Homemade Batteries

This web page explains how a homemade battery works. http://www.physlink.com/Education/AskExperts/ae314.cfm?CFID=995968&CFTOKEN=22339656

"When a rod made of a transition metal, such as copper, is dipped into a solution of its own ions, such as copper sulfate, an equilibrium is set up between the metal in its solid state and the metal as aqueous ions. (A certain proportion of the metal atoms exist in the rod as solid atoms and a certain proportion exist in the solution as aqueous copper 2+ ions). When some of the metal on the rod dissolves to become aqueous ions, electrons are given up by the atom (A copper 2+ ion has loses 2 electrons) and build up on the rod giving a negative electrical charge. This is called a half cell. The size of the negative charge depends on how good a reducing agent the metal is. (Reducing agents donate electrons in reactions). So if we take two half cells made of two different metals and join them together, as one will have a greater negative potential than the other, a potential difference is set up between the two metal rods. As a potential difference cause electrons to flow (from the rod with a greater negative charge to the rod with a smaller negative charge), a cell will have been created. When a copper half cell and a zinc half cell are joined together, they can generate enough current to light a bulb and it is the basis of a cell called the Daniell Cell. "

Here is another web page that shows how to make a simple battery that is strong enough to generate 1 Volt or 100 mA, which can power a light or a small motor-- http://www.exo.net/~jyu/activities/Al-air.pdf