EEVblog #508 – Can You Test Battery Charge By Dropping It?


Can you determine the charge of an alkaline battery by simply dropping it and see how high it bounces?
A followup to the KipKay video
It seems KipKay’s video is just a ripoff of this earlier ONE

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11 comments

  1. I wouldn’t call it that – I saw the video and didn’t believe it myself (and I had questions). Of course, I didn’t have an immediate means to test it, but since Dave tested it for me, I think it’s pretty reliable that it does work.

    And it’s pretty handy too if you have a box of batteries and need to figure out which ones are dead and should be recycled.

  2. My hunch, based on cellphone battery experience, is that the discharged battery bottom is NOT FLAT anymore. The crystallization of the alkaline carrier or chemistry causes expansion, which causes the bottom FLAT to BULGE OUT. The change in geometry causes the bottom to act more like a spring, hence the greater bounce.

  3. My explanation follows from the reaction on Wiki: http://en.wikipedia.org/wiki/Alkaline_battery

    Loaded, the cell contains liquid Kalium- Hydroxyde, which is consumed. The products are all “dry”, i.e. solid.
    The cell “dries out” during discharge, or in other words, gets crystalline.

    An interior liquid will damp the shock more than a solid, stiff, crystalline structure.
    A rigid body gives an elastic bounce, a non-rigid body an unelastic bounce, by absorbing the energy.

    Edys explanation is also worth to examine:
    During discharge Hydrogen gas will be emitted, and as the cell is hermetically sealed (up to a certain amount of pressure),this pressure might change the contour of the cathode.

    Nice experiment, nice brain-teaser.

    Frank

  4. perhaps this will die here, but dave, did the center of mass of the batteries change when discharged? also what happens if you drop them from the plus side?

  5. I posted this on youtube, but maybe you’ll notice it here earlier:

    Hey, most of the time you let the empty battery fall off from a higher distance! (And no, it is not the camera angle, since you change sides when you switch from full to empty)

    Did you even notice that yourself ?

    Is your subconciousness doing tricks on you ?

    You would need to do a test with double – blinds. Let someone hand you the batterys only labeled with a number, not giving you any information on the load state.

  6. hi!,I love your writing very much! proportion we communicate more about your article on AOL? I need an expert on this space to unravel my problem. May be that’s you! Looking ahead to see you.

  7. would this work with lithium batteries as well?

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