1st what voltage and current are you charging at?
it would have to be serious amps to create steam...
2nd... have you measured each cell when at 90%+ charge to ensure each cell is the same voltage?
I would guess the cell was way over voltage
sadly a starting capacitors don't store any energy on AC voltage.. what it does is phase shift the sin wave on the start windings allowing the anglers difference from the run windings to start the motor spinning..
1 you will need soft starts on each AC compressor
2 yes eg4 and growatt will do transfer switch
3 you will need a battery to start the units and deal with moving clouds.