Dear Omer's,
Warning lots of Engineering stuff follows.
II have been looking at various batteries to power some
new products I am developing at work. While I had Energizer/EverReady
technical staff helping me with information, I decided to find out more about
the 357 (SR44) style batteries we use in most of the OM cameras.
* The silver oxide batteries **from all manufacturers** contain something
like 0.3 to 1% mercury! This helps preserve the anode. Internationally up to
25mg of mercury per cell is considered acceptable.
* Although various battery books list that AgO cells lose capacity at up to
50er annum, Enegizer claims their cells lose capacity at 20a or less at
room temperature. Sealing is now so good that tested shelf life exceeds
10years. In accelerated (high temp aging tests) the cells have even longer
projected shelf life. This would means it is hardly worth refrigerating
cells. (Normally ~doubles shelf life for every 10C reduction).
* High current pulse rated cells like the 357 all use KOH electrolyte. Low
current rated cells like the 303 use NaOH electrolyte. Vendors like Duracell
(who don'r actua;lly make their AgO cells themselves) mark their cells
357/303 and ship only the high current version. It used to be that the KOH
cells were much harder to seal as the electrolyte is more active and attacks
the seals and cell seperators. The capacity was also a little lower as the
seperator needed to be thicker. This is no longer true. Why then, does anyone
make NaOH cells anymore? The answer is watch vendors often demand a NaOH cell
as they still believe the sealing is a problem and are worried that the KOH
cells are more likely to leak and cause damage. The sealing on some vendors
cells may still be problematic, so avoid generic brand cells.
* The 357 cell is capable of short circuit currents up to a couple of hundred
mA when new and for short durations (<100mS).
* The Energizer 357 cell capacity under low rate conditions is higher than
the nominal 175mAh rated , approaching 200mAh. (The very old data book values
used to be 200mAh but this was at 35C (wrist temperature, which helps a
little.) not 21C. This helps with OM4's and 2'S's which have higher "off "
standby current. The 357 cell has been significantly reformulated over the
years since first introduced for use on LED display watches.
* It would be interesting to compare Energizer's cells to those from other
vendors. In particular an accelerated life test would be interesting and a
high rate capacity test to see if there really are differences.
Regards,
Tim Hughes
>>Hi100@xxxxxxx<<
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|