Basically you need to have almost the same charging system that your 120VAC converter/charger unit gives you if you want to keep up with all of the parasitic drains.
You can get away with some smaller trickle top-off charge type solar charging if your batteries start out being fully charged but this will go away quicker than you think. If it is stored and unattended for a longer period then you are betting alot of expense on things will be ok when you return later.
To me it seems like the 100WATT solar charging setup with smart mode controller would serve you best. These solar system are readily available from several sources including AMAZON.
I have one of those 7 watt solar boards that you sit on the dash behind the windshield that plugs into your always ON 12VDC lighter socket. This is usually in high SUN just a few hours aday. It does great topping off my truck start battery but will start getting behind the charge curve is just a couple of days with all of the truck electronics still active I assume. My saving grace is I very seldom go longer than a couple of days not starting up my truck.
I count my blessings everyday that we area allowed by the county folks to keep our two trailers parked here at the house where we can keep a watch on things all the time...
Just a few observations here...
Roy Ken
