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Internal resistance of batteries

Discussion in 'Electronic Components' started by Norm Dresner, Sep 17, 2004.

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  1. Norm Dresner

    Norm Dresner Guest

    In "The Art of Electronics" [Horowitz & Hill, 2nd Ed, p9], they state
    "For example, a standard 9 volt alkaline battery behaves like a perfect
    9 volt voltage source in series with a 3 ohm resistor ..."

    Where can I find information on the internal resistance of other battery
    types and voltages?

    TIA
    Norm
     
  2. It depends on the state of discharge of the cell. Any info you get
    would be for the average of many cells, and your particular cell could
    vary widely from that average. ALkalines are much lower than
    zinc-carbon. You can calculate the value for a cell by doing this:
    http://www.buchmann.ca/Chap9-page2.asp
     
  3. Tim Shoppa

    Tim Shoppa Guest

    For a while :). There are battery specifications that go into far more
    details, if you really need them. The usual assumption is that
    the internal resistance remains constant as the battery is discharged
    but it goes up as the "perfect battery" inside goes down in voltage.
    Unless you have an esoteric (but becoming more common) pulse application
    the published discharge curves are quite usable.
    The big-name manufacturers are pretty good about offering tech information
    on their websites, e.g.

    http://data.energizer.com/batteryinfo/application_manuals/cylindrical_alkaline.htm

    http://data.energizer.com/batteryinfo/other_available/datasheet.htm

    and other links on that site. Often you don't see all the numbers
    for the 9V models but they are "just" 6 AAAA in series most of the time,
    and sometimes they offer the numbers/graphs for the AAAA's.

    Tim.
     
  4. Tim Shoppa

    Tim Shoppa Guest

    For some purposes, this is all the data you need. For most purposes,
    a discharge curve is more useful. For more esoteric stuff like
    pulse applications you can either synthesize the supplied information
    into a good guess, or measure your own discharge curve for your unique
    application.
    For example

    http://data.energizer.com/batteryinfo/application_manuals/cylindrical_alkaline.htm

    http://data.energizer.com/batteryinfo/other_available/datasheet.htm

    Different manufacturers offer different levels of detail (from zilch
    to excellent).

    Tim.
     
  5. Ross Herbert

    Ross Herbert Guest

    |In "The Art of Electronics" [Horowitz & Hill, 2nd Ed, p9], they state
    | "For example, a standard 9 volt alkaline battery behaves like a perfect
    |9 volt voltage source in series with a 3 ohm resistor ..."
    |
    |Where can I find information on the internal resistance of other battery
    |types and voltages?
    |
    | TIA
    | Norm

    Some good info here http://www.buchmann.ca/

    Haven't read it myself so can't comment on whether it has everything
    you want to know.

    Cadex http://www.cadex.com/default.asp are currently field trialling
    their new hand-held battery analyser (CA-12) which reputedly gives an
    asessment of Cold Cranking Amps CCA and Reserve Capacity (RC) for
    automotive and other industrial batteries.
     
  6. Ross Herbert

    Ross Herbert Guest

  7. Norm Dresner

    Norm Dresner Guest

    Looks like some good stuff there. I'll browse later when I have the time to
    explore.

    Thanks
    Norm
     
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