As an experiment in making a environmentally friendly DIY battery, I built a lemon battery
using a fresh lemon (electrolyte), a galvanized (zinc coated) nail and a 3" length of 12 gauge solid copper wire left over from a wiring job. The zinc gives up electrons to the copper, and gets "eaten" up by the process. Four lemons in series lit up one of my mega bright 10mm White LED's, another string of four paralleled provided more current. An article titled Build Your Own Battery
(.doc file - safe) suggests a nicely laid out lab experiment that tests the differences in electrolyte concentrations. With the info on different galvanic materials
, one could test a variety of electrodes as well and come up with a recycled material battery at virtually no cost, and environment friendly, as these are recycled materials. Sea water, if available, salt water (made from commercial or "found" salt), and other electrolytes
, apple, banana, orange, etc.) are possible.