power consumption after shutdown

quozl at laptop.org quozl at laptop.org
Sun Feb 15 20:24:48 EST 2009

On Sun, Feb 15, 2009 at 12:36:36AM -0500, Mikus Grinbergs wrote:
> My apologies for not being clear.  I'll try again:
> I want to feel that the battery that I just put into the XO I'm 
> walking out the door with is as "charged up" as it normally can be.
> 1)  If that battery came from an XO that was plugged into the AC
>      24/7 for the past week -- I *think* it is fully "charged up".

Yes, 95% likely.

> 2)  If that battery came from an XO that had been "shut down" for 48
>      hours; but then that XO had been plugged into the AC until the
>      'power' light went green -- I *think* it is well "charged up".

Yes, 95% likely.

> 3)  If that battery had been sitting on the shelf (not in an XO) for
>      a month -- what did I need to do to make it "topped off" ?

Discharge it to 90% capacity, then charge it.

(You can do this manually in OFW using the watch-battery command ... or
you can periodically attach the AC adaptor until you get an orange LED
instead of green.)

> Sorry - I did not mean that I cared exactly how "charged up" it was 
> -- what I want to know is how to ensure to myself, without going to 
> extremes, that the battery was "well charged up".   [Is 94% reported 
> by the pop-up for an on-the-shelf battery believable, or is the 
> 'true' value half that?  And if do I see 94%, do I need to worry 
> that "this is a battery that requires some more charging"?]

Given a battery with an unknown history, it is not practical to predict
the state of charge.

> I was under the impression that when the battery charge went 
> somewhere below about 97%, the XO would "charge it some more".
> So I was surprised to have it stay at 94%.   [If 94% being shown on 
> the pop-up is not low enough for "charging some more", then how can 
> I initiate charging being performed by the XO ?]

Discharge it some more.  (There is no facility for boost charging ...
one reason is that this would shorten the life of the battery.)

> >> 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
> > provided.
> Apologies for being unclear.  I'm not particularly interested in the 
> precision of the "state of charge".

My explanation of this precision was so that you would understand why
you cannot get what you want.  I had tried explaining that you cannot
get what you want but you persisted, so I thought you were interested.

> What I am interested in is "is 
> the battery as 'well charged up' as I can make it be by using the 
> XO's 'built-in' charger - I will want to get the most minutes of use 
> of my XO when carried to a place that does not have electricity" ?

Discharge to 90% and then charge to completion.  Power off, then remove
the battery.  Travel as fast as possible to the place that does not have
electricity, do not delay by a month.  Insert the battery and power on.
You will have the most minutes of use.

> And if it is not 'well charged up', what do I need to do to make it 
>   so?   In particular -- if it *were* 90% "charged up" when I took 
> it off the shelf, would I have to fully discharge it in order to 
> then "charge it up" (using the XO as the 'charger') closer to 97-99% ?

No.  Assuming a battery that has only been used in the XO, you need only
complete one charge cycle, from orange LED to green LED.  Since you
cannot cause this cycle unless the state of charge value was low enough,
you need to manipulate the state of charge value down, and the only way
to do this in the design is to discharge for a short time.  Usually
about five minutes, but it depends on how busy the XO is.

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

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