Board won’t charge :(

Hey guys- looking for some assistance. Built my 12s2p- charged it- took it for a spin

Came home charged no problem…

Went out for a 13 mile cruise w the gf- came home… plugged it In- charger won’t change colors ~ took it apart and I don’t see any loose connections-

How can I test what part has failed

Have my voltmeter handy - thanks for the help all :slight_smile:

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Oh, and it was wrapped up with shrink wrap- just removed to take a look at the interior workings of the beast

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Also, just tested the entire voltage of the pack- measures 36v

So, 3v each battery- is that possibly why

Probably a fault in the bms, the charger changes colour when it senses a closed circuit. If ur sure the circuit is closed its prob the bms

Dang. Where can I get a 12s Bms from ? The one i have is gargantuan and I wouldn’t mind getting a smaller one

check all the P groups, if one is discharged below 2.8 it can be possible that the bms doesnt wanna accept it. in that case just forcecharge it till 3V, or close to the other cells. waiting a bit can also help to get a more balaned pack again i think.

But im not the best at this so summoning @BluPenguin and @glyphiks @pjotr47 @Hyperion XD and the other battery builders

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Can you explain how to check all the p groups? Sorry- just don’t want to f it up-

Where did you get 36v reading? Out of connector or?
You can turn your bms upside down and check voltages between pins on balance connector. This way you will know if they are in right order and if they are all even connected.
Tbh your solder connections doesn’t look strong and you could isolate everything much better - there are many sharp corners and many crossed wires

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Measure voltages across all these points like that. All 12 groups. Do they all come to the same or very similar number?

I appreciate your critique- I Initially had 12 g wire running in pairs between p groups- but it was too tall - so removed it and used braided wire between p groups. That said, the battery worked fine (and still does- just won’t charge)- the board is not flexy and therefore not much is moving when enclosed.

How do I test using the Bms? Can someone drop a link or instruct me? Much appreciated and thanks guys. Stay safe out there!

Will do that now thanks for the diagram!

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Ok, just measured- each is at 3.0, giving me 12 groups at 36v total. Any more thoughts guys?


Hold first probe on first pin and move second probe pin by pin while holding first probe on first pin all the time. Write here all readings you got. And be extra super ultra careful so you won’t short pins (also you can short them if your probes touch while measuring)

Edit: I see you already did it. Do you get any voltage on charging port?

Thanks, Tinp, I can do that now- I guess this assures that all my Bms wiring is still alive and well? I just finished measuring p groups… they were all at 3v- can def do this now, too

I assume I keep the negative on b- and March down the line moving the positive probe to b1,b2 etc?

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I’ve been scared to touch charging port/ any advice on how to measure there?

Tinp- did the Bms measurement (at least I’m learning a new skill set!) and got the same numbers as I did across the p
Groups as before- so my Bms wires seem like they’re ok- now for charge port… I
Imagine i measure from the Inside where my wiring is and not through the barrel on the outside?

I guess you don’t have male plug for charging port?
Can you take some closer photo of charging port, inside enclosure?

So, I touched the voltmeter to where my positive and negative charge wires run and got 36 v from inside the enclosure- let me attach a photo of the charge port

I know that center is positive… but should
I really try to nudge the voltmeter negative around the outside barrel? Thanks all. Ain’t got shiz to do right now anyway so
May as well
Get my beast back up and running!!