You will need this project when you have an extra mobile battery or you need to charge any lithium, Lithium ion or Lithium Polymer battery.
Maximum current is about 650 milliamps. The circuit is designed for batteries of 900mah or higher. Power source can be a 12v Gell cell (Power panel), or can be powered by a car's cigarette lighter.
I use an old 12v DC wall transformer (800ma or more.)
Step 1: The Schematic
The Circuit is simple , you will need the following
LM317 variable regulator
2N2222A or any Transistor handles 800mA
2 Capacitors 0.1 uf
1ohm 1Watt resistor ( current limitor )
Adjust R4 to the required output voltage
R1 controls the output current