If you want to learn more about the electrochemical reactions that occur in batteries, you can actually build one yourself using simple household materials. One thing you should buy before you start is an inexpensive ($10 to $20) volt-ohm meter at your local electronics or hardware store. Make sure that the meter can read low voltages (in the one-volt range) and low currents (in the five-to-10 milliamp range). With this equipment on hand, you'll be able to see exactly how well your battery is performing.
You can create your own voltaic pile using quarters, foil, blotting paper, cider vinegar and salt. Cut the foil and blotting paper into circles, then soak the blotting paper in a mixture of the cider vinegar and salt. Using masking tape, attach a copper wire to one of the foil discs. Now stack the materials in this order: foil, paper, quarter, foil, paper, quarter, and so on until you have repeated the pattern 10 times. Once the last coin is on the stack, attach a wire to it with masking tape. Finally, attach the free ends of the two wires to an LED, which should light up. In this experiment, the copper in the quarter is the cathode, the foil is the anode, the cider vinegar-salt solution is the electrolyte, and the blotting paper is the separator.
A homemade battery can also be made from copper wire, a paper clip and a lemon. First, cut a short piece of copper wire and straighten out the paper clip. Use sandpaper to smooth out any rough parts on the ends of either piece of metal. Next, gently squeeze the lemon by rolling it on a table, but be careful not to break the skin. Push the copper wire and the paper clip into the lemon, ensuring that they are as close together as possible without actually touching. Finally, connect your volt-ohm meter to the ends of the paper clip and the copper wire, and see what kind of voltage and current your battery produces.
By now you should be well acquainted with the basic principles by which batteries discharge electricity. Read on to discover how some batteries can be recharged.
Despite all its drawbacks, gasoline continues to be the dominant fuel for automobiles. Why haven't batteries caught on? One of the biggest problems is with energy density -- the amount of energy a fuel can store in relation to its weight, which is measured in watt-hours per kilogram. Gasoline has an energy density of about 13,000 watt-hours per kilogram, while the best lithium-ion batteries currently available can hold only 200 watt-hours per kilogram [source: Manjoo].