battery that you can charge without external electricity

[magnegenix]

I came across this today, was an interesting design....

Magnet and Inductor and Rechargeable Battery Inside AA Battery

Would be good for the kids Wiimote

[hello_all]

Exactly I thought about this for cellphone battery , which can be shaken for extra time on call

[ewizard]

A couple things I see wrong there. Basic idea is okay BUT a couple things aren't realistic. One is you can't get with current battery tech 2500 mah out of a AA size cell where over half the size is occupied by a coil and magnet. Even getting 2500 mah out of a full AA size battery is optimistic. Secondly anyone who has ever had a shake light knows it takes a 'whole lot of shakin' goin' on' to keep even a tiny 5mm LED lit. In other words unless you ARE jogging for many miles the chances are you won't get enough shaking to keep the battery charged. Most shake flashlights used an Ultracapacitor which charges very quickly and they were very marginal in power. This person is proposing a Lithium Ion cell which charge very very slowly. Nice idea but I don't think it's realistic with current battery chemistry.

[wrtner]

Secondly anyone who has ever had a shake light knows it takes a 'whole lot of shakin' goin' on' to keep even a tiny 5mm LED lit.

Absolutely. Even a wind up spring, like the Trevor Bayliss radio, would be
a giant leap forward.