When living off the grid battery power, along with water capacity is king.
Good choice with going with AGM batteries. Put in as much as you have room for. Most RVs don't have much room for batteries so measure up and see what will fit. The more amp hours the better.
You likely have enough room for 2 group 27s, maybe 2 group 31s, a single 4D, possibly an 8D, or 2 6V GC batteries.
We have been using a single AGM 4D. The first one had a lifespan of nine years. The second has been in since 2018. Going strong. Don't anticipate replacing it until 2027, if we are still travelling.
There are some advantages of the AGM, in addition to their longevity. They self discharge at about the rate of the wet cells and while in use they hold their voltage longer, giving more useable amps per cycle than the wet cell. The better battery comes at a cost however. For the serious dry camper well worth it.
