We have been down this road plenty times, take a look at this tech article I wrote but be ready it is a little out of the box thinking but I checked my theory out with the owner of a battery company I know and a electrical engineer too.
How to set up your electrical system - www.Ridesidebyside.com Sponsored by www.hunterworks.com, www.hightechhp.com and www.3stepatvtires.com