Salt Water Battery
About 13 years ago, I made a salt water battery to operate a single AA battery quartz clock. It ran for several months until I got tired of adding water to compensate for evaporation. The batttery consisted of 5 cells each producing about 300 millivolts. As I remember, I used 5 small olive jars filled with about a cup of water and a tablespoon of salt to create 5 cells in series each producing about 300 millivolts for a total of around 1.5 volts. The positive electrode was made from a strip of double sided copper circuit board (about 1 inch by 4 inch) and the negative electrode was a similar sized strip of aluminum. I recently tried some galvanized iron instead of aluminum and found it produces a little higher voltage so the battery may be made with only 3 cells. But any two different metals used with salt water or citrus juice will create a low voltage battery. You might experiment using silver coins and copper pennies and various fruit juices to come up with a more powerful battery. The diagram below shows the 5 cells connected in series with the galvanized iron of one cell connected to the copper piece of the next. The battery produces a very low current of around 1 milliamp so it's not practical for much other than a quartz clock. You might get a low current LED to light using a few more cells and larger electrodes with greater surface area. You might also add a capacitor across the battery to supply higher current pulses for a flashing LED. It will probably operate the 1.5 volt flashing LED circuits shown on the main menu at a slow flash rate.
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