In this image the charge source is about to turn off when it hits the 2 hour mark. Net accepted current at 14.4V @ 1:58 is down to 11.6A.

DISCHARGING – 2 Hour Charge/Discharge Test .2C – Two Minute Mark

Here the electronic load has turned on and has now begun discharging the battery back down to 50% SOC. I did not pause and let the battery rest between charging & discharging because this is not actually done on cruising boats.

The object with this test is to see how much usable energy we can store in the battery in two hours at a .2C charge rate..

STORED ENERGY – 2 Hour .2C Charge/Discharge Test

After charging the battery from 50% SOC for two hours at 21A we were able to remove 35.28Ah’s and bring the battery back down to 50% SOC.

Let’s do the math: Baseline Ah Capacity = 95.69Ah

Discharge to 50% = 47.84Ah (left in the battery after discharge)

2 Hour charge then discharged and counted Ah’s delivered back to 50% SOC = 35.28Ah

47.84Ah + 35.28Ah = 83.12Ah of stored energy

83.12 is 86.9% of the baseline Ah capacity of 95.69Ah’s

RESULTS: The battery achieved approx 87% SOC from 50% SOC in two hours at a .2C charge rate

BEGIN: .4C – 2 Hour Recharge Then Discharge Test

Rather than bore you with multiple images that all look the same I am going to summarize the remaining three tests with the “stored energy” screen shot.

This test was a .4C charge for two hours and when discharged back to 50% SOC, after the 2 hour charge, the stored energy removed was 44.48Ah. While not a heck of a lot more than .2C it is the attained SOC that really makes .4C different.

Let’s do the math: Baseline Ah Capacity = 95.69Ah

Discharge to 50% = 47.64Ah (left in the battery after discharge)

2 Hour charge then discharged and counted Ah’s delivered back to 50% SOC = 44.48Ah

47.64Ah + 44.48Ah = 92.12Ah of stored energy

92.12 is approx 96% of the baseline Ah capacity of 95.69Ah’s

RESULTS: The battery achieved approx 96% SOC in two hours at a .4C charge rate

PERSPECTIVE: Charging to 100% SOC took 5:30 minutes so this means the last 4% of returned energy took 3.5 hours to complete at .4C and the first 46% of capacity could be returned in 2 hours at .4C. The problem still remains that the last 4% is critically important to AGM longevity.

BEGIN: .2C – 1 Hour Recharge Then Discharge

This test was a .2C charge for one hour and then discharged back to 50% SOC, after the 1 hour charge. The stored energy removed was 20.46Ah from a max charge rate of 21A.

CHARGE EFFICIENCY: As I have mentioned before bulk charging, where the charge source provides its full current before the battery reaches the limiting voltage, is nearly 100% efficient. Here we have a 1 hour recharge at a charge rate of 21A where the battery was able to store 20.46Ah of that 21Ah delivered to the battery. A 21A charge for 60 minutes is 21Ah’s of supplied energy. This means 97.4% of the energy supplied by the charger, or the 21A for exactly 1 hour, was removable as stored energy when we discharged back to 50% SOC. On this 1 hour .2C recharge the battery never attained the absorption voltage of 14.4V and was still in bulk when the charger turned off at the one hour mark. Bulk is very efficient!

SCALE IT UP: If we scale this test up, and it should scale well, a .2C charge rate on a 450Ah fairly typical cruising boats house bank would be a continuous 90A for 1 hour before your batteries even hit the absorption voltage set point. Yes, 90A continuously for 1 HOUR.. This is a metric $hit ton of work on a typical 90A – 120A alternator. This is why many a boater has burned up their alternators charging AGM batteries.

MYTH BUSTING: If you believe a battery monitor that counts Ah’s, and supplies a fixed charge efficiency number to the returned Ah’s (most all of them), can track your batteries accurately when you don’t recharge to 100% SOC with each cycle, this myth & lore is blown out of the water right here. In bulk this battery had returned energy efficiency of 97.4% yet the last 4% of returned energy, to 100% SOC, takes 3.5 hours! There is a major difference in charge efficiency throughout the SOC curve. Charge efficiency is not linear throughout the SOC curve, but most all battery monitors are linear in their application of charge efficiency. They simply apply a negative count factor for charge efficiency as the Ah’s are returned. For example if we return 10Ah’s with a 90% charge efficiency setting the battery monitor will only show that as 9Ah’s returned. If we were to stop charging in bulk we really do have closer to 10Ah’s returned. Do this a few times…….. Ouch! When you cycle more than a few times in the 50% to 90% SOC range there is no way for a typical Ah counter/battery monitor to accurately track your charge efficiency. For more info on this see the article on “Programming a Battery Monitor”.

Let’s do the math: Baseline Ah Capacity = 95.69Ah

Discharge to 50% = 47.44Ah (left in the battery after discharge)

1 Hour .2C charge then discharged and counted Ah’s delivered back to 50% SOC = 20.46Ah

47.44Ah + 20.46Ah = 67.90Ah of stored energy

67.90Ah is approx 71% of the baseline Ah capacity of 95.69Ah’s

RESULTS: The battery achieved approx 71% SOC in one hour at a .2C charge rate.

PERSPECTIVE: It is pretty clear that a 1 hour charge at .2C is an inadequate charge rate for AGM batteries that are routinely discharged to 50% SOC, unless you really like hearing your motor or generator run.

NOTE: Lifeline Battery recommends a .2C charge rate as the bare minimum for these expensive AGM batteries. Odyssey TPPL AGM batteries are recommended to be charged at a minimum of .4C.

BEGIN: .4C – 1 Hour Recharge Then Discharge

This test was a .4C charge for one hour and then discharged back to 50% SOC, after the 1 hour charge. The stored energy removed was 33.43Ah from a max charge rate of 42A.

SCALE IT UP: If we scale this test up, and it should scale well, a .4C charge rate on a 450Ah fairly typical cruising boats house bank would be a continuous 180A. This battery hit the absorption voltage point at approx 20 minutes when charged at .4C from 50% SOC. With a .4C charge rate your alternator or charger would only be in bulk, or running at its full output, for approx 20 minutes. While this certainly does not make the most efficient use of the alternator, or inverter/chargers, or generators it does charge the batteries to a higher SOC in a short 1 hour run.

Let’s do the math: Baseline Ah Capacity = 95.69Ah

Discharge to 50% = 47.98Ah (left in the battery after discharge)

1 Hour .4C charge then discharged and counted Ah’s delivered back to 50% SOC = 33.43Ah

47.98Ah + 33.43Ah = 81.41Ah of stored energy

81.41Ah is approx 85% of the baseline Ah capacity of 95.69Ah’s

RESULTS: The battery achieved approx 85% SOC in one hour at a .4C charge rate.

PERSPECTIVE: While .4C certainly does attain a higher level of SOC in 1 hour, approx 85%SOC, the gain in SOC makes pretty ineffective use of a .4C charge source while only utilizing it at 100% output for about 20 minutes. Most boaters charging AGM batteries would likely benefit from a compromise charge source current of about .25C to .35C for 1.5 – 2 hours +/- per day. Blended with solar you can get the bank to 85% SOC or so and let the solar take over for the long slow crawl back to 100% SOC.

The Difference Between .2C and .4C from 50% SOC to 100% SOC

Here is another way to look at the charge process with a doubling of charge current. In this diagram Bulk/CC is the orange area and Absorption/CV is represented by blue.

• At .4C the charge source is only working at full output, 42A, for 19 minutes then becomes voltage limited @ *14.4V
• At .2C the charge source is working at full output, 21A, for 1:16 before it becomes voltage limited @ *14.4V
• The difference in total charge time from 50% to 100% SOC, with this battery, when we doubled the charge current, was 12 minutes

NOTE: The blue charge acceptance curves are illustrative only. All times and voltages are accurate and taken directly from data points used in this test.

Another View of The Charging Process

Here is another way to look at the charge process. This was a *Lifeline GPL-31XT battery (125Ah rated that was charged at .15C or about 15% of its rated Ah capacity. *NOTE: This was not the battery being tested in this article, and it was used. This image is just for just for illustrative purposes..

BULK: If we start at the top left of the chart we can see that the current held rock steady at 18.75A for *1:42. This current, 18.75A is .15C or a 15% charging current of a 125Ah battery.

*NOTE: 1:42 of bulk charging (your alternator running at full bore) is more than enough to damage an alternator not otherwise protected for temperature or current limited to protect it. A charge rate of .15C would be an 80-90A alternator on a 400Ah bank, when accounting for the “hot” output, and not all that uncommon. I see lots of burned up alternators when they are under sized for the task.

VOLTAGE RISE: If we look at the left side of the chart we can see the voltage climbing to the absorption set point of 14.4V. It took 1:42 at 18.75A for the battery voltage to attain 14.4V.

1/3 From Left: This is the point where the charge current and voltage flip-flop. Voltage stops climbing and is held steady, and current changes from being steady/constant to declining. Once the BULK/constant current charge has driven the battery voltage to the absorption voltage limit, the voltage is now limited or held steady and the charging current begins to decline.

CHARGE TIME: As current declines, out towards the lower right of the chart, the time it takes to get that last few % in takes significant time. At .15C this slightly used AGM took a bit over 6 hours to reach 100% SOC. I have had sulfated AGM batteries take 7+ hours even at a higher .2C. The health of your AGM battery can impact your time to full.

TESTING SUMMARY:

50% to 100% SOC  @ .2C = 5:42 – Exited Bulk @ 1:16

50% to 100% SOC @ .4C = 5:30 – Exited Bulk @ 19 Minutes

50%  SOC @ .2C For 1 Hour = 71% SOC – Remained in Bulk

50%  SOC @ .4C For 1 Hour = 85% SOC – Exited Bulk @ 19 Minutes

50% SOC @ .2C For 2 Hours = 87% SOC – Exited Bulk @ 1:16

50%  SOC @ .4C For 2 Hours = 96% SOC – Exited Bulk @ 19 Minutes

DISCLAIMER: All batteries will test & perform differently based on age, type, chemistry and state of health. This battery and test are only really representative of this battery and test but should give some decent guidance as to what one may expect from a slightly used AGM battery. I purposely did not test a brand new AGM because that is not at all representative of what we as boaters have in use on-board our vessels for more than a short period of time. New batteries will perform differently but our batteries on boats rarely stay new for very long.

Good luck & happy boating!!

December 11, 2012

After having a discussion with one of my customers, about leaving his battery charger running on-board all winter, a practice I am certainly not a huge fan of, and one his boat yard specifically prohibits, I decided to venture into this article.

On December 11, 2012 I charged this used Group 31 used house battery using my bench-top DC power supply. In the shop here we don’t use traditional smart battery chargers and instead we use lab-type variable DC power supplies with independent voltage and amperage control. For shop use I find they are more flexible, extremely accurate and they don’t drop to float prematurely.

Preparing a Battery For Winter Storage:

In order to prep this battery for winter storage, I first charged the battery to an absorption voltage of 14.8V. I then held that voltage and allowed the current to taper down to approx 0.3A, while maintaining the 14.8V absorption voltage. By monitoring the absorption voltage, as well as the net current flowing into the battery, we can use the tail current amperage to tell use when a battery is actually full. To use tail current as an indication of 100% SOC you want to meet two criteria:

1- Absorption voltage set to the maximum safe level for your battery (brand and model dependent)

2- *Absorption Voltage is held until the current flowing into the battery drops to less than 0.5% – 1.5% of Ah capacity (eg: 0.5A to 1.5A or less for a 100Ah battery)

*Premature Floatulation – Premature floatulation is a term I coined years ago for battery charging devices that drop to a float level voltage well before the battery is actually full. This is a chronic issue in the world of so called smart chargers. If tied to a dock all week long this is not a huge issue, and battery charger manufacturers count on this, as the duration you have at float, when dockside, will eventually get the battery back to 100% SOC. In a boatyard with an extension cord, while winterizing your vessel, you don’t have the luxury of time on your side to wait for a premature floatulation charger to finish the job.

It is critical however, when charging batteries for winter storage, that you do not confuse the 0.5% in amperage, or less, at FLOAT voltage vs. ABSORPTION voltage. Just because your smart charger has dropped to float  DOES NOT MEAN THE BATTERY IS FULL. Charging a lead acid battery to 100% SOC can take many, many hours and even the best AGM batteries can take in excess of 5 1/2 hours, at best, to go from 50% SOC to 100% SOC and this without premature floatulation. If the charger drops to float too early it can literally take days to get the battery back to 100% SOC. Putting a less than 100% SOC battery into winter storage is simply not good for the battery, Sadly, too many so called smart chargers drop to float well before the battery is actually full. It is up to you to ensure the battery reaches 100% SOC before winter storage and this can be measured by absorption voltage and net current. Please do not trust any Ah counter or other battery monitors SOC screen to tell you when you have attained 100% SOC.

“My battery maker says tail current should be 2% of Ah capacity at absorption voltage to determine 100% SOC?”

I am well aware of this, and it makes good  sense from the perspective of a large manufacturer not wanting to risk seeing their batteries chronically over-charged. What I can say, based on many years of physically testing marine batteries, is that I’ve yet to test any battery that suggests a 2% tail current, at absorption voltage, that can deliver 100% of its rated capacity.  2% gets close, and is far better than the point most smart chargers get to before dropping to float, but it does not result in being able to extract 100% of the rated Ah capacity. In the end it will have to be your decision as to when, and at what tail current, you deem your battery full enough for winter storage.

Pre-Storage Equalization:

In this image a customers Trojan batteries are getting equalized before winter storage.

If your batteries are capable of being equalized (EQ), and most AGM and GEL batteries *can not be by the typical “marine charger” definition (*exception Lifeline AGM’s), this is an ideal time to do this. Once the battery or bank has attained 100% SOC you can then start an equalizing charge cycle. It’s critical to not start an EQ charge before the battery is already at 100% SOC. An EQ charge should always be temp compensated to a voltage of 15.5V to 16.2V on the battery, based on manufacturer EQ specs.  Run an EQ for at least 30 minutes, even if the cells show good matching specific gravity, or as many as 2-4 hours if the specific gravity readings are off.

The equalization process is a controlled, low-current, high-voltage charge that helps to bring all cells to 100% SOC in order to minimize cell to cell imbalances. EQ can also help reconvert any recoverable lead sulfate and can also help to knock some of the dead lead sulfate off the plate surfaces and yield a healthier battery. If you have never done an equalizing charge please research how your battery maker wants it performed.

This particular battery had good specific gravity (SG) balance between the 6 cells so the battery was then equalized at a voltage of 15.5V for a short 30 minute blast. Fall equalization is a standard practice for me when winterizing flooded or Lifeline AGM batteries before winter storage. The first thing I set up on a fall winterization of a vessel is the bench-top power supply. I start charging first so that by the end of the days work the batteries are 100% charged and ready for isolation.

It is critical, before winter storage, to charge your batteries at the maximum allowed absorption voltage until current declines to 0.5% – 1.5% or less or rated Ah capacity. Following that up with short equalization, when applicable, makes the process truly complete.

Placing the Bank Into Winter Storage Mode:

With the charging steps completed your next step is 100% isolation of the bank from the vessel and any batteries they may be in parallel with. This means completely disconnecting the bank from the boat and then removing any parallel connections. Leaving the batteries in parallel or connected to the vessel is an not the best idea. Parasitic loads or a single bad battery can ruin the entire bank. Occasionally a micro-leak in a seperator can cause a very slow self discharge of a battery cell. If this battery is in parallel with the others it will also drag them down.

Winter Storage Process for Lead Acid Batteries:

1- Prior to charging flooded batteries inspect the electrolyte level in each cell. If plates are exposed add just enough distilled water to cover the plates. For most flooded batteries this is approximately 1/8″ below the bottom of where the “fill well” ends inside the battery.

2- Charge the batteries at their maximum safe absorption voltage until current declines to 0.5% – 1.5% of Ah capacity or even less.

3- After charging flooded batteries re-check electrolyte level and top up as necessary.

4- Check the specific gravity (SG) of each cell if possible (not possible for AGM or GEL).

5- If cells show a good SG balance run a short equalizing charge on them, but only after they have been fully charged.

6- If cells SG readings are slightly out of balance, run an EQ cycle until cell SG is equal or the SG stops rising in all cells.

7- Physically disconnect the batteries from the vessel. This is often easiest on the negative posts but on some boats positive is easiest.

8- Physically disconnect any paralleled batteries from one another.

9- Leave batteries on-board, less risk of injury or dropping a battery doing this. Alternatively, if in a warm climate, remove & store in a cool dry location.

10- In the spring, re-test the open circuit voltage of each battery before re-connecting the bank. The batteries should all be within a few mV of each other.

Into The Shed:

Once I was done charging this test battery I carried it out to the garden shed.  The shed is unheated and closely mimics the environment of a boat during winter storage here in Maine. I suppose I could have just carried it up the ladder, and into my boat, but no sense in breaking my back, the temps are the same.

At this point I took the first open circuit voltage (OCV) reading, about ten minutes after discontinuing the charge. It read 13.77V and represented a “surface charge” that had not yet dissipated. After a good equalizing charge surface voltage can remain high for a bit.

100% Bank Isolation Is Critical:

This is an image I sent to a customer who wanted to know how to isolate his bank for winter storage. In most cases, with a cleanly wired bank, it is easiest to simply remove the negative leads from each battery on the boat and then wire tie them close by. The wire ties ensure that the cable will not simply fall back onto the battery post or into the bilge where the owner may not find it come spring.

Batteries stored on-board should be:

100% Disconnected from the vessel

100% *Disconnected from each other

*For batteries normally wired in parallel

Merely charging your battery bank to 100% SOC, without physically disconnecting if from the vessel, is almost always going to lead to trouble due to parasitic loads. On boats these days, the number of always on device / parasitic loads has grown exponentially over the last 20 years.

• Electronic bilge switches
• LPG alarms/sniffers
• Stereo memory
• Battery monitors
• Solar controllers
• Bad battery in a parallel bank
• ACR’s/VSR’s/Combiners/Echo or Duo type chargers

These are just a few of the items that can cause a depleted battery bank come spring.

The Shed:

This is a shot of the shed with the battery sitting on the green box. The temps in here mimic that of a boat on the hard, in the North East, quite well.

“Won’t my battery self discharge if left off a charger all winter?”

Battery self discharge is directly related to battery temperature. Battery type also plays a role with AGM and GEL batteries self discharging at a slower pace than flooded lead acid. Nearly 97% of the AGM batteries I winterize are still sitting at or darn close to 13.0V come spring. Most flooded batteries I winterize also still have an OCV reading of 100% SOC come spring.

EnerSys, the manufacturer of the Odyssey TPPL AGM batteries, states that an Odyssey battery at 77F is designed to be stored for at least two years, but at 40F they can be stored as long as 4 + years. The colder it is where your boat is stored, the less self discharge there will be.

Cold weather, off-season, on-board storage of your batteries is considerably less damaging than is often purported to be. Even the ABYC, in its courses, is now advising proper on-board storage of batteries in colder climates. Done correctly you’ll actually minimize risk not enhance it.

December 14, 2012 – Resting Voltage:

I placed the battery in the shed on Tuesday the 11th of December and on Friday the 14th of December I remembered to take a voltage reading. As can be seen here the temp was 19F and the open circuit voltage (OCV), after 4 days, was still reading well above the 100% SOC point. After three days the battery still had a full surface charge.

This battery, when at full charge, with the surface charge dissipated, measures approx 12.72V . The cold Maine winter temps have not even allowed the battery to drop to a “resting voltage” over a period of four days.

February 26, 2013 – Resting Voltage:

OK so much for my “article”…. Yes, I promptly got ADHD and totally forgot about the battery in the shed until today. D’oh………. When I remembered about the lonely battery in the shed I shoveled a path through the snow and took a voltage reading.

As can be seen this battery is still resting at 12.72V/100% SOC after two and half months! It sat here from December 11, 2012 to February 26, 2013 and was still reading 100% SOC…. Ideally I wanted to get bi-weekly readings, but so much for that.

My point here is to illustrate why leaving your batteries on -board your boat, in the winter, does not lead to their instant demise, as many on the net would have you believe. My family and I have done this for more than 40 years and bank longevity has always been good. As a professional marine electrician I winterize a lot of boats & batteries and most owners choose the charge to full, EQ if necessary, and isolation from the vessel approach.

Is a broken back worth it?

Removing batteries from a boat is not fun work nor is it really even necessary in colder climates. Lugging batteries up and down ladders is also rather dangerous & means the risk of a broken back, hip, leg or other mishap could end your season or your entire sailing career. Some boat yards like to remove batteries because they can charge you for it. In many cases that is their only good reason for doing so. They’ll often disguise this menu added charge as “healthy for the batteries“. The other reason, and it is legitimate, is liability & insurance. Some marina insurance policies disallow on-board unattended charging so with the batteries physically removed the yard knows the batteries are in-fact disconnected and not charging on-board, and it gives them peace of mind.

Does battery state of health impact the choice to store on-board?

This particular Wal*Mart battery (actually made by US Battery Inc.) was still performing better than both CCA & MCA specifications based on both Argus and Midtronics conductance analyzers, but these tools only represent short term cranking capability not Ah capacity. How do those measurements compare to a true 20 hour capacity test? Before conducting this test, at the end of the batteries 5th year of service, I conducted a 20 hour Ah capacity test. The battery delivered 79.4% of  its rated Ah capacity. The battery had lived every winter on-board the boat, uncharged. While the battery is technically at end of life (EOL), based on *industry standards, the battery could still have been used for near coastal house bank use for perhaps one more season. The bottom line is that even when technically at end of life the batteries state of health did not impact its rate of self discharge over the winter.

*End of Life by Industry Standards – A lead acid battery that can no longer deliver 80% of its rated Ah capacity is considered end of life.

This battery was an inexpensive Group 31 “deep cycle” Wal*Mart stickered, automotive group type, but it had led a rather mild life in a system that was purposely designed for shallow discharges. Due to fitment issues a G-31 was the optimal group size to use, and the owner did not want to spend the money on AGM or GEL. As a result of the group type of battery chosen the system was designed & implemented for shallow discharges of 70% SOC/30% DOD as the deepest. This battery, labeled/stickered/marketed as a “deep cycle” is not a really a “deep cycle” product, it can certainly work well enough just for a shorter life than a deeper cycling product. For more on that subject you may want to read:

What is a Deep Cycle Battery?

Solar was also added so the battery bank could get back to 100% SOC after each discharge. Based on capacity testing results, I often see this same exact automotive battery group to be failing a state of health test in just 1-2 years, this one is at year five.

What about freezing?

A fully charged battery will not freeze until approx -70F. I lived in Alaska, Fairbanks to be exact, and they have been using flooded lead acid batteries up there since they were invented. In most parts of this country we will never see the -60F they see up there. In Fairbanks you can literally spit and have it hit the ground frozen, not so in the rest of the country. I have yet to see any fully charged, then 100% isolated battery suffer from freezing. I’ve seen plenty of non-isolated batteries suffer from freezing due to parasitic loads taking them to a low SOC thus allowing them to then freeze, but not properly decommissioned batteries. Charge to full then 100% isolation is key.

Unattended charging can actually create a higher level of risk!

In my experience, as a marine electrician, I find the practice of; charge to full then 100% isolate to be safer and more reliable than being left on a permanent float charge, while the vessel is in storage and unattended.

There is just too much that can go wrong leaving unattended batteries charging over the winter. I see far more ruined battery banks when the batteries are left charging, without any supervision than left charged to full then 100% disconnected. If you absolutely feel compelled to charge them in the cold season visit the yard and occasionally hit with some good “bubbling” voltage, then disconnect them again. When I say hit them periodically them with a good “bubbling voltage” this applies to flooded batteries where stratification can be a concern. A good gassing voltage of 14.6V to 14.8V will get the electrolyte moving and minimize any stratification going on inside the battery from it sitting idle.

In the video below I discuss one of the more dangerous failure modes for battery chargers. While a failure to regulate (limit) voltage is somewhat rare this does happen and can happen. This charger lost its voltage regulation circuit thus becoming a 20A constant current power supply with no voltage limit:

Again, please be very careful with unattended battery charging.

“What the heck is stratification?”

Stratification is when the acid and water begin to separate due to sitting idle. The acid sinks to the bottom and the water rises to the top. It’s a common misunderstanding that a constant float charge prevents stratification. Let me be quite clear on this float charging DOES NOT prevent stratification. A constant float charge voltage really does nothing to prevent stratification. Most so called “smart chargers” or “battery maintainers” will not prevent stratification of the electrolyte. Why? Pretty simple really float voltages are intended to prevent gassing and are usually far too low to keep the electrolyte moving and in a well mixed state. Push the float too high and we suffer plate decay/erosion, too low and it does nothing to limit stratification.. This gassing or movement of the electrolyte, at absorption voltages or higher, can help limit stratification but float does not.

Smart chargers that can revert to absorption voltages every few weeks can help roll the electrolyte and limit stratification, but these are rare. Sadly most “smart chargers” don’t do this and are not really as “smart” as they are marketed as. Most “smart chargers” are really rather un-smart and are nothing more than glorified egg-timer voltage limiters.

Still, leaving batteries charging and unattended all winter will more often, not less often, result in damaged or dead banks, the exact opposite of the intended goal.

• Power outages occur
• Cords get unplugged
• Breakers get tripped and not reset
• GFCI’s get tripped due to moisture or other boats on the load circuit
• Yard employees physically unplug your boat due to yard policy
• Battery chargers fail
• A battery internally shorts & forces the charger back to permanent or repeated absorption cycles drying them out and ruing them
• Etc. etc.

Many “smart” chargers & solar controllers, or any smart enough to even consider leaving connected full-time, while unattended, may not restart, by design, if the battery voltage gets too low. This is a built in safety/liability feature to prevent the charger from charging into an internally shorted/failed battery or bank. This well intended safety feature can mean the charger will not re-boot, after an outage, if the banks voltage has dropped too low due to parasitic loads. The usable capacity of all lead acid batteries is decreased when it gets cold, but the chemical reactions such as self discharge slow, so even a small parasitic load gets essentially amplified in cold weather.

Boat owners should also be aware that many cold climate boatyards specifically prohibit unattended battery charging, and for good reason, safety & insurance issues. Always ask your yard if it is okay to leave the batteries connected and the charger on. Even if they say yes, you are still putting your batteries at greater risk.

As I have seen far too often, power goes out or the solar panel becomes occluded in snow/ice and the parasitic loads, there are many these days, suck the bank down while the charger is off. The power comes back on, or the snow melts, but now the battery voltage has been sucked below the safe turn on threshold and the battery continues to discharge until fully dead. This is not as rare an occurrence as it would seem. Power has been out three or four times in the last month here in Maine due to winter storms. Will your charger automatically re-boot? I have also seen some chargers freeze and lock up due to power outages. Lights are on but the chargers is not charging and the batteries are now at a death voltage..

With a fully charged and 100% physically disconnected battery bank noting except time, temp or an internal defect can discharge it, and when it is cold, you’ve got plenty of time. If the battery has an internal defect, even a mico-leak/short in a plate separator, you really don’t want it connected to any charger or other batteries anyway.

Please don’t let this be you emailing me;

“Rod,

Towards the end of last August the three year old batteries on our Cape Dory stopped working. On advice of our yard manager we purchased new AGM batteries from them. To keep the batteries good over the winter I connected a battery tender maintainer. During the storage period may have been unplugged. Our three new batteries are now showing 1.94 volts. They are new just 8 months old do you think they can be salvaged to a workable degree? I can drive them up to you if you think you can save them. Please let me know how much a recondition service might cost.”

September 9th 2013 – Oh $hit………..

On the morning of September 9th 2013 I walked into the shed and realized I had set gas can in front of the experiment and had totally forgotten about it. That damn ADHD thing is a bear……..

What this means is the battery sat from Dec 11, 2012 to September 9, 2013 100% uncharged…… Head bonk….

I Swear, it Was Not Intentional………..

Upon re-discovering the test battery I immediately went to the barn and grabbed my volt meter, totally figuring this battery was a goner. It tested with an open circuit voltage of 12.54V! This OCV after sitting in a freezing cold, then blistering hot shed, throughout an entire Maine winter and now an entire spring and summer, I found pretty amazing.

Quite honestly I was a total disbeliever at the resting OCV of a flooded battery that has sat 100% uncharged for nearly 9 months. I then went and grabbed my refractometer and performed specific gravity checks on each cell. They all agreed and all agreed with the volt meter at the SOC. Holy freaking cow, not too bad!

Not that this was intentional but it does cause me to wonder why there is so much concern around self discharge, especially over the winter, where we know it is slow to almost nil? I have to assume that perhaps 20-30 days of the 2013 summer saw the shed temps well over 110F. The shed is not insulated and has a black asphalt roof. It gets very warm in there. The tested OCV (open circuit voltage) and SG readings (specific gravity) put this battery at approx 90% SOC after no less than 9 months of sitting there uncharged.I would expect this for GEL or AGM but I did not expect it for a five year old flooded battery.

Interesting n=1 data, to say the least……

This mishap though did give me a great opportunity to charge, equalize and re-test this battery for Ah capacity. I would have guessd it to loose on the order of at least 5% due to the summer heat but it did not.

After bringing the battery back into the shop I  performed an equalization, then a few deep-cycles to 11.7V followed by full recharges. These back to back deep cycles followed by full 100% recharges can tend to re-open some pathways through the plates.  I then conducted another 20 hour capacity test on this battery.

It completed the test delivering 78.8% of the 20 hour rated capacity.

If you were paying attention early on in the article, this 5 year old battery had previously tested at 79.4% of rated Ah capacity. After sitting for nine months, through a full winter and then a hot summer in my shed, the battery lost only 0.6% of its previous tested Ah capacity. Batteries sometimes surprise me and this case is certainly one of them? My suspicion is that if I had tested it in April, when I had intended to, I would have seen minimal to no loss in Ah capacity. I further suspect the summer heat is what really caused this minor loss of capacity.

Considering this battery sat uncharged & untouched through an entire winter, spring and summer in Maine, I find that pretty darn amazing and this is not what I would have predicted at all. I honestly have no good explanation for how the summer heat in that shed did not eat more capacity of this battery. Perhaps the fact that late afternoons, evenings & mornings are often below 70F helped? Perhaps the thermal mass of the battery did not allow it to warm to ambient shed temps during the sun up hours at the same rate as the shed? I would have thought the stratification alone would have damaged it slightly, but maybe the winter hibernation helps inhibit the negative effects of stratification too? Certainly interesting results but I would not advise letting your own batteries sit like this for 9 straight months.

What about owners that haul out for storage in the hot summer months?

This is a different ball of wax from cold weather storage. As we know heat increases self discharge and shortens battery life. My answer to these owners is to very carefully remove the batteries from the vessel, use your boom and rigging as a crane if you need to, then charge them to 100% SOC then store them in the coolest location you can find.

Good luck and happy boating!

Battery After 20 Hour Capacity Test = 95.69 Ah Capacity

For this test I wanted to:

• Show the relationship of loaded voltage to SoC on a popular AGM lead acid battery.
• Utilize a battery not in perfect health to represent real world.
• Show why using a generic voltage to SoC chart may not work for your battery bank.
• Show the actual rebound voltage after discharging to 50% SoC under controlled conditions.

Customers SoC to Resting Voltage Chart

This image is an epic fail on our customers part, despite his very good intentions.

He located this voltage to SoC chart on the internet and I discovered it on his chart table. He was using it with resting voltages not under-load voltages as this chart was likely developed from. His battery bank was comprised of the identical battery being tested here.

If we cross reference this chart to the 20 hour discharge rate, under-load voltages, in this test they line up pretty closely but if using a chart like this for a RESTING VOLTAGE you will essentially be murdering your batteries.

Chart Resting Voltage              Actual Under-Load Voltage
90% 12.75V                                                      12.55V
80% 12.50V                                                      12.50V
70% 12.30V                                                      12.37V
60% 12.15V                                                       12.24V
50% 12.05V                                                      12.11V

Please be aware that some charts on the internet are for resting voltages. A resting voltage is 12 – 24+ hours of no loads or charging at 77°F. The “at 77°F” is absolutely critical because at temps above 77°F surface charge dissipates more rapidly and at temps below 77°F the surface charge dissipates more slowly.

As I type this I have a fully charged AGM battery in my storage barn that has been sitting 100% disconnected for well over a month, and the resting voltage is still 13.12V. Why? The battery temp is close to 40°F  right now and has not been much above 45°F since I set the battery in storage. I know this battery will rest at 12.93V once the surface charge has dissipated, but at 40-45°F this can take weeks or as long as a month or more.

Voltage to SoC Charts:

A Voltage to SoC chart should only come directly from the manufacturer of your batteries, or through physical testing of your own batteries, as I have done here. You should avoid the use of use generic charts off the internet. Why? Because every battery manufacturer will have a slightly different voltage performance curve under load. Deep Cycle AGM will be slightly different than dual purpose AGM or TPPL AGM or GEL or flooded etc..

Some charts you find on the internet do represent a “resting voltage” , but you’ll also find some for a 20 hour discharge rate or an under-load voltage. If you’re using voltage as an indicator of SoC, the rate of discharge, as well as battery temperature, can also affect your SoC to voltage points. Cyclic On/Off loads, like we have on a boat, can also tweak this relationship. Using the wrong Voltage to SoC chart only exacerbates issues related to using voltage for SoC estimation. Using the wrong chart can actually accelerate the murdering of your batteries.

Voltmeters:

On top of using an incorrect Voltage to SoC chart, using an inaccurate voltmeter or one connected or voltage sensed in the wrong location can also impact you negatively. Always use a good quality, known accurate voltmeter that can display out to the hundredths position, not just the tenths position. For example, a voltmeter that only reads 12.1 volts gives too little information. A voltmeter that can read 12.15V, or adds the hundredths of a volt position, will give you far better trend information. The voltmeter should have both it’s negative lead and positive lead directly sensing/measuring the house banks physical battery terminals, or within a few inches of the bank on a distribution bus fed by large gauge wire. Sensing voltage anywhere else in the system can lead to erroneous voltage readings due to circuit voltage drops.

95% SoC – 5.25A Load – Volts =12.59V

The battery used in this test is a very popular AGM, a Lifeline GPL-31T.

It is factory rated at 105Ah, at the 20 hour discharge rate, but this particular battery, off my brothers boat, was used and only capable of delivering 95.69 Ah’s. I chose this slightly used battery to represent a more “real world” scenario. A 20 hour discharge rate is simply:

Ah Capacity ÷ 20 = X

For this 105Ah rated battery the 20 hour discharge rate looks like this:

105Ah ÷ 20 = 5.25A

Despite the slightly diminished capacity, 91.3% of the factory rating, I chose to keep the discharge rate at 5.25A at a controlled battery temp of about 76.4°F. Ideally I would have liked to have spent the time to figure out the new 20 hour discharge rate but this entails numerous tests to 10.5V and was not critically necessary for this experiment, as no boat owner will ever do this.

The 5.25A discharge rate is slightly higher than what this battery can actually deliver for 20 hours, but close enough to make the points I wanted to share here. Perhaps less than .02% of boat owners ever test their batteries for actual Ah capacity, so using the 20 hour rate on this battery is still quite realistic.

For a 20 hour test, or to see where your bank stands against how it is rated for Ah capacity, a 20 hour SoH (state of health) discharge test is performed. To perform a 20 hour test the battery is first charged to 100% SoC and then it’s allowed to rest for 24 hours. It is then discharged at a constant 0.05C discharge rate or Ah ÷ 20= X to a terminal voltage of *10.5V. The Ah’s or time at discharge rate is then calculated to show the percentage of the rated Ah capacity the battery could deliver at its current SoH. A discharge rate of 0.05C is equal to 5% of the batteries 20 hour rated capacity so 5% of 105Ah is 5.25A.

*Assumes a 12V battery. During a 20 hour Ah capacity test the battery is discharged to 1.75V per cell.

On a cruising boat the battery bank would be considerably larger and a 20 hour discharge rate, at bank level, would look like this:

• 200 Ah Bank = 10A Discharge Rate @ 77°F
• 300 Ah Bank = 15A Discharge Rate @ 77°F
• 400 Ah Bank = 20A Discharge Rate @ 77°F
• 500 Ah Bank = 25A Discharge Rate @ 77°F
• 600 Ah Bank = 30A Discharge Rate @ 77°F

90% SoC – 5.25A Load – Volts =12.55V

In this image the battery is at about 90% SoC with an under-load voltage of 12.55V.

On a 400Ah bank this would be a 20A load in order to see this voltage at 90% SoC.  If you were discharging at 8A and saw 12.55V you would be at a lower SoC than 90%.

85% SoC – 5.25A Load – Volts =12.52V

Here we are crossing the 85% SoC mark at 12.52V. As cruising boaters the average discharge rate is almost always far lower than the 20 hour rate, and should be lower.

A typical cruising boat with a 400Ah bank will be discharging, on average, somewhere in the 5-6A range if averaged over a 24 hour period. Your under-load voltages should not drop this fast with healthy batteries. Conversely your SoC to loaded voltage will also not be the same as here. At the voltages to SOC show here, your SoC will actually be lower when discharging at a lower discharge rate. The reason for this is due to the Peukert Effect or what some call Peukert’s Law.

80% SoC – 5.25A Load – Volts =12.47V

Here the battery at about 80% SoC under the same continuous 5.25A load, and we are at 12.47V.

Voltage can be used as a guide for SoC but you really need to know the voltage performance of your battery bank, against a known discharge rate, and it takes work to figure this out. Of course once you’ve figured it out,  the voltage behavior under-load will change on you as the batteries age.

There is also another gotcha in the mix that I should mention. Loads that cycle on and off give the battery rest periods which also change and modify voltage performance at XX load. If your loads cycle on and off, and you choose to use voltage for SoC, you may be over-discharging your bank and never even know it.

This is why a generic *OCV to SoC chart will rarely help the average boater, and often serve to actually help prematurely damage the batteries.

*OCV = Open Circuit Voltage Reading

75% SoC – 5.25A Load – Volts =12.42V

Over the years I have realized that most boat owners drastically over discharge their battery banks when using voltage as a predictor.

In a recent battery use survey on SailboatOwners.com there were over 1000 responses, of which 98.4% were from sailboat owners. The survey was about marine battery use. Of those 1000+ responses, 1188 to be exact, 72.42% of respondents regularly discharged the bank below 12.1V. As Homer would say…. D’oh!!!!!

What’s bottom line with lead acid batteries?

Even at your average house loads the terminal voltage should not be dipping below 12.1V, when discharging at the 20 hour discharge rate.. That is if you expect any sort of decent cycle life from them. As you will see in this experiment, under a 5% load to Ah capacity discharge, 49.3% SoC is achieved, under load, at 12.10V. Most boaters however don’t discharge at the 20 hour rate, so read on.

70% SoC – 5.25A Load – Volts =12.37V

Here we are at 70% SoC and 12.37V.

Compare this to the chart from above at 12.30V that our customer was using as a resting voltage chart. This is not a resting voltage, it is an under-load voltage, and the battery has been under a constant 5.25A load now for nearly five and a half hours straight. If you were expecting a 12.30v resting voltage to represent 70% SoC, you are now way below 70% SoC…. Oops…..

65% SoC – 5.25A Load – Volts =12.30V

65% SoC under-load voltage = 12.30V.

60% SoC – 5.25A Load – Volts =12.24V

60% SoC under-load voltage = 12.24V…

55% SoC – 5.25A Load – Volts =12.18V

55% SoC under-load voltage = 12.18V…

50% SoC – 5.25A Load – Volts =12.11V

Here we are at 50% SoC, based on the -Ah removed from a baseline, under a capacity test.

It took approximately 9 hours at a 5.25A load to get to 50% SoC and the under -load voltage is still 12.11V. To put this in perspective, when this battery was discharged at 2X – 2.5X your average cruising boat house loads, the bank is crossing the 50% SoC threshold at approx 12.1V. This means on your average bank you had better be discontinuing any discharging at somewhere around 12.15V to 12.2V+.

If you expect or plan to use voltage as your indicator of SoC, and as an indicator of when to re-charge, I would strongly urge you to begin recharging at a maximum under-load voltage of 12.1V. You will be far better served to begin recharging at 12.2V or greater because your average discharge rate will be lower and you will also have cyclic loading of the battery which can artificially inflate a Voltage to SoC reading.

If your average house loads are a lower average load than the 20 hour discharge rate,  you will be better served to begin re-charging at a low of 12.15V – 12.2V+, in order to get the best cycle life from your bank.

49.3% SoC – 5.25A Load – Volts =12.10V

Here’s why I suggest you begin recharging at 12.15 -12.2V because at 12.1V this battery is already at 49.3% SoC while being discharged at 5.25A at 76F.

Resting Voltage – Approx 16 Hours @ 49.3% SoC @76°F = 12.32V

In this image the battery is at 49.3% SoC based on removed ampere hours.

The resting open circuit voltage has rebounded to 12.32V. If you had been using our customers chart for resting OCV you would have mistaken 49% SoC for 70% SoC and kept on DISCHARGING the bank. Ouch!

With this test it’s easy to see how battery assassins commit battery murder without even being aware of it. Please understand and use voltage for SoC very carefully. Also, keep in mind that as your batteries age they will cross a voltage threshold differently than they did when new. The only way to know this performance is to physically test for it.

For most boat owners we strongly recommend using a self learning battery monitor, for SoC, such as the  Balmar SG200

Points to Ponder:

• Always get your Voltage to SoC data directly from the physical manufacturer of your batteries, not from the net.
• Make sure you know what your voltage to SoC chart represents; eg: “resting  voltage” or  “under-load voltage”. They both exist and are not the same.
• Study and learn your batteries voltage behavior, under your average on-board loads. Run experiments if you need to.
• Use a known accurate voltmeter that displays to the hundredths position.
• Your voltmeter should only sense voltage at the battery bank terminals.
• Discharge rate affects your Voltage to SoC relationship.
• Cycling discharging affects your Voltage to SoC relationship.
• Battery temperature affects your Voltage to SoC relationship.
• Aged batteries affect your Voltage to SoC relationship
• As your batteries age the voltage behavior will also change.
• Battery temperature directly impacts the time it takes to attain an accurate resting voltage.
• Keep it simple, don’t discharge your Lifeline AGM bank below 12.15V to 12.20V even under your average house loads.
• Recharge your batteries to 100% SoC as soon as possible after each discharge.

Good luck & happy boating!

Note The Melting of The Battery Case

(originally published July 2012)

The connections to your batteries matter. How you make them, how you torque them and how clean they are all matter. Not following best practices or marine wiring standards can impact your personal safety.

While doing a winterization, and getting ready to equalize these batteries, I noticed something strange that I could not really put my finger on, then it hit me.

The battery case around the positive post was melted and uneven looking. When I grabbed the positive battery cable it was physically able to twist on the post with just minimal pressure.

Upon closer inspection it was apparent that the battery terminal had gotten so hot that it began melting the plastic of the battery case.

Why? Read on…..

The Nyloc Nut Still Had Plenty of Resistance & “loc”

I am not one of those marine insiders who is in the camp of “Nylocs are bad on battery terminals“. This example showed that the failure mode was not in-fact the Nyloc nut. I could not back this nut off with my fingers, even after it was loosened with a wrench. The plastic battery case melted well before the Nyloc failed to “loc” / lock.

Battery cases are made of polypropylene and Nyloc nuts are made of nylon, which has a higher melting point than the battery case does.

I do prefer to see a locking washer on battery post studs but sometimes they simply don’t fit, where a Nyloc may. In either case the nut must be properly torqued to battery manufacturer specifications, this nut was not.

The nut coming loose or vibrating loose was not the problem or the root issue here. This problem was simply poor installation practices.

The issues were:

#1 The Nyloc nut was not correctly torqued and showed clear evidence of pliers or another unsuitable tool being used for tightening.

#2 The lug had a SS flat washer placed under it. A SS flat washer should never be inserted between the lug and battery terminal. It is perfectly okay to use it under the nut, but it must remain on top of the lug & never underneath the lug.

The ABYC Standard that covers this:

Below: The correct installation sequence for a battery lug. A washer never goes between the lug and battery .

Why no Stainless washers between the lug & battery?

Below is a chart showing the conducting properties of varying metals. As can be seen, stainless steel is a very poor conductor.. A stainless washer creates high resistance, which leads to heat..

Holy meltdown Batman

This image represents the inherent failure potential when we connect our battery banks to high current devices such as large inverters, alternators or large inverter /chargers and we slap a washer in between the battery and the lug.

Image courtesy Heritage Marine Electrical

Nyloc Nut Deep-Dive….

I hear and see it stated quite frequently on the interweb not to use Nyloc nuts on batteries. The supporters then trumpet this around thenet as fact without doing any sort of critical thinking. Unfortunately they line up to defend this sentiment without doing any sort of research or examination of actual facts. Okay fine, it’s the interne. Let’s examine this a bit..

Safe Working Range vs. Melting Point

The Nyloc nutswe  use at Compass Marine Inc. are rated to 140C for the safe working range or “operating temperature range”. This is 284F.. If your batteries get to anywhere close to 284F you have other major issues to deal with! To put this into perspective, even the best marine UL 1426 battery cable is rated to just 105C or 221F. Sadly there are still thousands and thousands of boats out on the water, built in the 70’s & 80’s, using 60C / 140F rated battery cable, sad but true. If the Nyloc in the nut will melt and cause a failure then I suppose we may all need at least 140C rated marine wire too?

Of course we can’t just look at the safe working range if we want to see the point where an actual total failure might occur. Where would that likely occur? Probably somewhere well above the 284F safe working temp and closer to the melting point for the nylon 66, which is used in Nyloc nuts.

The actual melting point of the nylon 66, used in Nyloc nuts, is 515.9F. For examination purposes however, we can still use the safe working temp of 140C/284F.  What if you have soldered battery lugs? If you do, it is quite probable that you have a solder that actually melts at a lower temp than Nylon 66 does.. Yes, you read that correctly. Many electrical grade solders melt at a lower temp than the nylon used in a Nyloc nut does.

The point here is that the ABYC standards still allow soldered on battery lugs (with no mechanical connection eg: crimp) and the solders above are very typical of electrical work such as soldered on battery lugs..

Battery Case Melting Point?

What about the plastic used in the actual battery cases? Lead acid battery cases are made of polypropylene (PP), not nylon. Polypropylene (the battery case) actually melts at around 189F lower than the nylon 66 in the Nyloc nut does. We are seeing exactly that right here in this case. The Nyloc nut survived with plenty of locking still intact, yet the battery case had begun to physically melt.

I suppose we’d best get rid of those unsafe plastic battery cases and replace them with STEEL… Oh wait steel & acid, hmm better think this one through a bit more……..?. (grin)

What fasteners do battery makers ship batteries with?

Let’s also look at the way the vast majority of batteries for marine use actually ship to us? An insanely large percentage of “marine batteries”, even today, and our business installs hundreds of batteries still ship with hex nuts but, no locking washer. Yes, you guessed it, there is no lock washer to be found with many of the marine battery brands. Heck, there are still some brands shipping with wing nuts and no locking mechanism what so ever. The ABYC actually disallows wing nus for batteries using 6 AWG or larger wire.

Exide Marine Battery:

East Penn / Deka Marine Battery:

Exide and East Penn/Deka/Duracell (East Penn licenses the Duracell name) own a huge percentage of the marine market yet neither bothers to ship any locking mechanism. How is it that replacing a standard hex nut (no washer) with a Nylock is “worse” or “less safe”, than what these manufacturers ship batteries with? The answer is clear, a Nyloc nut would be safer than just a hex nut. I agree that these SS hex nuts are far superior to “wing nuts” but cutting corners on a locking mechanism is just poor form. I have many other images of “marine batteries” that do not ship with locking washers but, I won’t boor you. The way most batteries ship, without any locking washers, your failure mode is just one failure point, improper torque. Add a Nyloc and you now need two failures before anything bad could happen. Add a locking washer on top of a Nyloc and now you’d need three failures.

There are however a good number of premium battery battery makers, who actually do supply locking washers, such as;

• Odyssey
• Northstar
• Firefly
• Victron
• Full River
• Rolls
• Lifeline
• Mastervolt
• Lithionics

Plus just about every LiFePo4 prismatic cell manufacture I know of. All the batteries brands I just mentioned can deliver MASSIVE amounts of short circuit current into a dead short.

How many installers or folks that DIY do you suppose add any locking washer or Nyloc nut beyond what the battery manufacturer supplied the battery with? From our observations, as a marine electrical business, I can say that this number is about as close to 1% as it gets. A nut only may be okay, if the nuts are properly torqued, (each manufacturer provides a torque spec), the cable is properly strain relieved, and the battery physically can’t move, but I rarely see that. The ABYC standards actually allow for batteries to move slightly, up to 1″, and this is why some level of locking is considered a best practice.

A Simple and Honest Question:

Would using a Nyloc nut be worse than what many battery manufacturers shipped the battery with, if it’s a plain hex nut or wing nut?

Answer = NO! Adding a Nyloc is a level of safety beyond a standard hex nut or wing nut.

In this melted battery case, the Nyloc nut was still well “locked“, despite the battery case physically melting due to high resistance. I’d have to vote for the Nyloc certainly being better than no locking mechanism at all.

Why does all this matter?

Before your Nyloc nut can melt, the battery will have likely already begun to melt, as it did here. Even if you somehow exceeded the 284F, and and your battery has not exploded, and the Nyloc nut failed to perform its locking feature, this can only be considered a secondary failure when compared to what most batteries ship with. Before we can even get to a Nyloc failure, we would still need to have a primary failure or a nut torque failure first.

In this case we had a primary failure mode, lack of proper nut torque, which lead to high resistance and then to the battery case melting and the heat shrink melting. A physically melted battery case, and the heat shrink melted and yet a secondary failure of the Nyloc nut still did not occur.

We would need two failure modes to have the actual failure of a Nyloc nut. A melted Nyloc and an improperly torqued nut to begin with. Based on the factual data, including melting points, this suggests that before this Nyloc nut would have failed the battery case would have been so melted the owner would have been alerted to something, such as a fire or acid all over his vessel, well before the Nyloc nut became an issue.

Items That Melt Before the Nyloc:

– The battery Case
– Heat Shrink
– Solder
– Wire Jacket

But the Nyloc is the one that gets the bad rap by “docksperts”(dock experts)on the net??

In our business we see thousands of battery posts every year with no locking mechanism. Do we carry lots of 5/16″ and 3/8″ lock washers and 5/16″ and 3/8″ nuts,  & wire ties, you bet we do. We also however carry a lot of 5/16″ and 3/8″ Nylocs too and in cases of short battery posts, such as Trojan batteries. We also carry flanged self-locking nuts also called Wizz nuts. We go through multiple boxes of 100 each of lock washers and Nyloc 5/16″ and 3/8” nuts every year.
My personal preference here is to use a locking washer when ever I can, but when it won’t fit, I have no issues using a properly torqued Nyloc nut on a battery terminal.

Why Do Battery Manufacturers use Stainless Nuts and Posts if Stainless Steel is a Poor Conductor?

The answer to this is simple. The connection to the battery is between the lug and lead not the SS fasteners or SS posts. The nuts and posts are only there to provide compression and resist corrosion. Stainless is a fine solution to accomplish this.

How often do I see regular hex nuts, like price-point sensitive battery manufactures ship the product with, that lack a locking washer, actually come loose? Not all that often but, I do see it.. When I do, there are often signs or evidence they were tightened by a pair of pliers, as was  the case here.

When tightened with a wrench, & properly torqued, it’s actually pretty rare to see a loose standard nut, even without a locking washer, come loose. When I do see this the battery installation has been sloppy, allowed too much battery movement and had sub-optimal strain relief for the large gauge wire. The key words are “properly torqued“. Properly torqued is the reason the ABYC, USCG  & marine industry has moved away from allowing wing-nuts.

Boat owners and sloppy marine techs far to often opt to not to use a wing nut wrench or pliers to apply the proper torque. They improperly believe proper torque means with thumb and fore finger. It’s simply not possible to properly torque a wing nut with your thumb and fingers. It is also not advisable to torque standard nuts with a pair of cheap pliers. Would you torque your vehicles lug nuts with pliers………..??

I can personally point to numerous instances of loose wing nuts, but not a single case where a Nyloc came free because it melted and then vibrated loose. In almost every case of a wing nut coming loose it was because the installer made the nuts “finger tight” which is a far cry from properly torqued..

It’s also interesting to note that the ABYC safety standards specifically prohibit wing nuts above 6GA wire but they make no such prohibition for Nyloc nuts.

My only point here is to suggest that I would prefer to see a Nyloc used rather than the option of a regular nut with no lock washer or a wing nut with no lock washer. My first preference, if it will fit the post, is for a Nyloc nut and locking washer, second choice would be a hex nut with lock washer, as many premium battery makers ship with. A Wizz nut would be a third choice. The fourth choice a regular nut without a locking washer. All of these choices, of course, properly torqued.

Unfortunately, there are situations where a regular nut height, or even a half-height nut is all that will fit on the post & Trojan Battery is notorious for supplying extremely short posts. In this case proper torque and the use of a Wizz/Serrated Flange Nut nut is a must. A standard Wizz nut is the same height as a standard nut but has a built in serrated locking washer.

CAUTION: Using Wizz nuts for batteries that will be decommissioned each winter can reduce the thickness of the lug over time. The reversing of a properly torqued Wizz nut causes copper and tin plating on the terminal to be removed more so than that of a standard locking washer/flat washer combo or a Nyloc/flat washer combo. You can out a flat washer under a Wizz nut but the entire point of a Wizz nut being used is due to a lack of battery terminal height.

Rant officially over…. (smile)

It Actually Got Hot Enough To Melt The Heat Shrink

This lug got very, very hot, hot enough to physically melt adhesive lined heat shrink. Even my industrial grade Milwaukee heat gun has never melted heat shrink like this.

It should also be noted that this battery was protected by a 200A ANL fuse. The fuse and holder are perfectly fine and never blew. Why? Fuses won’t and can’t protect against high-resistance which is what caused this situation. A high-resistance situation can start a boat fire at well below a fuses trip rating.

Huston, We Have a Problem…!

Here’s the other half of this problem. The first half was caused by improper torquing of the Nyloc nut with pair of pliers. Please DO NOT use pliers to tighten and torque battery terminals.

The second problem arose because the person who connected these batteries left the flat SS washer on top of the lead battery post. This means the SS wahser was sandwiched between the lug and the lead of the battery post. Stainless steel is a horrible conductor, one of the worst.

In battery installations flat washers should never be placed between the lug and battery post. They can only ever reside on top of the lug compressing it not being compressed.

Here’s the relevant ABYC standards from E-10 Storage Batteries:

“10.8.3 Battery cables and other conductors size 6 AWG (13.3 mm²) and larger shall not be connected to the battery with wing nuts.

10.8.4 Multiple conductors connected to a battery shall be installed with the highest ampacity conductor terminal closest to the battery, followed by successively smaller ampacity conductor terminals.

10.8.4.1 A maximum of four conductor terminals shall be permitted to be installed on a single battery stud.

10.8.5 Flat washers, if used, shall only be installed immediately under the split lock washer and nut of the attachment stud.”

The Case & Post

Here’s another shot, and close up, of the melting of the plastic case around the positive post. This battery will now be retired because its ability to hold electrolyte may have been compromised. We have no way to see inside, to inspect actual damage to the electrolyte post seal, so as a safety precaution this battery will be recycled, even though it still tests fine. Sad really.

If you click on the photo, and look closely, this terminal does not appear to have been cleaned before the terminals were re-connected in the spring. There are signs of “hot spots” in the lead and what appears to be some melting close to the stud too.

This termination point was creating tremendous resistance and lots of heat thanks to a combination of not just one, or two terminal installation errors but a third as well. The third failure mode here is that poor cleaning and housekeeping of the terminals themselves was evident.

Another View

Here’s another view of the physical melting, of the battery case, around the base of the post. It should not look like this. Issues like this can start small but can quickly  become quite problematic, especially if left unchecked.

Please keep a watchful eye when connecting and disconnecting your battery banks for anything unusual.

I apologize for the poor quality photos. The lighting on this boat was rather pretty poor.

Lock Washers

This particular battery is an extremely high current capable AGM variant called TPPL or thin plate pure lead. This Odyssey, a single group 31, can deliver 5000A of current into a dead short. You really don’t want your connections loose on a battery like this. EnerSys, the parent company of Odyssey, thinks it’s important enough to include a “locking mechanism” or lock washer with their product as do many other premium battery manufactures. In this image the kit is still taped to the battery as it shipped.

Trojan Battery Document

This image is from a document I received at a Trojan Battery training seminar at a solar conference. In this document Trojan is saying exactly what myself and the ABYC standards say. You can not place a washer between the lead or brass battery terminal and the cable lug because it creates a high resistance point which can lead to a melt down.

Also note where Trojan Battery is showing the use of lock washers despite only currently including washers with their Reliant AGM batteries. Perhaps the lack of a locking washer, on some of their flooded products, is due to the “shrinking post syndrome” some of their batteries have been suffering from that feature the ELPT (embeded low profile post) terminals.

In this image and illustration we can actually see where the ABYC weighs in as highlighted in yellow.