------- Forwarded Message Follows -------
From: HI100@xxxxxxx
Date: Mon, 24 Sep 2001 06:55:38 EDT
Subject: [OM] My beautiful OM4Ti
To: owner-olympus-digest@xxxxxxxxxxxxxxx
At 20:22 9/23/01, Tom Scales wrote:
>I can't explain it well, perhaps others can, but the SR44 and 357 are NOT
>the same battery. I believe the SR44W and 357 are the same battery (W
>stands for Watch, as in wristwatch, I believe). If I remember, the 357
>handles high-drain situations (like an OM camera) better than the SR-44.
>
>Anyone else want to jump in?
There is an International Electrotechnical Commitee (IEC) standard which
standardises case size and a few other aspects of batteries. IEC cell
designation size SR44 refers to a generic silver oxide cell of specific
case size. IEC spec LR44 refers to a generic alkaline cell which actually
has the same nominal physical size as the SR44. Some manufacturers then
use these case designations as part number for their cells especially as
electronic manufacturers often refer to the IEC generic size number.
Sometimes vendors add SW to the IEC number designating this as a "Silver
Watch" cell. Within the SR44 case size, cells can be optimized for slightly
different applications. This may lead to different cells from the same
manufacturer, with different part numbers. For example the Everready 303
cell is the same SR44 size as a Everready 357 cell but is rated for lower
discharge rates. Sometimes the designation on the cell may be more a
marketing issue than reflecting any difference in characteristics. For
example, Duracell brand sells both 303 and 357 cells but these are now the
same part. Duracell like many battery vendors does not make these cells
themselves. By varying things like the amount of depolarizer you can make
the cell capable of higher discharge rate but usually at the cost of other
characteristics like overall cell capacity at low discharge rates.
Originally there were two common electrolytes used either NaOH or KOH. It
is harder to seal the KOH cells leading to watch makers prefering NaOH
cells from a leak/reliability point of view. KOH cells are better for high
rate applications but were slightly more costly because of sealing
difficulty. Today watch batteries are still often made with NaOH
electrolyte because watch makers are still biased against KOH cells. Such
cells would not work so well in OM because the voltage dips more under the
heavy pulse load. Apparently KOH cells have been improved so that sealing
is no longer an issue, so high rate KOH cells like the 357 really have no
disadvantage over NaOH cells. (This may be less true for generic brand
cells.) The Everready 357 cell was originally designed for use in early LED
watches which had very high pulse drains when the dispaly was activated.
The original 357 cell characteistics were specified at 35C "wrist
temperature". The spec and the cell design has aparently changed somewhat
over the years as the applications have changed. The part is now specd at
21C. Everready now claims a much lower selfdischarge than some other
vendors but it has a slightly lower specified intial energy capacity. This
is probably a good tradeoff as it is difficult to know how long the cells
have been sitting around before you buy them and you also don't need to
worry about refrigerating them. It appears there can be significant
differences between vendors products, but it is hard to determine the
differences from just the part number and the vendors are not very helpful
in supplying sufficient information.
Regards,
Tim Hughes
>>Hi100@xxxxxxx<<
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