Our rig originally came with two 12V lead acid wet batteries. After the second set failed, I switched to a pair of 6V AGM batteries. Doing so required a setting change in our on-board battery charger.
WOW, what an improvement in battery reserves and years of longevity. Year number 4 and they are still performing exceptionally. Both sets of 12V lead acid batteries provided only 2 good years, year 3 was marginal, year 4 was one year too late.
Both sets of 12V batteries discharged and recharged at different rates causing an imbalance, acid boil-overs, an undercharged battery, and an over-charged battery. The two 6V AGMs discharge and recharge in unison, hence a perfect marriage for power. I bought them at Sam's club for $180 each, brand is Duracell.