🚀 go-pugleaf

In article <clemon.4914@lemsys.UUCP>, clemon@lemsys.UUCP (Craig Lemon) writes:
>
>         I'd like to start a little discussion on NiCd memory (notice
> little, I don't want to be solely responsible for starting a noticeable
> bandwidth flare-up net-wide. Moderate's OK :-)

Okay, here's my $0.02

What I'm posting here has been gathered from talking with many people who have
used nicads, including some who have worked extensively with them, and reading
a lot of literature about them (including this and other newsgroups). Obviously
everybody has their own opinion about these things, and I'm no exception,
however I do think that what follows represents a resonably informed opinion.

As I understand it, the nicad memory effect does exist, BUT only in very
special circumstances. If a nicad is constantly charged and then discharged to
WITHIN A FEW % OF THE SAME AMOUNT EACH TIME, it will eventually develop a
memory. Note that it needs to be very precisely the same amount of
charge/discharge each time. This effect was found in satellite systems, where
the charge/discharge cycle of the nicads was extremely regular. For your
average domestic (or even industrial) nicad user, the memory effect effectively
does not exist.

What does degrade the performance of nicads is poor charging, in particular
overcharging.  Although they are designed to withstand an overcharge, constant
overcharging seems to gradually destroy them - it appears that leaving nicads
on a constant float charge is the worst thing to do to them. The reason for
totally discharging nicads (down to 1.0-1.1 volts per cell) then is so that
when they are subsequently charged for 15 hours (depending on the charge rate
of course) they are fully charged but not excessively overcharged.

Other factors also cause nicads to fail. As several posters have already
mentioned, heat is a major factor. A good indication of when a cell is fully
charged at a high charge rate is that the cell temperature rises 5 degrees C (9
degrees F). Any higher than this indicates that the cell is being overcharged
and is not good for it. If the nicad is hot to the touch after charging, it is
probably being damaged.


*********************************************************
Chris Kaiser
Postgrad - Elec Eng Dept
Canterbury University
Christchurch, NEW ZEALAND

E.MAIL: kaiser@elec.canterbury.ac.nz
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	"When you're fresh out of lawyers
 	 You don't know how good it's gonna feel"
		- Al Stewart, 1988
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