My BMS just caught on fire while soldering. What did I do wrong?

My battery is fine thank god.

I think I may have soldered the balance leads in the wrong order. I went 1, 2, 12, ground. Started noticing smoke and flames right when I soldered ground (b13).

Only one resistor on the BMS is completely fried.

Anyways at this point I’m not sure whether to drop another $80 on the same BMS or just to skip BMS and charge and discharge manually. Kind of at a loss right now.

I’m not quite sure what could have happened but I wouldn’t recommend manual charging. Maybe just get a charge only bms for cheap on ebay

1 Like

I remember when I hooked up my first bms I mistakenly soldered the balance leads backward. Me and I soldered 10th cell to the 1 cell slot on the bms. It almost caused fire.

Third option is to buy a charge only bms.

Was batt +and - connected to the bms before connecting balance leads?

No they were not

They probably should have been. At least on the SuPower bms, it specifically sais that if you connect balance leads without batt + and - already connected, you’ll fry the bms.

1 Like

Thanks @Sebike I just ordered another BMS.

I’ll connect battery + and - first.

Then b1-12.

Then b13 to ground? Or should this one be connected before b1?

Man I watched a few videos on YouTube too and no one stated the importance of the order of soldering the balance wires.


A charge only BMS will fry if the balance leads are connected incorrectly. I would get another $80 bms and start over but this time, take your time, don’t get in a hurry. Make sure you got it right before connecting anything.

Can you post a pic of the bms you are using?

1 Like

You have to double, triple check the wires before connecting to the bms, making sure voltages are correct on the balance leads, 3,7; 7,4; 11,1 aso. If you get this wrong, you’ll also fry the bms.

Make sure you check everything before connecting the bms next time!

1 Like


Did you get a wiring diagram with that bms? That is Bestech’s newer version.

If this is the same type of bms (apart from your being 12s and not 10s), you’ll find a wiring diagram and some info on how to connect the bms.

Where did you buy it?

The seller should be able to provide you with the correct wiring, or else I would try getting it from Bestech.

1 Like

Hey @Namasaki, your profile picture resembles mine a bit. Wanna be friends?




awww cute.

My first friend :heart:

So, ahh . . . could I join too?

1 Like


I wonder if you replaced that resistor, if the board would work ok. It’s worth a try. As long as nothing else got fried. 31%20PM

1 Like