Charge Your Phone Just by Walking

A new device that channels kinetic energy and fits in your backpack.
Courtesy Tremont Electric

The new nPower PEG allows users to charge mobile devices without an outlet, without sunlight or wind—without anything but a little bit of motion. Users, for instance, can throw it in a bag while they’re walking, strap it to a bike, or take it jogging, and then plug in their phone to recharge it. Movement causes a spring-mounted magnet to bounce and pass repeatedly through a coil, charging the battery. It’s especially useful for people who need to power their mobile devices while they’re off the grid.

The new PEG (personal energy generator), which launches this spring and will be sold for $170 at, was developed by Cleveland startup Tremont Electric. Tremont first introduced the device in 2009, but the new charger has a 2,000-mAh (milliampere-hour) lithium polymer battery—double the capacity of the old one—which allows it to fully charge an iPhone 3, and charge an iPhone 4 as much as 75 percent. An iPod nano needs about 1 minute of walking time for 1 minute of listening time, while an iPhone requires about 25 minutes of walking time to generate 1 minute of talk time.

Tremont Electric doesn’t have its sights set only on phones. Tim Russo, a spokesman for the company, says: “It’s also scalable. The bigger the device, the more power. So we can build something the size of a car and put it in open water, and capture energy from waves to put commercial scale electricity into the grid.” The company also has a development contract with a military contractor to build a charger in soldiers’ body armor, which it will try to sell to the government.

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