Powerful Lithium Polymer Rechargeable Gomadic Brand Battery Pack High Capacity Portable Charger Compatible with Magellan Maestro 4700 with upgradeable TipExchange Technology Specification: Internal Battery (7800mAh lithium polymer), Input port (microUSB), Output Port (Standard USB), Onboard Circuit Design (Magellan Maestro 4700 Specific), Dimensions (2.75 X 3.25 X 0.75 inches), TipExchange enabled (Yes) Integrated circuitry tailors output voltage and charging current to exact specification of the Magellan Maestro 4700 (accurate to 0.1v). Very easy to operate. Simply connect Magellan Maestro 4700, press activation button on pack, and charging begins. Quick start guide included. Elegant, compact design is approximately the size of a standard deck of playing cards. Rugged exterior is built to last and backed by Gomadic Lifetime Warranty Built with high capacity lithium polymer rechargeable battery technology (28 Wh / 7800 mAh) in a compact design.