How Does a Crank Flashlight Work?

by Joe Steel
Keep a battery-powered flashlight as back-up.

Keep a battery-powered flashlight as back-up.

Hand-cranked flashlights have proven to be a boon to campers, alleviating the need to lug batteries into the wilderness. Along with other hand-powered electrical devices such as radios and cell phone chargers, they also have helped to revolutionize life in parts of the developing world where electricity is unavailable or in short supply. They also come in handy if a storm knocks out power to your neighborhood.

How It Works

Most hand-cranked flashlights have a winding handle on the side. You crank for a minute or two to provide enough of an electrical charge to run the flashlight. Other models may be charged by shaking or squeezing the device. Inside the flashlight is a small generator, or dynamo. As with larger generators like hydroelectric-powered turbines, which spin around large coils of copper to produce electricity, the turning of the crank produces an electrical charge. How long the flashlight will burn depends on how luminous it is, what kind of lights it has -- LED lights use less electricity -- and the maximum capacity of the flashlight, in addition to how long you've cranked it. Many hand-cranked flashlights are combined with a radio into the same device, so if you run the radio along with the lights you'll use up the available electricity that much faster.

Good in an Emergency?

While hand-cranked flashlights can be helpful if the lights go out, one company that specializes in emergency-preparedness gear cautions that you shouldn't rely on them for your disaster kit. If left a long time without being charged, the internal battery may completely discharge. It then can be difficult to work up a sufficient charge to get the device working again. To compensate for that, use a hand-cranked flashlight that also has a back-up battery that works independently of the dynamo-powered internal battery.

About the Author

Joe Steel is a Northwest-based editor, writer and novelist, former news editor of an outdoor weekly. He also was an editor at a Seattle-based political weekly and editor of a monthly business magazine. He has been published in the "Seattle Times," the "Washington Post" and the "Foreign Service Journal," among other publications.

Photo Credits

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