Mag-Lite flashlights are some of the best you can buy. They’re heavy, well built, incredibly bright, and last a good long time on the batteries you put into them. Still, those batteries are disposable. Instructables user monjnoux didn’t like that idea, so he tweaked his for easy outlet recharging instead.
His Instructable is a bit light on the details of how he did it, but the crux is pretty simple—instead of standard batteries, he got some 11000mAh NiMH rechargeable cells, an adaptive voltage charger, a brighter LED to replace the one that’s stock in the Mag-Lite, and the necessary jack and socket connectors to wire the whole thing together. One thing he does note is that while he used a 3-cell model for this trick, you could do the same with the smaller 2-cell model, or the even larger police-style five-cell Mag-Lite, whichever you prefer.
Some sharp soldering and re-wiring later, and monjnoux had a rechargeable model that cost much less than the official Mag-Lite rechargeable battery, and lasts longer than the official model at that. If you want to do this one yourself, you’ll have to follow along with his wiring diagrams at the link below, but all things told it doesn’t look too difficult—just time intensive (and you may have a little trouble finding the parts, since he got them all from eBay—although he does include a full parts list.) Hit the link below for the step-by-step.
Hack a Mag-Lite torch into a rechargeable led torch | Instructables via Hack a Day