Also, with a bigger battery comes higher limits on how fast you can charge. If you have a 300kWh battery you should be able to charge it at 300kW all day long.
That said, it doesn't really exist since there is no market for it at the moment. RV sales aren't exactly high, so the niche for EV RVs is even smaller. Plus there's no real infrastructure out for it now.
I suspect once EV Semis become more mainstream we'll see that trickle down to RV users. They can charge at the same place a semi would charge at.
Also, there will undoubtably be hybrid options where you can have a multi fuel generator charging your batteries.
https://www.ford.com/trucks/f150/f150-lightning/2022/#towing...