RE: [Paddlewise] PaddleWise:Battery Life

From: Blaauw, Niels <nblaauw_at_foxboro.com>
Date: Wed, 14 Mar 2001 08:34:40 -0500
<<question for battery capacity of different kinds<<

Since I needed some capacity indications myself, I have been searching the
internet, and was quite surprised how difficult it is to find these data.
What I found comes from a vendor of geigercounters:

(I assume you have some knowlegde about currents, flows and resistors. I do,
although I might misuse some words, trying to write English.)

>>>
We now have Alkaline batteries that have high current capacities in the 1
1/2 volt size. ( Duracell capacity ratings) 

               AA Alk.   2850 MAH = Milliampere Hours. 
                C Alk.   7800 MAH 
                D Alk.   15,000 MAH 

To translate what this means, if you put a AA Alk. battery in a circuit that
uses 40 milliamperes to operate, the battery will have a useful life of
71.25 hours. At the same rate (40 MA) a D size would run for 375 hours. 

<<<

According to the Duracell site, the "Alkaline Ultra" or whatever they call
it, has a capacity of about 1.5 times the normal alkaline version. As for
other kinds of batteries, I have no data.

As far as I know, the capacity of a battery does not depend on the usage.
However, since a battery behaves as a resistor, the output voltage will drop
when the used current rises.

During the life of a battery, the voltage will drop from about 1.5 to 1.2
volts gradually. After that the voltage will drop fast. The hardware using
the battery will decide for itself when it is time to shutdown: This may be
at 1.3 volts in a camcorder (meaning the battery is depleted for only 2/3)
or much lower in a flashlight that you will use until there is no light left
at all. For things like photo cameras and GPS's I have no idea when they
shutdown. I expect an electric pump to drain the batteries completely.

Hope this is of some help,

Niels Blaauw


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Received on Wed Mar 14 2001 - 05:32:33 PST

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