I thought I'd mention one alternative for batteries. I've not used these in an RV, my only application was an electric bicycle. They're incredibly popular among the radio controlled airplane crowd, for the same reasons as the bike crowd; light weight, great charge times, great discharge, and lastly safety.
The company is A123 systems. They use nanotechnology to make a lithium battery cell that you can drive a nail through without them exploding or catching fire. They also currently offer a module combining cells into a battery that is compatible with automobile batteries and chargers.
The only downside is the only auto-compatible module they offer for sale is small and only gives 4.6 AH. Here are the specs for that module:
Nominal voltage: 13.2 V
Max Discharge Current: 30 A
Charge Current: 10 A
Nominal Capacity: 4.6 Ah
Energy: 60 Wh
Power: 345 W
Cycle Life: >7,500 Cycles at 25įC, 0.8C/0.8C, 100% DOD
Core cell: ANR26650 Cylindrical Cell
Dimensions: 5.95 in/151.0 mm x 3.93 in/99.7 mm x 2.54 in/64.5 mm
Weight: 1.875 lb/0.85 kg
A123 Systems ALM 12V7
The main web site is annoying, they mention a 60 AH module as a replacement for 12v
lead acid, but not a lot of info:
They're purchase site could also use some work:
A123 Systems Cells and Battery Modules
The main thing is the cells can be stacked to around 13V and then can be charged with a standard car battery. They hit 90 percent surprisingly fast, the last 10 takes much longer.
I haven't sat down to do a cost or feasibility analysis for an RV. But I built an electric bike that could go way faster than I ever wanted to go on a bike.
Don't know if it helps, but back when I was involved in the electric bike community, it was hands down the leader.