Normally, you should have a separate AC electrical panel inside the boat, usually next to your DC panel. On the AC panel, there should be one master switch that you throw to allow AC power to the other breaker switches on the panel. One of those other breaker switches should be labelled "battery charger" and you would have to turn that switch on to send power to the
battery charger.
However, and please do not take this as a put down because it's not intended that way, are you certain your boat has a
battery charger? I have seen many AC panels with a labelled switch for a
battery charger, but no charger was ever installed.