I agree that you should just get a 9 volt battery unit for peace of mind.
Do you have LED lights in your camper? If not by converting to LED bulbs you can save a lot of electricity and maybe then not need to charge up your batteries before bed by running the generator.
I have heard that some refrigerators have a electric element in the door to keep it from getting frosty. Check out yours, if you can't shut it off some of them can be unhooked behind the refrigerator light.
The radio memory wire can have a switch put in it saving a little too. Every little bit counts.
Any other electric saving changes you can do will help too.
Read the other posts on this forum about saving electricity or, start another thread on the subject.
Have a nice Day