The battery charger should be wired directly to the batteries so that you can charge your batteries when the battery switch is off. That's how it has been in boat's that I have had. My battery charger had status lights on it so I could actually see that the battery charger was on even when the battery switch was off. I suppose that someone could have wired your charger so that it required the battery switch to be on, but that doesn't seem logical or likely. Is there a circuit breaker for your battery charger on the shore power side of the system? If there is a light on your battery charger? See if it's on when the shore power cord is plugged in or sometimes you can put your ear up to it and hear if it's humming or not. I don't think that battery chargers came stock from the factory on this boat at that time, so I guess it's possible someone might have wired it strange. Do you know where the charger is or what kind/brand it is? Is there a DC volt meter on the boat? You can tell when the battery is charging by looking at that too. Mine would usually read about 14 volts when it was charging.
