There are probably a million of these floating around but I wanted to post my own.
An ipod, connectors, a couple 470ohm resistors, and a 5v regulator, and some soldering skills are nice to have.
Step 1: 5v Regulator Circuit
This is real simple it takes the 9.6v input and puts it as a 5v output to the usb. But the ipod has to have pull up resistors on the data lines.
Those reistors have a value of 470ohm
On the regulator it is advised to have a heatsink to keep the chip from overheating.
Step 2: Enjoy!
put in a container of some type and plug in a battery pack and an ipod and your good to go!