How to Make a Very Simple Aluminum Air Battery

Aluminum air batteries are just an awesome simple technology. I've seen them used in videos for the electricity to power air nailguns in remote places! You can even make these batteries from materials you probably already have inside your own home. These batteries output of roughly 500 millivolts if constructed well, and can be set up in series to achieve even higher voltages.

Materials:

• Cardboard
• Salt
• Water
• Copper Wire - Broken lamp cord or wire from a hardware store will do fine. You only need about a foot.
• Aluminum Foil - You can find this at any grocery store - the link just happens to be a good price for a lot of Aluminum Foil
• Pencils - Just your standard No2 kind will do - we just need the carbon inside.
• Charcoal Filters - Optional - For the lazy, you can use these instead of the pencils. Charcoal Filters can be found anywhere that sells aquarium equipment. 
• Tape or Hot glue (Optional) - This is to secure the wire, but you can just bend it into place.

Tools:

Cup
Plate - Ceramic, plastic, or disposable is fine. Non waxed paper or metal plates won't work though.
Wire cutters (Optional)


Instructions:

1. Cut off a section of aluminum foil. 6 inches by whatever the width of your sheet is should do fine for this experiment.
2. Cut a piece of cardboard. Preferably the same size as your aluminum foil.
3. Next, you need your carbon source. So get your charcoal or graphite. 
• If you went the charcoal filter route, you're done. Proceed to step 4.
• If you are going the pencil route, you can do this in one of two ways:
• Easy Method - Take your pencils and draw all over one side of the cardboard, you want to press down pretty hard and darken the cardboard as much as possible. If done right, one side of your cardboard will be entirely black and slightly shiny.
• Harder method - Cut or burn off the wood exposing the graphite interiors. Crush the interiors into a powder and rub that all over one side of the cardboard
4. Make salt water. Add warm water to a cup. Add salt. The higher the concentration of salt, the higher current you will get from your battery, but that also means you'll drain your battery quicker too.
5. Pour a little salt water on the plate. 
• Put the cardboard down into the salt water to soak it up. 
• If you went the pencil route, it would be best to keep the graphite site up so the graphite doesn't smear onto the plate.
• Add more salt water if needed. You want the cardboard to be damp all the way through. It doesn't have to be soaking wet.
• Take your damp cardboard out and dry your plate.
6. Cut a foot long piece of the copper wire. 
• If it's bare, you can just bend it back and forth a few times to break it off.
• If it isn't bare, you'll need some cutters. Also make sure to expose a bit of bare copper wire on both ends.
7.  Now you have all of the components you need, so now it's time to build your voltaic cell (battery)
1. Put one end of the copper wire down. Keep about 4 inches on the plate and the rest hanging off the edge.
2. Put the aluminum foil sheet down on the plate.
3. Put the damp cardboard on top of the foil.
1. If you went the graphite option, make sure the graphite is face up and not touching the aluminum foil.
4. If you bought the filters, put this on top of the damp cardboard.
8.  Now you should have a foil>cardboard>carbon sandwich. The last step is to bend your copper wire so that the other end is touching the carbon top of your sandwich. 

Voila! you have a battery! If you want to power something with it, you can cut the copper wire in the middle and attach the copper to the leads of your device. It powers LEDs easy, as well as some small light bulbs.

You can also make a stronger battery by attaching many of these in series - or you can just make a bigger sandwich, so long as you continue to alternate between: Foil>Cardboard>Carbon>Cardboard>Foil>Cardboard>Carbon

You can stack it as tall as you want!

Here is an interesting way to build this very same thing and use it to power a night light.

Here is another interesting battery that uses cardboard - The Termite Battery