Dad Scientist | copper aluminum battery @ET2uscg | Uploaded October 2011 | Updated October 2024, 1 hour ago.
Aluminum post about 2 inches long and paper towel wrapped around it then a copper wire 12 gauge wrapped around that. Put salt water on the towel and hooked all in series to get about 4 volts and 4 milliamps . It runs the led from a yard light .