This was a free flashlight from Harbor Freight that saw little use because of its AAA batteries. I thought the best solution would be to use a reclaimed 18650 cell from a laptop that had a less than desirable capacity so both items would have a new life.

Tube extender was remixed to fit HF flashlight threads and accommodate 18650 cell. A ground wire (copper strand from random scrap) is fed through the extension to create the electrical connection. 18650 spacer was remixed for clearance.