MY own personal rule is two batteries, 150% current of one battery. So with two batteries each capable of 100 amps, with 2 in parallel, you can pull 150 amps, so even if there is a 50 amp difference, the high battery is only at 100 amps, and the low one is providing the other 50 amps. Go to 4 batteries, and now you should be safe pushing 225%.