On Apr 11, 1:01 pm, (Dave Martindale) wrote:
"z" writes:
I don't know if this is the best newsgroup for the question, but....
those little button batteries, for watches, etc... I always thought
they were 3 volts, but idle curiosity yesterday made me measure a few
and they were closer to 1.5.... of course, the package won't tell you.

In my experience, the package often does tell you if you look.

But if you can't find it, the battery has some sort of type number,
which you can look up in a battery data book, which will tell you the
the chemistry, voltage and capacity ratings, and just about anything
else you might want to know.

As a general rule, cells that are very thin for their diameter, rather
like coins, are usually some sort of lithium chemistry and the voltage
is about 3 V.

Smaller diameter but thicker cells are often either silver oxide or
alkaline, both with about 1.5 V when new. In fact, for many standard
sizes, you can get both chemistries (e.g. LR44 is alkaline, SR44 is
silver oxide). Silver oxide is more expensive but has higher capacity
and more stable voltage during its life.

Cells that have an air hole, and a small piece of tape covering the
hole, are zinc-air cells. There used to be 1.35 V mercury batteries,
which provided very stable voltage, but these have mostly vanished now.

Dave

Ah; the lithium vs. silver oxide facts are useful. Thanks. I assumed
that the silver oxide was also 3 volts.
I remember mercury cells; used to seek them out for powering my cute
little radio shack/allied/lafayette multimeters.