> ll be running my PIC chip at the absolute lowest possible speed. It
> doesn't take much processor power to count... I'm sure a 32khz
> crystal will be overkill in this case.

It does take "some" power though, and you'll have to decide which
part of the PIC you keep awake to do that

I haven't hit the books, but things to consider include -

Does 32kHz LP use less power than 1kHz RC ?
Do you keep the PIC asleep and use WDT to count ? (if so, the
suggestion is that you use a HS mode to count - awake shorter)

If you asssume X years is what you'll get from the battery,
that means working backwards to find the consumption to
get to X years

eg 87,600 hours in 10 years, 1uA Iq = 87.6mAh capacity, ignoring
voltage drooping at cell end-game. If your circuit can run on eg 2V
that would give you extra time

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