On Fri, 19 Jul 2019 17:30:54 -0700, (Dave
Platt) wrote:

A decade ago, I was happily buying the Kirkland-brand AAs from Costco,
getting good in-service lifetime and no problems to speak of.

A few years ago, something changed. I began to find their AAs
starting to leak, while still fully charged (never put into service),
while still in the original storage box or shrink-wrap package, well
before their labeled "use by" date.

It was more than a few years. In 1996, mercury was removed from
alkaline and other batteries. Mercury is what prevented leaks:
https://en.wikipedia.org/wiki/Alkaline_battery
When introduced in the late 1960s, the zinc electrode of
alkaline batteries (in common with the then ubiquitous
carbon-zinc cells) had a surface film of mercury amalgam.
Its purpose was to control electrolytic action at impurity
sites, which would reduce shelf life and promote leakage.
With reductions in mercury content being mandated by
various legislatures, it became necessary to greatly improve
the purity and consistency of the zinc.

I don't know whether they changed suppliers, or whether their old
supplier's quality fell through the floor... but the result was the
same. I've stopped buying the Kirkland batteries.

Since they can't use mercury, they have to use highly refined zinc
which I assume is expensive. In theory, using only the purity of the
zinc, they could adjust how long the battery will last before leaking
by simply controlling the impurity level in the zinc.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558