1. Subscribersonhouse
    Fast and Curious
    slatington, pa, usa
    Joined
    28 Dec '04
    Moves
    52724
    25 Dec '05 20:56
    Just wondered, obviously with a dvm you can make a good prediction
    of the life left in a battery, like the AA cells for instance. Is it possible
    to figure out the charge left if you had a sufficiently accurate
    scale? Like Picograms or some such. Wouldn't a battery get a tiny
    bit lighter as it used up charge? Hmm, its hermetically sealed mostly
    but maybe gasses could escape. What do you all think?
  2. Joined
    05 Jan '04
    Moves
    45179
    27 Dec '05 03:551 edit
    Originally posted by sonhouse
    Just wondered, obviously with a dvm you can make a good prediction
    of the life left in a battery, like the AA cells for instance. Is it possible
    to figure out the charge left if you had a sufficiently accurate
    scale? Like Picograms or some such. Wouldn't a battery get a tiny
    bit lighter as it used up charge? Hmm, its hermetically sealed mostly
    but maybe gasses could escape. What do you all think?
    Practical application of knowledge is for the birds.
  3. Standard memberXanthosNZ
    Cancerous Bus Crash
    p^2.sin(phi)
    Joined
    06 Sep '04
    Moves
    25076
    27 Dec '05 04:44
    Originally posted by sonhouse
    Just wondered, obviously with a dvm you can make a good prediction
    of the life left in a battery, like the AA cells for instance. Is it possible
    to figure out the charge left if you had a sufficiently accurate
    scale? Like Picograms or some such. Wouldn't a battery get a tiny
    bit lighter as it used up charge? Hmm, its hermetically sealed mostly
    but maybe gasses could escape. What do you all think?
    As far as I know most batteries (NiMH, NiCad, Li-Ion) aren't giving off gases as they are used. If this is true then conservation of matter states that the weight won't change as charge does.
  4. Standard memberAlcra
    Lazy Sod
    Everywhere
    Joined
    12 Oct '04
    Moves
    8623
    27 Dec '05 10:29
    Originally posted by XanthosNZ
    As far as I know most batteries (NiMH, NiCad, Li-Ion) aren't giving off gases as they are used. If this is true then conservation of matter states that the weight won't change as charge does.
    Do electrons not "move out" of the battery? If so, a tiny loss of mass would occur?
  5. Standard memberXanthosNZ
    Cancerous Bus Crash
    p^2.sin(phi)
    Joined
    06 Sep '04
    Moves
    25076
    27 Dec '05 12:07
    Originally posted by Alcra
    Do electrons not "move out" of the battery? If so, a tiny loss of mass would occur?
    They also 'move into' the battery at the same rate, conservation of charge and all that.
  6. Subscribersonhouse
    Fast and Curious
    slatington, pa, usa
    Joined
    28 Dec '04
    Moves
    52724
    28 Dec '05 17:29
    Originally posted by XanthosNZ
    They also 'move into' the battery at the same rate, conservation of charge and all that.
    Thats for sure! Maybe one or two strays would go in or out but I don't
    think we can weigh one electron yet. If there is energy used,
    molecules will swap mass and mass is usually lost. If it isn't, THAT
    is breaking the law of conservation of energy. Just like a fusion
    reaction, some atoms whack together fiercely enough to fuse but
    some of that energy is given off in various forms and the system
    losses mass, even if say an electron is converted to a photon,
    the mass goes down because the electron is now a photon which is
    massless but the total energy will be conserved, ala E=MC^2.
  7. Donationrichjohnson
    TANSTAAFL
    Walking on sunshine
    Joined
    28 Jun '01
    Moves
    63101
    28 Dec '05 22:46
    Originally posted by sonhouse
    Thats for sure! Maybe one or two strays would go in or out but I don't
    think we can weigh one electron yet. If there is energy used,
    molecules will swap mass and mass is usually lost. If it isn't, THAT
    is breaking the law of conservation of energy. Just like a fusion
    reaction, some atoms whack together fiercely enough to fuse but
    some of that energy ...[text shortened]... lectron is now a photon which is
    massless but the total energy will be conserved, ala E=MC^2.
    I could be wrong, but I don't think any mass is converted to energy in batteries. Energy is conserved because, for each unit of electrical energy produced, the battery loses a corresponding amount of chemical potential energy.
  8. Standard memberXanthosNZ
    Cancerous Bus Crash
    p^2.sin(phi)
    Joined
    06 Sep '04
    Moves
    25076
    29 Dec '05 01:42
    Originally posted by richjohnson
    I could be wrong, but I don't think any mass is converted to energy in batteries. Energy is conserved because, for each unit of electrical energy produced, the battery loses a corresponding amount of chemical potential energy.
    This is correct.

    A ball would gain a lot of energy if you took it to the top of a building. It doesn't lose mass though.
  9. Standard memberBowmann
    Non-Subscriber
    RHP IQ
    Joined
    17 Mar '05
    Moves
    1345
    29 Dec '05 02:26
    Potential energy is nonsense.
  10. Subscribersonhouse
    Fast and Curious
    slatington, pa, usa
    Joined
    28 Dec '04
    Moves
    52724
    29 Dec '05 14:17
    Originally posted by XanthosNZ
    This is correct.

    A ball would gain a lot of energy if you took it to the top of a building. It doesn't lose mass though.
    Good point, relativistic effects aside.
  11. Subscribersonhouse
    Fast and Curious
    slatington, pa, usa
    Joined
    28 Dec '04
    Moves
    52724
    29 Dec '05 14:18
    Originally posted by Bowmann
    Potential energy is nonsense.
    Useful nonsense though.
  12. SubscriberSuzianne
    Misfit Queen
    Isle of Misfit Toys
    Joined
    08 Aug '03
    Moves
    35688
    02 Jan '06 11:41
    Originally posted by Bowmann
    Potential energy is nonsense.
    So kinetic energy is nonsense as well?
Back to Top