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Thread: Homemade battery tester?

  1. #1
    Flashaholic Led-Ed's Avatar
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    Help Homemade battery tester?

    I have been testing batteries using a 10ohm resistor and 2 multimeters-one to monitor voltage drop across the load, and another to monitor current .I could get by with one and figure the current from the voltage drop but I have the meters so why not use them?
    Has anyone else done their own testing without a "proper" battery tester?
    If so what do you use for a load and/or what criteria for good vs. bad.

    I just don't want to spend $40 on a tester when I have instruments I can use right here.
    Ok,now shut off the lights in the room....

  2. #2
    Flashaholic*
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    Default Re: Homemade battery tester?

    Yes, I use your method to produce a 1A drain and sometimes compare those results with the acid-test of a short-circuit reading when I'm feeling nasty. I've got lotsa VOMs & DMMs laying around, so why not use them. I believe this method is as good or better than a ZTS or whatever.
    I'm absolutely certain that I need another flashlight.

  3. #3

    Default Re: Homemade battery tester?

    Quote Originally Posted by Led-Ed
    I have been testing batteries using a 10ohm resistor and 2 multimeters-one to monitor voltage drop across the load, and another to monitor current .I could get by with one and figure the current from the voltage drop but I have the meters so why not use them?
    Has anyone else done their own testing without a "proper" battery tester?
    If so what do you use for a load and/or what criteria for good vs. bad.

    I just don't want to spend $40 on a tester when I have instruments I can use right here.
    But.... if you know the value of the resistor, is not enough one multimeter to monitor the voltage? Then you can find the current with the Ohm law I = V / R...

    Right or not?



    P.S.: I have done something similar but my results arent very accurate :/...

  4. #4
    Flashaholic Led-Ed's Avatar
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    Default Re: Homemade battery tester?

    Yes realize that I only needed one meter-I have used 1 ohm 1 watt 1% resistors from cathode to ground in tube amps to monitor current draw for biasing purposes.
    It's just when i first set up this "test rig" i was using odd resistor values and didn't want to have to use a calculator to figure the current each time.So I settled on a 10 ohm resistor but still left the meter in line .
    Jayflash,you are using a smaller value the me if you are getting an amp from a 123 batt-I think I was getting around 300ma from a new 123 cell.so I would guess you are using around 3.3ohms or so? I went with 10 because I didn't want to totally short out a cell.
    Ok,now shut off the lights in the room....

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    SilverFox's Avatar
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    Default Re: Homemade battery tester?

    Hello Led-Ed,

    Energizer or maybe it was Duracell has a paper where they discuss measuring cells. They call it "flash amps" and it is measured through a 1 ohm resistor with a volt meter.

    I thought CPF had come up with the "flash amps" term, but I guess not.

    Tom
    Behind every Great man there's always a woman rolling her eyes...

    Most batteries don't die - they are tortured to near death, then murdered...

  6. #6
    *Retired* NewBie's Avatar
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    Default Re: Homemade battery tester?

    Quote Originally Posted by SilverFox
    Hello Led-Ed,

    Energizer or maybe it was Duracell has a paper where they discuss measuring cells. They call it "flash amps" and it is measured through a 1 ohm resistor with a volt meter.

    I thought CPF had come up with the "flash amps" term, but I guess not.

    Tom

    You will find it here in the battery basics, on page 8:
    http://data.energizer.com/PDFs/alkaline_appman.pdf

  7. #7

    Default Re: Homemade battery tester?

    This is interesting!

    "Although short circuit current (flash amps) does not indicate battery freshness or potential service, circuit designers should be aware of the maximum current that a battery could supply if a component failure occurs."

    A page or two later, they explain the relationship between Open Circuit Voltage and service life. They state that 1.1 volts is 20% remaining, and over 1.5 indicates 90% remaining service left. I wonder how linear the region between 1.1 and 1.5 volts actually is regarding service life estimation?

    Paladin

  8. #8

    Default Re: Homemade battery tester?

    I use my Fluke 187, PC and a resistor and successfully test mAh capacity of my batteries

  9. #9
    Flashaholic*
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    Default Re: Homemade battery tester?

    Quote Originally Posted by Paladin
    This is interesting!

    "Although short circuit current (flash amps) does not indicate battery freshness or potential service, circuit designers should be aware of the maximum current that a battery could supply if a component failure occurs."

    A page or two later, they explain the relationship between Open Circuit Voltage and service life. They state that 1.1 volts is 20% remaining, and over 1.5 indicates 90% remaining service left. I wonder how linear the region between 1.1 and 1.5 volts actually is regarding service life estimation?

    Paladin
    It's all in the design. It may have been my Fluke 189 DMM or something else that shows low battery at 1,15V/cell. It was either the Fluke or a Radio Shack scanner.
    Bill

    I'm a retired mechanic not a electronic/electrical engineer!

  10. #10
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    Default Re: Homemade battery tester?

    Quote Originally Posted by Handlobraesing
    I use my Fluke 187, PC and a resistor and successfully test mAh capacity of my batteries
    I think the question is about a tester and not testing for remaining capacity which renders the cell useless after the test.
    Bill

    I'm a retired mechanic not a electronic/electrical engineer!

  11. #11
    Flashaholic Led-Ed's Avatar
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    Default Re: Homemade battery tester?

    The way I understand it,you can tell the charge of an Alkaline battery fairy well with out having to put it under load.This does not work for Lithium primaries well.Not sure about Nicad and NiMH.
    Ok,now shut off the lights in the room....

  12. #12
    Flashaholic*
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    Default Re: Homemade battery tester?

    Quote Originally Posted by Led-Ed
    The way I understand it,you can tell the charge of an Alkaline battery fairy well with out having to put it under load.This does not work for Lithium primaries well.Not sure about Nicad and NiMH.
    The ZTS works on alkaline, Ni-CD, Ni-MH and lithium primaries. How good it works is a matter of opinion!
    Bill

    I'm a retired mechanic not a electronic/electrical engineer!

  13. #13
    Flashaholic Led-Ed's Avatar
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    Default Re: Homemade battery tester?

    I think the zts puts the battery under load for a small amount of time and figures charge from that.
    Almost $40.00 though. Probably worth preventing an explosion....
    Last edited by Led-Ed; 09-07-2006 at 05:47 PM. Reason: added more
    Ok,now shut off the lights in the room....

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