Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934877AbZLPJkX (ORCPT ); Wed, 16 Dec 2009 04:40:23 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S934866AbZLPJkV (ORCPT ); Wed, 16 Dec 2009 04:40:21 -0500 Received: from ey-out-2122.google.com ([74.125.78.24]:11250 "EHLO ey-out-2122.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934863AbZLPJkR (ORCPT ); Wed, 16 Dec 2009 04:40:17 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=sender:message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:content-type:content-transfer-encoding; b=bvq0jp+OLpt9BzV6/X320S+mEjnkLoRCIVQv3WrB+OJKEsd3ziA7/X3ZMIKbUsYkpN xcFyFiqMWnKzhdvPTtS/4nSngpHLba6Rb9t2cbXbbbIXvyjhsohyxqJkn/bptodudDnY mDl9eTiwHQJ3jjJuPEl5ozYZuHy43Ww6z/rwI= Message-ID: <4B28AAFC.5010108@warmcat.com> Date: Wed, 16 Dec 2009 09:40:12 +0000 From: Andy Green User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.4pre) Gecko/20090922 Fedora/3.0-3.9.b4.fc12 Thunderbird/3.0b4 MIME-Version: 1.0 To: Stanislav Brabec CC: Aras Vaichas , Bill Gatliff , thommycheck@gmail.com, Linus Walleij , linux-embedded@vger.kernel.org, lenz@cs.wisc.edu, dbaryshkov@gmail.com, Brian Swetland , arminlitzel@web.de, Mark Brown , LKML , Dirk@opfer-online.de, cbou@mail.ru, rpurdie@rpsys.net, omegamoon@gmail.com, Pavel Machek , Cyril Hrubis , eric.y.miao@gmail.com, dwmw2@infradead.org, zaurus-devel@www.linuxtogo.org, linux-arm-kernel Subject: Re: [POWER] battery calibration parameters from sysfs References: <20091207114825.GA26965@rakim.wolfsonmicro.main> <20091207165628.GA24981@rakim.wolfsonmicro.main> <20091213132413.GB1437@ucw.cz> <20091214121247.GB22388@rakim.wolfsonmicro.main> <20091214212257.GA9213@elf.ucw.cz> <4B26FC52.6060307@billgatliff.com> <1260919938.10441.18.camel@utx.utx.cz> In-Reply-To: <1260919938.10441.18.camel@utx.utx.cz> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1532 Lines: 34 On 12/15/09 23:32, Somebody in the thread at some point said: Hi - >> 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) > > 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, 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. I didn't see it mentioned yet but the biggest problem I saw with battery state monitoring by voltage alone is what happens during charging: the charger is artificially raising the voltage by an amount depending on current limit in the charger and battery capacity level. That's what you see when you go and look at battery voltage during charging. 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. -Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/