LiFePO4

Photo: The cells were very well packed and got here in great shape.

The Li-Ion chemistry chosen for this bank is called lithium ferrous phosphate, LiFePO4 or LFP for short. There are a few variations on this chemistry such as LiFeMnPO4 & LiFeYPO4 but the end result is still essentially an LFP bank that has the same inherently safe characteristics. For this build I chose four 400Ah Winston LFP prismatic cells, and the bank is set up in a 4S or 4 series cells configuration.

What the heck is 4S?

4S just means four 3.2V cells in series to make a 12V nominal pack. The pack/bank is really closer to a 13.3V pack as the resting & nominally loaded cruising voltage of these cells is around 13.2V – 13.35V.

If you want to do other than a 4S configuration the cells are typically connected in parallel first and then in series. Parallel first is done so that you only need to monitor 4 cell voltages for a 12V nominal pack. The parallel cells stay naturally balanced which means a less expensive BMS can often be used. If you were to choose series-first you would require more cell level monitoring. The nomenclature system you will most often see for a 12V nominal house bank is as follows;

4S = Four Series Cells



2P4S = Two Parallel Cells / Four Series Cells



3P4S = Three Parallel Cells/ Four Series Cells



4P4S = Four Parallel Cells/ Four Series Cells

etc. etc..

There are many ways to configure LiFePO4 Cells in series or in parallel/series. When possible, I tend to prefer the simplicity of a 4S configuration, if that cell size works for the desired Ah capacity. 4S requires less overall connections and less work when doing cell balancing. Some would argue that if a cell is ruined with a 2P4S bank you could re-wire it and use the remaining cells. At sea? While anything is possible, I personally prefer the simplicity of a reserve or start/reserve lead acid bank as opposed to a complete LFP re-configuration at sea. A lead acid reserve bank or start/reserve allows you to take the LFP bank off-line while addressing any potential issue. Rewiring & re-balancing an LFP bank at sea is not a task you’d ideally want to perform.

LiFePo4 Battery Bank Type Definitions:

Factory Integrated Lithium-Ion Battery – A lithium battery designed to work as a factory integrated system including the charge sources

System Integrated Lithium-Ion Battery – A lithium battery system with the capability of system interaction/communication with external charge sources, vessel loads, alarms or safety systems.

Drop-In Lithium-Ion Battery – A self-contained lithium battery, with or without an integral BMS and contactor/s, which lacks external system communication with charge sources, vessel loads, alarms or safety systems.

Examples:

Factory Integrated Lithium-Ion Systems – Victron & Mastervolt are about as close as it gets because they sell both the charge sources and the LFP batteries as a factory integrated system.

System Integrated Lithium-Ion System – Lithionics ex: Genasun & well executed DIY – Designed to work with third party products and can communicate with them.

Drop-In Lithium-Ion – If the internal BMS is sealed, and the battery can’t tell an external charge source when to stop charging or a load to stop discharging, then this is considered a drop-in battery. Whether or not a drop-in batteries are well suited for your use will depend upon many factors.

There are three basic options of getting LFP on your boat, with DIY being the least expensive, and most technical. The categories are:

DIY Builds:

This is a real cost saver but is not for the faint of heart or the limited skill DIY’er. In a DIY build you source the cells, confirm the cells are well matched for Ah capacity, choose all the components, choose the BMS, design the system schematic, choose the high voltage cut and low voltage cut relays, main contactor, wire and assemble everything, balance the pack and chose chargers, solar or alternator regulators that can be programmed to suit LFP. A well executed DIY build, and there are many of them out there, is a a time consuming project. If you have the gumption to forge ahead, it is method that can save over 50% of the cost of a factory made bank.

Marine Specific Factory Made LFP Systems:

Lithionics/OPE-Li3, Victron & Mastervolt all build LiFePO4 batteries for marine specific applications. These systems are well engineered, well executed yet also at or near the top end of the pricing spectrum. You do however tend to “get what you pay for“. If you want LFP and don’t have the ability to DIY, of these three companies I can certainly recommend the Lithioncs/OPE Li3 system. The Lithionics/OPE Li3 battery system at the top of the list for us and checks every box for a marine specific application. I personally have the most experience with Lithionics, Genasun (now defunct) and Mastervolt marine LFP systems.

What About Drop-In LiFePO4 Batteries?

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. 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 315Ah Lithionics GTX12V315A 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 rebranding/sticker application brands are buying from the same exact Chinese factories. Unfortunately, the reputable part is harder to guarantee than one might imagine.

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 industry. The demand for this type of battery, especially in third world countries, is absolutely staggering.

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 industry. For boaters this can mean the low-grade “orphaned” or “rejected” cells wind up in batteries that may look the same but are sold on Ali-xxxx, eBay or through other less reputable sources.

Sadly Ai-xxxxx has literally become a 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. Frustrating? You bet it is.

Drop-in batteries will be a huge part of the future of LFP, and there are currently a few good manufacturers working to improve the marine specific shortcomings but, in my opinion, many of them are still not prime time ready, so purchase carefully. At this point in time there are only two LFP drop-in batteries I can personally recommend;

#1 Lithionics G125 & G315

#2 Battleborn/Dragonfly Energy

Drop-In LiFePo4 – Things to Consider:

#1 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. This is part of the “marine specific engineering” I mentioned. 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, windlass’, large inverters, electric winches, 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, one of the biggest currently available, 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. 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 is.

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

Compare that to many of the drop-in batteries being sold out there which have very low-current handling capability due to the use of FET based switches. The manufacturers building “marine specific” LFP batteries know what a cruising boat needs in terms of current handling and they engineer this into the product.

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 Blue Sea Systems ML-RBS 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 limited by the cells but rather the internal BMS’s current handling capabilities.

Companies that are re-stickering, what are essentially streetlight pole batteries, as “marine grade“, do not use heavy duty contactors inside these batteries. What you’ll often find is a diminutive 100A continuous rated FET switching BMS installed inside a 300Ah LFP battery. This may be fine for small boats with small loads, but if you have large on-board 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.

When it comes to FET based BMS batteries we always advise smaller individual batteries, in parallel, 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. A 300Ah 8D format drop-in, like the one addressed below, can really only handle a 50A (0.17C) charge and a 100A (0.33C) discharge. When in doubt with FET based BMS systems smaller batteries in parallel are a better solution than one large battery with a low current rated BMS.

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 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 format, the claim that it was an exact drop-in replacement for his lead acid 8D battery, and the 300Ah capacity rating.

He felt comfortable because it was, what he considered, a “reputable manufacturer“. He quickly destroyed three alternators and the BMS kept disconnecting when he was inverting with his large 3kW inverter/charger. The BMS disconnecting while inverting also damaged his inverter/charger. When I pulled up the spec sheet on the 300Ah drop-in battery he 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 15A to 50A for a 300Ah battery. Again, this is not a limitation of the cells inside the battery it is a limitation due to the inexpensive FET based BMS that is used to protect this battery.

PURCHASE FAIL! For this particular application this drop-in battery 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.

#2 Vibration – Many of the 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.

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?



This is a reality of what you’ll often find buying your batteries of Ali-xxxx… 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. Purchassing LFP anything on Ali-xxxx is a very strong buyer beware!

Not all drop-in batteries use cylindrical cells however and a prime example is the Lithionics Group 31 125Ah drop-in. This battery uses extremely high grade 5C rated prismatic cells featuring Stoba cell technology. The Stoba additive makes these cells fire-proof. The prismatic cells in the Lithionics G-31 battery are bolted together using extremely thick nickle plated copper buses. Unlike most “drop-in” batteries, this battery can also be used for engine cranking due to is USA manufactured heavy duty internal BMS.

Compare the above cell block from Ali-xxxx to the photo below of a Lithionics drop-in battery. This battery uses impeccably matched aluminum encased LiFePO4 cells. The cells are fixed in place by a molded jig that protects them from movement and vibration failures. The busbars are high grade nickel plated copper and self locking flange 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, but at this point in time this is the only drop-in battery we at Compass Marine Inc. are willing to sell.

#3 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?

#4 BMS Shortcomings – Some of the drop-in batteries coming out of China may lack a BMS altogether and others only have a single low rated FET based switch that disconnects the bank on low or high voltage only. Drop-in batteries should also have temperature protection, for each 3.2V cell, but many don’t. The BMS protection switching (really just a MOSFET switch), as discussed above, is often rated at a ridiculously low continuous amperage capability of around 50A and maybe as high as 100A, if you’re lucky. The drop-in manufacturers are essentially relying on you paralleling multiple batteries together, and sharing the load across multiple BMS switches. Depending upon your particular expected use this may wind up being an under-engineered BMS switch.

#5 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.

While the ABYC standard is not yet finalized, 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.

Email from MHT Reader:

“RC,

The alternator for the Volvo MD2030 with 300 Amps lfp 14.6 max lasted a few hours. I believe BMS was switching on to off I to keep the lfp 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.

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 I did exactly this. Using the alternator test bench here at CMI the 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 would do to protect the LFP cells. Poof went the alternator diodes and the light bulb! 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 Device!

The Sterling Power Alternator Protection Device 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. The only real way to do this, without an Alternator Protection Device is to keep a buffer “load” on the charge bus at all times (load = a battery on the systems charge bus). Typically this “load” will be a lead acid start or start/reserve bank than is fed through a diode or FET based isolator but a paralleling solenoid can also be wired in & set to activate when ever the alternator or transformer based charge source is running.

Alternatively, one can use use a DC to DC charger, such as the Sterling Power Battery to Battery Chargers, to charge the LFP bank from the lead acid battery. The Sterling Power battery to battery chargers are designed to handle a BMS load dump.

NO EXTERNAL BMS WARNINGS OR EXTERNAL COMMUNICATION CAN BE DANGEROUS



#6 Series Wired System – 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. With a series bank (or a single drop-in LFP battery) one batteries BMS taking itself off-line spells disaster at sea. I know one Alixxxxxx buyer who hit a 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 propulsion power, while going under a bridge.

#7 Fan Boys/Girls – When watching videos on YouTube or reading blogs showing cruisers, off-grid or RV owners, touting LFP batteries in only glowing ways, keep in mind this is a technology they may actually know very little about, other than from the glossy marketing materials. I recently watched a video by a very popular YouTuber where he was touting a “very good deal” on a drop-in battery. The sad reality? It was absolutely not a drop-in battery, and had ZERO BMS PROTECTION!!!! After that video was published our email started blowing up with questions about these batteries and also a few owners who had already destroyed them because it lacked an internal BMS disconnect, which the popular YouTuber claimed it had.

Please be aware that some of these fan-boy installs may have been HEAVILY SUBSIDIZED BY THE BATTERY MAKER. I know this because I’m one of the folks who’s been contacted by companies who are trying to gain marketing growth through social media / high-view You-Tubers or high reader volume bloggers. For us to take on a drop-in battery, as we have with the Lithionics drop-ins, it must meet what we consider to be a reliable design for a typical cruising boat. Bottom line here? Don’t 100% rely on the research of others, including this article.

#8 A Drop-In BMS is Often Catastrophic Level Protection Only – Please don’t assume your drop-in batteries BMS will manage your battery for maximizing cycle life, it may not do that. The BMS in many drop-in batteries is designed for catastrophic level protection only. What this means is that the BMS is only there to protect the cells from thermal run-away conditions and can have BMS disconnect voltages exceeding 16V for a 12V nominal battery. It is up to you, the owner, to ensure the battery never exceeds a save operating envelope and that *charge voltage guidance is followed. The BMS disconnect parameters for HV, LV or battery cell temp. Some drop-in batteries use an internal BMS that does protect the battery from a maximizing cycle life perspective. Batteries built to maximize cycle life will have much more conservative HVC and LVC voltage levels.

#9 Understanding Cycle Life Claims – When an LFP cell manufacturer rates a cell at 2000 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 and charges differently than the way the cells were tested.

*IMPORTANT: Drop-In Charging Voltages – Follow the manufacturers guidance! The charge voltage recommendations made in this article are intended for the DIY builder, where the owner has paid close attention to cell matching, physically capacity tested the cells to be used & tested & matched them for internal resistance. A build like this allows for the batteries to remain in balance, without a need to continually push into the upper-knee in order to re-balance the cells on each cycle. Most drop-in batteries are not using cells that are impeccably matched. Lithionics would be an exception to this.

Unfortunately with most “drop-in” batteries you don’t know what is inside, or how well matched the cells or cell block are. You are essentially shooting darts with a blind fold on. Lithionics and Battleborn are the only two drop-in manufacturers we know of that pay very close attention to internal cell matching. Lithionics can actually supply a performance test sheet for every cell in their drop-in batteries.

“Rod why should I follow the drop-in charge voltage guidance even if I think the voltages are too high?”

1) 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 up to 0.05A.

2) The passive balancing in these batteries 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. 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 always done at the top-of charge with a FET based BMS.

3) The manufacturers, for obvious reasons, want a short absorption voltage duration, some as short as just 2 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 may never catch up.

4) If or when the cells do become out of balance, most often because the cells were not well matched to begin with, the mA level balancing circuitry may never catch up. When this happens it can be all down hill from there.

What I’d like to see to support more widespread use of drop-in’s?



#1 Externally communicable BMS, at a bare minimum Bluetooth, (this of course has its own issues).

#2 Internal BMS contactors / switches capable of handling the amperage’s found on cruising boats. A 50A continuous rating on a 300Ah LFP battery is simply unacceptable. 1C continuous charge or discharge current would be where to start looking for a battery with a sealed BMS or a BMS/battery that is capable of engine cranking (The Lithionics 125A LiFePO4 Battery is capable of engine cranking).

#3 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.

#6 Cells that are using internal fire-prevention additives such as Stoba.

#7 Internal wiring gauge & temp rating specifications

#8 External BMS alerts that can externally warn of a trend towards a disconnect.

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

The Future of Drop-In?

We will see at least a couple of manufacturers step up the game on all these points. Today the only drop-in battery I would install on my own boat, or customers boats, would be the Lithionics 12V125A-G31-5CND-LRB. We looked at every available drop-in product we could find before moving forward with the Lithionics product. Yes, Lithionics does manufacture a drop-in battery, and it is a darn good one that features a full suite of Bluetooth monitoring.

I have discussed future changes with a couple of drop-in manufacturers, who are actively working on making these batteries better suited for marine house bank use. These changes, include heavier duty internal BMS switching, and external communication to avoid dangerous and damaging voltage transients upon a BMS disconnect & some are already using UL tested cells. If it seems to good to be true, and it is sourced from eBay or Ali xxxxx it probably is. At this point in time I still urge a very, very strong Caveat emptor for eBay, AliXpess grade, LFP drop-in’s for use on cruising boats. Safe enough now for a trolling motor on a bass boat? In many cases yes, but not quite ideal yet for a cruising boat.

What about insurance?

No one knows where the ABYC standards will land on Li-Ion batteries being used on boats yet, (I actually do but am under NDA until the ABYC TE is published). What if the standard requires a batteries BMS to be able to communicate externally, and yours does not? This is but one example. There will be many questions answered when the ABYC finalizes the first TE report. Until then, it is anyone’s guess. If you are moving into into LFP, pre-ABYC standards, as I have done on my own vessel, be prepared to be denied insurance and be able to absorb that cost if your battery bank does not meet these standards. Nothing wrong with gambling, just be able to accept losing, if you picked the wrong product.

PLEASE DO YOUR RESEARCH



When in doubt go with Lithionics-OPE-Li3, Mastervolt or Victron marine specific design. Alternatively, a drop-in by Lithionics or even Battleborn if your use/loads fit the bill.

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 warranty. Please understand this is not a 10 year warranty that covers any sort of cycle life, it only covers manufacturing defects. That said, kudo’s to Battleborn for trusting their engineering enough to back it with the best construction warranty I know of. We have seen the internal build quality of the Battleborn, not our place however to share these images, and it is pretty decent compared to most of the Chinese imports. We have also seen/cut open a number of Chinese LFP imports and what’s inside can be HORRIFYING!

As a US business owner, I still have some qualms, with what I consider, a level of dishonesty Battleborn puts forth with their “Made in USA” claim. I don’t really understand how the FTC is allowing them to get away with this? After all, their internal BMS board says right on it “Made in China” (yes we have the images to back this up), the cells are “Made in China” (most all LFP cells are), the plastic battery case is also made in China. Made in USA? Perhaps “Engineered & Assembled in the USA” would be much easier pill to swallow? The battery itself does in fact say; “Engineered & Assembled in USA”. However, the web site still says, and references, “Made in USA”. As a fellow US business owner, and manufacturer of products that actually made here in the USA, this level of misleading marketing bugs me a bit.

A Major Battery Maker Enters the Drop-In Market:

In late October 2018 Trojan battery officially announced their entrance into the LiFePO4 market. The initial formats are supposed to be a Group 24 92Ah 12V and a 110Ah Group 27 12V format.

The batteries are using 26650 cylindrical LiFePO4 cells and the batteries, only the group 24 version initially, will be able to communicate externally using the CAN-bus protocol. I appreciate that Trojan has developed (in partnership) a “drop-in” LFP battery that features some level of external communication .

The 26650 cells (26mm diameter X 65mm long), used inside the Trillium’s, are not being manufactured by Trojan but, they are built to “Trojan’s specifications” under contract in China by Trojan’s partner company, which is also US based. While I do know who the manufacturer of these batteries is, it is not my place to out them. My only frustration is getting good information of of Trojan on these batteries. Seeing as Trojan is “contract building” them their support team really has very little experience with LFP..

Trojan’s entry into LFP, I believe, helps to legitimize the underlying LiFePo4 chemistry. There are also other large lead-acid US battery manufacturers are working on this too. Up until Trojan entered the LFP arena, the “drop-in” market has been flooded, other than for Lithionics & Battle Born, with US based sticker application companies.