I seem to recall reading a thread about said unit that there was no way of turning off the battery side of the charge, the switch mounted on the unit or remote panel only turned off the inverter part of the unit, as long as there is mains supply to the unit then the battery charger is on, If you were to fit a disconnect in the 12v cable between the unit and the batteries then I assume you would be able to turn this off cutting supply to the batteries and leaving the unit to bypass the 240v supply throu it, Doing this so the solar can charge the batteries but the 240v supply stays on for running the fridge so it does not burn gas unnecessary.