This project details a small and simple, but very powerful USB charger for your mp3 player, camera, cell phone, and any other gadget you can plug into a USB port to charge.
The Minty Boost is a small, make-it-yourself, battery-powered charger for USB devices, built into an Altoids gum tin. The tin is not absolutely necessary to the devices operations, but it protects the works, makes the charger portable, and looks great. If your device can charge via USB then this can give the device a little bit of extra juice should the batteries run low. Minty Boost runs on common AA batteries, so it is easy to use on the road. According to inventor, a Minty Boost will run an iPod 2.5 times longer than a 9VUSB charger. Minty Boost is well-known in the world of open-source, DIY technology.
It charges when there is a current draw on it. It will work the same as when your iPod is plugged into a charger. It will charge the battery and play if there is enough power, and will play the ipod until the AAs run down- then the ipod will use its own batteries.