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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