Joule Thief Flashlight for Used Batteries

Introduction: Joule Thief Flashlight for Used Batteries

Give your used batteries a second life with this Joule Thief Flashlight!

It works with dead batteries that won’t power your devices anymore.

Note: this will drain the batteries "down to the last drop", which is not good for recyclable batteries.

Be green and enjoy DIY…

Step 1: Parts


10mm white LED.

Ferrite toroid core.

Insulated wire.

1kΩ resistor.

BC547B NPN transistor.

Batteries holders for AA and/or AAA.

AA or AAA used batteries.

Perfboard (optional).

Soldering kit.

Hot glue gun.

Step 2: Build It

a. Replace the original light bulb with the LED (refer to photos).

b. Solder the batteries holders in parallel (this will allow to use the flashlight with only 1 or more batteries).

c. Build the toroid inductor by winding two wires around the toroid (refer to photos).

d. Solder and assemble the other parts as shown in the circuit diagram.

That’s it!

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    2 Discussions


    4 years ago

    There are better Joule Thief circuit this is a good build though


    Reply 4 years ago

    Could you link your favorite or so?