battery tester -dry cells

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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...

Re: battery tester -dry cells
On 6/4/2014 3:55 PM, Lew Hartswick wrote:
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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.



Re: battery tester -dry cells
rickman wrote:
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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.

Re: battery tester -dry cells
Robert Baer wrote:
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Thanks. That is what I was looking for. somewhere around 30 and 10 ohms.

Re: battery tester -dry cells
On Wed, 04 Jun 2014 13:55:27 -0600, Lew Hartswick

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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.
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