[lug] question about laptop battery

[Nate Duehr]

On 1/18/2010 1:43 PM, Kenneth D Weinert wrote:
> [quote]
> If the laptop is going to be powered from AC for more than 2 or 3 days,
> the battery should be removed. Leaving the battery installed in the
> laptop while the laptop is powered from the AC for long periods of time
> is what kills the battery.
>
> If the laptop is going to be used for more than 2 or 3 days on AC, the
> battery should be allowed to go doen to about 50 to 60% charge, then
> removed and stored in a cool place
>
> [/quote]
>    

I think this all depends on the charge controller. Those that keep the 
battery completely "topped off" at 100% do damage the battery over time, 
according to the engineering guys on other lists.

My work IBM/Lenovo machines have settings for this, and they're set to 
"manage for me" vs. 100% or you can type a percentage to allow the 
battery to drop to before the charger comes back on.

Apple has notes on their website for SOME models that tell people not to 
freak out if the battery doesn't stay at 100% when hooked to the 
charger, so they probably do something similar but just completely hide 
it from the end-user.  (Maybe available via command-line hacks, I've 
never looked into it, and only some models have these "notes" up on 
support.apple.com ... so different laptop models probably handle it a 
little differently.  Newer generally probably means "we learned more" 
and handles the battery better.

My experience has been with the IBM/Lenovo machines and Apple machines 
is about 3-4 years of heavy "cycles" and the battery is below 1/2 
capacity.   Again in the commercial OS's there's usually tools to query 
the battery and ask it these things.  I don't know what Linux has these 
days.  Maybe that stuff is proprietary.

On the other hand, I have a 3rd generation hard disk iPod that doesn't 
seem to have lost much capacity and it's been totally abused over many 
many years.  So... hard to say.

I do know this.  The faster a battery is charged (people like fast 
chargers), the more heat and the more potential for damage.  LIon 
tolerate this much better than old technologies, mostly because the 
charge controller inside the battery can "see" and control the voltage, 
current draw, and most importantly TEMPERATURE during the charge, but I 
find that a totally dead laptop charging with a modern fast charging 
system gets a lot warmer than I'd like if I were going for maximum life 
on any battery.  (Note here that I've used Ham Radio batteries on 
various hand-held radios for years and years too, and LIon is "king" 
there also, but my best behaved batteries there are on a Kenwood radio 
that takes many many many hours to slow-charge, even thought it's LIon.)

As far as needing a new charger for a bigger battery, I doubt it.  
Usually you're plugging into the laptop's power supply, and it's 
providing the power to charge the battery, and since no changes are 
being made to that portion of the "charging system" that's built into 
the laptop, it must have the same limitations for voltage and current 
draw it always did.  So I think it'll just take longer to charge your 
bigger capacity battery if you upgrade to more cells.  There could be 
exceptions, but probably not many.

The power supply in the laptop would be more complex if it could handle 
multiple voltages and currents, and usually that would add weight and 
cost.  Most fast-charge laptops you'll notice these days have a big 
honkin' "wall wort" or "brick" that provides 90W or more of power at 
12-16 VDC, depending on brand.  They do that to move the heat of AC/DC 
conversion outside the case of the machine and also to make the laptop 
itself lighter.  If you had to put a big linear or smaller switching 
power supply inside the laptop, then you'd need a safe connector for AC 
direct into the machine, etc.  It'd make no sense.  Usually these 
"bricks" nowadays also have circuitry in them to handle 100-250VAC for 
international travel, but not all.

(A friend was retrofitting an old warehouse to office space this 
weekend, and had a printer that wouldn't power up.  A Voltmeter finally 
was used and they found that the building was "floating" (voltage-wise) 
well above 130VAC but below 140VAC. The printer didn't have an 
"international" power supply and its power supply was just shutting down 
to protect itself.)

All sorts of fun reading out there, but generally -- the answer these 
days is "follow the manufacturer's recommendations" - then look up their 
policy for warranty replacement.  (Example, Apple will replace iPhone 
batteries if they are under AppleCare and they fall below a certain 
capacity in those years.  However, one "gotcha"... there's no way for 
you (or them) to see the capacity on any display.  They have to take 
your word for it, or keep the phone for a number of hours to see it 
discharge.  So whether or not anyone's ever brow-beat them into changing 
out a battery... well, what they actually do is swap out your phone and 
send the "dead" one to the remanufacturing facility for 
testing/diagnostics/rebuild... who knows?  Google might.  :-)

Nate