The battery disconnect switch is used to separate the batteries from the 12-volt distribution panel and converter charging system.
When the switch is turned to ON and the trailer is plugged into an external AC power source, the 12-volt distribution panel will receive power from the converter and the batteries will be charged through the converter charging system.
When the switch is turned to OFF and the trailer is plugged into an external AC power source, the 12- volt distribution panel will still receive power from the converter, but the batteries are disconnected from the system. The batteries will not be drained with the switch in the OFF position. The converter will not charge the batteries with the switch in this position.
The charge in the 12-volt batteries can be replenished, depending on the tow vehicle, from the tow vehicle alternator through the 7-way cord. This charge will flow to the batteries regardless of the battery disconnect switch position. Likewise, if on or off, the solar panel is still charging the batteries.