My current bracket car with two group 24 RV/Marine batterys stays charged up by running a 100 amp single wire Powermmaster alternator mounted off of the front motor plate I will put a slow charge in it with a variable 6 amp charger for several days before racing when the car has set for more than a month to make sure they are both topped off, slow charging batterys at a low rate works a bunch better than a quick charge at a high rate like 30 amps.