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Thread: Trying to use a multimeter to check battery life

  1. #1
    Flashaholic jlomein's Avatar
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    Default Trying to use a multimeter to check battery life

    I just got a cheap digital multimeter and find it rather fun to play with. I am able to successfully test the voltage of some Sanyo AA Nimh's I have. They are stated at 1.2V, and off the charger they test around 1.39V.

    I also want to check the capacity, as it claims to be 2500mah. I'm not quite sure what to switch the multimeter to. I switched it to the "10A" settings, which I assume is measuring current. That gives me a value of 11.00 usually with these batteries.

    Is this right? Or am I doing this wrong?

    thanks

  2. #2
    Administrator Norm's Avatar
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    Default Re: Trying to use a multimeter to check battery life

    You can't test battery capacity with a multimeter. You need something like the ZTS Multi-Battery Tester shown on this page http://www.batterystation.com/cpf2.htm
    Norm

  3. #3
    Flashaholic* abvidledUK's Avatar
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    Default Re: Trying to use a multimeter to check battery life

    Quote Originally Posted by jlomein
    I just got a cheap digital multimeter and find it rather fun to play with.
    I also want to check the capacity, as it claims to be 2500mah. I'm not quite sure what to switch the multimeter to. I switched it to the "10A" settings, which I assume is measuring current. That gives me a value of 11.00 usually with these batteries.

    Is this right? Or am I doing this wrong?

    thanks
    Yes.

    DON'T DO IT.......

    It's a quick way to explode your cell, burn down your house etc....... !
    Last edited by abvidledUK; 02-24-2007 at 06:51 AM.
    Batteries, batteries, I need more batteries ........

  4. #4

    Default Re: Trying to use a multimeter to check battery life

    The ZTS also won't tell you the mAh capacity of your cells. I use the BC-900 and MH-C9000 chargers to measure the approximate capacity of my cells.

  5. #5
    Flashaholic*
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    Default

    If switched to "10 A" You can measure current.
    When You now put the wires to "+" and "-" of the batt, You are shorting it out and Your "11" is the AMPERES that are now pumped through.


    Hook any circuit up and put the meter just in between (f.e.: get tailcap away and put one wire to the battery, the other one to the flashlight body).
    That way You see the current that the light is drawing now. Check for how long this goes and You have Your total mA the batt has.

  6. #6

    Default Re: Trying to use a multimeter to check battery life

    *
    Last edited by macforsale; 08-28-2007 at 12:32 PM.

  7. #7
    Thread Killer Illum's Avatar
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    Default Re: Trying to use a multimeter to check battery life

    multimeters test the batterys voltage and amperage....but cannt tell what the remaining capacity. only way to do so is through the ZTS mentioned above which utilizes a current load and caliberation to determine under a set of benchmarks where your battery may lie, it sounds complicated, but its really pretty simple.

    most store bought multimeters, especifically battery meters measure voltage only when testing batteries, which makes them rather inaccurate

  8. #8
    Flashaholic*
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    Default Re: Trying to use a multimeter to check battery life

    A multi meter can provide reasonably close results with primary cells but not NiCd & NiMH rechargeable cells.

    Primary cells will provide more voltage into a load and more short-circuit (flash) amps when new. Fresh AA alkaline cells begin life at six or more amps into a short circuit. CR123 cells usually range from 7 - 11 (flash) amps when new. Once the CR123 drops to about five amps it's close to the end of life for high drain applications but are fine for lights needing only a few hundred mA of current. Once alkies reach three short circuit amps they are nearing the end of life.

    A short circuit (flash) amp test should only last a second or two at the most. Measuring voltage across a one amp load is easier on the cell but does not seem to correlate quite as closely to remaining capacity. I have found that once a CR123 drops below 2.2 volts across a one amp load, it is on the way out for higher drain use.
    I'm absolutely certain that I need another flashlight.

  9. #9
    Flashaholic jlomein's Avatar
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    Default Re: Trying to use a multimeter to check battery life

    Thanks for all the help. I guess I am lucky I didn't burn my face off or something. I really wish my multimeter came with a manual, or at least some basic safety info haha.

  10. #10

    Default Re: Trying to use a multimeter to check battery life

    *
    Last edited by macforsale; 08-28-2007 at 12:33 PM.

  11. #11
    Enlightened
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    Default Re: Trying to use a multimeter to check battery life

    Quote Originally Posted by yellow
    If switched to "10 A" You can measure current.
    When You now put the wires to "+" and "-" of the batt, You are shorting it out and Your "11" is the AMPERES that are now pumped through.
    I test alkalines usually by measuring short-circuit current briefly, only 2-3secs.
    Also good indicator between nimh cells to find out half-dead cells out after charging them.

    Dont measure litium-batteries or batteries bigger than AA-size in this manner!

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