linux-kernel - Re: [POWER] battery calibration parameters from sysfs

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Message-ID: <20091218084850.GA1513@ucw.cz>
Date:	Fri, 18 Dec 2009 09:48:50 +0100
From:	Pavel Machek <pavel@....cz>
To:	Andy Green <andy@...mcat.com>
Cc:	Stanislav Brabec <utx@...guin.cz>,
	Aras Vaichas <arasv@...ellan-technology.com>,
	Bill Gatliff <bgat@...lgatliff.com>, thommycheck@...il.com,
	Linus Walleij <linus.walleij@...ricsson.com>,
	linux-embedded@...r.kernel.org, lenz@...wisc.edu,
	dbaryshkov@...il.com, Brian Swetland <swetland@...gle.com>,
	arminlitzel@....de,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	LKML <linux-kernel@...r.kernel.org>, Dirk@...er-online.de,
	cbou@...l.ru, rpurdie@...ys.net, omegamoon@...il.com,
	Cyril Hrubis <metan@....cz>, eric.y.miao@...il.com,
	dwmw2@...radead.org, zaurus-devel@...ts.linuxtogo.org,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [POWER] battery calibration parameters from sysfs

Hi!1


>>> Yes, but in that case you might as well just purchase a coulomb
>>> counter with a built-in accumulator and an I2C/SPI/microwire interface
>>> save yourself some PCB space and cost (maybe)

Hardware is already given.

>> Well, Pavel attempts to implement a "poor man's Coulomb counter" or at
>> least "poor man's Ampere meter" for devices that are not equipped with
>> any of it.
>
> I think the "poor man's Coulomb counter" is a loser, the errors will  
> overwhelm you too rapidly.  The estimated rate of discharge could
>> work,  

Actually android phones do "poor man's Coulomb counter", and it seems
to mostly work.

> based on what clocks, regulators and so on are running, but I am not  
> sure how useful that number is really given you can't realistically  
> integrate it due to the big error it is bound to have.
...
> Otherwise for L-ion batteries, looking at the voltage level alone,  
> filtered to remove GSM transmit slots etc, is really quite workable for  
> estimating charge status.

Well, you have to compensate for backlight power; and yes, that's what
I'm trying to do.
								Pavel 

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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