One of our long term visitors is an e-biker. One of his batteries was on the blink. There was no output on the normal output connectors, but there appeared to be an output via the charge port. We suspected that the balance circuit was shot, but when we opened the battery case, it looked like one of the cells was physically damaged. Lots of pics here.
We ordered a replacement cell. When we removed the bad cell, we noticed some others damaged. It looks like we need 4 replacement cells in all. We plan to cannibalise these from an old spare battery. We tested the remaining cells and they seem able to take a charge and deliver reasonable current. A 2 Ohm power resistor came in handy. Check back with us to see how the rest of the repair went.