[arber333]

I've been reading and searching but haven't come up with the information I've been looking for. The forums here are quite extensive so I'm hoping a couple of regulars can point me in the right direction.


I've been given a ZAP Xebra (you can quit laughing any time.....) that has no batteries. I also have a very large stock and continuing source of 18650 cells. I build and ride electric bikes so battery packs and their BMSs are familiar to me. But, I'm having trouble figuring out how a BMS will scale up to 100+ ah battery at 72-84 volts. There is no problem getting a BMS for 72 volts but it can't do the 200-400 amps out needed for even a little car like the Xebra. I suppose there must be "auto" rated BMSs that I haven't discovered yet or are BMSs for this type application used just for charging and bypassed for run-time? Is a single battery pack at 50p x 20s and one BMS preferred or 5 packs in parallel of 10px 20s and 5 BMSs the way to go?


Can someone point me in the right direction with possibly a few links that can fill in my lack of knowledge in this area? I appreciate your patience and knowledge.

I have two DIY cells each made from 32P 2.8Ah 18650 cells. There is a central rail with two rows of cells on each side connected with fuse wire.
Up to now those cells work well with rest of Kokam 85Ah cells. Admittedly they are softer than Kokam LiPos. Under load they sink lower and when charging they reach balancing level before. However i compensated that with "a bit more Ah" so my car works now for more than 2yrs with 102s cells inside.

I use my DIY BMS with it. It monitors cell voltage and has two outputs in daisy chain. When single cell gets low chain is joined and it puts car in turttle mode. Likewise if cells are full BMS will shutoff charger by this loop.

If you use bikers BMS you leave power line unconnected. Rather you use this line and its transistors to turn on one relay which will stop charger.