Inverter/charger provides DC-to-AC inverter with automatic line-to-battery transfer and integrated charging system serves as an extended run UPS, standalone power source or an automotive inverter. It supplies up to 6000W of continuous 208/230V sine wave AC power from any 48V battery or automotive DC source. When hardwire AC input is energized, commercial power passes through to connected equipment and the battery set is recharged via 3 stage, 23/90A charging system. In UPS mode, the APS system responds to blackouts and severe voltage fluctuations with near instantaneous automatic transfer to battery-derived AC output. It includes set of high current DC input terminals for simple installation. Built-in automatic voltage regulation (AVR) corrects line power AC brownouts and overvoltages without using battery power during battery charging and UPS standby modes. It supports an unlimited amount of runtime with any number of user-supplied batteries connected. It is highly adaptable to variety of applications and site conditions with adjustable charger settings for wet/gel battery types and selectable line to battery power transfer voltages.