At 5:23 PM +0000 4/5/02, olympus-digest wrote:
>Date: Fri, 5 Apr 2002 03:54:12 EST
>From: HI100@xxxxxxx
>Subject: [OM] Storage of mercury oxide and silver oxide batteries
>
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>Joe wrote about silver oxide batteries:
> >>
> Section 12.4.3 (on the shelf life of silver oxide batteries)
>plots shelf lifetimes at various temperatures, the lowest being 21 degrees
>centigrade, but one can extrapolate. The low-rate cells used in watches can
>easily last 10 years at 21 degrees centigrade (room temperature). Our
>beloved 357 battery is considered ultra high-rate (it's a matter of battery
>cell construction). High-rate cells will lose 30f capacity every three
>months at 21 degrees centigrade. In three years, the total loss will be 10%.
> I guess that ultra high rate may lose more. At 4.6 degrees centigrade, the
>loss rate is 0.65 0.000000e+00very three months. Anyway, the max shelf life
>they talk
>of is ten years for low-drain, and three years for high drain cell
>constructions.
>As with mercury batteries, the ultimate limit is that the barrier film
>between anode and cathode eventually dissolve, and also the silver migrates.
><<
>
>That data from the "Battery Bible" is now a bit out of date. Seals and
>seperators have been greatly improved so the differences between KOH cells
>and NaOH cells are no longer an issue for reputable vendors.
Great. So that's the difference between low-rate and high-rate cells.
>The performance of Silver Oxide batteries has greatly improved over the years
>depending on vendor, so for example the Everready/Energizer Brand 357's
>actually have a demonstrated shelf life of 10years in both actual and
>accelerated aging tests. Vendors sometimes claim more like 2-3 0a loss at
>21C. It is often a variable rate over the cell life and because of impedance
>issues (see below), it depends a lot on how you run the test. The Energizer
>cells have a lower rated capacity than some vendor's but a lower rate of
>capacity loss and a more stable impedance, so probably achieve better
>performance despite the lower capacity.
>
>Certainly reducing temperature will help in the normal way as with most
>batteries but the seals are damaged by stiffness/contraction at very low
>temperatures (particularly if the temperature cycles when you open the
>freezer door!), and condensation+salts cause surface leakage. So don't push
>your luck. Remember dropping the temperature only 15C (refrigerator
>compartment ) will more than double shelf life.
At what temperature does the electrolyte actually freeze? I recall from the
2nd edition of the Handbook of Batteries that the potassium or sodium hydroxide
electrolyte was so concentrated that it would not freeze until -60 degrees
(don't recall if that was F or C). My fridge gets down to 0 degrees farenheit,
or maybe -10, but that's it.
Joe
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