The water heater and fridge can run off propane so as long as the switch is turned to propane and there is enough D.C. power to do the little stuff then they'll run OK too. So basically just the a/c and TV won't work, right? Remember, no generator!
Correct. But know that the furnace especially, will run your battery (s) down very very quickly.
Do you have a way to plug the RV into a 120 electrical outlet and can keep it connected for 24 hours? If so, that is an excellent way to fully charge your battery (s). Also, once a battery has had a couple of complete discharges where they are down to nothing, the life of the battery will be shortened.
If you replace the battery, in order to keep them charged and in good condition, either disconnect one of the leads or put in a disconnect switch. That way when it is just sitting, the battery won't drain down. There are always phantom loads. As someone mentioned prior, you may have a 12volt disconnect switch.
If you elect to keep the RV plugged in while not using it; be sure and check the water levels in the batteries. All this information is in our library.