Am Donnerstag, den 21.02.2013, 00:50 +0000 schrieb Ben Hutchings: > > while my BIOS/UEFI reports a battery charge capacity of 92% for my notebook- > > battery, upower still reports a charge capacity of 100% (AFAIK upower gets > > this > > information from the kernel - I believe this to be a kernel ACPI bug). > > The kernel driver doesn't do anything very interesting so it's actually > very likely a BIOS bug.
You were right, this really seems to be a BIOS bug. I checked the battery information in Windows with 'powercfg -energy': The reported values for 'Design capacity' (= ENERGY_FULL_DESIGN) and 'Last full charge' (= ENERGY_FULL) are the same: 59940. At first I thought that Windows gets the correct values because the charging level percentage reported by Windows corresponded to the percentage reported by the 'HP Support Assistant' program which shows me the correct battery info (including a realistic battery capacity value). I don't know why or how this works, but the charging level percentage seems to be quite accurate even if all the other reported values differ. I also used a freeware tool in Windows to get more information on the battery and it showed me the same info I get with 'cat /sys/class/power_supply/BAT1/uevent'. > Apparently, for some systems and batteries, ACPI reports full capacity > as 100 and current level as a percentage. In this case the ACPI battery > driver cannot know what the true full capacity is. Its workaround is to > assume it is equal to full design capacity. Unfortunately there doesn't > seem to be any way to find out whether this workaround was enabled. The upstream maintainer, Lan Tianyu, provided a patch to comment the quirk (see comment #6 in the upstream report). However, after applying the patch the kernel reported the same values, so I guess the workaround wasn't enabled in my case. Since I can confirm that this is a BIOS bug I'm going to close this report. For more information please have a look at the upstream bug report. Thanks, Stefan.
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