Forever Flashlights by Excalibur
by Warren McLaren, Sydney on 11.11.05
In a strange quirk of fate, on the very same day that Collin was regaling you with stories of the batteryless calculator, I was given, as a belated birthday present, a torch that worked on the same Faraday principle. The blurb says “Never needs batteries, never needs bulbs, waterproof, visible for over a mile.” Using a super bright blue LED light, if you can shake the “Forever Flashlight back and forth for 15-30 seconds, enough electricity is generated to light the LED bulb for up to five minutes of continuous light.” The box for mine actually reckons 1 minute of shaking will give 30 minutes of light, but it seems to use two coils, so maybe this helps pump in a bigger burst to the rechargeable capacitor? (And Excalibur do suggest the market is awash with imitations.) Apparently the strong magnetic coils can upset pacemakers, credit cards and cathode ray tube monitors, so is best kept a distance from such items. The Excalibur models range from about $20 to $40 USD and they’ve added a new dynamo version for about $25 USD. (1 min of winding for 45 mins of light.) ::Forever Flashlights.
Um forever might be a while for a grown up, but it wasn't long with my 6yo - it got pulled apart several times and worked for only about a week.
I bought two of those a year back and was rather disappointed. You have to shake the light violently for at least 3 minutes (you're arm will get tired) before it produces enough usable light. You can shake it less, but the light output is too weak. I later bought the winding dynamo version and I was very impressed. Go with the dynamo if this is something you are considering.
Lastly, I cannot stress enough how powerful the magnets are in the Forever Light. Just don't put it in the same pocket as your wallet as it will destroy your credit cards.
I've been thinking attaching one or two of these things to a bicycle wheel and using them as light-weight generators to charge standard size rechargeable batteries. Haven't yet figured out how to do it and am looking for help from anybody else who might be interested in such an experiment.
gmoke, that probably won't work, since the centripital force of the spinning wheel would prevent the magnet from moving up and down.
You could strap it to your leg perhaps...