Idea popped, and so I'm here. :) Can someone calculate maximal amperage and how long could an AA size mechanical battery (with spring inside) produce electricity at standard AA battery voltage (1.5V). ------------------------------------------- Description of that mechanical battery: - Casing would be made of an extremely physically resilient material (titanium?). Of course thick walls are required. - It would have a single spring (made of some rigid, yet elastic enough material) which requires 10-80kg of pressure to be compressed (you would buy these batteries according to your body weight -- basically you convert force of gravity affecting your body mass into electric energy). - It would be compressed by placing a battery into a holder (an object with a hole where you place the battery) then you insert a rod attached to a surface, which you would lean onto, into the battery. Those two parts would be what you call 'charger'. :) - Inside the battery there would be a miniature DC generator (i.e. neodymium magnet and coper coils -- rotor/stator). - The spring would be pressing a motion converter (linear pressure would become rotation of the miniature generators' rotor). I guess amperage and voltage would depend on size of coils and the speed generator rotates. - This "battery" would generate electricity until spring comes to a relaxed state. Maybe there could be a regulator which would detect that circuit is closed (it would mechanically start/stop/speed-regulate the rotor (which allows/disallows the spring to expand)). So that's it. Clean reusable energy source for portable electronic devices (no fancy chemistry, no fire danger, no pollution).