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Spring Battery

  1. Aug 28, 2008 #1
    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).
  2. jcsd
  3. Aug 28, 2008 #2


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    The energy stored in a spring is = 1/2 * force * distance.
    The 1/2 is because the force is zero at the start and only amaximum at the end, so we use the average.

    So if we made the spring the ful length of the battery 50mm and used 80kg
    Energy = 0.5 * 80*9.8 * 0.05 = 20J, a little disapointing, an Alkaline AA battery normally stores about 5000J.

    You could use a coiled spring using some sort of crank handle - a coiled spring is exactly the same principle, it's just the compression length is longer.
  4. Aug 28, 2008 #3
    OR: :)

    Let's see...

    energy = 1/2 * force * distance; force = mass * G

    5000J = 1/2 * force * 0.05
    force * 0.05 = 10000J
    force = 200000 N :) %.

    mass = 20387 kg :D Gimme foOoOoOod!
  5. Aug 28, 2008 #4
    Actually it could be easily achieved by leverage, but what material can handle 20t of pressure?
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