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Re: Battery Voltages

To: Betti Ann & Preston Smith <prsmith@ns.sympatico.ca>
Subject: Re: Battery Voltages
From: Roger Gibbs <rgibbs@pacbell.net>
Date: Tue, 13 Apr 2004 19:43:38 -0700
On Tuesday, April 13, 2004, at 10:59 AM, Betti Ann & Preston Smith 
wrote:

>
> Somehow, my separate batches of 'good' and 'bad' household batteries 
> got mixed together.
>
> So, what are the voltages below which alkaline and conventional 
> battery types AA, AAA, 9 v, C, and D should be thrown away. I have a 
> digital meter to help with this task.
>

Preston,

I have not developed a good correspondence  between voltage and "good" 
batteries for alkaline type cells.  I do, however, find the short 
circuit current output as a good measure.  My digital meter has a 20 
amp dc capability.  A fresh AA cell will put out 10 to 12 amps, a fresh 
D cell more than 15 amps.  (Pretty impressive, at least I thought so.)

Obligatory caution: these cells are not designed for this current 
output and so it is probably hazardous to do this for a sustained 
period.  It takes me about 1 or 2 seconds to make this measurement.

I have not measured AAA or 9 volt cells.

Also, clearly this is a test that is much, MUCH more stringent than any 
application you will use this batteries to provide power.  But I find 
it the most useful test I can easily perform.  A better test setup 
would probably be to measure the voltage with a more reasonable load.  
Alkaline battery voltage output is surprisingly constant without a 
load, even when the battery is nearly spent (as Trevor noted due to the 
high input impedance of the DVM it does not load the battery).

-Roger






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