You CAN have that much capacity, but you would basically have to build the RV out of battery cells. I'm assuming they meant 20kwh, which is still HUGE for an RV, but they did say they never needed shore power in the last 2 years of living, so I guess, its possible.
With the kind of draws described, I believe OP got the terms confused and meant "200ah". We've got a 200ah house battery in our RV, and you can run low-load stuff like a laptop and a monitor for a long time on that battery. Hell, fire up the 1100W microwave and heat some lunch. Just do it early so that the solar panels can refill before dark.
And of course 200 Ah (@12VDC) is 2.4 kWh. BTW, I have a couple of these LiFePo 100Ah batteries, and they are great. But I do get a kick out of how the capital cost is about $800 USD to store 1 kWh, or $0.15 worth of electricity (omitting solar cell cost solar charge controller cost, which are comparatively minor)! Still, the grid independence (for sustainable Tiny Electrical Living) is a wonderful thing.
