Mechanically-powered Flashlight - Crank Powered Design

Crank Powered Design

Crank powered flashlight disassembled to show parts: (1) Crank (2) Reduction gears (3) Brushless AC generator (4) Rechargeable lithium-ion cell (5) Full-wave rectifier (6) On switch (7) LED lamps

Another common type is the windup or crank-powered flashlight. In this design, the light is powered by a battery which is recharged by a generator turned by a hand crank on the flashlight. One minute of cranking typically provides about 30 to 60 min of light. It has the advantage that it doesn't have to be pumped continually during use like the dyno torch or shake flashlight. However it may be less reliable as an emergency light since the rechargeable battery it contains eventually wears out. The lithium-ion cells typically used are rated for around 500 charges.

Crank powered flashlights often have radios and other features. One popular feature is a USB jack for recharging cell phones when an outlet is not available.

In an alternate "Clockwork Torch" design, produced by Freeplay Energy, the energy is stored in a flat spiral wound mainspring, rather than a battery. The owner winds the spring up by turning the crank. Then when the light is turned on, the spring unwinds, turning a generator to provide power to run the light. The purpose of this design, originally invented for use in the developing world, was to improve its reliability and useful lifetime, by avoiding or reducing reliance on a battery. As of 2012, the original design is no longer made, but updated smaller hand-cranked models using LEDs are available.

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