As I understand it Parallel gives you more cranking amps, etc, but the voltage stays the same. I believe you can charge them with a two bank charger since the positives and negatives are hooked together on each bank, just hook the two different charger, one to each bank. I'm not an expert by any means so hope someone else sounds off on this. What I have described above is the way I am doing it. A year now and no known problems.