How to Build a Flashlight with Dead Batteries

How to Build a Flashlight with Dead Batteries

For those of you that love to tinker with gadgets, Popular Science put out a great how-to guide on building a flashlight with dead batteries. In a nutshell, batteries from devices that we use are thrown away after they are unable to power up our devices. Although the batteries are considered dead, they actually have about 15% of a charge left. By combining multiple “dead” batteries, it is possible to have a 100% fully charged battery that can be used to build a flashlight. This looks to be time consuming and expensive, but like I stated above, this is for those that like to tinker and show their gadgets to friends. If you are extremely cheap and are looking at this as a method to save money, then this isn’t for you. Instead, inquire about our wholesale battery prices.

Tools Needed for the Job

  • Soldering iron
  • Wire strippers
  • Scissors
  • Double-stick foam tape


  • D-size-battery box with leads
  • Battery-shell-adapter set
  • 10 mm superbright white LED
  • 24-gauge wire from old network cable
  • Toroid transformer core, at least ¾-inch ID
  • Flashlight push-button switch
  • 1-kilohm resistor
  • 1-inch round protoboard
  • 2N2222 NPN transistor
  • Dead AAA, AA, C, or D alkaline battery

 For detailed instructions on building this flashlight, please see the full guide on Popular Science. This is mostly for showing off to your friends. You could just buy replacement batteries from BatteryClerk. This seems like an expensive flashlight with the materials you need to buy, but if you want bragging rights feel free to build it!