Power Mate Plus portable backup iPhone battery. The Power Mate Plus provides you with hours of extra use of your iPhone 3GS/4/4S. Just charge it, put it in your bag and use when needed. Imported.
Built in lithium-ion battery charges via USB to computer or power adapter. Charge time: 3 hours. Capacity: 1000mAh. Input/output: 5V. Battery life will depend on device and usage.