The master disconnect switch:
Some (many in fact) older rigs have a converter called a Magnetek often the 6300 this unit is a known battery killer..Monitor batteries, The problem is it does not work well without either a battery or a battery simulator.
I would monitor battery status and when full cut it off..I would also upgrade that model (A hardening condnser from a high end automotive audio store makes a good battery simulator by the way)
More modern RV's may well have 3-stage converters.. With those Leave the batteries connected.
Find the make and model of your converter and google it for info on what you have.