How to diagnose the lithium battery BMS damaged or the battery cells damaged?

How to diagnose the lithium battery BMS damaged or the battery cells damaged?

It must be a really bad experience that if an electric bike lithium battery runs out of power but could not be charged anymore.

How can we do next for this situation? To replace with a totally new battery pack is the easiest method but may cost high. To repair the battery seems to be economic but how?

First, we should know if the battery BMS damaged or any battery cells damaged.

There is an easy way to help for diagnosis of lithium battery BMS.

1. Measure the voltages of B+ to B- (Vb), the voltages of P+ to P- (Vp), the voltages of C+ to C-  (Vc) with a multimeter.

2. Compare the three voltages.

3. The BMS is good when Vb= Vc = Vp and inside the working rage ( for a 36V battery, the voltage is 36V- 42V generally), or the BMS is damaged.

For the BMS damage, the battery may work after replacing with a new BMS.

Generally, we suggest measuring the voltages of the cable bus at the same time to check if any series of battery cells damaged or not.

Measure the voltage of two adjacent cables, all the voltages should be same with a small. If any voltage differs greatly from others, then there may be any cell damaged. We could measure each cell in this series to find it out.