By Chris Deziel – Updated March 24, 2022
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Batteries convert chemical energy into electrical energy. While a lemon battery gives only a modest output, it demonstrates the same principle that powers car batteries. This guide shows how to build a functional electrochemical cell at home using two everyday items: Coca‑Cola and vinegar.
A basic electrochemical cell consists of an anode, a cathode, and an electrolyte. The anode (negative electrode) and cathode (positive electrode) are made from two different metals that react at different rates. In isolation, electrons flow too slowly to generate useful current. Immersing the electrodes in an electrolyte—usually an acidic solution—creates a chemical gradient that pushes electrons through an external circuit. As long as the chemical reaction continues, the cell produces a steady voltage.
Any soft drink containing phosphoric acid can serve as the electrolyte; Coca‑Cola (regular or diet) is a popular choice. Cut a strip from the aluminum can, then sand the paint off to expose the metal. Use a small copper strip for the anode. Place both strips in a glass of Coca‑Cola and connect a voltmeter. You should read roughly 0.75 V. The aluminum acts as the cathode, while copper serves as the anode.
Vinegar, which contains acetic acid, is an excellent electrolyte. For the anode, use a copper strip. A zinc electrode—such as a galvanized nail coated with zinc—serves as a better cathode than aluminum. Submerging the two electrodes in vinegar yields about 1 V. To power an LED, connect two cells in series: attach the LED between the anode of the first cell and the cathode of the second, then bridge the remaining electrodes with a wire.
Because vinegar is clear, you can witness the reaction in real time. After running an LED overnight, inspect the zinc electrode. A dark, black deposit of copper atoms will have formed as hydrogen ions combine with electrons and settle on the zinc surface. You may also see bubbles of hydrogen gas forming on the copper strip—hydrogen ions gain electrons to become hydrogen atoms, which pair into H₂ molecules.
