AIMS Power 4000 Watt Pure Sine Low Frequency Inverter, single phase with built-in battery charger and transfer switch. This inverter charger is perfect for medium-sized industrial applications that depend upon power being available even under heavy load. This heavy-duty inverter charger is ready to go wherever you need it. Use this product for renewable solar, off-grid, business back up power, mobile and emergency backup power applications anywhere that uses 100/110/120 Volt of alternating current. This product also has auto frequency detection that allows users to operate at either 50 or 60 Hertz. This AIMS power inverter charger features a powerful 45 Ampere charger and is capable of accepting any source of 120 Volt AC power to charge batteries, including a gas or diesel generator or shore power at an RV park/truck stop. It will even accept power from an extension cord plugged into your wall outlet at home. The 4000 Watt inverter charger is capable of a 12000 Watt surge for 20 seconds and can run at 4000 Watt continuously. This inverter will never completely drain your batteries as it’s low-voltage shut-down keeps the voltage at either 20 Volt or 21 Volt depending on your selection. With the battery priority mode, you can set your inverter to run directly off of a battery back-up system instead of a generator or tertiary source of AC Power. The inverter charger comes with a power saver mode that pulses every 30 seconds, attempting to detect a necessary load of 25 watts or more before it will turn on. Otherwise, the inverter will “sleep” and draw right around a half an amp per hour, saving you precious reserve power in your batteries until you need it.