power consumption after shutdown

quozl at laptop.org quozl at laptop.org
Sat Feb 14 22:30:44 EST 2009

On Sat, Feb 14, 2009 at 08:26:13PM -0500, Mikus Grinbergs wrote:
> This gets more and more bizarre !!

No, it's just physics and chemistry, constrained by engineering.
Please, if you think it is bizarre, explain why you think so, and I'll
happily explain the physics that I know.

> What I am now interested in is understanding a "correct" state of 
> charge value after having my battery out of the XO for one month. 

Not possible without discharging the battery fully to determine the
state of charge it had.  The test is charge destructive; once it is
completed there is no usable charge in the battery.

> [When I insert that battery and plug in the AC adapter, the 'power' 
> light is green, and the software pop-up says 94%.  But I notice that 
> after an hour, the software pop-up *still* says 94%.]

I hope you aren't surprised.  No reason it should change.  Battery is
not being used.

> I presume that when I merely "shut down" the XO, and leave it 
> sitting for two days with the battery still in the case:  Then when 
> I again connect the XO to the AC adapter (and let it charge until 
> the 'power' light goes from yellow to green), I should be able to 
> trust that what the software pop-up says is accurate.

No.  It will be close to the true value most of the time, unless there
is damage.  By close I mean within 20% or so, 90% of the time, assuming
no external use of the battery.  I'm just giving you personal estimates
there, I don't have all the data.

> But when the software pop-up is between 90-96% (for a previously 
> out-of-case battery), and despite the AC adapter being plugged in 
> that value does not increase in an hour -- what ought I to do to 
> find the "state of charge" ?

No possible way except a full discharge while measuring the power

The state of charge value that you refer to is calculated.  It is an
estimate.  It often represents reality.  The calculation is done by the
EC based on a measurement of current flowing into or out of the battery,
since the battery was manufactured.  The measurement is over time, so it
is called accumulation.  Measurement is done by the EC using the battery
support chip in the battery pack.  The results are stored in the chip.
Measurement does not occur of either chemical self-discharge, or
external discharge by some other means.

James Cameron    mailto:quozl at us.netrek.org     http://quozl.netrek.org/

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