There are several different easy to create batteries that you can make inexpensively at home. A battery can be made when you place any two different types of metal into a conducting solution. Typical homemade batteries include sticking copper and zinc strips into a lemon or a potato.
Zinc-air batteries are metal-air batteries powered by oxidizing zinc with oxygen from the air. The battery has a high energy density and are inexpensive to produce. Zinc-air batteries are widely used in hearing aids, where they have replaced toxic mercury-based batteries in providing a small but steady stream of power. They supply more energy for their size than any other battery, because they draw some of their power straight from the air.
You can make your own zinc-air cell at home by placing a strip of zinc and a strip of copper into a solution of one cup of water with a tablespoon of salt mixed in. Attach a wire from a voltmeter to each of the strips of metal. You will find that the zinc-air cell will produce about three quarters of a volt.
To get higher voltages, which will be needed to run an LED, you will need to connect two or more cells in series to make a battery. Two zinc-air cells in a series will produce about a volt and a half. This should be enough to make your LED light up. If you want the LED brighter, you will need to add more cells in series.
If your LED still isn’t lighting up, try reversing the leads. A diode only works in one direction. The leads on the diode usually have one lead longer than the other to show which way it should be connected. Try connecting the copper electrode to the longer lead on the LED.
Another way to make the cell produce a higher voltage is to change the chemistry of the solution. By adding some hydrogen peroxide to the salt and water solution, you will receive a high volt output.