Can you Charge a Dead Lithium battery? Lets be careful and try it - Repairing is Fun!

[@LegsAJimbo]

As others have said, the dangers of a single dead cell are very real and likely what the BMS has picked up on. I know the Xiaomi's let you view the BMS data over bluetooth, that would be worth checking, if it has this feature. Finally, rather than upping the amps on the PSU, leave the amps low and up the voltage. Check the voltage rating on the battery and go no higher than 95% of this. If it's a 37v battery, go to 35v, that will put you at 3.5v/cell (assuming balanced!) at which point the BMS should be happy to do the rest. If it was me I'd be checking Bluetooth data, or taking the pack apart to test for dead cells... If this wasn't an option I'd be charging it outside, the risks are just too high, especially when bypassing the BMS

[@philbrooke-little7082]

the problem you can have is that you have a dead cell, the bms will protect against that. if you bypass it you can over charge the other cells with the associated risks of unpleasantness. If it won't run / charge via the BMS then you have a problem either with the BMS or you have an out of spec cell that it is protecting you from.

[@timtaylor8557]

The proper charger should have been able to take over by now. If it doesn't charge, something is VERY wrong with the pack. Charging it the way you are will not balance the cells. Not worth the risk. I would just buy another battery. Even if you do get this thing to operate somewhat, it will likely be very poor output/runtime.

[@repairsnstuff]

yes I do plan to replace the battery if everything else tests ok (motor, brake and speed controller) , finding it hard to find a battery pack to match the spec.