Path: utzoo!attcan!uunet!dalcs!lane
From: lane@dalcs.UUCP (John Wright/Dr. Pat Lane)
Newsgroups: comp.sys.ibm.pc
Subject: Overcharging NiCad batteries?
Keywords: NiCad rechargeable batteries, laptops, foreign power
Message-ID: <3008@dalcs.UUCP>
Date: 25 Sep 88 07:38:18 GMT
Organization: Math, Stats & CS, Dalhousie University, Halifax, NS, Canada
Lines: 68

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
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