A strange battery problem

[TheBikeMan]

I start by saying that I build batteries from scratch and can repair most non fatal issues. This one has me scratching my head. I it is a 36V 375w battery. The bike was not coming on at all so I put a power supply to it and it is fine. So I check the voltage of the battery and the voltage is fine measuring at 38.6V. I have a battery load tester so I hook it up to that and the battery immediately drops to 18V. I haven't started the load test on the tester. Just hooking it up to the tester so that the tester can read the battery causes it to drop to 18V. I tested the voltage into and out of the BMS and it has 38V going in but only 18v coming out So I changed the BMS and it is still the same. Any thoughts? Thanks all.

 

[Woosh]

The cause is likely due to one of the blocks in the serial chain is damaged.
As soon as there is a load, the faulty block's voltage drops, the BMS will cut off the output.
put the battery on a load directly between B+ and B-, then check the voltage of the balance wires to B-.

 

[Nealh]

Imv either a cell bank or two are shot or cells in a bank or two are shot, which ever it is they are bringing the pack down.