What happens to a car battery internally, that causes it to “go bad?”
In: Chemistry
Car batteries are two thin sheets of lead alloy, separated by a solution. As the battery charges, lead is plated from one plate to the other. As the battery discharges, the process is reversed.
In an ideal world, the lead ions would be perfectly uniformly distributed in the solution, and the plates would remain completely flat. So, that’s not how it really works. One plate gets a little bump from random concentration imbalances. That makes the gap between the plates a little smaller. The smaller gap makes that point a more active part of the battery. Over time, a little stalagmite starts to grow toward the other plate. One day, it touches, and the battery has an internal short. Lots of heat in generated, and the plate might be damaged, or even crack and come loose. Not to worry, there are a couple dozen plates in each cell, and the other ones are working fine, for now.
Over time, more plates are damaged. that’s why it’s bad to run a battery dead, this is the stage where the maximum plating effect occurs, shortening the overall life.
Latest Answers