all decent advice if your need is a fair bit off grid.
In my opinion though, 1 battery is fine if that's all you need...and even one marine/hybrid type battery is fine if that's all you need. Save the money and keep it simple.....
more batteries = more cells to keep watered + more connections to maintain + longer recharge times
(remember we want to maintain them at a fully charged state, and if your recharge can only get you to some lower level such as say 70%...then you'd be cycling between that and whatever your deep discharge level is...which as I understand it is harder on the batteries.)
For me, we do use our MH dry but mostly no more than 1 night before we drive again to recharge &/or run the genny to recharge... or use battery while 'on the road' during stops, keeping the fridge going while we go to play tourist someplace, etc....so the junky hybrid battery worked ok for us...oh, we aren't relying on an inverter for fridge use which might make a difference....
anyway, when my house battery started to go, I tried to replace it with a 12 volt trojan (or other brand true deep cycle "golf cart" battery).... but where I was at the time I couldn't find one that fit.... I mainly wanted just to increase my capacity a little just in case. Since I couldn't find a convenient one, I ended up just going with a larger group marine hybrid then what I had.
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