Here's what I randomly figured out. Using just a 9V Battery to charge your device. The only problem is that you may need to turn off your device to get it charged as the battery consumption when your device is on is higher than how much it's charged. Not an native English speaker so I'm sorry for any grammatical errors.
If possible, give me some advice on increasing the voltage of the 9v to 12v so that it charges the device!
Step 1: Materials
What you need:
1) A Car Charger, take the plastic off.
2) Button Switch
3) 9V battery
4) 9V battery clipper
5) Some wires
6) Soldering Irons
7) Soldering tool
8) Project Enclosure (optional)
9) USB cable for your device
Step 2: How to Solder All These Things Together
This is pretty self-explanatory. Connect the red wire from the battery clipper (Positive) to the switch then to the Spring part of the charger. Then solder the black wire to the metal strip beside the USB charger .
Step 3: Done
Solder everything together and it's all done!
P/S: I need some help to increase the voltage from 9V to 12V. Does 9V battery+x2 1.5V battery works?