Herbert,   you are right that "real world testing" is always better.
But here we are talking about Alkaline penlight batteries, not re-
chargeble's.
I'm pretty sure that 0.5 ma can be delivered over such a long time,
it is within the spec. area of those batteries.
Only if larger currents, ranging from ca. 0.1 upto 1C are drawn
(here 0.3 to 3Amp) other rules play their part, and supply capacity
goes way down.
Alcaline's hold their capacity very well over a few years, (up to 10).
Age and  nr. of discharge cycles of course only apply to rechargeble's.

Greetings, At vW.


From: "Herbert Graf"
Subject: Re: [EE:] Battery life estimation


> > Hi Mike,
> >
> > Say that two alcaline penlight cells have a capacity of 3000ma/h.
> > You don't want that 3A over one hour but only 0,5ma during X hours.
> > 3000/0,5 = 6000 (x 1 hour). Which is ca. 250 days, or ca 10 month,
> > before the cells are empty. And empty is about  1.3v each.

>         While that makes "math sense" in the real world that just isn't
that useful
> a technique. The reason is the "capacity" of a battery is dependant on the
> load. Some batteries are far better at handling smaller loads over long
> periods of time then others "i.e. alkaline vs. nicad).
>
>         Therefore, while a battery may state 1000mAh, that does NOT mean
it can
> supply 1mA for 1000 hours. What it means is usually the bit of information
> that's left out of a quick spec: the load current where you get that
rating.
>
>         The ONLY ways to realistically get good numbers is either to spec
the
> SPECIFIC battery (from the manufacturer) or to do real world testing.
>
>         Oh, and on top of all of this, the capacity of a battery is
dependant on
> more then just current, most batteries are VERY dependant on temperature,
> age is also a very important figure, as is number of discharge cycles.
TTYL

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