Going thru my pile of old batteries, I discovered 3 1995 Polaroid pola-
pack batteries. They still read above 7.2 V. I think they were 7.5V
when new. Whatever chemistry they used has held up for 16 years.
I'm wondering what the chemistry of these batteries is that they
haven't self-discharged after this long period of time. Does anyone
know for sure what Polaroid used?

Just because the voltage hasn't dropped much, doesn't mean the cell hasn't
deteriorated. It might have lost a lot of its capacity.


Google for "Polaroid Polapulse Battery" and you'll find plenty of
photos and references.
The P80 and P100 are 6V at 250mAh and Zinc-Manganese dioxide.
The P500 are 6V at 1400mAh and Lithium-Manganese dioxide.
Note that they can be recharged successfully a few times.

Thanks for the update.

My understanding was that they were originally carbon-zinc. They were
designed and made by Ray-O-Vac, but when they turned out to be unreliable,
failing unexpectedly (I had one fail when I left the camera in a warm -- but
not hot -- car), Polaroid redesigned and manufactured them itself. Polaroid
gave away a cheap AM/FM radio powered by the battery in a discarded film
pack, to take advantage of what would otherwise have been wasted energy.

It's unfortunate there are no standardized rechargeable battery packs for
portable devices. This might have been doable when they were powered by AA
and C cells, but modern devices are so small, and the battery is so tightly
mechanically integrated, it isn't possible.

I recently replaced the battery in my Palm T3 PDA, after seven years of
service. I was surprised at how easy it was to do; I expected a fuss-fest.