Whether it be for everyday carry (EDC), outdoor adventure, or disaster preparation, flashlights tend to be found towards the top of must-have items. But one common aspect of these luminescent devices is that they're only as good as the batteries inside. If you've ever switched on a flashlight only to experience a flood of frustrated disappointment, you might appreciate owning an "eternal flashlight." Lumen is designed to be powered by body heat, never needing batteries.
The finger-sized Lumen flashlight uses a small thermoelectric generator (TEG) to power a single 5-mm ultrabright Cree LED. We've seen successful use of such technology in consumer products before, such as with Power Practical's PowerPot. Researchers have been experimenting with wearable TEGs to extend the battery life of small devices, and, quite famously, a Canadian high school student created a working prototype of a body heat-powered flashlight as a science fair project. Lumen, however, could be the first of its type to be readily available to the general public.
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Lumen works to transform heat into electricity through a difference of body and ambient air temperatures. So if it happens to be 82 º F (28 º C) where you're at, Lumen is designed to produce about 15 mA at 3 V, enough to power the LED for 3000 mCd (millicandela of output. Any excess power is stored in an internal capacitor. The body of the Lumen flashlight is made of machined aluminum or titanium, weighing 1.2 oz (35 g) for the former and 1.5 oz (45 g) for the latter. These metals are not only durable, but they double as a heat-sink to help make the TEG work more efficiently.
While Lumen may not be able to compete with its battery-powered brethren in shear lighting power, it looks to offer more than enough light output to find objects, safely navigate, or read while in the dark. But with Lumen, you get to feel a little greener since you're the energy source and not a battery which, eventually, ends up being disposed. EDC enthusiasts will certainly appreciate the hole drilled through at the bottom, ideal for attaching to gear with split rings or paracord. And those who want to enjoy a bit of extra glow (for up to 10 years) can opt to choose one equipped with a tritium vial.
The Lumen flashlight is currently funding on Kickstarter, having raised 326 percent of its US$5,000 goal in just two days, with another 28 days left to go. A pledge of $35 sets you up with one Lumen in machined aluminum, $45 for machined titanium. Units with tritium vials run $15 more for each.
If you check out the video below, you can see that the creator's machining equipment appears ready and waiting. So if materials purchasing, production, and assembly go according to schedule, backers can expect shipments of the Lumen flashlight to start sometime in February, 2016.