Powerful Lithium Polymer Rechargeable Gomadic Brand Battery Pack High Capacity Portable Charger Compatible with Samsung Nexus S with upgradeable TipExchange Technology Specification: Internal Battery (7800mAh lithium polymer), Input port (microUSB), Output Port (Standard USB), Onboard Circuit Design (Samsung Nexus S Specific), Dimensions (2.75 X 3.25 X 0.75 inches), TipExchange enabled (Yes) Very easy to operate. Simply connect Samsung Nexus S, press activation button on pack, and charging begins. Quick start guide included. Integrated circuitry tailors output voltage and charging current to exact specification of the Samsung Nexus S (accurate to 0.1v). Designed with a front facing LED display that clearly display the current battery capacity at the touch of a button Continue to use your Samsung Nexus S for hours OR recharge it on the go without being tethered to a wall outlet