Joule Thief Charger

Step 1 Make the Charger

Use this schematic to build a standard Joule Thief circuit with the added diode.

My joule thief uses twisted network wire passed through a small ferrite core. I use 6 turns of wire. You can find a core from a burned out compact fluorescent bulb. You can see how others have wound the coil and built the Joule Thief, since so many have done so. Just add a diode and LED in series with the charging battery. The LED is useful as a charge indicator.

A high-speed schottky diode would be the most efficient. The 1N4005 was handy at the time and works.

Comments

[flying pie]

circuit is too small and can u add a solar panel to the "charge donor " so u can charge it without using up a battery to charge a diffrent battery

[A good name]

Are you serious? The circuit is too small? Adding a solar panel would defeat the purpose. You're using a next-to-dead battery to charge another battery.

[botronics]

Next-to-dead batteries still have a lot of joules left. I have nite lites that run for months using next-to-dead batteries. We are just transferring whats left to something more useful.

[lolzertank]

Wouldn't the led eat up a lot of power? Assuming that its a red led (2v), then the total load is 0.7v (diode) + 2v (led) + ~1.3v (battery) = 4v * (your charge current). Without it, it would be 2v * (your charge current) total, increasing the efficiency dramatically. Of course, since you're using dead batteries, this might not be important at all.

[webmasterpdx]

 Shottky diode shouldn't be .7V. Probably could use a germanium too. Either gives you capability of working with lower input voltage. personally, I'd get rid of the LED too (maybe have a pushbutton to see if it's working. You could also pass it through a capacitor to remove the DC component and the try a full wave rectifier. Might get better results....I'm not sure.