[sdiy] Typical load for 9V alkaline batteries?

[Speth, John]

They key battery parameter is capacity.  Looking at the datasheet for the Energizer 9V, the capacity is 625 mA-hours at 25 mA continuous drain.  Lacking any specific drain or duty information, that translates to 25 hours of continuous use at 25 mA.  As you know, YMMV due to the various conditions you listed.

Take a look at the energizer data sheet at www.energizer.com.  Look for battery type 522 (in the selection tree: primary, alkaline, energizer, consumer/OEM, 522).  Take a look at the discharge curves for various applications.

You can predict the service time by applying V=IR.

John Speth