K7ITM wrote:
A friend who uses alkalines in his insulin pump told me he was
surprised to find that, in that particular application, he's seeing a
significant difference between standard Duracell and Energizer alkaline
AAs. "Your mileage may vary."

I've always had horrible luck with Duracells. Every five years or so I
go out and buy another set to remind myself of this, but the results are
never different.

Harry G. mentions getting good prices on Energizers at Home Depot. Seems
like the HD stores around here never ever have the good deals I read about
from other people on the 'net; batteries there are about the same price as
Walgreen's around here. People talk about borrowing free tools to replace
cartridges in Moen faucets and then getting free replacements at HD; ours
will sell us a plastic tool for $18 and then we get to decide which size
cartridge is appropriate, at full retail price, of course. But the (local?)
Menard's chain usually has Ray-O-Vac AA's at 30 for $9.99, and I get great
life out of them, nearly as good as the Energizers for about half the price.

Roy Lewallen mentions Costco; they haven't had their particular brand
(40 for $10) for literally years here, all they sell is Duracells now
and they want 25% more than Menard's and the Ray-O-Vacs.

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.

--
If John McCain gets the 2008 Republican Presidential nomination,
my vote for President will be a write-in for Jiang Zemin.

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

Roy Lewallen wrote:
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.

And the funny thing is, at a high load such as my GPS III+, those alkalines
with their capacity diminished by the high current draw still last longer
than the NiMH that supposedly like high current draw. (I said the NiMH
compare favorably, not that they outlast alkalines.) I agree with you,
I've been playing aloud with numbers that don't always belong in the
same arena. And too many other factors impinge; I save money using the
NiMH in the GPS, but I'd kill them in flashlights that I routinely
leave on and forget. And then there are those sulfated wet-cell batteries
in the garage... *sigh*

--
If John McCain gets the 2008 Republican Presidential nomination,
my vote for President will be a write-in for Jiang Zemin.

And the funny thing is, at a high load such as my GPS III+, those
alkalines
with their capacity diminished by the high current draw still last longer
than the NiMH that supposedly like high current draw. (I said the NiMH
compare favorably, not that they outlast alkalines.) I agree with you,
I've been playing aloud with numbers that don't always belong in the
same arena. And too many other factors impinge; I save money using the
NiMH in the GPS, but I'd kill them in flashlights that I routinely
leave on and forget. And then there are those sulfated wet-cell batteries
in the garage... *sigh*
==================
I had the same experience with my ancient Garmin GPS 40 ;alkaline batts held
longer than NiMHs.
Possible reason is that alkalines cells are 1.5 V and NiMHs 1.2 V
It is well possible that although the NiMHs are only considered discharged
when the voltage has dropped to below 1 Volt (per cell) this voltage (or its
multiple) is too low for the GPS to operate, whereas alkalines hold a higher
voltage for a longer period.
I noticed that when the GPS switched itself off when using NiMH batteries
,the cells apparently were not fully discharged.
Using an automatic NiCad /NiMH charger operating with an initial discharge
period as part of the overall cycle,
it took quite a while ,before the NiMH cells were discharged before charging
commenced.

Frank GMØCSZ / KN6WH

clifto wrote:
. . .
Roy Lewallen mentions Costco; they haven't had their particular brand
(40 for $10) for literally years here, all they sell is Duracells now
and they want 25% more than Menard's and the Ray-O-Vacs.
. . .

That's too bad. I just got back from Costco, where I found their store
brand Kirkland AA alkalines at $9.59 for 48. They also had Duracells, 16
for $8.19.

Roy Lewallen, W7EL

Roy Lewallen wrote:
clifto wrote:
Roy Lewallen mentions Costco; they haven't had their particular brand
(40 for $10) for literally years here, all they sell is Duracells now
and they want 25% more than Menard's and the Ray-O-Vacs.

That's too bad. I just got back from Costco, where I found their store
brand Kirkland AA alkalines at $9.59 for 48. They also had Duracells, 16
for $8.19.

Yep. Used to go for the Kirkland units at just about that price; they
disappeared from our local Costco a few years back. I'm thinking their
Duracells are right around that price too, but (1) I don't buy Duracells
and (2) that's over 50 cents per battery when I can get 30 Ray-O-Vacs
for $9.99 any day of the week at Menard's. Sometimes even better at
Menard's; the last batch of AAs I bought were 12 for $2.59 with a $2
rebate on up to two packs, or just under a nickel per Ray-O-Vac.

Back when I got the Kirklands regularly, they were about half the cost
of the name brands I was finding and had a little better than half the
lifetime, not a bad deal at all.

--
If John McCain gets the 2008 Republican Presidential nomination,
my vote for President will be a write-in for Jiang Zemin.