battery tester -dry cells

Years ago when I worked in the "trade" there was a little black box for testing cells Carbon-Zinc Alkaline etc. Does anyone have an idea of the load resistors used for the various size cells? D, C, AA, AAA. at least. With all the "stuff" that is using such and an open ckt. test that always reads very close to the new voltage, I want to build a simple tester so even the wife can check the "batteries" in the TV remote etc. :-) ...Lew Hartswick...

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Lew Hartswick
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I suggest that you not worry so much about the load and just let the circuit measure the open circuit voltage. Any time I take alkaline cells out of service I find the voltage is 1.2 or lower. A fresh cell is always higher than 1.4 volts. My mouse eats a pair of AAAs in a month or so and the terminal voltage is about 0.9 open circuit.

What the load test tells you is the internal resistance of a cell. That can rise as the cell nears the end of life, but is just duplicate info to the open circuit voltage. The internal resistance can tell you something about rechargable cells however. They will have a very different open circuit voltage being a bit above 1.2 for a fresh NiCad. I think their open circuit voltage is fairly constant until nearly depleted, but more importantly the internal resistance will rise as they get worn and won't hold as much charge.


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Err...Alkaline cells nominally read 1.65 brand new to as bad as 1.55V "fresh" but sitting around for a while. The Radio Shack tester 22-090 uses 1mA load for 1.5V button cells and

3V lithium cells; 50mA for AAA and N, and 150mA for AA, C, and D. The meter does not specify the loading for 6V photo, 9V, 12V, 15V or 22.5V batteries.

And it is rather useful to test under load; a weak battery may initially indicate near full voltage, but will show a sagging reading as the meter is left connected to it (2-15 seconds). Note a no-load test will not show a weak battery.

Reply to
Robert Baer

On Wed, 04 Jun 2014 13:55:27 -0600, Lew Hartswick wrote as underneath :

These type testers are so cheap (even cheaper from China!) its not really worth messing around with... I dont use for more than a second if testing on button cells! The load resistor is the same for all ~1.5v types, higher for PP3. eBay item number:

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Thanks. That is what I was looking for. somewhere around 30 and 10 ohms. ...lew...

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Lew Hartswick

Copied from their website:

Battery Tester (220-0090) Specifications Faxback Doc. #


Current Drain During Test for each type of battery is as follows:

Battery Size Current

1.5V (AA, C, D) 150mA AAA and N 50mA Lithium 3V 1mA Button Cell 1.5V 1mA 6V Photo 10mA 9V 10mA 12V 10mA 15V 10mA 22.5V 10mA
Anyone wanting to run for any political office in the US should have to 
have a DD214, and a honorable discharge.
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Michael A. Terrell

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