Get Power from ‘Dead’ Batteries by Building a ‘Watt Wringer’


| 6/4/2015 11:46:00 AM


Tags: batteries, energy efficiency, LED lights, electronics, recycling, upcycling, Tennessee, Bob Post,

Dead Batteries

Batteries have a limited working life. Even the best batteries won’t last forever. When your electronics say “low batt” it means just that: The batteries are low but not dead. They can still have useful energy in them.

The energy that remains in seemingly dead batteries can be used in this simple night light project that you can build at home in about one hour. Your new night light will shine for months and is reusable for years, powered by “dead” batteries.

How to Wring All the Energy from a ‘Dead’ Battery

New, single-use batteries start with 1.5 volts. However, modern electronics generally stop working when the voltage in a battery reaches 1.2 volts. To be clear, we're not talking about bringing a “dead” battery back to life but simply harvesting the rest of the energy that remains inside. Until now, remaining energy was wasted when a battery was recycled or sent to a landfill. That wastes energy and money.

This isn't a new concept. It's based on the Joule Thief circuit that has been around for decades. I don't like the term Joule Thief so I renamed it a “Watt Winger.” The teaching version of the Joule Thief circuit uses transistors and a homemade transformer. Fortunately, a solar-powered garden light has compressed all of this onto a single electronic circuit board—much better for use with the Watt Wringer. Repurposing the circuit board from a garden solar light into an attractive and efficient nightlight is easy.




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