At 10:53 PM +0000 9/11/02, olympus-digest wrote:
>Date: Wed, 11 Sep 2002 14:55:57 -0700
>From: Jim Brokaw <jbrokaw@xxxxxxxxxxx>
>Subject: Re: [OM] Battery Eaters
>
>on 9/11/02 12:46 PM, Doggre@xxxxxxx at Doggre@xxxxxxx wrote:
>
> >
> > It sure would be nice to be able to do a voltage check and then know that
> > your battery is still at, for example, 700f its useful life, and leave for
> > a shoot in confidence, instead of never knowing when the camera will die.
> > So
> > what we need is a LOAD test?
> >
> > Rich
>
>You probably could test using a DMM in series with a resistor of some value,
>though I don't know what value, to simulate the camera's load on the
>battery. Of course, you'd want to have a heavy load, so you don't want to
>run the test too often or for too long. I suspect there is some
>electrical-wizard calculation that could be done to derive the best resistor
>value, maybe the necessary value resistor is something that could be gotten
>at Radio Shack.
The datasheet for the 357 battery gives the game away. The 357 is designed for
low drain with pulses of heavy drain, the pulses lasting from 0.1 to 2 seconds.
Basically, the pulse is the heavy drain when taking a picture, when
electromagnets must be activated.
The standard load is 100 ohms. Such resistors may be bought from Radio Shack,
as suspected. Such resistors are cheap: a pack of ten 1/8-watt resistors might
be US $1.00.
Attach the DMM leads to the resistor, then touch the resistor leads to the two
sides of the 357 cell, and read the value from the DMM display as soon as it
stabilizes. Then, disconnect the battery, to avoid running it down. Don't
draw current for more than two seconds.
If the loaded voltage exceeds 1.55 volts, the cell is new, being 0 0ischarged.
If the loaded voltage exceeds 1.40 volts, the cell is less than 40 0ischarged.
If the loaded voltage exceeds 1.34 volts, the cell is less than 80 0ischarged.
The above are measured at room temperature, 21 degrees C.
This is the best test available, is simple, and is sanctioned by the battery
manufacturer.
To get the 1-page datasheet, go to <http://data.energizer.com/>. Select
"Active Batteries" (under Battery Index Guide), scroll down, then select the
number "357". (You may need to select 357 a second time.) This will take you
to the battery's datasheet. Or, select "Silver Oxide - Minature", then 357 to
get a pdf file directly. I find that this site works best with MS Explorer,
but that crashes as well, so download the pdf file and work with it.
Joe Gwinn
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