10s2p battery pack BMS not giving me output anymore

Hi Everyone,

I have a 10s2p battery pack made out of 30q cells that has been running great. Recently I was unable to get the board to power on and I checked the voltage with each cell at 4.0v - I only got 36v across the pack. I replaced the two dead cells and now get 40v across the pack (nice).

The issue here is when trying to get output from the pack, If I read across the pack from positive to negative (direct connection not via BMS) I will get 40v, If I read the output from the BMS I will get nothing.

Just reading from Positive BMS to pack I can get 40v but BMS negative to pack will give 0v - It starts at around 2/3v and then slowly drops to 0v…? Strange.

Im a little out of my depth here in figuring out whats going on, possibility is to replace the BMS but I need to know if its actually dead or not. No BMS wiring has been changed since it was working.

I can answer any other questions you have or if you need images, any help would be greatly appreciated I miss commuting on the board so much :frowning:

Kind regards, Harry

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pics of wiring pls

BMS usually shows a few volts less not sure why

I took the BMS off so that it was just giving full output and powers the board fine, was obviously just to test and charging it this way is dangerous unless monitored carefully.

You should be able to see the wiring in the photos, there is no voltage across the XT60 cable output from the BMS.


Measure the total voltage going into the BMS, if that is fine then you can eliminate lose wiring. Which would mean

either the connection going to the BMS or coming out is the problem, or your BMS is dead.

Personally I don’t use a BMS, I just balance change my battery pack and don’t need to worry about a BMS dying on me. Also I will catch any bad connections or cell group failure in the balance charger. I have a peace of mind my battery pack is healthy each time I charge.

With the BMS, you have no idea what is going on and will find out when it’s too late.

A BMS will not get your battery pack up to an optimal charge also.


What balane charger do you use? i cant seem to find one over 8s

I got a dual 6s charger, my battery pack is 12s6p and I broke it up into 2x 6s connected in series.

I bought this model off Amazon and it’s awesome!

HTRC T240 Duo Lipo Charger 1-6S Touch Screen

so do you just put the two outputs in series?

Correct, when I go to change my battery pack I disconnect the series connection and charge each pack as a 6S6P.

Each 6S6P battery pack will have it’s own 7 pin balance connector.

this might also be a weird question but doesnt that mean you have to open your enclosure every time you want to charge your esk8?

I have a battery box I 3d printed, it’s strapped down and easy to pop off the lid.

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ohhh you have a top mounted battery haha

You could do it with a bottom mount if you have access to a 3D printer to print a custom case, the wire could be put is an easy access compartment you just pop open to charge.

This is also assuming you know how to create your own battery pack.

i mean a similar thing could work for lipo i think

usually lipos are too thick imho to be bottom mounted, and the slims one won’t deliver power or range. i would stick with cells for bottom mounting. but this is just how i feel.

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