[beeje]

First off, if the key can be removed, the batteries are disconnected from the panel, to me meaning (off). No the batteries will not charge with the key off. I have owned 3 campers, all with this switch and for the life of me I see no reason why anyone would need to turn it off, other than working inside the panel. I have never turned any of my disconnect switches.

There are several items such as the propane detector that are connected directly to the battery and will continue to draw even with the switch off.

If there is a need to totally disconnect the batteries, put a disconnect switch on the negative battery cable. Then there would be no draw on them at all.