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Spent Batteries feel lighter

  1. May 10, 2010 #1
    I'm 99% sure this is a purely psychological effect, but I find it very interesting. I can't think of any way a battery could actually lose a noticeable amount of mass from being discharged, but to me when I go to replace a pair of spent batteries, they always feel substantially lighter than fresh ones.

    I'm just curious if other people have noticed or experienced this effect.
     
  2. jcsd
  3. May 10, 2010 #2

    Borek

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    They are lighter, but I doubt there exist balance precise enough to measure the difference. It won't be hard to evaluate mass change using E=mc2 and battery voltage/capacity.
     
  4. May 10, 2010 #3
    The only time I've "felt" that is when, say, I replaced a drained "no-name" brand with, say fresh Duracell. The only true reason for that difference is that Duracell is a heavier battery.
    So, perhaps your phenomenon is more related to manufacturer differences.
     
  5. May 11, 2010 #4
    The only reason I can think of for a battery to FEEL lighter would be a leak of the acid, and I think you'd notice that.
     
  6. May 11, 2010 #5

    Borek

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    As far as I can tell there is no acid in replaceable batteries. Ammonium chloride (or zinc chloride) paste is slightly acidic, but calling it an acid is an exaggeration. Leaks from alkaline batteries are definitely caustic.
     
  7. May 11, 2010 #6

    Ivan Seeking

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    Surely someone here has access to an old and new battery of the same make and type, and a scale or balance.
     
  8. May 11, 2010 #7
    Look, it's really simple.

    New batteries are often "name" brands, whereas existing(in device) batteries are often the cheapest around. Those cheap batteries often have a lower weight. AKA cheap.

    Since one does not often check(or hand weigh) the batteries of a working device until it goes down, when one replaces the batteries, the replacement batteries are usually more heavy due to manufacturer differences.

    This is likely the reason for the confusion.
     
  9. May 11, 2010 #8

    Ivan Seeking

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    No need for speculation when we can make a simple measurement.
     
  10. May 11, 2010 #9
    I do not think that any common scales could differentiate the electron weight loss, much less a human hand.
     
  11. May 11, 2010 #10

    Evo

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    It's the loss of phlogiston.

    I'm going to get banned now, aren't I?
     
  12. May 11, 2010 #11

    Ivan Seeking

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    I don't either. So confirm the conjecture that nothing else happens that could cause a loss in mass. "We can't think of a reason why this would happen", is hardly a proof.
     
  13. May 11, 2010 #12

    Borek

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    Electrons are not lost, whatever charge exits on one side enters back on the other.
     
  14. May 11, 2010 #13

    Borek

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    Yes. There is no phlogiston in batteries. I think the correct term is electriston.
     
  15. May 11, 2010 #14

    Ivan Seeking

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    Yes, I meant to add that it is a change in the binding energies.
     
  16. May 11, 2010 #15

    Ivan Seeking

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    For example, is the paper used to wrap the batteries treated with something that could sublimate or slowly evaporate?

    Before you look, if you don't already know, then any conclusions were premature.
     
  17. May 11, 2010 #16
    Ok, replace "acid" with "electrolyte" and we have the same result. My point is that if you've ever picked up an old battery that has rusted through, whatever is coming out and burning your hand (and it DOES burn, caustic perhaps?) could "leak" or sublimate. However, that battery MUST be compromised! Think about it, if the **** in batteries could sublimate out, that would have included mercury for a very long time (and still in some cases), which as we all know, is no good to health.

    Note, the OP did not say, "are spent batteries actually lighter" or, "why do my Acme brand AA weigh less than my Sony AA's" it is, "Spent batteries FEEL lighter?". The answer is NO!!! I think we can all agree that the human hand could never tell the difference.

    I should ask as well, why is a cheap battery a lighter battery? It seems to me that using cheaper materials might make it heavier, as is the case with many batteries.
     
  18. May 11, 2010 #17
    Through a load? Perpetual motion? Nice! :eek:
     
  19. May 11, 2010 #18
    ...And here I thought that the little bobbing birds were the only way to power my flux capacitor! :rofl:
     
  20. May 11, 2010 #19
    This is a situation that could be very easily verified or nullified by experiment. Equipment: A handful of batteries of various manufacture, an accurate scale on which to weigh them, and a flashlight or something with which to deplete aforementioned batteries. Measure, deplete, measure.

    Get on it, scientists.
     
  21. May 11, 2010 #20
    Electron depletion weight of a battery is too small to measure.
     
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