3 leds, joule thief, play-doh battery, instant light, last seemingly forever. Video explaining and showing more at https://youtu.be/RIxeOI9tI00 (https://youtu.be/RIxeOI9tI00)
I built the original play-doh battery some time back, but when testing non stop use I only got from a month to 3 of use from it when running non stop because of electrode erosion. But I wanted the play-doh battery to last years to decades supplying power just like my original water batteries do. Then I thought about it, even the standard AA battery has a shelf life. That means after a certain amount of time it drains regardless if its used or in circuit or not. And thats because the internal chemical activity and erosion of its electrodes never stops even if an AA battery just sits on a shelf. The next thought was how to stop that activity so the battery last longer, and only supplies power when needed. The answer was separate what causes the chemical activity. So in the case of the play-doh battery. Once the magnesium and play-doh are in contact chemical activity and the slow erosion of the electrodes starts and electricity is generated. But once the magnesium is separated from the play-doh then chemical activity stops and the erosion of the electrodes stops, so everything is at an almost stand still then. You could stick the dissembled play-doh battery on a shelf then and 20 years later take it off and assemble it and you have instant electricity. So theoretically you can make the play-doh battery last seemingly forever this way by using the contact/no contact method between the magnesium and the play-doh.