This one would make a nice centerpiece for your Halloween party. It’s a battery with tiny pumpkins serving as the cells. [EM Daniels] shows us how to clear out the pumpkins, fill them with some freshly mixed electrolyte, and he even throws in the directions for baking the pumpkin seeds.
Each pumpkin will need a pair of conductors made of dissimilar metals to serve as the anode and cathode. Copper wire is used for one, aluminum for the other, and both wires have a spiral pattern bent on one end to increase the surface area that contacts the electrolytic solution. Now just boil up a slurry of vinegar, gelatin, and salt, then let it sit in the fridge over night. [EM Daniels] was able get 1.5V out of this project (enough to light one LED) for two hours, and 1.4V for six hours by using seven of the pumpkin cells in series.