clemon@lemsys.UUCP (Craig Lemon) (06/24/91)
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 :-) I know that in 1985 when I
bought my first cordless phone (Radio Shack, ick!) NiCd memory was a thing
known only to Electronics hobbyists and professionals. It was never really
worried about too much by the general public. The phone manual instructed
us to leave the handset on charge whenever we weren't using it so it would
be ready whenever we wanted it because it didn't affect the batteries
anyways. I knew about memory but I ignored it and left it to charge when I
wasn't on the phone.
As you can imagine, cordless phones are probably _the_ best
"medium" in which to create cases of NiCd memory : on 0:15, charge 30:00,
on 0:30, charge 0:05, on for 0:30 again etc...etc... I was particularly
bad for this. Now these batteries are badly memorized or just plain worn
out. It'll still let the phone standby for 12 hours (which is all some new
manufacturers claim) and talk for a good hour I think. The Bat Low light
comes on but the phone takes a long time to die after that.
Now time have changed. Just as the 'net _seemed_ to declare memory
a fallacy, the cordless phone manufacturers and vendors have caught on!
I've been shopping for a new cordless phone and I've wasted more time
listening to EVERY salesman tell me over and over to charge the handset for
16 hours, and then not charge it again until the BATTERY LOW light comes
on. The Panasonic dealers even said that after the initial charge I
should run it down and charge it again before using. This woman also said
that I should put tape over the chargin contacts if I'm tempted to hang it
up!
The above seems like an awful lot of bother to prevent an effect
that doesn't exist. Have there been any further discoveries into : NiCd
Memory : Fact or Fiction (the Saga Continues...). ? I thought that my
previous battery lasted pretty good and I'm not sure if getting 6 more
months out of a battery is worth always having a 50/50 chance that you'll be
able to finish a phone call on the present battery power.
I know that some people will say, "You don't want to bother with
it. Just charge it all the bloody time and don't bother us with it!". I
don't want to turn this into a strictly cordless phone discussion but it's
just an example. What's happening with the memory scene? Even if these
habits do not prevent the maybe non-existant memory, is it better for the
NiCd anyhow? What about those new rechargables developed in Canada (Yah!).
I think that they were Chromium something. (Sorry, I've handed my OAC
Chemistry textbook back already :-) They claim to have 50% more energy and
are 50% cheaper to produce. If anyone is familiar with these please post.
Do _they_ have a rumoured memory?
Disclaimer : I hope I don't have a problem because I metioned Panasonic in
this post :-)
--
Craig Lemon - Kitchener, Ontario. Amiga B2000 UUCPv1.13D.
clemon@lemsys.UUCP lemsys!clemon@xenitec.on.ca | Please Mail any binaries
xenitec!lemsys!clemon@watmath.waterloo.edu | to 'files' at this site
..!uunet!watmath!xenitec!lemsys!clemon | instead of 'clemon'elec140@csc.canterbury.ac.nz (06/25/91)
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 ********************************************************* "When you're fresh out of lawyers You don't know how good it's gonna feel" - Al Stewart, 1988 *********************************************************
tonya@hpldsla.sid.hp.com (Tony Arnerich) (06/26/91)
Fact #1: ALL NiCad manufacturers claim that "The memory effect has
been eliminated/solved/relegated to the past."
Fact #2: ALL manufacturers will say the above, even when it is not true.
Make that "especially when it is not true", and the other
manufacturer's have beaten you to the claim of having solved
the problem.
Fact #3: My rechargeable shaver used to be able to give 3 weeks of
shaves per charge, now after 2 years it can only do 2 weeks
per charge. It has a 1-hour quick-charge, after which it switches
to trickle (I think - at least the "charge" light changes from
steadily on to flashing at end of quick cycle. At least some
part of the charge circuit knows when a "full" charge has been
reached). I discharge to a fairly consistent level (when the
motor speed suddenly poops out), and usually let it go beyond
the quick charge cycle, and through the night (boy, I *hope*
the charger drops to trickle rate!) In no case do I ever drain
the batteries to absolute zero, nor do I do partial charges. It's
probably gone through only about 50 charge/discharge cycles.
Hearsay #1: A friend at work claims to really drain down his Makita
power tool batteries after each drain below useful voltage. He
swears this is the secret of treating NiCads well.
Hearsay #2: The number of woodscrews he says he can drive is much higher
than the number I have been able to drive (I know, different screws,
different wood,...). It still makes me think I'm a NiCads' worst
nightmare.
tonya@sid.hp.comzimmer@calvin.stanford.edu (Andrew Zimmerman) (06/27/91)
After last night, I might be tough competition for NiCads' worst nightmare. I had two battery packs get so hot that the plastic around the cells split open. :-( However, the batteries still work fine! Andrew zimmer@calvin.stanford.edu