The cover on the top was designed in Photoshop although Paint or GIMP could be used. It was then laminated and glued to the case. The case was a gift box that contained a wallet. i had no other use for it and thought it would be nice to give it a new life as my USB charger.
A clasp was added on the front as the magnets that used to close the lid were a bit weak. I found when the battery rattled round (later fixed anyway) the magnets would fail and the box would open.
Inside, there is the circuitry of a cheapo in car/lorry usb charger that was iPod compatible. I connected it's guts to a a two way switch to select whether the transformer (or Wall-wart) (seen on the back) or the battery was the main power source.
The battery was from an old RC car and packs a punch. My iPod and other USB devices charge very quickly. Also, the device can take any input power source from 5v to 24v so it is very versitile.
Feel very free to leave any questions and/or comments!
Joe, 16, England