2 years ago I built my own board with a fully DIY 12s 3p battery pack. Unfortunately this spring I went to plug it in and my BMS didn’t power on. This lead me to test the voltage on main leads coming off my pack… 2.3 v .
Now its been a while since I built this but if my memory serves me right I should be sitting around 48+ volts when I measure it this way right? If that’s the case I assume this pack is trash and I need to figure out how to recycle it immediately. Any ideas what could have caused this? I left it in my garage for a few months on accident in the cold but that shouldn’t have caused it to drop to nothing right?
I do have my ESC set up to bypass my BMS for safety, maybe I left it powered on for a period of time?
Leaving it on with the BMS bypassed likely killed your battery. It’s permanently dead and needs to be replaced. Though it could be argued, that may be long enough to kill it even if it wasn’t left on. If the battery was full, and it wasn’t left on, you’d have a really good chance of having a usable battery right now. This is all assuming you’re using a loopkey and not a fancy power circuit that also draws power.
Unfortunately with the current state of battery technology, Li-Ion cells do this. The cells have a very small self discharge and the electronics (bms and esc) have a very small but not negligible drain when sleeping. It can be mitigated somewhat with a loop key but even then it’s really a bandaid for one of the drawbacks of the cell chemistry - below a certain voltage the cell eats itself. Rip your pack, another victim of transition technologies.
One silver lining is cell prices if you aren’t going after an increase in performance have dropped significantly. P42a’s can be found for $2 a cell and if you’re looking for more performance a bak45d will outperform it by about %20 or more for about double the per cell cost.
