The BatteryFREE Wireless Optical Mouse does not need a battery to keep powered on. It works with its ingenious Mouse Pad. The Mouse Pad will transfer constant power to the mouse and whenever the mouse is placed on the mouse pad which is plugged to the computer via a USB connector. Lift the mouse way above the mouse pad, and it receives no power. But as you lower the mouse onto the pad, you’ll see it light up, indicating its started to receive power, wirelessly, from the mouse pad!