Faraday Flashlight

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The Faraday Flashlight (formerly known as the EverLife Flashlight) is an electronic flashlight heavily marketed via direct marketing campaigns beginning in 2002.

Unlike conventional flashlights, the Faraday Flashlight does not use conventional batteries, instead relying on a small super capacitor and charging mechanism that uses induction to power the high-intensity white LED array. Simply shaking the light for about thirty seconds provides about five minutes of light. According to the website, prolonged use of the Faraday is as simple as shaking the unit for 10 to 15 seconds every 2 or 3 minutes as necessary.

Unfortunately, many users have reported poor results with the flashlight, noting that eventually they must shake the light constantly to get any light out at all. This may be due to the large number of "fake" Faraday Flashlights that actually use watch batteries but look very similar to the real thing.

[edit] Mechanism

The LED array is powered by a small super capacitor that essentially acts as a battery. The capacitor is charged with the shaking motion which causes a magnet to travel up and down through a spool of copper wire. Current is induced through the loops in the copper wire to create an AC current as Faraday's law of induction shows. A full wave rectifier consisting on 4 diodes converts the AC current to DC. The DC current is then used to charge the small super capacitor.