DISCLAIMER: This tutorial is meant for and geared toward people who are used so using soldering irons. If you are new to using soldering irons or have no idea what a soldering iron is, please ask someone else who knows how to use a soldering iron and have them teach you. Either way, whether or not you know how to use one or not, use the proper safety gear. I am not responsible for any injuries that you may receive or deal out, nor am I responsible for any type of damages caused to your Apple devices.
Tools
Soldering Iron
List of Parts for Circuit
PCB board
USB female socket
2 75k ohm resistors
2 50k ohm resistors
1 7805 5V regulator
2 100nF capacitors
This will be a general overview of building the circuit for the battery pack and the detailed instructions for the case will be given in part 2 of this post.
NOTE: When soldering the USB socket, face the open part to the right with the connector pins facing left, as in the schematic. Inside the socket, you will see that there are "2 halves", a hollow half and a half with pins. Make sure that the hollow half is on the bottom and the pins are on the top.
Circuit Schematic
This circuit is necessary for the charger to be accepted by the Apple device. Basically, the USB socket must have exactly 5V on the first pin, 2V on the second and third pins, and ground on the fourth pin. I cannot give step-by-step instructions for soldering in each and every resistor, wire, capacitor, regulator, ect. because depending on the type of PCB board you buy, the pre-made copper insertions on the back of the board are different. Any type of battery above 6 volts will work for this circuit. To use this circuit, just plug in your USB charger cord and plug it into your Apple device.