The industry standard house battery size used in most RVs, Campers, and #VanLife builds is the DL 100Ah battery. This is a drop in replacement for AGM and most lead acid batteries. If you are charging off your engine’s alternator we recommend a Victron DC-DC smart charger. If charging off solar panels we recommend a Victron Smart Solar charge controller, or if you have a solar charge controller choose the lithium setting. A handy size chart for number of batteries needed by size of RV is available here.