Who has a clever idea for storing AAs ?

Discussion in 'Digital Photography' started by Bob Thomas, Mar 2, 2004.

  1. Bob Thomas

    Ron Hunter Guest

    Paul,
    Maybe you should read some of the manufacturer sites about the
    problem. It seems THEY think it is a significant risk. Never had it
    happen, but don't doubt that it could.
     
    Ron Hunter, Mar 6, 2004
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  2. Bob Thomas

    Ol' Bab Guest

    The flashlight in question (that was my post) has the cells wired in
    series/parallel (3 volts to the lamp). This reduces the chance of
    reverse-charging damage by some large factor, but not to zero.

    The flashlight is an "Energizer", also marked "DoubleBarrel".

    Ol' Bab
     
    Ol' Bab, Mar 6, 2004
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  3. Bob Thomas

    John Navas Guest

    [POSTED TO rec.photo.digital - REPLY ON USENET PLEASE]

    In <T8o2c.115644$> on Sat, 06 Mar 2004 17:47:31
    not at all. A flashlight left on will cheerfully flatten and damage
    rechargeable batteries no matter how they are wired.
     
    John Navas, Mar 6, 2004
  4. Bob Thomas

    Ol' Bab Guest

    Hi John. No idea here why I thought the risk would be reduced by a
    *large* factor. BUT I will stick by a *small* factor based on chance
    combinations of four all-different cells extending the total charge
    removed before reversal starts. (Compared to a 6 volt all-series
    setup). Giving the operator a little more time to realize the lamp is
    too orange.

    Oh God I love to pick nits...

    IIRC, when reversal starts, hopeless capacity reduction is "immediate".
    What ever that precisely means.

    Ol' Bab
     
    Ol' Bab, Mar 6, 2004
  5. Bob Thomas

    Lionel Guest

    How can a single cell flashlight drive the cell into reversal?
    (I'm referring back to my original post in which I suggested using a
    such a flashlight to discharge such cells.)
     
    Lionel, Mar 7, 2004
  6. Bob Thomas

    John Navas Guest

    [POSTED TO rec.photo.digital - REPLY ON USENET PLEASE]

    In <> on Sun, 07 Mar 2004 11:15:11
    <http://data.energizer.com/batteryinfo/application_manuals/nickel_metal_hydride.htm>:

    To prevent the potential for irreversible harm to the cell caused by cell
    reversal in discharge, removal of the load from the cell(s) prior to total
    discharge is highly recommended. [MORE]
     
    John Navas, Mar 7, 2004
  7. Bob Thomas

    Mikey S. Guest

    Reversal can only occur if there are two or more cells in series, one dies
    first and then the other one continues to discharge through it, reversing
    the charge on the dead cell.
    Since he specified a SINGLE cell flashlight this can not happen in this case
    , the cell can only discharge to a zero potential, not reversal.

    --

    Mikey S.
    http://www.mike721.com

     
    Mikey S., Mar 7, 2004
  8. Bob Thomas

    John Navas Guest

    [POSTED TO rec.photo.digital - REPLY ON USENET PLEASE]

    In <> on Sat, 6 Mar 2004 20:18:41 -0500,
    Not true.
     
    John Navas, Mar 7, 2004
  9. Bob Thomas

    Nibbler Guest

    easy. a *single cell* is made up of cells internally as well, how many
    depends on manufacturer. even cells within the cell can discharge at
    different rates.
     
    Nibbler, Mar 7, 2004
  10. Bob Thomas

    Nibbler Guest


    incorect. well, not reversal to the external connectors if standing alone,
    but a cell within the cell certianly can.
     
    Nibbler, Mar 7, 2004
  11. Bob Thomas

    Nibbler Guest

    easy. cells are combimed within. larger (say c / d ) have more in parrallel,
    hance more current, buttons have less. the external voltage will not go
    reversed, but cells within the cell will be destroyed from the voltage
    reversing within the constructed cell.
     
    Nibbler, Mar 7, 2004
  12. Bob Thomas

    Nibbler Guest

    How can a single cell flashlight drive the cell into reversal?
    batteries are made of sanwiched layers, (each layer is a cell) capacity is
    increased by new chemistry, or thinner layers allowing more cells in the
    same package. voltage is incresed by increasing the surface area of those
    stacked cells... each layer (or cell element) will vary slightly in
    thickness / surface area / electrolyte (or equiv) coating, hence *small*
    differences. if discharges too far, the other cells will reverse bias this
    cell and oxidize the contacts (or electoplate, or otherwze errode). upon
    recharge, this will not repair it's self and the battery will have reduced
    capacity *if* it still works due ti increased internal resistance. didn't
    anyone build batteries in HS science?
     
    Nibbler, Mar 7, 2004
  13. Bob Thomas

    Lionel Guest

    Actually, Mikey's explanation is exactly correct. If you're claiming
    otherwise, how exactly could charge reversal occur on a single cell?
    (Absent some other external source of power, obviously.)
     
    Lionel, Mar 7, 2004
  14. Bob Thomas

    Lionel Guest

    More info:

    Here's a very pertinant excerpt from
    <http://data.energizer.com/batteryinfo/application_manuals/nickel_metal_hydride.htm>,
    regarding discharging a *single* NiMH cell completely:

    "Prolonged Storage under Load
    Maintaining a load on a cell (or battery) past the point of full
    discharge *may eventually* cause irreversible changes in the cell
    chemistry and promote life-limiting phenomena such as creep leakage. "
    (My emphasis.)

    In other words; running a single cell completely flat will only harm it
    *if* you leave it attached to the load for some (undefined, but
    presumably lengthy) period of time. So, as long as you take the cell out
    of the flashlight within some reasonable period after the bulb goes
    completely dark, the cell should be fine.

    Relating back to the subject of what happens if you short-circuit NiMH
    cells in your pocket (or wherever):
    "Nickel metal hydride cells can generate high currents if shorted. These
    currents are sufficient to cause burns or ignition of flammable
    materials."
     
    Lionel, Mar 7, 2004
  15. Bob Thomas

    Ron Hunter Guest

    Well, yes, but we were always careful to distinguish between 'cells' and
    'batteries'. The voltage of a cell is a function of its chemistry, alone.
     
    Ron Hunter, Mar 7, 2004
  16. Bob Thomas

    Nibbler Guest

    well, to a point... depends how many layers for that's chem's design. for
    example, NIMH *could* be bummped up to 1.5v if another layer or so could fit
    in the standard package sizes... so it *is* limited by chemistry, to a
    point... BTW, thats' why odd shaped NIMH have different voltages for the
    given package size... different amounts of layers.... it it was chemistry
    alone, every sized "cell" would have the same voltage.
     
    Nibbler, Mar 7, 2004
  17. Bob Thomas

    Ed Guest

    This is an interesting point, as stated "removal of the laod from the
    cell(s) prior to total discharge in recommended."
    Were this to be done how is the cell to be totally discharged without a load
    to discharge the charge into?
    Explain that !
     
    Ed, Mar 7, 2004
  18. Bob Thomas

    Nibbler Guest



    well then, how does my nimh retcangular cell for my casio have [email protected]?
    the 3rd party is [email protected] ? what about other non-multipule of 1.25v cells
    in different physical configurations? many are out there.
    Cell/pda/proprietary/etc...

     
    Nibbler, Mar 7, 2004
  19. Bob Thomas

    Nibbler Guest



    well then, how does my nimh retcangular cell for my casio have [email protected]?
    the 3rd party is [email protected] ? what about other non-multipule of 1.25v cells
    in different physical configurations? many are out there.
    Cell/pda/proprietary/etc...

     
    Nibbler, Mar 7, 2004
  20. Bob Thomas

    John Navas Guest

    [POSTED TO rec.photo.digital - REPLY ON USENET PLEASE]

    In <> on Sun, 07 Mar 2004 13:43:50
    See "Discharge Termination" at
    <http://data.energizer.com/batteryinfo/application_manuals/nickel_metal_hydride.htm>.
     
    John Navas, Mar 7, 2004
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