[Leica] Batteries in cold weather

[lrzeitlin at gmail.com (Lawrence Zeitlin)]

Steve,
I'm certainly not a battery expert. I once threw away a whole box of
expensive silver oxide batteries that I had stored in a freezer because the
voltage tested low when I took them out. But after a while I learned that
the condition was normal. Most batteries based on chemical reactions appear
to lose power when tested in cold conditions. As you recall, from basic
chemistry, chemical reactions slow down 50% for each 10C drop in
temperature. Batteries will fully recover power when warmed to room
temperature. There are few camera batteries that will function adequately in
sub-freezing conditions. Here is a short paragraph cribbed from a mountain
climbers site about the cold weather performance of batteries.

*Carbon-zinc*

These are the plain, old-fashioned batteries, and have power of 950mAh with
a sloping discharge curve. Operating range is only down to 20degF and shelf
life is 1/3 to 1/10th of other types - about 3.5 years. They perform very
poorly at low temperature; at -5degF their service life is decreased by 75%
and output drops quickly as the temperature drops below room temperature. On
the plus side, they're cheap.

*Alkaline*

The Energizer has 2850mAh and the new Energizer e2 has about 15% more, or
3135mAh, and both have a sloping discharge curve. Operating range is down to
0degF and shelf life is 10+ years. They're not much better at low
temperature; at -5degF their service life is decreased by 60% and output
drops quickly as the temperature drops below room temperature. Although
they're more expensive, they're comparable to carbon-zinc in terms of cost
per hour of use.

*Silver oxide*

These are the small (dime-shaped) batteries often used in cameras and
calculators. Since they don't come in AA size, comparative power output is
meaningless, but they have a flat discharge curve. Operating range is down
to 14degF and shelf life is 10+ years. They're a better at low temperature;
at -5degF their service life is decreased by 50%. Output decreases slowly
until about 40degF but below that output drops quickly.

*Lithium*

Lithium AAs won't outlast alkaline, with equivalent power of 2900mAh but
with a flat discharge curve. Operating range is down to -40degF and shelf
life is 10+ years. They're significantly better at low temperature; at
-5degF their service life only is decreased by 20% and output decreases
slowly as the temperature drops. They're also much more expensive.

*Rechargable batteries*

NiCads and Nickel-metal-hydrides have less storage capacity - only half that
of alkalines, they supply lower voltage, and also drain much faster by
themselves. They do not perform well at low temperatures, roughly equivalent
to carbon-zinc.


Larry Z