from KOA...gasp!
http://rvservices.koa.com/rvinformat...-batteries.asp
Excerpt:
Deep cycle batteries come in all different sizes. Some are designated by Group size, like group 24, 27 and 31. Basically, the larger the battery the more amp hours you get. Depending on your needs and the amount of space you have available, there are several options when it comes to batteries.
You can use one 12-volt 24 group deep cycle battery that provides 70 to 85 AH.
You can use two 12-volt 24 group batteries wired in parallel that provides 140 to 170 AH. Parallel wiring increases amp hours but not voltage.
If you have the room, you can do what a lot of RVers do and switch from the standard 12-volt batteries to two of the larger 6-volt golf cart batteries. These pairs of 6-volt batteries need to be wired in series to produce the required 12-volts and they will provide 180 to 220 AH. Series wiring increases voltage but not amp hours.
My 5er came with one group 24. I replaced with two group 27's
Slides work great on battery alone. Lasts long time!