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Testing alkaline batteries

Discussion in 'Electronic Basics' started by Jacobe Hazzard, Jan 17, 2004.

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  1. I have an enourmous pile of used AA alkaline batteries.
    Before I dispose of them, I would like to know if any have any juice left,
    and could be used in low power, non-critical applications. I would hate to
    throw out batteries if I could use them.

    What's a good way to test alkaline batteries? I know they need to be under
    load during the test, what's a typical load current/resistance? Does OC
    voltage play any part in determining how much life is left?

    Thanks for any tips.

    Adam
     
  2. Dont you have some of those coloured "thermometer" style testers from the
    battery packs ??
    Otherwise get a resistor that will load them to whatever current suits and
    read the voltage, ie for a 1.5v cell 100mA would need a 15ohm resistor.
     
  3. Joe

    Joe Guest

    Hi Adam,
    I had a similar problem a few weeks ago. I got some good ideas from this
    page:

    http://archilochus.netfirms.com/battest.html

    What I ended up with was a black box with an analog 15v panel meter on it
    and a push button. When the battery is connected, the panel meter shows me
    how much voltage I have open circuit. When I push the button, a 50 ohm
    resistor is switched in to load the battery. Then I hold the load on the
    batt for about 5 seconds, release the button and see how long it takes the
    voltage to come back to its open circuit value. I tested it with a brand new
    battery to see what it looked like (measured a little over 9V OC, and
    dropped by maybe a few 10ths of a volt with the load and instantly
    recovered. By contrast, I had a 9V battery that I had removed from a smoke
    alarm that was beeping its low battery alarm and that battery measured about
    6volts OC and dropped to about 4V with the load applied. Took about 10
    seconds to recover to the OC voltage. That was a dead battery.

    Try googling for 'home brew battery tester' and you will get lots of ideas.
    hth,
    Joe
     
  4. Bill Bowden

    Bill Bowden Guest

    The voltage has little meaning. I usually just short them
    out with a DMM on the 10 amp scale. A good alkaline AA cell
    will deliver 3 amps or more into a short circuit. If it's
    less than 1 amp, it's probably not worth keeping.

    -Bill
     
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