First post, Erik pointed me at this forum, as I’m the guy that built the original board that he is using… My personal suspicion about the reason for the battery problem (and I have told him this) is that he is exceeding the current draw rating for the batteries.
The design for this board is a bit non-standard, as Erik is using the board while in a wheelchair. Among other things this means that ALL the propulsion has to come from the motor, he can’t help things along with a kick like a walking person can… (Google for his videos, they are impressive!)
The Zippy batteries that he is using were picked to match a different setup that we changed mid build to solve some issues with the original design plan. They are theoretically spec’d at 30C discharge, but that is ONLY a peak rating, the steady discharge should ideally be kept under 10C.
My original build used 3 batteries in parallel, (thus 1S12P) to give a theoretical 90C peak discharge, or 30C sustained. Multiplying this by the 4.2Ah rating on the batteries is about 360A peak, 120A sustained, which is close to the rated output of the ESC, and even at peak load doesn’t over strain the batteries.
After he had mastered the board at the (estimated) 8- 10mph that the original setup gave him, Erik decided he wanted more speed, and modified the box and wiring to the 2S8P configuration shown… This means he only has 240A peak, and 80A sustained, which is running much closer to the ESC rated draw, and is also probably drawing a higher sustained current due to the higher speed…
I had suggested when Erik said that he wanted more speed, that the proper approach would have been to keep the 3P wiring and add two more batteries to the 4 he already had so as to get a 2S12P pack which would have kept the current draw on the batteries within a more reasonable range.
Incidentally, I was the person that suggested using the LiFePO4 batteries instead of LiPos, for safety reasons - While LiPo fires are fairly rare, when they happen they are bad news indeed, and being in a wheelchair limits the ‘RUN AWAY’ options… OTOH, the LiFePO4 batteries are much safer, they are less prone to failures and when they do fail it is less catastrophic…