u/maschiltz

My Kobalt 80v battery was draining a lot faster than it used to, which is understandable as it’s about 5 years old. So I ordered some cells to rebuild it. The charge indicator light works, and there charger accepts it apparently, but when I put it into any tool, it runs for a second before the bms shuts down.

I charged all cells before building the pack, and the voltages at all of the bms solder points look correct. I used 0.2 mm nickel strips and slotted them by hand. After the battery shuts down, I can feel one part of the bms is warmer than the others, near where one off the four sets of wires connects.

Hopefully one of the battery gurus here has an idea of what I screwed up.