Critical LifePo4 BMS Data You Should Not Be Without!

The Critical Information You Miss
In the image above this brand new 100Ah PowerQueen, (no bluetooth BMS)  has cut-off charging at just 13.81V.

As can be seen in the image below,on the left, two of the four cells in this battery are grossly exceeding the max safe cell voltage of 3.65V. I was able to fix this battery by adjusting the point at which the BMS initiates cell balancing. If you don’t have a BMS that allows visibility into how the cells are behaving you’re essentially Mr. Magoo on the Autobohn…

Other Brands:

Full featured brands such as Kilovault, Epoch & SOK all have a bluetooth BMS so you can see exactly how the cells are behaving.

MHT Recommended drop in Batteries?

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Kilovault HLX+  Batteries are the drop-ins we have  the most experience with.  They’re an amazing value and great batteries! Having sold hundreds of these with zero issues they are simply great batteries. It should be noted, the Kilovolt BMS has the highest peak current handling of any FET BMS  we know of. So, if you have electric winches windlass etc. Kilovault batteries would be an excellent choice!

Buy Kilovault Batteries


Epoch – IP67 Series

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 friend Ben @ Panbo did an excellent Epoch review .
Panbo Epoch Review

 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 LiFePo4 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. Please Email us for the coupon code: compassmarineservices at gmail dot com

Buy Epoch Batteries @ Epoch Batteries

Budget Friendly Drop-In Batteries

Below we have Included Chins & LPF Max. Chins are one of the top selling LFP batteries  on Amazon and LPF /Max has all the right features & a good build quality  at an absolutely amazing price. These batteries ship directly from the manufacturer, like Power Queen but, they both have been pretty responsive on the customer service front.  Before I ever add a battery, to our Amazon Store, I pretend to be a DIY and ask a few questions via email. How the manufacturer responds and how accurately they answer is all going into this decision. These batteries are an excellent value but, they do not  lack the critical features that are found on the slightly more expensive Epoch & Kilovault batteries…. If your budget is tight, it’s hard to beat Chins or LPF Max.

Buy Penny Saver Drop-In Batteries @ Amazon


Debacle  Du Jour

One of our old customers begged me to come out of retirement and help him with his LFP conversion/design. I am not doing the physical install, I  physically can’t, just the design, and only because he is a good friend.

Don’t Let Budget constraints drive  your choice of  LFP battery!

This  customer, is  a sailor with very limited space, & budget. After doing his energy calcs and  measuring space availability 350-400Ah’s was the goal. He really wanted a 400Ah bank but nothing in a group 24, 27 or 31 case size would fit.. I tried to steer him to Kilovault or Epoch, both amazing batteries for the price.  He said, they were too much money…. I made damn sure he was aware of the risk in buying dirt cheap LFP batteries especially models without a bluetooth BMS. This is why he agreed to buy one and have me test it first. Trust me, I tried like hell to talk him out of this but he “read the reviews” on Amazon. I tried to explain that Amazon’s review process is glorified BS but he didn’t care? In his mind he’d done his homework

100Ah “Mini” form factor = Very Cool

Recently three Chinese brands. Redodo, Li Time & Power Queen launched a “mini” 100Ah battery in a G-51 case size. This is the same case size as the battery in a Honda Civic, pretty darn compact, and at only 19 pounds, Wow!. The problem? None of them are offered with a Bluetooth BMS. Frustrating!

The sad part of all this is that this form factor is perfect for tight spaces and someday these will make perfect boat batteries but without being able to see individual cell voltages (eg: bluetooth BMS) you have no way to know how your batteries are performing.

How Small & Light?

Many brands under one Roof!

I knew that three manufacturers; Redodo, Li-Time (Amperetime) and Power Queen all offered the same “Mini” group 51 case size in a 100Ah battery with a 100A discharge BMS.

I also know that Shenzhen Lizu Time Technology Co., Ltd also owns the Ampertime/Li-Time trademark/brand yet the Li-Time 100Ah mini was $369.00 vs. $300.00 for the PowerQueen. My misguided thinking; why pay $369.00 for a battery that comes out of the same factory & company?

The Chinese have become good at marketing and they appear to be  trying to brand Li Time as a “Premium product” which it is not, and perhaps Power Queen as their loss leader? The only way to build a loss leader in this industry is to use non automotive/non-EV grade cells and cut corners on critical features.

I have previously dealt with Amperetime and customer service was decent so I figured Power Queen would be the same, I mean its the same company.  I was wrong, dead WRONG! As always, I physically test and cycle every LFP battery I sell or install.Most are perfectly fine because I typically stick to high quality brands such as Lithionics, Kilovault, Epoch, SOK Battleborn, Victron, master volt etc. etc…….

PowerQueen and Li Time/ AmpereTime = Same Company

The Problem
A 12.8V LFP battery uses 4  3.2V cells in series. Unlike cells in parallel, series cells don’t always stay at the same voltage and have no way to self-balance. This can be due to many factors

1- Low quality reject grade cells
2- Poor cell matching/batching
3- varying cell to cell internal resistance
4- Variations in cell to cell Coulombic efficiency.

The image below illustrates the issue:

I know the battery cut off charging at 13.81V but, without a bluetooth BMS the illustration below is just an educated guess based on factors that we do know. We know there are 4 cells, we know the pack voltage was 13.81V at cut-off and we know the battery cuts charging when any cell hits 3.65V.

It should be noted these batteries do not cut-off charging based on SoC, only when any  cell hits 3.65V is charging cut off. In other-words, for this battery to be cutting off at 13,81V there is a very large cell to cell balance  issue. I call this defective, Power queen says 13.8V is basically full so no problem…..? D’oh!

The Power Queen Conundrum:

1- This battery is a 100% sealed box, physically glued together. This is common with all price point LFP drop-ins. Trying to open it to fix it (balance the cells) will destroy it. Brands such as Epoch, Lithionics, Kilovault & SOK, all batteries we recommend, can be opened and fixed with a few simple screws!
2- This battery has no way to know what is going on with the cells inside the battery. You are 100% flying blind, if or when, the $hit hits the fan as it did here. on cycle #1.

3- This battery was physically cutting off charge current at just 13.81V, recommended charge voltage is 14.2- 14.6V  This premature cut-off is clearly indicating imbalanced cells and a runner cell,or two, causing an HVD. Because this cut off is happening well before cell balancing kicks in @3.525V the battery is a brick & useless because it is impossible to get the cells in balance with no ability to: A) open the battery  B) no Bluetooth BMS.

Runner Cell: A cell in the battery that has a lower capacity than the rest, a different internal resistance or a different Coulombic efficiency.

HVD:  High Voltage disconnect

Because this cut off is happening well before cell balancing kicks in the battery is a brick & useless because it’s impossible to get the cells in balance. After nearly two weeks of back and forth, through Amazon, (after I gave them a 1 star rating) they finally relented and told me the cell voltage when balancing begins is 3.525V or 14.1V. That’s right this battery was disconnecting well before the balancing level voltage could even begin to balance. Without cell voltage visibility it is impossible to know when or how long the runner cell exceeds 3.525V and shunt balancing can start. Even if the high cell was above 3.525V for 30 seconds or more before the HVD, it would not be enough to fix this issue.

What’s the big deal if it cut’s-off  charging early?

1- Many inexpensive MPPT controllers can be damaged by disconnecting the battery side before disconnecting the PV side.

2- Any Charge source that uses a large transformer such as an inverter charger can throw a spike onto the DC bus if the battery disconnects during charging.

3- Any alternator can also throw a spike if the battery is disconnected during charging…

No Problem: I’ll reach out to Power Queen

Balance voltage & Minuscule balance current

As can be seen above Power Queen’s solution was for me to buy a new battery and when I returned the bad one they would issue a credit. They had zero confidence I would not get another defective battery! Sorry but no! If they said the next one won’t do this and we stand behind that, maybe..This was the first piece of correspondence where they actually answered the questions I had asked!  They informed me that the battery begins to balance when any cell hits 3.525V or 14.1V at the pack voltage level. They also informed me the BMS can shunt 0.035A  or 35mA. Lets assume the 100Ah cells have a capacity variance of 1.5% which is pretty tight and doubtful… If this is the case it could mean the BMS needs to burn off as much as 1.5Ah’s of charge current to allow the lagging cells to catch up.  The problem here is, I am guessing, because these cheap batteries do not come with a spec sheet telling you what each cells tested capacity was.  For a $hits and grins calculation, the high cell would need to be above 3.525V for a minimum of 42 minutes to shunt off 1.5Ah’s. The split second this battery hits 13.81V the BMS cuts-off! With no charging there is no balancing!

Dealing With Power Queen

I contacted Power Queen and to say their tech support hd no clue what they are talking about would be an understatement. See first sentence where the next CSR is apologizing. I sent them all the relevant testing data and they tried to tell me the battery is fine. They then  tried to put the blame on me…. When I really dug in with more data and a two page explanation of why this battery is defective they ghosted me and stopped communication. This is why it is absolutely-critical to purchase a battery that has US based tech support!

Frustrated With Power Queen’s lack of technical knowledge and inability to offer a solution, I reached out to Amazon directly. Amazon initially they told me there was nothing they could do because Power Queen was a third party seller, not Amazon.. I then asked the Amazon CSR to read the correspondence between myself and Power Queen. All was quiet for about ten minutes then she said we are so sorry Mr. Collins Amazon will fully refund your money an we will get the money from Power Queen.

As I always say buyer beware when buying direct from China (I should have listened to my own advice)! Power Queen is a company that doesn’t seem to care about quality control. Customer service is also spotty at best. Here’s a thought, send me a new battery and when I test it and it works I will box the other one and send it back.. No, there solution was; “you buy another battery and then when it gets there send the old one back.  I may had done this if they had the slightest bit of confidence the replacement would not suffer the same problem. They could not offer me that guarantee. It seem’s to me this is an issue they may already be aware of….?

Why Don’t all drop-in LFP Batteries have a Bluetooth BMS?

That is a damn good question, because  the information is critical. Here are my thoughts.

1- Bluetooth BMS’s result in lots of tech support email/calls by folks who don’t know what the data means. No BT BMS falls under  the “can’t see it must not be a problem” umbrella of customer service….

2- Not all drop in batteries are using auto/EV grade batteries and a BT BMS would expose this pretty quickly.

3- Not all manufacturers batch & match cells well and this saves them a ton of money

5- Manufacturers who install a BT BMS are putting their money where their mouth is. Manufacturers who don’t are simply hiding the corners they’ve cut on cell matching/quality.

4- This is not about cost! At the manufacturing end adding BT to the BMS is pennies.


-Tried to blame it on my charger even when they had all my data and settings

-Tried to get me to buy another battery with zero guarantee it would not happen again.

– Took more that two weeks to get a response about balance voltage start point and balance current

-Told me the battery is essentially full at 13.8V so there was no problem


Do not purchase batteries where BMS data is hidden from you. I am crossing my fingers Lizu Time adds bluetooth to both the PowerQueen and Li-Time Brands because the “mini” form factor is amazing.. At this point however,  I cannot recommend either Li-Time or PowerQueen When Chins and LPF Max have the features already…



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