On 3/11/19 9:29 AM, Dan Baker via EV wrote:
I see on Aliexpress that they have 12v and
48v 100ah packs with built in BMS that look be the best prices I've seen.
One issue with using multiple 12v or 48V drop in replacement batteries in an EV is that the BMS system may ONLY work at a maximum of 12 or 48 volts. (e.g. if you put multiple in series, to get a total pack voltage of 120-144 volts (or more), the mosfets, etc used in the BMS to disconnect the individual batteries in a low-power or over-charge scenario may fail (spectacularly).

For example, the BattleBorn 12 volt battery specifically say that you can ONLY put them in series up to 48 volts (I expect they are using 60 volt rated mosfets).

This depends entirely upon the BMS/battery construction (some of them just have a balancing BMS which is isolated, and does not even try to disconnect the battery from the rest of the system in an over or under voltage type of situation...these guys are actually safer to put in series...

Jay
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