I have used two 6 volt batteries with two 35 watt solar panels on my last two 5 wheel and have dry camped lots, the longest stretch was 21 days on solar alone and that in south eastern BC where we don't get as long a days as you get up north, as well were are in the trees a lot of the time.
I bought my solar pallets and controller up here at Canadain Tire and it's all plug and play, pretty easy to hook up.
I didn't mount the solar panals because when you camp in the trees you have to move them around a couple times as day as the sun move across the sky. Best investment I ever made.
Also remember that in newer RV you are always draining the battery a little bit when your not even in it.
The new propane fridges us power for the electronic thermostat as well the Co detector an some rigs are also hooked up to the battery of the rig. Im my new rig the lights on my stereo are always on when running on 12 volts as well, so even if your not in the rig it can and will drain the battery in time. Also when the Fce kicks in it will use a lot of power and fast, so keep an eye on that.
In my old 5th Hweel I had a panel that was built in from the manufacture that showed in volts and amps and on a bar scale the amount of Juise the batteries had in them at all times, it was great and I wish I had it in my new rig. You can get after market units so maybe one day I will up grade the new 5er
The last few years we have been seasonal camping at a mountain lake campground with full hook ups. The area we are in is prowl to power outages "a lot" so I always leave the solar panels hooked up leaning against the rig in case the power goes out if we are away for a day or two so that the bateries stay changed if the power does go out. This is important for the electronic system on the new fridges that require power to operate in the "auto" setting so if the power did trip, the fridge would switch over to propane automatically .
Soup
2018 Northern Lite 8-11 EX Dry Bath
2017 Sierra SLE, 3500 HD / 4x4 / Duramax with a 6 speed Allison Trans
Torklift Super Hitch 20K, 48" Super Truss, front and rear frame mounted tie downs
Fast Gun Long Range SS Turnbuckles, Fast Gun locks