Gomadic Advanced HTC HD2 compatible AA Battery Pack Charge Kit &ndash; Portable power built with upgradeable TipExchange Technology Specification: Input Voltage (4 X AA Batteries), Cable length (6 inches), Dimensions (5.0 X 1.5 X 0.75 inches), Circuit Design (HTC HD2 specific), TipExchange enabled (Yes) Integrated circuitry regulates output voltage specific to the HTC HD2. Advanced logic maximizes overall charger efficiency. Built using the unique Gomadic TipExchange Technology that protects your investment by providing the ability to upgrade charging ports by simply swapping physical connectors. Safely engineered with reverse polarity protection, in the event batteries are accidentally put in incorrectly. Easy to operate. Simply insert batteries, toggle on/off switch and your HTC HD2 will start to charge.