D cell.

Discussion in 'General Electronics Chat' started by bug13, Jul 16, 2013.

  1. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
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    Hi guys

    Has anyone tested the short circuit current of a D cell, I would like to know if you have any info, thanks guys
     
  2. TheComet

    Member

    Mar 11, 2013
    88
    12
    Rule of thumb is 20mA.

    Refer to the data sheet of the specific IC for more information.
     
  3. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
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    The data sheet only give up to 500mA discharge current, it doesn't give short circuit current tho.

    Edit: I am referring to D type dry battery like this one here
     
  4. Ramussons

    Active Member

    May 3, 2013
    557
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    I've seen a fully charged NiCd D cell giving 8A on a short; a New Alkaline 4A.

    Ramesh
     
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  5. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
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    Alkaline D cells sometimes have internal resistance above an Ohm, so maybe one Amp or less.
     
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  6. Shagas

    Active Member

    May 13, 2013
    802
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    Good guys energizer generously provide datasheets for their batteries :


    Alkaline D cell -> http://data.energizer.com/PDFs/E95.pdf
    150-300mohm IR , you can extrapolate from there

    Nicd D cell ->> http://data.energizer.com/PDFs/CH50.pdf

    20-30mohm IR !!

    Nimh D cell - >>> http://data.energizer.com/PDFs/NH50-2500.pdf

    11mohm IR charged !!! (i'm starting to sweat now)

    Judging by the datasheets the max current very heavily depends on the Battery chemistry. Alkaline being the wimpiest , followed by Nicd and Nimh taking the gold and 2 hot babes home
     
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  7. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
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    I am dealing with Alkaline here, it looks like I need to add a current limiting circuit just in case there is a short circuit.

    Thanks for your info Shagas!
     
  8. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    sounds like a job for a fuse.
     
  9. Shagas

    Active Member

    May 13, 2013
    802
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    What are you making?
     
  10. Shagas

    Active Member

    May 13, 2013
    802
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    Doesnt neccessarily have to be . Might be current limiting for a motor or something
     
  11. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
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    Since you suggested, the total resistance in the path (I am switching a RC servo off when not use) is:
    • 150mOhm x 4 (I am using 4 D cell)
    • 600mOhm (fuse resistance)
    • 60mOhm (mosfet Ron)

    This will give about 4.7A when short circuit in fresh batteries.

    I am thinking using this fuse (the B one in the table and graph) and this mosfet, how's my choice??

    I am guessing the RC starting current is about 1A, normal operation is under 100mA
     
    Last edited: Jul 16, 2013
  12. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    What make and type of RC servo are you trying to switch off? You realize that unless power is maintained and a signal repeated to a hobby RC servo, it cannot maintain its position and will move under pressure?
     
  13. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
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    Just a RC/mini 6VDC servo, when it is not used, there won't be any pressure. The goal is to maximum standby power.

    I have already built one up, now I need to maximum standby power and add protection if necessary.
     
  14. BobTPH

    Active Member

    Jun 5, 2013
    782
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    Don't base the fuse on the that battery might supply, base it on what the cicrcuit should draw. Set it to maybe twice that.

    Bob
     
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