How to build USB Battery
http://www.hackaday.com/entry/1234000520028239/
Here is what you need:
- 5.1v zener diode
- 100ohm or slightly greater resistor
- 9v battery connector and 9v battery
- flat female usb connector that mates with your device�s usb cable. this is the hardest part to find.
Wire it Up.Connect everything up as shown. The top two wires go to the battery and the bottom two are connected to the female half of the usb cable.
Test it. Connect the battery and test the voltage over the diode. It should be close to 5 volts. If not, make sure you have everything wired correctly. Pay special attention to the polarity of the diode.
Try It. You should be able to use any low power device that charges via usb.
Finish the Job. Be meticulous with your soldering.
Jason Striegel -- "How to make a USB Battery" via Lee Hosty on Open.
Seen on IrishEyes -- "DIY USB Power"
x_ref101ib