[sdiy] Typical load for 9V alkaline batteries?

[Glen]

I know we all hate those "how long is a piece of string?" type questions,
but I think this one is a little easier to answer than that. (I hope.) What
is a "typical" recommended maximum load that should be placed on a 9V
battery and still expect to see "several" hours of run time?

Yeah, I know it depends on what voltage level is still acceptable for your
circuit being powered. It depends on whether the current drain is constant
and continuous, or intermittent and variable. It depends on temperature. It
depends on brand, composition, and age of the battery. I guess it also is
affected by dumb luck (ie, getting batteries that are not already dead when
purchased.) It also depends on the exact definition of "several hours".   :)

All I really want to know is what is a very common amount amperage to draw
from your typical alkaline 9V battery? If you have some very rough idea of
how long the battery might last at this current, it would be good to
mention it. 

I'm designing a small battery powered circuit that I want to be able to use
right away, and don't have time to test battery life by waiting for the
silly thing go dead. I just want to know what a "typical" well-designed
circuit would expect of a 9V battery.


thanks,
Glen Berry  (Who hasn't built much 9V powered stuff, as you can tell.)