Another simple answer regaring the Tesla question: Because some tesla packs at least use around 7000 18650 3.2v cells, puting them all in series you would end up with around 25000 volts. Great if you get your hands on a train motor (here in Quensland Australia at least, the electric trains run on 25KV - a single phase of the 33KV lines in star configuration obviously) Another interesting fact about this is our first generation electric trains have 135KW motors, similar in size to most production EVs but 4 to 6 motors in each 6 car set as there were several varients. I'm not sure if they are AC (BLDC) or DC motors but they were designed and built late 70s - early 80s. I've got no plans on using an ex train motor, and don't know of anyone else who is either, although Queensland Rail are in the process of decommisioning and scrapping these first generation EMU (electric multiple unit) trains. 25KV is way higher than the maximum you would want in any EV build really. The railways just use it for overhead lines to prevent losses over these huge distances they cover - so stay away from them in case you didn't see any of the signs!
Just on the subject of paralel and series packs and BMS, I have a newbe question on an Upgradable batery pack: Say I want to start with a basic cheap system with around 10KWH (won't go far I know), and then later upgrade to around 40KWH once I fully test my build and am confident with it, and want around 320volts (around 100s for each string) before and after upgrade, can I start with a BMS that handles 4 100s strings and just use one of these strings to start with and then buy 3x the same batteries again that Im already using as an upgrade and use all 4 strings for the 40KWH system. I just don't know if BMS systems can be switched to use only one of thier strings or if it is a good idea to be using old bateries in one string and new, and possibly slightly diferent manufacture bateries in the other strings. Does anyone have any recomendations on a good value BMS that would do this if this is possible? Is it a better idea to just have 4 seperate packs in the end with seperate BMS, and is it still possible to parallell complete packs and still charge them the same and have regen braking work the same.
Sorry if this has already been covered - I haven't been able to find much info online about this though.
I am using Damien/EVBMW Prius Gen3 dual motor inverter controller and just recieved partially built board, completing it myself as I am electronics technician by trade.