From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Garrett Subject: Re: Completely discharging LION batteries Date: Sat, 21 Dec 2002 03:48:55 +0000 Sender: acpi-devel-admin-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Message-ID: <20021221034855.GA28610@srcf.ucam.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Errors-To: acpi-devel-admin-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Help: List-Post: List-Subscribe: , List-Unsubscribe: , List-Archive: To: acpi-devel-pyega4qmqnRoyOMFzWx49A@public.gmane.org Cc: Frank Mehnert List-Id: linux-acpi@vger.kernel.org On Tue, Dec 10, 2002 at 08:59:52PM +0100, Frank Mehnert wrote: > capacity is 34560 mWh. After completely discharging the battery, the > maximum capacity to which the battery can be charged is only 28120 mWh, > so I lost about 2000 mWh or about 8 percent of the battery capacity!!! My understanding is that the microcontroller in the batteries IBM ships only recalibrates capacity loss when the battery becomes completely discharged. It's likely that your battery had lost 8% of its capacity over a longer period of time, but only noticed this when it ran down "completely" (where "completely" is the point at which the microcontroller decides that the battery shouldn't be discharged any further, rather than when there's really no charge left in it) http://gimel.esc.cam.ac.uk/james/resources/tp240bat/bq2040.pdf is a datasheet for the controller used in Thinkpad 240 batteries - it may well be used across the rest of the Thinkpad range. A brief reading seemed to suggest that the controller will stop charging the battery once it reaches the "last full charge" capacity in the associated EEPROM, though I may well be misreading that. You should be able to reprogram the EEPROM over the SMBUS, but the Linux i2c drivers will refuse to load on Thinkpads due to the possibility of killing the motherboard if the wrong address is read. -- Matthew Garrett | mjg59-1xO5oi07KQx4cg9Nei1l7Q@public.gmane.org ------------------------------------------------------- This SF.NET email is sponsored by: The Best Geek Holiday Gifts! Time is running out! Thinkgeek.com has the coolest gifts for your favorite geek. Let your fingers do the typing. Visit Now. T H I N K G E E K . C O M http://www.thinkgeek.com/sf/