Beneficial to Solar or Wind System: On cloudy or windless days when your battery gets low, it will automatically switch to grid power, protect your battery. LCD display: Battery real-time voltage;working status of public power,inverter and battery. The controller switches automatically between inverter and AC mains while protecting theinverter against external voltage. Automatically switches over to grid power on those cloudy or windless days and yourbatteries get low.Take charge over your battery bank. The controller will switch to grid when batteries are low to cut off point, once the batteries areback to recovery point, it will switch back to battery power.