linux-kernel - Re: [ltp] Re: [PATCH v2] Re: Battery class driver.

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Date:	Thu, 2 Nov 2006 23:01:45 +0100
From:	Pavel Machek <pavel@....cz>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>
Cc:	Greg KH <greg@...ah.com>, Shem Multinymous <multinymous@...il.com>,
	David Zeuthen <davidz@...hat.com>,
	Richard Hughes <hughsient@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Dan Williams <dcbw@...hat.com>, linux-kernel@...r.kernel.org,
	devel@...top.org, sfr@...b.auug.org.au, len.brown@...el.com,
	benh@...nel.crashing.org,
	linux-thinkpad mailing list <linux-thinkpad@...ux-thinkpad.org>,
	Jean Delvare <khali@...ux-fr.org>
Subject: Re: [ltp] Re: [PATCH v2] Re: Battery class driver.

Hi!

> Well, "Wh" measures energy and not power, and "Ah" measures electric charge
> and not current, so it would be better to make that:
> 
> capacity_*_energy  (Wh-based)
> 
> and
> 
> capacity_*_charge  (Ah-based)
> 
> Also, should we go with mWh/mAh, or with even smaller units because of the
> tiny battery-driven devices of tomorrow?

Okay... So I have cellphone here, 700mAh battery, ~2.8Wh battery. It
could last 14 days if we were *very* careful. 

echo '(700 mA * hour) / (14*day) \ A' | ucalc

ucalc> OK:  0.002083
ucalc>

...that is about 2mA in low power standby mode (but still listening on
GSM, getting calls, etc).

...so, mAh are probably good enough for capacity_*_charge, but would
suck for current power consumption, as difference between 2mA and 3mA
would be way too big. We need some finer unit in that case.

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