How to Avoid Sleazy Vendors

Easy, Don’t Import directly from China on your own

Vendors  will lie and think nothing of it:

This cell is made in China

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 etc. etc. so be very careful when ordering direct from China because you’re on your own once you do..!

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

This battery was sold as grade A!

Sadly Ali-xxxxx and others have 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 DIY 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 US (insert your country here) 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 thepoorly matched cells. We then tried to charge it and to get the cells balanced for three straight days. Nothing we did, and we have tricks for this, 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.


Miniscule BMS‘s

The Miniscule BMS below (bottom pic)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!

Dead FET BMS (too much current)

Dead FET BMS (Windlass in-rush)

Do You know the quality of the FET’s ?


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

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


The specification also claims 2000 100% SOC to 0% SOC cycle which is 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 Yogurt balls, that’s fast!

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 the subject, drop-in battery makers will try to sell you anything you want to believe. They pray on this. Educate yourself and do the research.


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 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 his 300Ah drop-in battery 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.

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…

Direct From China LFP Fails

*These images are “direct from China” 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!

                                                                     Image courtesy MHT Reader

What’s Wrong here?

Look closely at the series connection below

The”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.

What horrors are hiding in that “direct from China” plastic box?

*Cells ballooned/swelled  due to over charging. This BMS was catastrophic protection only and allowed the cells to hit 15.6V before the BMS disconnects

15.6V is enough to ruin the cells and  brick the battery

One last warning about buying direct from China

Amazon Also sells Direct From China LFP

Amazon, It can still be a direct from China scam..

What About DIY LFP cells? 

Mainland China is producing many thousands of cells each day. With even a low percentage of cells that don’t meet the EV/automotive grade cut, it still means a lot of rejected cells. Sadly China has a nasty habit of selling everything that comes off the assembly-line. Reject or low grade cells are sold out the “back-door” at auction, in large lots, to the highest bidders. These cells then often wind up in the hands of dishonest vendors and flood places like Aliexpress & eBay.Very often reject cells have the original QR code removed or scratched off before auction.

The issue of scammers claiming they had A grade cells got so bad for EVE ( a large LFP manufacturer) that EVE started marking auction cells with a B.

Some manufacturers do this for rejected cells

If you can get well matched B grade cells they are occasionally fine for this application but they will have a shorter cycle-life, typically a higher IR (internal resistance) and performance is not a guarantee like it is with A grade. B grade can be a good value if you buy from a reputable seller that can guarantee cell matching. Current Connected sometimes has some well matched B grade cell at significant savings.

When buying cells or a drop in battery do you ever see this tidbit? Below is the recommended SoC operating window for EVE cells!

There are Reputable sellers

Buy Raw Cells From a Reutable supplier

Below is an example of an EV grade cell with intact barcode and no B.

Unless you’re a professional gambler don’t risk a direct from China Purchase!


MHT Recommended drop-in Batteries?

Our current favorite = Epoch

The Epoch Batteries offer Amazing construction, a 1.2C BMS, built in heating ,built-in bluetooth BMS (one of the best we’ve seen), waterproof, CAN communication, remote display/alarm exceeds ABYC, cell compression, even the BMS is made by them not an off-the-shelf product. All this at a price that can’t be beat and one that includes free shipping and an 11 year warranty! Our fried Ben @ Panbo did an excellent review Here. Currently the price/value/feature leader for drop in batteries. Epoch batteries are built  by RoyPow one of the best manufacturers in China. RoyPow is a division of EVE. Eve is one of the largest cell makers in China. This is how they have such amazing cell to cell consistency, they get true EV/automotive grade cells.

We have secured a 10% Epoch discount for MHT readers. Email us for the coupon code: compassmarineservices at gmail dot com

Buy Epoch Batteries- Epoch Batteries


Below we have curated a store with the Premium LFP batteries sold by Amazon. You won’t get product support from Amazon but each of the batteries in the Premium category has excellent USA tech support.

Buy Premium Grade Drop-In’s – Amazon




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