EnergyFlux Lite 2600mAh Portable External Back Up Battery/Hand Warmer Compact and lightweight (3.8 x 1.37 x 1.37 inches, 2.7oz), fits easily into any pocket or bag. Gives little more than a full charge to iPhone 5/4s/4/3G/3GS and most digital devices. Warms on one side of unit for 5-8 hours (at 111F to 122F) in room temperature. Compatible with digital devices that are charged via USB Output: 5V, 1A Input:5V, 0.8A