A colleague recently brought the Hydra Light to our attention, a personal flashlight and charging station that runs on an electrolyte battery. While this design is patent pending, the basic technology behind it is as old- or older- than the pyramids. There is evidence that electrolyte batteries were known in ancient Persia and Egypt, and possibly across the ancient world. The windowless pyramids were lit with electric lights.
But how do electrolyte batteries work?