Subject: Re: Reducing contact resistance for low volt use?
Summary: What do you think of these ping times eh?
Reply-To: You can't see me, and I pass right through planets...
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Date: Mon, 06 Jan 2003 00:03:56 GMT
NNTP-Posting-Date: Sun, 05 Jan 2003 19:03:56 EST
On Wed, 11 Dec 2002 01:15:55 GMT, jmuchow@SPAMMENOTcamlight.com (John
Muchow) Gave us:
>>>>There is a special electrically conducting grease used to improve contact
>>>>on car battery lugs. Nye make one.
>Thanks, I'll check it out..
>>>>If you're planning to discharge cells at 100 A they have presumably been
>>>>designed with connections for that purpose. In which case RTFM. Otherwise,
>>>>I would advise you not to do it.
>That's a misplaced assumption in this case. And I would love to read
>a FM, or even a regular M, on such cells. But alas, no such document
There ARE spec sheets on EVERY battery made that is made by a
>Sub-C, C, and D-sized NiCd and NiMH cells are regularly used at up to
>100A discharge current levels by R/C plane, car, and combat-robot
NOT from an individual cell, however. For one thing, they will NOT
produce that much energy.
> Typically, they are built in packs of 4-30 cells, soldered
>together in series with copper battery bars and hefty leads.
Such a battery pack MIGHT produce 100A. Silver plated teflon wire
used for military applications would likely exhibit less resistance
than the copper bars. It would weigh less as well.
>cells don't survive very long at these discharge current levels, but
>in the struggle to extract the maximum performance from the smallest,
>lightest package, battery life is often only a minor concern.
Then, what is your need? A 1600 mA/H battery is NOT going to
produce 100 A at ANY load resistance, and the terminations for testing
them individually does NOT need to be of such heft.
>I have regularly done destructive-test discharging at current levels
Bullshit. A dead short on a single cell with copper or silver will
NOT deliver such currents. If you are testing banks of cells, you are
making a mistake.
> To date, this has been with series-connected battery
>packs. To test the real performance of different manufacturer's
>cells, we need to test them individually to eliminate the variables
>introduced by all the interconnects, soldering, etc.
No shit. You don't need 100 Amp connections either.
Discharge the battery into a 0.1 ohm load that can handle the power
level expected, and read the current with a voltmeter across the .1
ohm resistor. Pretty simple. Reading across dead short loads will
not give real data, and if you are reading current by way of a series
shunt meter, you are dropping voltage on it anyway.
>This lead to my desire to extend the functionality of the discharger
>I'm working on to include 100A current levels with single-cells.
Spot welded steel strips or hard soldered connections are your best
bet. 100 A levels should not be expected from a single cell.
If you are getting 100 A out of 1.2V cells, and still read 1.2 volts
on them, I want to know what brand they are.