You know the part of Monty Python and the Holy Grail when that old man says he's "not dead"? Well, the next time your batteries stop working in your device of choice, you should recall that line before you recycle them.

That's because Popular Science recently published step-by-step instructions on how to create your very own flashlight that runs on dead batteries.

How is this possible, you ask? Even when a battery stops powering a device, as much as 15 percent of its original voltage is still inside the battery, according to Popular Science. In order to access that last boost of energy from the batteries, you can wire a circuit that goes by the delightful name of "joule thief" and get enough power to light a white LED. The circuit does this in pulses that are too fast to see — making the LED seem constantly lit, even though it's only powered less than half of the time.

The "joule thief" consists of a battery box on which you'll affix a switch, a protoboard with an LED light and resistor, and a toroid transformer core placed over the protoboard. Of course, there's quite a bit of wiring and soldering involved here — so if you haven't worked on something like this before, it could be a challenge to complete what Popular Science has deemed a medium-difficulty project.

But once you get the hang of it, you're set: the instructions apply to several different types of batteries, including AAA, AA, C or D alkaline batteries, so you can tailor it to your personal battery usage. Obtaining the parts seems to be fairly simple and affordable as well. Many of the materials can be found online, and Popular Science estimates that the whole project will cost you about $30 and two hours of your time.

If this project from Popular Science seems like a breeze or an impossible undertaking, there are plenty of other tutorials on how to make a "joule thief" flashlight around the Internet, so you shouldn't have any trouble finding the best one for you.

Photo: John Seb Barber | Flickr

Via: Co.EXIST 

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