lane@dalcs.UUCP (John Wright/Dr. Pat Lane) (09/25/88)
I just noticed in the User's Manual for my Zenith 183 some rather critical
operating information buried in the middle (well, on page 1 of chapter 3).
And no, I didn't read the whole thing when I got the machine...shame on me :-)
(seriously, it's the thickest, most detailed User's Guide for a computer I've
ever seen).
Anyway, they say that there is a considerable danger in overcharging the NiCad
batteries and that repeated overcharging will reduce the length of time the
batteries will hold a charge to virtually nil. They recommend charging for
8 to 10 hours and *no* more. I've, of course, been leaving mine plugged in
virtually all the time (ulp!). Further, they say that damage can be done by
charging the batteries before they are fully exhausted.
They suggest the following operating cycle:
1. Run the thing on batteries alone till the battery low beeper sounds
2. Save your stuff and continue operating on batteries (listening to the
annoying beep every few seconds!) until the screen goes (yeah, right!)
3. Then plug it in...it's unclear whether you have to save your stuff (if
you can!) and turn it off at this point.
To me, this sounds wierd as h*ll.
Are they for real about this? I'd be interested to know how other people
use their laptops and other NiCad battery operated equipment. I'd also be
interested in hearing from the technically knowledgeable on the subject.
Specific questions:
1. The 8 to 10 hours recharging time...is that affected by whether the machine
is on? Would that mean that you should not use the machine on and plugged
in for more than 10 hours...after 10 hours, unplug and use the batteries
till they're gone, then go back to external power for another 10 hours and
so on...till you give up and go get some sleep :-)
2. Should you plug and unlplug the external power while the machine is on or
power down for the switch to and from batteries...if the latter, does this
not make Zenith's advise about running on batteries till the machine packs
it in rather risky for saving your work?
3. Would this all not apply equally to all equipment using NiCad's (such as the
Diconex 150 I also use)...funny this is the first place I've seen these
warnings.
4. As I said, I've been leaving my machine plugged in alot, while I'm using it
and otherwise, and I'm getting about two hours on batteries before it starts
beeping at me. Given the relatively large backlit screen and 20Meg HD, this
did not seem that unreasonable and I've notice no degradation in this since
I got the machine but I wonder if I should be getting longer battery life.
Side issue:
I have a car cigarette-lighter adapter as well. The instructions warn against
having the laptop on and plugged in when starting the vehicle which seems
sensible. They also say that the battery cannot be charged while the machine
is on when running from a car battery because there is not enough power. I was
curious about this because (I could be wrong here) I thought the regular ext.
power adapter supplies 12V-DC and if the voltage is the same, would the laptop
not try to draw enough amps to run the machine and charge the batteries both?
How would the machine know it was in a car?
Another side issue:
A friend with the same system is going to Europe and was wondering about his
options. We both thought it should be safe to use one of those cheap voltage
converters (that do not change the 50 cycle line frequency) with the external
power adapter (which converts the juice to DC so the freq. should not matter)
for both charging the batteries and actually running. Are we right?
Sorry about the length of the article and appreciate any advise/comments.
--
John Wright ///////////////// Phone: 902-424-3805 or 902-424-6527
Post: c/o Dr Pat Lane, Biology Dept, Dalhousie U, Halifax N.S., CANADA B3H-4H8
Cdn/Bitnet: lane@cs.dal.cdn Arpa: lane%dalcs.uucp@uunet.uu.net
Uucp: lane@dalcs.uucp or {uunet,watmath,utai,garfield}!dalcs!lane srm@topaz.rutgers.edu (SRM) (09/26/88)
In article <3008@dalcs.UUCP> lane@dalcs.UUCP (John Wright/Dr. Pat Lane) writes: > Specific questions: > 1. The 8 to 10 hours recharging time...is that affected by whether the machine > is on? Would that mean that you should not use the machine on and plugged > in for more than 10 hours...after 10 hours, unplug and use the batteries > till they're gone, then go back to external power for another 10 hours and > so on...till you give up and go get some sleep :-) My personal experience with my own Z181 and others Z183 is do not under any conditions leave the unit plugged in while in use. The best practice is as you mentioned from the manual. Let it go until almost dead (Low power light blinking and beeps). Recharge for 8 to 10 hours with the unit OFF! Then everything is safe. I do admit though I do not always follow what I preach thats why I've gone through 2 batteries on mine to date. > 2. Should you plug and unlplug the external power while the machine is on or > power down for the switch to and from batteries...if the latter, does this > not make Zenith's advise about running on batteries till the machine packs > it in rather risky for saving your work? I have plugged in the external power while the unit is on with out any problems. > 3. Would this all not apply equally to all equipment using NiCad's (such as the > Diconex 150 I also use)...funny this is the first place I've seen these > warnings. The problems described by the Zenith manuals concerning their batteries is common among all nicad batteries as far as I know. I would assume the same with the Diconex 150. > 4. As I said, I've been leaving my machine plugged in alot, while I'm using it > and otherwise, and I'm getting about two hours on batteries before it starts > beeping at me. Given the relatively large backlit screen and 20Meg HD, this > did not seem that unreasonable and I've notice no degradation in this since > I got the machine but I wonder if I should be getting longer battery life. I don't really know with the Z183. With my Z181 I originally got about 5 to 7 hours usage which dropped to about 2 hours {I didn't beleive the manual either :-)}. I replaced the battery and all was fine again till it dropped to about 30 minutes {I've learned my lesson now}. All of the above has been with full 8 to 10 hour charges. I recall reading about a software product that will monitor the battery level and prevent overcharging. I think it was by Traveling Software but I'm not certain. I could be helpful but I beleive it's very costly. The reason why I don't have it now :-). Scott R. Myers srm@topaz.rutgers.edu
koonce@brahms.berkeley.edu (tim koonce) (09/26/88)
One strange fact about NiCad batteries is that if they are not sometimes _completely_ discharged, they will develop a ``memory'' which will shorten their charge life. Occasionally, they need to be discharged as completely as possible. (Best to take the batteries out and strap a 1k resistor across them for a day, but leaving the computer on until everything dies is a close substitute.) If you have a set of NiCads which run down very quickly after charging, this may be the problem. Just charge them completely, and then run them down completely several times, and they should be fine. Odd trivia: Several people I know have successfully restored ``bad'' NiCads by putting a high charging voltage (24 volts or higher across a 1.5 volt cell) on them for a short while. This seems to burn out small bridges that form internally after a while. - Tim Koonce
jim@belltec.UUCP (Mr. Jim's Own Logon) (09/26/88)
There is method behind their madness. If you are constantly trickle charging
your Ni-Cads they develop some sort of memory effect. You drain them 20% then
charge them 20%, over and over again. Soon, the batteries only have 20% of
their original capacity (if it used to power your portable for 10 hours, it
would now only run it for 2).
This has something to do with growing 'fingers' of Cadmium across the
cells of the battery. By draining the battery down to nothing *occasionally*
and then recharging it, the charge current helps remove these fingers. All
the papers I've read on this advocate the complete discharge on a periodic
basis, and not all the time.
For batteries that have already become unable to hold their normal charge,
there is the mad scientist solution to crush through a large current in order
to vaporize the fingers. It requires a short, burst of high(er) voltage. I've
tried it a few times on hurting Ni-Cads; never worked.
-Jim Wall
Bell Technologies Inc.
The above is for someones edification, and not something that I advocate anyone
to try. So if you try it, and it doesn't work; don' call your lawyer (unless
he also sells batteries).malpass@vlsi.ll.mit.edu (Don Malpass) (09/26/88)
In article <14705@agate.BERKELEY.EDU> koonce@math.berkeley.edu (tim koonce) writes: >Odd trivia: Several people I know have successfully restored ``bad'' >NiCads by putting a high charging voltage (24 volts or higher across >a 1.5 volt cell) on them for a short while. This seems to burn out >small bridges that form internally after a while. > A safer trick is to charge up a BIG capacitor to some large voltage and then use clipleads to zap the nicad with it. It'll give an instantaneous current spike that burns out the short, but won't then go on to destroy (aka explode) the battery from over-voltage. -- Don Malpass [malpass@LL-vlsi.arpa], [malpass@spenser.ll.mit.edu] My opinions are seldom shared by MIT Lincoln Lab, my actual employer RCA (known recently as GE), or my wife.
darrelj@sm.unisys.com (Darrel VanBuer) (09/26/88)
I use NiCds as a ham, but characteristics are general. On charging: once the battery is fully charged, the extra current goes into heating up the battery and disassociating water into hydrogen and oxygen. Both of these are hard on the battery. On discharging: NiCds eventually "learn" how you use them. If you use 25% and recharge regularly, they eventually will give out after 25% use. While its not necessary to go all the way down every time, you should do so regularly. BUT don't over discharge either, because if you go beyond the capacity of the weakest cell in the battery, it gets run in reverse which causes whiskers of metal to grow and eventually short out the cell. Also with a partial discharge, its hard to guess how long to charge without overcharging.
gates@nsc.nsc.com (Tim Gates) (09/28/88)
NiCad batteries have something called Memory. This is when the
battery is partially discharged then recharged many times. The
battery then begins to act as if it can only store a small amount
of energy (the normal discharge amount).
The storage capacity of the battery can be restored by FULLY
discharging the battery, then fully charging it. This should be
repeated 3 or more times. Each time you will increase the storage
capacity of the battery.
To fully discharge the battery, just leave the computer turned on
until it is dead, then connect a low value (2 to 5 Ohms) resistor across
the battery terminals for several hours. I suggest that a high wattage
resistor be used (3 times the expected power dissapation).
If you are concerned about data integrity when the battery is low,
use only the resistor to discharge the battery. This will take longer.
Allow 3 hours for each amp/hour of capacity for which the battery is rated.
If you are interested in other NiCad battery problems and their
solutions, send me mail. If there is enough interest, I will post.
--
Tim Gates
National Semiconductor
{amdahl|decwrl|hplabs|nscpdc|pyramid|sun|voder}!nsc!gates
"Where the men are men, and the computers run scared."herman@marlin.NOSC.MIL (John W. Herman) (09/28/88)
There is an article on ni-cad batteries and the charging of same in the September issue of "Ham Radio" magazine. There is also a description of a pulse charging that the author claims will multiply the life of the batteries by a significant amount. Recommended reading. -- John Herman ARPA: herman@marlin.nosc.mil
ray@micomvax.UUCP (Ray Dunn) (09/29/88)
In article <3008@dalcs.UUCP> lane@dalcs.UUCP (John Wright/Dr. Pat Lane) writes: >... >Anyway, they say that there is a considerable danger in overcharging the NiCad >batteries and that repeated overcharging will reduce the length of time the >batteries will hold a charge to virtually nil. They recommend charging for >8 to 10 hours and *no* more... >... Further, they say that damage can be done by >charging the batteries before they are fully exhausted. Ah. NiCads. There should probably be an entry in the net.announce.newusers "commonly asked questions" to cover nicads! It's usually in consumers.house or models.rc or whatever but it *does* come up once or twice a year, and is a subject full of myths and old-wives-tales! Hope this is of use and worth the volume. >Specific questions: >1. The 8 to 10 hours recharging time...is that affected by whether the machine > is on? Would that mean that you should not use the machine on and plugged > in for more than 10 hours...after 10 hours, unplug and use the batteries > till they're gone, then go back to external power for another 10 hours and > so on...till you give up and go get some sleep :-) 8-10 hours is *NOT* a trickle charge, so the batteries *will* overcharge if left longer at this rate, or if left for a full 8 hours when they were only partially discharged. Overcharging causes permanent chemical changes which reduce the life and capacity of the cells. Use an outlet timer when using this charger. Normally, a trickle charge is the 14-16 hour rate, which is about 1/12th to 1/10th of the current of the one hour capacity of the pack - thus a 1.1 amp-hour nicad is charged at about 100ma for 16 hours. At trickle charge rate, nicads will *not* suffer significant damage if left charging for longer than 16 hours, but see below. Most equipment comes with a trickle charger. This makes life easier but charging times longer. Problem number 1: If *kept* fully charged permanently, nicads will loose capacity. If routinely discharged by only a fraction of their capacity, the available capacity will tend towards this fraction. This "memory" (actually a chemical change in the cells) can be avoided (and to a certain extent reversed) by cycling the cells through *complete* charge/discharge cycles. So, for *best* performance, don't plug them in during equipment use, or routinely charge between uses unless the cells have fully discharged. Although it *is* a good idea to fully discharge between charges, it is often a pain in the neck. Going through a full discharge cycle a couple of times a month, say, is often a good compromise. Balance the cost of possibly replacing the nicads prematurely, or getting less capacity, against the inconvenience of handling them "properly". A good solution to the problem is to have two or more battery packs, to match your use pattern. One in use, the other(s) on trickle charge. This may not be convenient if the pack is built-in to the equipment. Problem number 2: A nicad pack is a battery made up of several cells. Individual cells discharge before others. If current continues to be drawn from the pack after one or more cells have discharged, then current is forced through these cells and they become *deep discharged*, an irreversible chemical change takes place. Nicads have a very flat discharge curve with a sharp "knee" near the discharged point, so as soon as a voltage dip is seen (e.g. screen dimming, shaver motor slowing down etc) the pack should be considered dead and recharged. Continuing to use a pack until it is completely dead will always deep discharge one or more cells to some extent. Damage is cumulative. Odd tips: A bad pack often only has one or more bad cells, and can be recovered by replacing only the bad cells, not the whole pack. *Occasionally* a cell will "die" because a crystal of chemical grows internally and shorts the electrodes inside the cell. Such a pack can often be recovered by "zapping" - discharging a high value electrolitic capacitor through the cell to burn away the crystal. Deep discharged cells cannot be recovered in this way. Radio Shack now cells, sorry, sells, a few odd-sizes of nicads in acceptable capacities - e.g. sub-C. I only say this because they are convenient, and are often cheaper than original-equipment too. The manufacture and disposal of NiCads represent an environmental problem. Cadmium is an important heavy metal pollutant. >Side issue: >I have a car cigarette-lighter adapter as well... >... They also say that the battery cannot be charged while the machine >is on when running from a car battery because there is not enough power... Surmise: If the nicad pack gives 12 volts (10 cells - actually 12.5-13volts at full charge), then the car battery's 12 volts (actually 14.2 when fully charged) is approximately the same. Potential difference to charge the nicads is now marginal at best, and the current taken to run the machine *could* create enough loss in the cable from/to the lighter to tip the scales. > I was >curious about this because (I could be wrong here) I thought the regular ext. >power adapter supplies 12V-DC and if the voltage is the same, would the laptop >not try to draw enough amps to run the machine and charge the batteries both? If the external supply gives 12 volts, it will probably do so when the specified current is being drawn - if you put a voltmeter on the output when it is not connected, you will probably see 18 volts or so (I assume a typical simple non-regulated external supply). Regulation (to 5 and 12volt?) will probably be provided in the machine. >... [can we use a cheap 220/110 voltage converter] Yes. Disclaimer: These are my own musings, not necessarily representing any connection with the real world, and certainly not with my employer. -- Ray Dunn. | UUCP: ..!philabs!micomvax!ray Philips Electronics Ltd. | TEL : (514) 744-8200 Ext: 2347 600 Dr Frederik Philips Blvd | FAX : (514) 744-6455 St Laurent. Quebec. H4M 2S9 | TLX : 05-824090
brown@nicmad.UUCP (Mr. Video) (09/30/88)
In article <6625@nsc.nsc.com> gates@nsc.UUCP (Tim Gates) writes:
<To fully discharge the battery, just leave the computer turned on
<until it is dead, then connect a low value (2 to 5 Ohms) resistor across
<the battery terminals for several hours. I suggest that a high wattage
<resistor be used (3 times the expected power dissapation).
What makes for a great discharge circuit, it is too simple (but it works),
is to use a 100ma (there-abouts) lamp. One of those small things that are
used in flashlights. Get one with a voltage equal to or larger than your
battery voltage. Just hook it up across the battery terminals. It will be
bright (hopefully) when it starts and then go dead. Recharge the battery and
do it all over again. You don't have to use your computer to run it down,
just use the lamp.
The parts can be obtained from your local Radio Schlock shop.
I use this technique for my camcorder batteries and it has worked wonders
in making them work longer in the camera.
--
harvard-\ att--\
Mr. Video ucbvax!uwvax!astroatc!nicmad!brown
rutgers-/ decvax--/
INTERNET: astroatc.UUCP!nicmad!brown@spool.cs.wisc.eduray@micomvax.UUCP (Ray Dunn) (10/04/88)
A long article has just appeared in rec.models.rc on this subject (Message-ID: <1486@ektools.UUCP>) having been previously posted in rec.ham-radio (Message-ID: <8809291805.AA02420@decwrl.dec.com>). It contradicts several things that have been said (including by myself) on partial discharge memory for example, and confirms others. Read it in that newsgroup. It may be more authorative than other sets of "facts" posted on the subject, or may not, but it at least demonstrates the dangers of requesting technical "information" on the net (:-). The saga continues.... -- Ray Dunn. | UUCP: ..!philabs!micomvax!ray Philips Electronics Ltd. | TEL : (514) 744-8200 Ext: 2347 600 Dr Frederik Philips Blvd | FAX : (514) 744-6455 St Laurent. Quebec. H4M 2S9 | TLX : 05-824090