Do you know the feeling? You have a collection of identically looking batteries, and there's a traitor among them...
One of the batteries is indeed dead, flat, kaput, and it spoils it for all the others—and for you! In the old days, there was no way around testing them one by one. Not anymore.
The Drop Test
Ordinary folks have whispered about the trick to test the battery, but it has actually been confirmed by a scientific test from the prestigious Princeton University in the US. The trick simply involves observing that dead batteries bounce higher when dropped from a moderate height.
How to Test Your Batteries
This test can be performed on most of the batteries we use for household items, toys, and gadgets. This includes AA, AAA, C, D, and 9-volt batteries. The method is simple and can be performed without any additional props.
Here's how you do it:
Drop the battery with the flat side down from about 30 centimeters in height.
If the battery bounces, it's on its way out.
If it falls and stays close to the ground, it likely indicates that it's a fairly new battery.
It should be noted that the test does not reveal if the battery is completely dead or half-dead. Batteries at these two stages in a battery's life bounce in the same way.
If you want to hear more about the scientific explanation behind the test, you can read about it here.
