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From: jmuchow@SPAMMENOTcamlight.com (John Muchow)
Subject: Re: Reducing contact resistance for low volt use?
Date: Tue, 07 Jan 2003 06:05:07 GMT
Organization: MindSpring Enterprises
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X-Server-Date: 7 Jan 2003 06:06:59 GMT
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>>>>When did you introduce those basic rules and what consultation process
>>>>did you go through?
>>> Hey, if you want to separate yourself, and "help" this guy with this,
Hey, John has helped plenty...and there were none of your damn
quote-marks on that help either.
What the heck is bothering you so much about my
>>>>We do occasionally get stuff here about high-energy experiments that
>>>>damage either the test object or the energy source. It's all part of
>>>>life's rich pageant.
>>> Yep. As is doing it right. Destructive testing has it's place. I'd
>>>be willing to bet that the battery makers have more comprehensive data
>>>than he could ever desire. They have the capitol to make the fixtures
>>>right, and the equipment to log the data better. One might even be
>>>able to get said data from them, up to a point.
>>> Attempting it blind is only asking for invalid data.
No, you don't mean "as in doing it right". You mean "as in doing it
Doing it wrong would be using a stopwatch and an analog meter to log
the discharge voltages. Doing it wrong would be building this
discharger without getting the great advice I've gotten from this
newsgroup. Doing it wrong would be saying "DarkMatter says this data
would be invalid so we can't do the tests".
We most certainly did not want to spend the time and money building
this thing if the data was already available....as interesting an
engineering challenge it is.
We've contacted Sanyo, Panasonic, and Varta asking for information
regarding high-current discharging. They had none to give us. Sure,
they all had hard data up to about 10C (24A-36A or so for our cells),
but after that they said we'd need to extrapolate the existing
curves....which isn't going to give us "valid data" for our higher
current applications. Not to our satisfaction, at least. All the
engineers were fascinated by our application though. After a few
moments of disbelief and insistence that the cells wouldn't take this
abuse for long, they came around and started talking to us when we
told them that we *don't care* if they didn't survive very long.
And while battery manufacturers do have lots of capital, they're not
going to use it for testing at discharge current levels only seen by
0.000001% of their users. And our logging hardware is way beyond
what's needed for this testing. Anything with more than +/-50mV
accuracy at a 30 samples/min rate is overkill. We're just testing
batteries here, not atomic clocks.
What is "blind" about our attempt to plot discharge curves for very
high current levels. If the damn cells dropped to 0.00V after 50mS,
great! We've learned all we needed to know about the cells at that
current level. Then we select a lower level and plot that curve.
What's invalid about our data? You just mean that it doesn't fit your
idea of what batteries *should* be used for or how they should be used
What is wrong with testing at higher current levels when the
application for these cells already draws these current levels? Not
testing doesn't make the application go away. There are many, many
folks out there who want to know what these cells will do at 20+ amps
discharge. They don't say that the cells will last very long, or even
that they won't explode immediately (they won't, of course). They
just want the information, and so do we.
There is a lot of BS out there regarding battery life, "zapping" of
cells, high-current vs. low-current charging, storing cells, etc. Our
device can begin to answer a lot of those questions for us and many
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