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.
Step 3: Polarity and Connections
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.