Need battery testing expertise

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  #1  
Old 01-08-12, 01:31 PM
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Need battery testing expertise

I need to test Energizer A27 12V miniature alkalines (manganese dioxide). I'm using a multimeter with battery load test function for 12V batteries. For 12V test it delivers a load current of 200mA.
The specs for the A27 battery are at:

http://data.energizer.com/PDFs/a27.pdf

The "typical capacity" of the battery is 22 mAh to 6.0 volts (rated at 20K ohms at 21 degrees C).

The drain is 0.36mA continuous. The specs show the load at 20K ohms and includes "cutoff voltage" of 8.8V, 37 hours; 7.2V, 42 hours; and 6.0V, 45 hours.

I don't understand what this means. My concern is whether the 200mA load of the tester will deplete the A27, in other words, is it an overload?

I assume a typical 2 second test would not drain the battery to any significant degree.

Could someone give me their insight into this issue and the "discharge durations" from the specs?

Thank you.

________________________________

There are no stupid questions, right? Right? :-)
 
  #2  
Old 01-08-12, 04:12 PM
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I'm not quite following the specifications, but I would say a 200 ma short test is way too much for what this battery is designed for.

They are implying a load design of 20k ohms. 200 ma would be a 60 ohm load on a 12 volt battery.

It sounds like you need to test more than one, is that correct? Why?

A normal battery test places a load on the battery and measures the drop in voltage. The drop is an indication of its internal resistance, but should be well within its designed operating range. Your meter is basically placing a short circuit on this poor little thing.

Are you familiar with ohms law where you could determine a load resistor to touch across the battery while monitoring the voltage? Is your meter digital or analog?

Bud
 
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Old 01-08-12, 07:17 PM
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Thanks for your response, Bud. I have researched ohms law in the past, but my eyes just glaze over! I have no expertise in this area, which is why I'm here. I have read in several sources of the use of the resistor, but it was my understanding that my multimeter built that function in, with its battery load test feature. Supposedly, the load it applies is appropriate to the battery volt range being tested. The stated use of the tester is household batteries.

Here is the multimeter, if it is of help: The Equus Innova 3320 digital multimeter

I have been experimenting tonight with some cheap new and used AA/AAA alkalines and AA rechargebles, using the load test, and it seems to be giving appropriate results without detriment to the batteries. I was just reluctant to try the A27 after looking at its specs, which I could not fully interpret.

Any other thoughts?

Bob
 
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Old 01-08-12, 08:26 PM
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Your tester will be fine. The meter will not load the battery beyond it's capacity.

This is one of those "don't over-think" this stuff, things.

Generally the simple way to check a battery is to simply use a voltage check with the battery in place in the device it's in place for. (not always possible, I know)
 
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Old 01-09-12, 08:52 AM
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MrRon: Thanks. And, no, I can't test this one in the device.

Can you or someone explain those Energizer specs on cutoff voltage? Does it mean, for example, that with 37 continuous hours, the battery drain will reduce it to 8.8V, at which point the battery is essentially dead?

If that's the way it words, I don't understand three cutoff voltages--7.2V at 42 hours and 6.0V at 45 hours.

And, if my tester applies a 200mA load how long would the probes have to be in contact with the terminals before it would drain the battery to a cutoff point or damage it? (Not that I intend to exceed about 2 seconds for a test, but the question arises as to whether even a brief test damages this battery.)

I wrote to Energizer but had no response. Maybe they can't explain the specs to a novice either!

OK, I'm "over-thinking" it again? But I'm really trying to understand this stuff.

Thanks for any help.
 
  #6  
Old 01-09-12, 09:52 AM
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Those are simplifications of the battery discharge graph at a .36mA constant discharge rate. They list those voltages because they are common break points for equipment battery monitoring devices.

It has more meaning for someone designing a device that would use this battery, than for an end user.
 

Last edited by MrRonFL; 01-09-12 at 01:55 PM. Reason: fix typo
  #7  
Old 01-09-12, 10:21 AM
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Ron, I'm curious.
You say 36ma, but they show 0.36ma for the graph, with a typical load of 20K ohms. IMO, that's a very small load for a battery. Although I agree that a short test would probably not harm the battery, that battery just doesn't seem to have a lot of capacity, i.e. 22 mAh to 6.0 volts. I guess I would just not recommend testing it very often.

Bud
 
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Old 01-09-12, 01:53 PM
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It was a typo. I missed typing the decimal point.

Batteries of this type are intended for low draw over long periods of time. A short term heavy draw, such as in a tester like this is not really an issue. The tool is designed not to destroy what it's supposed to be testing.

Batteries really aren't that complicated...
 
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Old 01-10-12, 08:22 AM
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Thanks guys...

...I appreciate your time.
 
 

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