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PICList Thread
'battery life - Surprise!'
1999\07\24@032925 by Russell McMahon

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From: Brian Aase <spam_OUTulcsaTakeThisOuTspamESKIMO.COM>


\ For an AA Alkaline battery, the Eveready data book lists the
\ following loads vs. hours, to a cutoff voltage of 1.0 volt:
\
\ 1500 ohms = 1850 hours
\ 300 ohms = 340 hours
\ 150 ohms = 160 hours
\ 75 ohms = 82 hours
\ 50 ohms = 54 hours
\ 30 ohms = 32 hours
\ 10 ohms = 7.8 hours
\ 4 ohms = 2.3 hours
\
\ Hope someone will find this to be helpful.



Let's turn Brian's figures into milliamp-Hours to see how they vary
with load.
Assume an average battery voltage of 1.2 volts (which won't be
correct but is a good starting point.

We get

Ohms , Hours , mAH
1500 , 1850 , 1480
300 , 340 , 1360
150 , 160 , 1280
75 , 82 , 1312
50 , 54 , 1296
30 , 32 , 1280
10 , 7.8 , 936
4 , 2.3 , 690

ie the battery for which I have a 1993 claimed rating of 2250 mAH is
far worse than this.
1480 at low load and only 690 mAH at high load.
Even assuming a 1.5 volt average voltage (which is very wrong) we
only get 1850 mAH best case.
I wonder what happened between 1993 and 199




       Russell McMahon


cc to Tjaart who has made specific comment on battery capacities
before today.

1999\07\24@041534 by Dave VanHorn

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> I wonder what happened between 1993 and 199


They did take the mercury out...

1999\07\24@071544 by Bob Drzyzgula

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On Sat, Jul 24, 1999 at 03:09:00AM -0500, Dave VanHorn, without
identifying the source so that if I didn't modify this line
inserted by my UMA it would look like I was saying Dave
wrote this and then he'd gripe about being quoted as writing
something he didn't, appears to have quoted someone as saying:
> > I wonder what happened between 1993 and 199
And then Dave replied:
>
> They did take the mercury out...

It's also possible that Eveready simply makes lousy
batteries. In the Digi-key catalog, they give ratings
for Panasonic "industrial" batteries; all lifetimes
are for drain into 100 Ohms continuous:

D   1200 hours
C    380 hours
AA   170 hours
AAA   65 hours
N     48 hours
9V     6 hours

At 1.2V, the AA rating will work out to 2040 mAH; if you
make the poor assumption of a linear voltage decline from
1.5V to 1.2V over the 170 hours, you would have an average
potential of 1.35V, giving a total capacity of 2295 mAH,
which is well in line with the 2250 mAH that Russ has in
his 1993 spec.

--Bob

--
============================================================
Bob Drzyzgula                             It's not a problem
.....bobKILLspamspam@spam@drzyzgula.org                until something bad happens
============================================================

1999\07\24@102653 by Dave VanHorn

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> It's also possible that Eveready simply makes lousy
> batteries. In the Digi-key catalog, they give ratings
> for Panasonic "industrial" batteries; all lifetimes
> are for drain into 100 Ohms continuous:


This would make a great web page, if someone wanted to sacrifice a few
batteries to science.  I just popped up the mercury, as the largest change
in alkaline battery chemistry in recent memory.

It's nice that at least one battery maker is willing to put up hard data.
(or do we thank digi-key for that one?)

Duracell does have the new "ultra" batteries, I wonder if they are relabling
the "Good" chemistry... Nah, they'd NEVER do that, right?

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