There’s an easy way to see how much life is in a battery. Simply drop it.

A peer-reviewed study at Princeton University, which was published in the Journal of Materials Chemistry, backs the old claim of battery testing. The study shows that the more the battery discharges, the greater its bounce.

The research discovered that in the process of discharging, there also a physical, as well as chemical, change in the nature of the battery. Some of the discharge will turn from gel form to ceramic and form outside of the battery. It then creates bridges between parts of the battery, acting like types of springs.

Check out this video below for a more detailed look, or to understand what the hell we’re talking about.