Step 1: Get the Things Needed-
1: An LM7805 5v voltage regulator
2: A 9v battery (or anything you have between 6-12v, rechargeable or non-rechargeable)
3: A micro-usb male cable
4: Two electrolytic caps. 1uF and 10uF
5: A portable plastic box for your charger.
Step 2: The Circuit Diagram.
Make connections as per the diagram. You can either use solder, or heat shrink tubes, or whatever you wish. Just make sure of no short circuits.
Step 3: Polarity and Connections
Your usb cable might have two wires- one red and another black/white. The red one is positive, that is current enters through it. And the caps. already have markings on them.
The 9v battery's +ve will go to the 7805's input. The output will go to the USB's input(red).
Both the grounds will be connected to the base(center) of the 7805. The caps. are in parallel.
Step 4: Here You Go!!¡¡!!
Connect your phone and you are ready!!!!