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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.
     
  22. May 12, 2010 #21

    Borek

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    Think about it. Assuming your approach - that electrons are lost - is correct, after the battery have been used it will be charged, and we are talking about charges in the range of kC for the 1000 mAh AA sized battery. Calculate force with which two kC charges in two AA batteries placed side by side repel themselves. In your world grenade is safer than your TV pilot.

    And there is no perpetual motion. Battery works as a pump - it pumps electrons through the load, pushing them from negative end and sucking through the positive end. Once internal energy of the battery is spent, it stops pumping.
     
  23. May 12, 2010 #22
    It was one of Einsteins favourite illustrations to state that an object when hot is more massive than the same object when cold.Paraphrasing this we could state that a battery when charged is more massive than the same battery when discharged.When the battery discharges there is no loss of electrons,there is a loss of energy.The resultant mass change can be calculated from E=Mc squared and is far too small to be detected by weighing techniques.
     
  24. May 12, 2010 #23

    Borek

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    Mainly because it doesn't exist.

    On the other hand... assuming it exists. 1000 mAh battery gives 1 A current for 1 hour. Thats 3600 C, or 3600×6.241×1018 electrons. At 9.109×10-31 kg that means something like 2×10-8 kg, or 20 μg. XP56 balance, made by Mettler Toledo, has readability of 1 μg and can be used to weight objects up to 52 g (AA battery weights around 23 g).

    Looks like the effect could be easily measured (if it existed).

    --
     
  25. May 12, 2010 #24

    Matterwave

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    You see, when a battery is being drained, it's inflaton field interacts with the electromagnetic field created by the moving charges, essentially "reheating" the battery operated object while draining the battery of its mass. Although the inflaton field is extremely tiny in our current universe, the field interactions, through positive feedback processes, amplify the effects exponentially (e-folding # N is on the order of 4242). Add to this effect, the quantum fluctuations found within the vacuum energy if space, and you have a net effect which can decrease the mass of the battery.

    Now, I know you must be wondering: "These amplification effects would eventually rip even the tightly bound atoms of the batteries apart!" The solution to this paradox is that the atomic bonds of the battery are borrowing energy from the so-called "attractor" which is bringing our M-brane closer to another M-brane in the 5th dimension. If this "attractor" potential were not present to bind our batteries together, the very fabric of the space-time continuum may rupture leading to the creation of micro-black holes (or possibly other exotic phenomena!). In fact, the observation that batteries don't explode spontaneously is one of the chief observational confirmations of the Steinhardt–Turok model of the Universe.
     
  26. May 12, 2010 #25

    Borek

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    Apart from standard tricks - like reading first letters, every second word and so on - I even tried to read a mirror reflection of what you wrote. To no avail. I don't understand a word. I was not aware AA batteries are that complicated.
     
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