[HELP] Smart BMS Not Charging

Hey guys, I got this smart charge and discharge BMS. However, I am trying to bypass the discharge. I wired up B- to battery negative, C- to charger port negative and charging port positive to battery positive. Then XT90 out to VESCs.

Should be correct right? All voltage added up on each balance lead and whole pack is at 41V (12s), all cells group at 3.49ish voltes.

Once I plug in the charger, the charger just stays green, did I bricked this BMS already? It’s a new pack, haven’t been charged even once lol. Any help would be great! Thank you!


So do you measure 41v at C- and battery positive?

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Main discharge lead on XT90 is about 41V

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Disregard main discharge lead, because you need to find out of you are getting voltage through the BMS. If not then the charger obviously will not work. You should get full voltage through charging port.

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I will check tomorrow!

Great idea! Thank you! So C- and battery positive should show 41V as well, correct?

Yes, remember that it is a discharge BMS as well, which means it is fully capable of output power in parallel with the charge port.

Double check this is what you did on schematics to bypass.



Thank you! Will report back tomorrow!


@IndianGummy do I remember correctly and you had the same issue? If so what did you do about it?


If it’s 12s and it has 13 balance wires then the last one is b- and it should connect to pack -. So the last p group should have two balance leds connected to it. Atleast that’s what my problem was


I think I did it like that. B- to battery negative. And first is also on the same group.

@BluPenguin main leads XT90 shows 42V and C- and battery positive shows 39.5V… I am not sure why. Any ideas?

What about positive to B-?

-Measuring at the BMS

Also measure the voltage of the charger output before plugging in, then measure C- to positive with charger plugged in.

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Positive to B- is 42V

When charger plugged in positive to C- is 50.4V

Have you looked on the app to see what the BMS doing with the charger plugged in? Did you set all the voltages and cutoff parameters?

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I’ve seen that happen with evolve bms… bms was fucked.

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What’s the voltage when on your charge port itself? Not the charger.

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when you say two balance leads on it, do you mean one on negative and one on positive of that p group?

my BMS doesn’t seem to charge, but reports all cell voltages and balances just fine

If you have a bms with a balance jst plug with 13pins but you have only 12 cells in serious it means that your bms needs the b- as balance lead as well and doesn’t get the b- from the B- via bms pcb.
So first cell in your pack had a balance lead on the negativ terminal and on the positive terminal. All other cells have the balance lead just on the positive terminal.