Sun, Jun 1, 2008, 6:39pm (EDT+4)
From:
[email protected] (Palindrome)
Just A Guy wrote:
Roy said
I don´t think he read that RS
link page on batteries or
he wouldn´t have had to ask
I did not, but I have now read it, and it did not help. My goal is a
better understanding of the mysterious world around me, with the hope
that through a more "accurate" model of reality, I will be better
equipped to predict and control my environment.
Or, in more practical terms, for about 2 years I have owned a Kodak
digital camera. In reviews of this camera in sites such as Amazon.com,
owners often complain about the difficulty of finding batteries which
will make this camera work. I've been using a variety of different
brands of NiMH batteries. Lately, some batteries which worked fine
before will not now operate the camera, although all these batteries
grade similarly in the RS battery tester, and all will operate an FM
radio.
So I'm trying to figure out what's going on. What is it about this
camera that is so fussy about batteries? Why are these batteries
starting to lose their uumph? Is there a different sort of meter that
will more accurately predict whether a battery will work my camera? Why
do they all test good in the RS tester?
The problem is that digital cameras tend to both draw a high current and
need a high voltage from the battery, at the same time. Your tester
almost certainly is not drawing a high enough current to give a
realistic reading of what the voltage will drop to when in the camera.
Different cells, from different manufacturers, of different ages, at
different temperatures, of different mAH rating, will perform
differently under the camera load - but will look to be doing much the
same on the tester as it is at the moment.
The answer is to modify the tester so that it does draw the same
current, when testing, as the camera does when running. Which will mean
adding an additional resistor between the two test terminals of the
tester.
I happen to have a new camera here with new freshly recharged batteries,
(intended as a gift for someone). So I measured the current to see what
sort of current is drawn. This one, with 4 cells, draws 0.5A.
The nearest preferred value resistor as a dummy load to test individual
cells would be 2.2 ohms in my case. You would probably need something
similar, but you could measure the current that your camera takes and
adjust the value to suit, if necessary.
A modified tester should show you a significant difference between the
readings of "good" and "bad" batteries, for your purpose.
Note that the "bad" batteries will still be good enough for many, many
applications that aren't as demanding in current and voltage as a
digital camera.
--
Sue
You're not kidding - There are special batteries for digital
applications - alkaline and other gp batteries fail mimicking dead after
a few repeated clicks on the battery powered device [cam etc.]
most batteries repond well to instantaneous repetitous demand on low
charge devices where the demand is greater & more dependent on voltage
than on current flow [as in the glow of a grain of wheat lightbulb] -
but with digital devices the demands is both for current & voltage this
can cause severe drainage to the cells charge almost instantaneously.,
leaving the lcd screen on will only affect the chemicalization process
more that which maintains the charge turns null....
I always wondered if I [one] could get radioactive waste and make good
barreries from it but got stopped by how to turn metal waste into
paste}
The batteries for digital devices/cameras are made up so that the cells
don't drain on instantaneous repeatitive demand...
one thought is the individual cells are probably just stacked closer
together inside the battery and electrons flow through easier....plus,
"the stuff" inside has to be more lucid
as with lithium ...
Roy Q.T. ~ US/NCU ~ E.E. Technician
[have tools, will travel]
