In my case it re-charges 4 * 1.2 V NiMh batteries.
Things you need:
1. Solar Panel ( I used a 9 V one to charge 4 batteries. Each battery requires about 2 V to charge so you can accordingly adjust the size of the panel ).
2. Wires ( I used jumper wires as I dislike soldering but you can use normal wires too.)
3. Battery Case for the battery.
4. Diode( Buy it or pull it out of an old electronic device. You could also use an Led instead )
5. Led ( optional )
Schematic also given.
Attach the diode to the + end of the solar panel. The striped but must be away from the + side and closer to the - side.
If you are using only Led and no diode ignore above step and continue.
Make a hole in a box and put an Led in the hole. Connect the longer end of the Led(+) to the + of the panel. The other end of the Led goes into the + of the Battery/Battery case.
Connect the - of the Battery / Battery Case to the - of the solar panel.
Close the box and tape it in place.( do not glue it as you will have to re-open it to remove or put in batteries)
Turn the contraption over and put under a light / sun.
The led will glow to indicate that the batteries are charging.
After about a day your batteries will be charged, for FREE!!
If you liked my Instructable please see my others too.