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Mac Forum / General / Portable Macs / November 2005



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strange battery problem

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velivolus@gmail.com - 05 Nov 2005 14:10 GMT
I have been experiencing this problem for awhile now and was wondering
if there is a known glitch. What happens is that any time I am running
my computer on the battery and using a CD, after about 10 minutes the
screen goes black and there is no way to access my computer again save
by plugging in the power adapter. Once I do this the desktop comes back
and I can continue working. But the system believes the battery were
completely drained and at 0%, and tells me it is going to take hours to
recharge. Yet I had only been running the computer ten minutes or so on
the battery! After recharging for awhile the system seems to realize
its mistake and sets the battery back to 100%. This whole problem only
seems to occur if I am using the computer's CD drive while running on
the battery. I have never had this happen while running the computer
without a CD inserted. I also remember once or twice, even when the
computer was plugged in, going to use it, and there being a black
screen and the computer was very hot. These were also times when a CD
was in the drive, so I am thinking this may all somehow be related.
Tom Harrington - 06 Nov 2005 00:31 GMT
> I have been experiencing this problem for awhile now and was wondering
> if there is a known glitch. What happens is that any time I am running
[quoted text clipped - 12 lines]
> screen and the computer was very hot. These were also times when a CD
> was in the drive, so I am thinking this may all somehow be related.

It just sounds like your battery is old and worn out.  When there's a CD
in the computer you're drawing more power from the battery than when
there isn't a CD, so that's probably the reason you notice this more
then.

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Tom "Tom" Harrington
Macaroni, Automated System Maintenance for Mac OS X.
Version 2.0:  Delocalize, Repair Permissions, lots more.
See http://www.atomicbird.com/

velivolus@gmail.com - 06 Nov 2005 02:12 GMT
I considered this. The only thing is it happens very quickly after
beginning to use an application on a CD. In other words, I can use the
computer for 2 or 3 hours with no problem in battery mode. Put in a CD,
and within two minutes the screen goes black. But likewise I can put in
a CD right away and the same thing happens.
pailface88@yahoo.com - 07 Nov 2005 20:20 GMT
velivo...@gmail.com wrote:
> I considered this. The only thing is it happens very quickly after
> beginning to use an application on a CD. In other words, I can use the
> computer for 2 or 3 hours with no problem in battery mode. Put in a CD,
> and within two minutes the screen goes black. But likewise I can put in
> a CD right away and the same thing happens.

This can still be a worn out battery. Batteries fail in many different
ways. They cannot put out as many amp/hours, not put the power out as
quickly as in the past, individual cells can die before they all die,
etc.  If your battery is fairly old it is likely to be on its way out.
They start to die the first time the are used...actually they start to
die as soon as they are manufactured.

As an ecperiment, try running your CD on battery power but with the
screen brightness turned completely OFF. The screen backlight is a
significant power user and this may allow the CD to play longer. This
is obviously not a solution to the problem but it may give some insight.
Juri Munkki - 28 Nov 2005 23:50 GMT
>I considered this. The only thing is it happens very quickly after
>beginning to use an application on a CD. In other words, I can use the
>computer for 2 or 3 hours with no problem in battery mode. Put in a CD,
>and within two minutes the screen goes black. But likewise I can put in
>a CD right away and the same thing happens.

Lithium Ion batteries corrode inside over time. This increases the internal
resistance of the battery. Ohm's law states that U = R * I, where U is
the voltage drop over a resistance R and current I. So when the current
draw from the computer increases, the voltage drops because of the internal
resistance. When the internal resistance is high enough, the voltage drop
is significant and the computer thinks that the battery has been totally
depleted and goes into emergency sleep.

The solution is to get a new battery. The catch is that you have to make
sure that the battery hasn't been sitting on a shelf for a few years...
I was lucky when I got a NewerTech 7.2Ah battery for my Pismo: I get a
full day of power from that single battery (9 hours in one test case).

One more tip (and this is a big one): use the old battery whenever you
have the computer plugged in at home or use the computer without a
battery, if the old battery is too far gone. The reason for this is
that the batteries corrode faster if they are hot and it's usually
pretty hot inside an PowerBook that is doing anything.

I only keep that new PB battery in my Pismo when it's being charged or
discharged. If it doesn't have to be in the Powerbook, it's sitting on
a shelf, ready to go in the PB if I need to go somewhere. Lithium Ion
batteries have a very low self-discharge rate, so it's almost as good
as freshly charged even if it hasn't been in the Powerbook in weeks.

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Juri Munkki - http://www.iki.fi/jmunkki - Windsurfing: Faster than the wind.

 
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