Don’t throw away those bouncing batteries.

Researchers at Princeton University have found that the common test of bouncing a household battery to learn if it is dead or not is not actually an effective way to check a battery’s charge.

“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 and the Andlinger Center for Energy and the Environment.

The battery bounce test, popularized in online videos, shows that fully charged batteries bounce very little when dropped, while those that have been used for a while bounce higher. The height of the bounce increases as the batteries discharge, and that has led to the common conclusion that internal changes related to the reduction in charge are the cause of the higher bounce.