Archived from groups: comp.sys.laptops (
More info?)
"Ye Electrik Fanne Clubbe" <ian.shorrocks@baehisclothessystems.com>
wrote in message news:428c5a5f_1@glkas0286.greenlnk.net...
Date: Thu, 19 May 2005 10:28:30 +0100
[Talking about whiskers within Ni-Cads and some snipping was necessary
above and below]
EFC: The phenomenon has been noted in batteries that are charged
but not used. Then initial thin whisker is too high a resistance to
be blown by the 1.2 volt cell voltage.
Hi Ian... Hmm... I haven't seen any evidence that these whiskers are too
high in resistance to be burned off. But I am not doubting the possibly
that what you say is true. <grin>
> Hmm... I completely understand it. As it is a simple chemical
> reaction. So what's so hard to understand?
EFC: It is apparently not a chemical reaction. Thre phenomenon is
well documented in circumstances where no other reagents are
present. Tin is also known to exhibit the phenomenon and will
hapily grow whiskers in an inert atmosphere..
The story that I have heard that Ni-Cads were invented back in WWII. I
was clueless about them until I discovered them in the early 70's. I
purchased a bunch of them and still some of them that still works (their
capacity stinks compared to when they were new though).
Anyway I read somewhere and I'll try to find it again that explained
this whisker factor so well, that I was totally convinced they nailed
it. And I'm almost sure it was in the radio control (RC) camp that knows
a great deal about rechargeable batteries.
> We used to use a car battery and just quickly give it a shock of 12
> volts just briefly. Sometimes one or two more times were necessary.
> Although not all cells would always come back.
EFC: 12 volts may shift some of the larger (and low resistance)
whiskers, but may not be enough to shift some of the smaller ones.
You might have something there. As I seem to remember about a 10%
success rate with a car battery. How much would you say your method
worked? As once they are shorted by whiskers so bad to drain them,
little can be done to bring them back. But not unheard of.
> Actually it has nothing to do with inactivity. As the whiskers are
> always in production during the life of the cell. The reason why
> you don't notice it with a charged cell is because as soon as they
> get created, they are blasted away from the charge in the cell.
> This probably explains why Ni-Cads bleed off their charge faster
> than any other battery type.
EFC: Except that the self discharge rate of Nickel Metal-Hydrides
is much higher.
Really? That is the opposite of what I have heard. It is also the
opposite of my experience as well. Well most of that experience is from
30 year old Ni-Cads which isn't anything as good as modern Ni-Cads. Yes
I have a few of them and I'm really impressed how much better modern Ni-
Cads are over the last 30 years.
I can tell you that modern day Mi-MH blows away 20 to 30 year old Ni-
Cads for shelve life (even when those Ni-Cads were new). As those old Ni-
Cads when new, you were lucky to let them sit for about two months and
still have some useful capacity left in them. Nowadays both Ni-Cads and
Ni-MH (as well as Li-Ion) can go for a year or two without losing a
great amount of charge.
> All of my Li-Ion devices like cell phones, PDAs, etc. except for my
> Toshiba laptops, will kick the charger back on after a period of
> time if left on the AC. My Toshiba laptops will never kick the
> charger back on unless you remove and insert the battery or the AC.
EFC: Indeed, most of my Li-ion devices vary in this respect. My
laptop will carry out a further charge after about 3 days, but only
for about 5 mins or so. I have a walkman, that won't even entertain
charging a battery until it is about 20-25% discharged. Whether
this is down to individual battery manufacturer variations or
charger designers' interpretations, I couldn't say.
There is something that I have heard and I so far believe it. That is
once a rechargeable Li-Ion falls below a given voltage, the Li-Ion
battery is basically useless. Although I have no idea where this limit
is per cell. But I don't normally allow anything less than 3.6v per cell
and that has worked wonderfully for me. I'm not sure, but this is
probably around 40% capacity for most laptops.
My Palm IIIc has a Li-Ion battery soldered in. Normally it lives on the
charger. And I'll catch it charging a few hours almost every night
around 2AM to 4AM. I have a hard time believing that it picks this time
to kick in (although it does know the correct time and date). And this
Li-Ion battery has been performing the same as it did 6 years ago. I ran
it down once and I believe it would run for 12 hours straight. Today I
don't see any evidence that it would be any less today.
>> One aspect of laptop design that causes battery life problems, is
>> that in order to cheapen the internnal design, some manufacturers
>> use a tap on the battery to power lower voltage circuits. This
>> unbalances the discharge of the individual cells, and poses
>> considerable charge problems.
> Supposedly for Ni-Cads, Ni-MH, and lead-acid batteries, trickle
> charging will rebalance the cells once again even if wired in
> series.
> On the other hand, I've never heard of a laptop manufacture tapping
> off a cell or two for some lower voltage use. How do you know of
> this practice?
EFC: By the fact that I have encountered laptops where this is
done. Some of the Internet sites covering repair of Li-ion battery
packs have also mentioned it.
Well as I have noted in the past, I don't really discount silly designs.
And while trickle charging works pretty well to balance a series wired
pack. But to do so purposely (to unbalance the pack) is just really
dumb! I'd really like to know more about the manufactures whom partake
of such a design.
> For Ni-Cads and Ni-MH batteries, I believe they call it the delta
> drop off. And how this is done is to electrically remove the charge
> and monitor how quickly the voltage drops off. If it drops fairly
> quickly, the fixed current charge is reapplied and checked later
> once again.
EFC: I understood delta drop off to be the phenomenon that the cell
voltage falls slightly as it approaches full charge.
Well this is very cool with battery packs wired in series (and quick
charging too)! As these smart battery chargers doesn't need to know the
total number of cells or anything. There are different values between Ni-
Cads and Ni-MH batteries which I still don't know the exact settings
(although the ballpark figures I do know).
And modern Ni-Cads can be quickly recharged with the highest of amps
without much problems (upwards of 4C). Modern Ni-MH can be done the same
except that they will overheat if too close to full charge (and much
less of 4C -although 1C or maybe 2C seems okay). C means by the way the
rating of the pack per hour. Thus if you had say 4000ma (aka 4 amps)
battery pack (the capacity noted), 4 amps for one hour is 1C. 2C would
be 8 amps. Everyone got that right?
While I have a charger that can handle Li-Ion batteries (a Triton
actually). I've never used anything other than the approved manufacture
chargers. While I understand Li-Ions batteries pretty well enough. I
just don't like that bursting into flames part! <sigh>
> -- written and edited within WordStar 5.0
EFC: Good grief! But then I do sometimes still use Wordstar 4 of
floppies on an Amstrad PPC640D (remember them?) running MS-DOS 3.3.
The only reason is tht it is the only thing available that is slow
enough to talk to a very slow Minidisk titler.
What can I say, I still use WordStar v5 to this very day. It is very
perfect for formatting 7-bit plain text. The earliest WordStar version I
have ever used was WordStar v2.26 on an Osborne. Which was about '81 era
if I remember right. Under MS-DOS, I did purchase WordStar v5.0 ('89-89
era) and WordStar v7.0c (92 era). And unlike *most* WordStar fans, I
like WordStar v5.0 the best. As the later versions tried to be too much
like desktop publishing which it doesn't do as well as our modern
software.
I've heard a rumor that Bill Gates used to program in WordStar's non-
document mode. One report claims that they even had a picture of Bill in
his office with WordStar running on his computer (long after MS Word for
DOS was released). Although I have never seen this so called picture.
Although I *love* to have it. <grin>
Many believe that MS Edit came from CP/M's edline (sp?) (or earlier
DEC's version). Since I know all of them well, I personally believe MS's
Edit came from WordStar's non-document mode. Just a theory on my part,
but I don't think I am off by much. <grin>
I don't know if you know this or not. But after WordStar v3.x, WordStar
laid off, fired, or something with the current programmers (it hasn't
been totally clear to me). But they started their own company called
NewWord. They had much success so soon that WordStar bought them out.
And WordStar v4 and later was built upon what they did. <grin>
Cheers!
______________________________________________
Bill (using a HP Pavilion 8655 & Windows 2000)
-- written and edited within Word 2000