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Re: Short battery life on Powerbook Prismo



I'll pass on what little battery wisdom I learned from some saavy friends
and a bit of web research.

Whatever you do, don't drain the batteries "all the way".
Lots of people do that thinking it will purge them of "memory".

	* Most new batteries don't have memory effects.

	* The ones that maybe did were NiCad batteries, and
	  there's good reason to believe they didn't have it either.

	* Draining any battery "all the way" is one of the best
	  ways to kill it. It will probably reverse a cell. Bad.

	* Draining a computer battery to the level where it
	  won't run the computer is probably OK (for the
	  battery at least....) but don't drain it in sleep
	  mode, or use it run a flashlight-bulb, etc.

	* The most common cause of premature battery 
	  fatigue is...

		OVERCHARGING

	  More charging when the battery is near capacity
	  can start to cook off electrolyte.  That's why
	  most serious battery enthusiasts (amateur radio,
	  cavers) have trickle chargers.

	* Trickle charge (10 or so hours to charge) isn't practical 
	  with laptops.  Laptops use (hopefully) intelligent
	  rapid-charging, backing off the current as the 
	  the battery reaches capacity. I'm told it's not as
	  good, but can be OK, depending on the quality of
	  the backoff.

	* So it's kinder to recharge your battery while running
	  the laptop -- less current available for charging.


If your battery is overcooked, I'm not sure you can do much. You've
already tried several recharge cycles (with, I hope, not "all the way"
discharges).

In theory, it's good to use the battery regularly because then it doesn't
spend all of its life being charged while already at capacity.

But the details probably depend on knowing more about your systems
electronics than I do.



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Charles R. Twardy, Postdoc, Monash University, School of CSSE
ctwardy@alumni.indiana.edu   +61(3) 9905 5823 (w)  +61(3) 9905 5146 (fax) 
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"History teaches that grave threats to liberty often come in times of
urgency, when constitutional rights seem too extravagant to endure."
                            - Justice Thurgood Marshall (1989)
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