For the AC200P, if I plug it into electricity and then plug my fridge, does it just pass through grid power until that is disconnected like UPS? Or does it start using the battery then recharge simultaneously or every so often? In case of power cut does it continue to power fridge and then when electricity is back does it automatically start charging the battery or I need to do something like setting something or plug in plug out? Basically can I leave the fridge for a week and be sure that with frequent power cuts it will flawlessly continue to work and charge my AC200P?