Here's the Truth About Testing Batteries by Bouncing Them

Within the past year, you may have come across this life hack making its way around the Internet: To see if a battery is dead, drop it and see if it bounces. Good batteries will sort of thud, and not bounce, but dead batteries will have some "spring in their step."

Here's a video demonstrating the test:

We've all stared at a pile of AAs before, not sure which ones we just removed from our remote and which were fresh from the package. So this trick would be super handy — if it actually worked.

A group of engineering researchers at Princeton University recently debunked the battery bounce test. Though their study comes with a fancy name (The relationship between coefficient of restitution and state of charge of zinc alkaline primary LR6 batteries — phew!), the bottom line is this:

"The bounce does not tell you whether the battery is dead or not, it just tells you whether the battery is fresh," said Daniel Steingart, an assistant professor of mechanical and aerospace engineering.

Steingart and Shoham Bhadra, a doctoral student in electrical engineering, found that as a battery is used, more zinc oxide is created inside, which causes it to be bouncier. But while this reaction is true when a battery is 0% charged, it can also work when a battery is 50% charged, or even more — totally enough strength to power your remote for a little longer.

Check out their bounce test to see the results in action:

Good thing popping batteries into your portable radio and hitting "play" is a test that's nearly as simple.