Is there a simple *digital* battery tester that will test 'AA's' under a *load* .

TooManyGizmos

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I want to know what my fully charged NiMh batt's are dropping to in use after the charger says done @ 1.44v . Isn't that how you know if a batt. is bad , even tho it tests good showing high voltage *at rest*.

What is the most accepted way to put a load on it and test. Sometimes it may not be so easy to test it while in use in an electronic device.

Does the load have to differ depending on if it's a ' C,D,AA or AAA' battery ?

Testers with an analog , needle dial display are not accurate enough - that's why i'm asking about digital.

Is there a free standing digital tester commercially available - worth it's salt..............please tell some of us less knowledgeable newbies.............thanx .



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Outrider

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Take a look at the ZTS testers. They can be found under CPF advertizers and i believe they have a 10% discount for CPF's - see Green led's sticky thread for CPF specials. I have had one for about a month and really like it. Much better than any of my analog or digital DMM's.
Or a cheap way is just use a resistor in series with the battery and your meter.
 
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paulr

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I'm not sure I understood the question. These tester gizmos do discharge curves, maybe fancier than you're asking. If you want to measure the voltage under load, just put a resistor or light bulb across the battery and measure with your DMM. It won't tell you much. It will be around 1.2v for nimh.
 

the_beast

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I've never done it, but (as the previous poster suggested), just load it and put a DMM across it to measure the load.

If you want to get a bit more fancy but still keep the costs down, put a variable resisitor in series with a meter on the current setting) with your battery. Then connect a second meter across the battery, set to read voltage. Cheap meters will be more than up to this task - you can get them for less than $5.

You should then be able to dial in the current you want to test at, so you'll know how the battery will perform. You could even do run-time tests like this, but you could end up sitting wathcing the numbers for a very long time!

The currents you'll be able to get will depend on the meter and the resistor you choose. You might be able to get 1amp or more from a nimh battery though, so be careful and get a variable reisitor that will take this current. If you want to test lithiums then be very careful - they can dump a lot of current very quickly. Always start with the variable resistor set high (to give a low current value to start) so that you won't flash anything. Make sure you test everything before you turn on the current (a switch in series with the battery will help here too), and don't overdischarge the batteries.

Hope this helps.
 

flashlightguy

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You can check the internal resistance of the cell by measuring the open circuit voltage. Then, put a load resistor across it. 1-5 ohms should be good. Measure the current going through the resistor. Divide the open circuit voltage by the current. This will give you the total resistance of the circuit including the internal battery resistance. Subtract the resistance of the resistor, and you have the internal battery resistance. I measured around 0.2 Ohms
 

Doug Owen

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The Energizer Point of Sale tester uses 10 Ohms as a load for 'general use' D, C, AA, and AAA cells. Minimum 'good' voltage is 1.1 Volts.

For 'camera, motor drive and flash' the load is only one Ohm, same voltage.

For a ten cent resistor (or two) you can do the same with your DMM.

Doug Owen
 

spock

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like outrider above, just received zts tester about 3 days ago. it does a great job. i have a radioshack one(needle type)but it does not test 123s very well. it measures voltage drop under a load. the zts uses a pulse test that tells you how much life or charge is left in your battery on a percent scale. http://www.greenbatteries.com/batterytesters.html this site has them slightly discounted and ship was $6. they are made in cinn, ohio which is about 60 miles from me. the zts website will explain the differences in the three testers. a low zts reading(40%)may still be useful. these work fine in my streamlight luxeon 4aa because of the regulation.
 
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