Battery on Board [About This Issue]

When I was young, I never thought much about how batteries worked. I knew that if D cells were left in a flashlight or radio for too long, they would eventually stop working and, even worse, leak and cause damage. As the years went by, batteries got much better—they lasted longer and leaked less. Then rechargeable batteries appeared, and they got better and better as well. But how batteries worked was mysterious; I wasn´t about to take one apart to find out.