A4Tech BatteryFREE Wireless Optical Mouse Review

This is not your average mouse and pad. Inside both are rings of copper wire which generate an electric charge. That power moves from the pad to the mouse and vice versa through induction (in layman's terms, electricity "jumps" from one charged object to another nearby object). Hence the lack of batteries. The benefits are twofold: first, you don't have to spend money on batteries. Second, even mice with rechargeable packs are still heavier than the corded variety and are therefore slightly harder to move around. This way you get the best of both worlds: the light weight of a corded mouse with the freedom of a cordless one (albeit limited freedom).