What kind of batteries to get?

I'm in the "two six volt golf cart batteries" group.

A six volt and twelve volt batteries are about the same size, but the six volt has three cells and the twelve has six. Since the cells in the 6 volt are larger, they can tolerate the deep cycling much better than a twelve volt.

Costco and Sam's Club tend to have the best prices on batteries. Good luck.

(I have four 6 volt batteries wired to provide 12 volts, but my coach has more electrical stuff and I need that much amperage. As others have posted, don't use the 12 volt option on your frig. Use the propane or 120 volt when available.)

Moved from Forum Technical Support

Our batteries power a few more things than just lights. So take some time, enjoy your rig, and figure it all out. :)

If you don't camp off grid very much or very long then 1 deep cycle would be fine. Otherwise either 2 12v deep cycles in parallel or 2 6v golf cart batteries in series.
You can literally find 100 or more threads on here of people debating back and forth over which of those set ups is best. I'm in the golf cart battery camp.
By the way, if you try to run your refrigerator on 12v while traveling you will likely kill your batteries. The refrigerator draws a lot of power on 12v, more than the average tow vehicle charge line can supply due to the small wire size and length. You can run all new heavier wire in the van and the TT or you can just do what most people do which is run the refrigerator on propane while traveling and never use the mostly useless 12v setting.