clifto wrote:
. . .
Doug McLaren mentioned his experience that alkalines have higher
capacities than rechargeables, but I'm finding that my new Eveready
2500 mAH NiMH batteries compete quite well with a fresh set of Energizers.
KenRockwell.com lists alkalines at 2700 to 3135 mAH, sounds reasonable.

The capacity of alkaline cells is much more dependent on discharge rate
than that of NiMH cells. Note the capacities of alkalines shown at the
bottom of the list at
http://www.imaging-resource.com/ACCS/BATTS/BATTS.HTM. With the 5 ohm
load used for those tests, the alkalines have less than 800 mAh
capacity. The capacities you quote would be obtainable only at much
lower current drains. But I didn't look carefully at the page to see if
he used a different cutoff voltage for the alkalines. A NiMH cell is
just about fully discharged when its voltage reaches 1.0 volt, so that's
a common cutoff voltage for testing and using NiMH cells. But an
alkaline cell still has considerable energy remaining at that voltage --
a device has to function properly down to 0.9 volt, or at high drain
more like 0.8 volt per cell to extract all the energy from it.

This is yet one more confounding factor in trying to compare cells of
different chemistries. Performance depends heavily on the particular
application and conditions of use, so a single answer to which is best,
or even which has the greater capacity, simply isn't possible.

You don't need to take my word for any of this -- data sheets for common
cells are readily available on the web, and it takes only a few minutes
and a bit of poking on a calculator to discover this from the curves.

Roy Lewallen, W7EL