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9 volt alkaline battery

Discussion in 'Electronic Basics' started by fashazee, Feb 6, 2006.

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  1. fashazee

    fashazee Guest


    Technically speaking, at what voltage is a loaded 9 V alkaline battery
    considered dead?

    Thank you in advance,

  2. BobG

    BobG Guest

    6.6V? (1.1V/cell x 6 cells)
  3. Chris

    Chris Guest

    Hi, Mike. When consumer batteries are rated for A-h (amp-hours), they
    are typically given a constant load, and are considered dead when the
    output voltage reaches 60% of specified voltage (in the case of a 9V
    transistor battery, that would be 5.4V)

    Of course, any battery is _really_ dead by the time it reaches 60% of
    rated voltage. I'd consider a 9V battery with a 25mA load very dead by
    the time it got to 7V or so. Once the output voltage slides below 80%
    of nominal, it's got one foot in the grave.

    Good luck
  4. Phil Allison

    Phil Allison Guest


    ** When whatever it is powering ceases to function properly.

    ........ Phil
  5. I just got a look at:

    Looks to me there is a bit of a "knee" in the discharge curve with the
    "center of the knee" at 7 to 7.2 volts (1.1667-1.2 volts per cell), but
    the "knee" only stands out a little. With intermittent duty and a
    constant resistance load, the time to 5V is about 50% longer than the time
    to 7V.
    The constant current discharge curves show mAH about or slightly more
    than 7/6 as great when discharged to 4.8 volts as at discharge to 6 volts.

    Meanwhile, as for what voltage to design something to work at with this
    battery? Since the datasheet has constant resistance and constant current
    hours-to-specified voltage curves (as a function of resistance or current)
    only for 6 and 4.8 volts, I would design something using this battery to
    keep working at least until the voltage decreases to 6 volts.
    Although I think it's OK for a product using this battery to work but
    not quite meet its specifications below 7.2 volts, I believe that a
    product designed to use this battery should work reasonably at least down
    to 6 volts.

    Meanwhile, in general design of products using alkaline batteries: I
    believe they need to work well with NiCd and NiMH that are typically 1.2
    volts per cell, and considered discharged at 1.1 volts per cell *or less*.
    So I believe a product needs to work well at 1.1 volts per cell.

    - Don Klipstein ()
  6. Phil Allison

    Phil Allison Guest

    "Don Klipstein" :

    ( snip agreed stuff)

    ** There is no need to assume that a Ni-Cd or NiMH battery ( made to
    replace the 9 volt single use size) will have only 6 cells - 7 cell
    examples of both have been available for a long time and more recently 8
    cell ones too. These have nominal 8.4 and 9.6 volt ratings as opposed to
    7.2 for the old 6 cell ones.

    Also, where an item uses a 9 volt single use battery and no mention is made
    in the handbook of suitability of use with rechargeables, owners are not
    wise to assume it is safe to do so.

    A NiCd cell ( and many NiMH too now) can deliver a dangerously large current
    if shorted or reverse connected and the item concerned must be designed to
    cope with this without damage if the use of rechargeables is allowed.

    ........ Phil
  7. Energizer specify the capcity of their 9V alkaline to a discharge
    voltage of 4.8V
    This makes sense as alkaline batteries are typically physically
    constructed of 6 "AAAA" batteries in series, and single AAA/AA/C/D
    cells are specs to be "dead" at 0.8V. So 0.8V x 6 = 4.8V
    So in theory, to use all the available capacity of a 9V battery, a
    device should be designed to operate down to 4.8V. Not many devices are
    though, they will die at a much higher voltage and hence won't use all
    the capacity of the battery.

    Dave :)
  8. redbelly

    redbelly Guest

  9. Rich Grise

    Rich Grise Guest

    When it won't operate the thing it's powering any more.

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