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Ingenious trick shows in seconds whether batteries are empty or full

To check whether batteries are charged or not, you don’t have to insert them into a device or even buy a battery tester. There is a simple trick for this.

If you want to know whether a battery is full or empty, you should drop it on a table. This is because they behave differently when they hit the tabletop, depending on their charge level. atechbook explains why this is the case and what the drop test reveals in detail.

Inner gel of empty batteries becomes solid

The test works for all cylindrical, non-rechargeable alkaline batteries – especially the common types AA and AAA. From a height of ten to 20 centimeters, you simply drop them onto a tabletop, work surface or similar and observe what happens. If the battery jumps up a bit from the floor, it is empty. If it simply tips over after hitting the ground, it is full.

The reason for this reaction is a jelly-like zinc mass that is inside. When fully charged, this dampens the impact of the battery. If the battery discharges, however, the jelly-like paste becomes solid and can no longer cushion the fall. The battery jumps up. The higher a battery flies in this test, the lower its charge. If the battery jumps about as high as it is long, it is probably dead. If you want to be completely sure, you can also do a comparison test with a guaranteed full battery and compare the jump heights.

Another battery trick

This is not the only trick about batteries. If you ever don’t have the right size battery on hand, the following trick can help. Did you know that you can turn a small AAA battery into a larger AA battery with very little effort? You can see how it works in our TECH-HACK video or read it in the instructions on atechbook. All you need to do it is a piece of aluminum foil.

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Here you can find more TECH-HACKS

If you like our TECH-HACK about batteries, feel free to check out our YouTube channel. There are more hacks and many tests there.


  • Life Hack