It works by using electromagnetic induction. Pretty much only Faraday's Law but with an electromagnet. Also this technique is used in charging high-end toothbrushes and Splashpower Devices.
Step 1: Get the materials
1. Lots of wire. I used 18 guage wire.
2. A piece of steel that your going to wrap wire around.
3. A capacitor, one with high capacitance.
4. A diode.
5. Batteries, I used 6 nine volts.
6. A multimeter so you can see if everything works.
7. And something to make it a little easier, Alligator clips.
Step 2: Making the Coils
Then, to make the Reciever Coil I put the non-sticky side on a D Battery and then wraped the wire on the sticky side. Make sure the reciever coil is around the size of the unless the steel piece is huge. Or if you have magnet film to see the where greatest amout of magnetism is. Once you are done winding the coil you can slide the coil off the battery.