Squeeze More Juice Out of a Dead Battery!
This article explains the physics behind a 'joule thief' circuit, which allows users to extract remaining energy from batteries that are considered dead. It uses the principles of Faraday's law of induction to power LEDs from low-voltage sources.
Why it matters
It provides practical educational insight into electrical engineering and energy efficiency for hobbyists and students.
That's not as crazy as it sounds. When a battery-powered device stops working, we say the battery is “dead”—but it's not really. It still contains chemical energy, and the voltage isn't zero; it's just not high enough to run a current through the light bulb or LED (or whatever load you have).
But with a little physics chicanery, you can indeed get that light to run longer. Much longer! I'm going to show you how to build a simple electrical circuit, pairing a transformer and a transistor, to tap that residual energy. It's waggishly called a “joule thief” circuit. Get it?
It's not only fun to build and kind of mind-blowing, it's also a great illustration of Faraday's law of induction, the same principle that's used in electric generators—and induction cooking stoves, for that matter. Let's do this!
Basic Battery and a Light Bulb
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