Gomadic High Capacity Rechargeable External Battery Pack suitable for the Phonak Venture ComPilot II/ComPilot Air II Integrated circuitry tailors output voltage and charging current to exact specification of the Phonak Venture ComPilot II / ComPilot Air II (accurate to 0.1v). Very easy to operate. Simply connect Phonak Venture ComPilot II / ComPilot Air II, press activation button on pack, and charging begins. Quick start guide included. Specification: Internal Battery (7800mAh lithium polymer), Input port (microUSB), Output Port (Standard USB), Onboard Circuit Design (Phonak Venture ComPilot II / ComPilot Air II Specific), Dimensions (2.75 X 3.25 X 0.75 inches), TipExchange enabled (Yes) Internal circuit protects the Phonak Venture ComPilot II / ComPilot Air II from various power ailments including surges, overcharging and short circuiting. Advanced logic maximizes charger efficiency Built using unique Gomadic TipExchange Technology that protects your investment by providing the ability to upgrade charging ports by simply swapping the physical connector.