Michael Watterson wrote:
> The Camera type Primary Lithium  batteries (non-rechargable) may not be=20
> the same kind as used in Memory/Clock backups, not sure. They almost=20
> certainly perform better in constant low current drain than in=20
> intermittent high peak current applications though.
>  =20
I meant in comparison to Alkaline - and in applications where a larger=20
(say AA-sized) battery would be in use.

The 'rated' capacity of a Lithium AA and an Alkaline AA are nearly the=20
same - about 3000mAh.  However, the Alkaline can only provide that at=20
the low end of the current scale - say under 50mA of load.   So, if=20
you're drawing under 50mA, and within normal temperature ranges, it=20
doesn't seem to make any fiscal sense to use Lithium over Alkaline,=20
considering Lithiums are easily 2x the price of an Alkaline.     For=20
better comparison between the two, the datasheet at=20
http://data.energizer.com/PDFs/l91.pdf seems to do a really good job.

You can also compare to the datasheet of an 'industrial' Alkaline at=20
http://data.energizer.com/PDFs/l91.pdf .   Of particular interest are=20
the 'busty' voltage curves on this and the datasheet above.

I will say that Lithiums are definitely more usable in a wider range of=20
temperatures and applications.  Personally, the 'Emergency Primary'=20
batteries I keep in the car are almost all Lithium cells.  For memory=20
backup, I'd use a lithium coin any day over about anything else - except=20
perhaps a supercap capacitor (1F or larger) if the amount of time for=20
backup was in line with what could be stored in the capacitor.

-forrest

--=20
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