> > http://www.maxim-ic.com/appnotes.cfm/appnote_number/1793

> Yes, the above technote, and it's graphs going to 75 years, gave me
> much hope. :)

Ah, but.... notice the cut-off line at 10 years. You can calculate
for many years past the physical life of the battery. eg throw in
10Ah D cells and you'd think, oooh, at 10nA Iq I could get more
than 114,000 years out of those. Except the batteries will leak
and rot before the end of Hilary's second term

> Come to think of it... If I'm charging up a large capacitor bank,
> I'm essentially shorting out the batteries. This would be bad

I've used the LM317 it in a similar situation to what you want to
do. My application had four solenoids that needed to be activated
as quickly as possible to fast-forward a four-face tower clock
(each solenoid drives a ratchet and pawl). To do this without a
large cap for each would have collapsed the 0.25A PSU I wanted
to use. I had the luxury of enough reserve to overcome serial
losses and Iq of the LM317 though. You'd have to find a low-
current way to limit both losses and capacitor charging if you want
as long a life as possible out of those coin cells. Any chance at
all of including some supplemetary supply ? Solar cell ? Except
they have a use-by date too ;-((  Induced charge ?

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