Working principle: The solar or mains power comes to the UPS. The AC is converted to DC and this DC is constantly charging the battery. The output of the battery is fed to the Sine wave inverter and it converts DC to AC and this feeds the equipment. Since power out is always drawn from the battery, there is no time lag when mains switches off or power is lost; it just stops the battery from being charged and the UPS continues to supply power till the battery runs out Solar charging priority than city power mains charging. Solar power chargers battery as primary power source, if solar power is not available then inverter will automatically be switched to charge battery from city power electricity as a secondary source 2 in 1: INVERTER + UPS -LCD display include voltage input ,output frequency, output voltage, load, battery capacity, normal, unusual, overload. -Low frequency and high quality, Automatic protection function -Can use AC power supply to charge battery(UPS function) -Advanced performance by CPU control -Auto voltage regulation(AVR), wide input voltage 145V~275V accurate output, AVR function -Generator compatibly and external battery connection achievable -Adapts to all kinds lf bad electric environments -It can automatically start up with mains supply -Advanced automatic constant charging circuit, prolongs battery life -It has battery under-voltage, overload, over-discharge, short-circuit protections Features: Type: line Interactive DC to AC inverter Compatible battery: 2 x 12v Lead acid, Gel or deep cycle batteries (Lead acid is recommended) KVA ratings: 3000VA Peak power: 4000W/4KW Rated power: 2000W/2KW DC voltage: 24VDC Inverter structure: Power frequency structure Inverter output: 220VAC/50Hz Output waveform: Pure sine wave Display: LCD Range of application: mobile phone charging, laptops, lamps and lanterns, camera, TV, shaver, CD, fan, video game, security, professional tools, instruments of all electrical power.