If your batteries are in series and not being charged by a multi-bank charger it is recommended that you fully charge the batteries individually once a year. This will balance out the entire battery bank to ensure the batteries will reach its expected life span.
one BMS control one battery pack unit is easy to handle. but if you connect them in series, MAYBE, there will be potential problem. because you connect in series 2 BMS.
more simple with less problem.
Nobody ever expects a battery to fail, but if one does (bad bms), it's possibly a bonus if your battery bank configuration can be reconfigured with less Ah, vs being dead in the water while a battery is being warrantied out.
Nobody ever expects a battery to fail, but if one does (bad bms), it's possibly a bonus if your battery bank configuration can be reconfigured with less Ah, vs being dead in the water while a battery is being warrantied out.