Generally a battery disconnect switch disconnects the battery from any load in the RV. The switch does not disconnect the battery from the converter/charger, which continues to charge the battery from the house current. It also supplies power to the 12V system, which allows you to run lights, fridge, and water pump.
In theory the converter/charger will quit charging when the batteries are maxed out. But many of the less high-tech versions will continue to "force" charge in which causes the batteries to lose water. Enough of this and they will boil dry and quite often are ruined.
If you can find out the exact brand and model of the converter, and read up on it, that would be good. Quite likely others here have experience with it and can advise you.