Here is what I have done in our 29 RE and it works for me. I have added two six volt golf cart batteries in series for an additional 12 volts. The original 12 deep cycle volt that came with the trailer remains in place. This is how I pieced it altogether, first I added a battery selector switch which allows me to select batt 1, batt 2, both or off. Off really means off absolutely nothing powered, it also means if plugged into shore power batteries are not charging, so to charge batteries you simply select both!!! Now the feed from the battery select switch go to the OEM bus bar and after that it's all factory. I select the 2-6's to provide most if not all of my required power (boondocking), I monitor them with my tri-metric batt monitor. I also ran a 2 ga, wire from the bus bar to a 1000 watt psw inverter just on the other side of the bulkhead from the bus bar. Inverter is controlled by a remote inside the RV. and it only powers the entertainment system thru a 3 way sw. Why all this? Well I think it answers some of the debate on 6 volt versus 12 volt, because the 12 volt is hardly used, and can be an emerg backup in the event of one or both of the 6's failing. The 6's provide more available power than one 12 v, and I believe are more of a true deep cycle. This of course is only my opinion and my solution for boondock camping. P.S. Solar yet to come after more research! Keep on camping.