It\'s rechargeable high-capacity battery is compatible with many devices, with a USB output for use with other charge cables. The 2.1 A output is perfectly designed for charging tablets, and the LED indicators show the amount of charge remaining. Long Standby The long standby time allows you to keep handy for emergencies, and the compact design is convenient for storage. Compatible with most USB devices USB devices compatible including Apple iPhones, iPads and iPods, when connected to their USB charge cable (not supplied). Specifications Battery technology: Lithium-Ion (Li-Ion) Battery capacity: 4000 mAh Charging source: AC, USB Battery voltage: 5 V Output voltage: 5 V Colour: Black LED indicators Battery voltage: 3.7 V