Battery level polling issue

[peabrain]

Hello everybody.

I'm having a problem with the battery of my T60 (2008-66G, running on ArchLinux). The problem is that somehow ACPI gets the charge level all wrong when on battery power. The battery at full charge is reported to have about 24 Wh.

When starting to discharge, if at idle and powersaving modes off, the discharging is pretty linear, taking slightly under 1.5 hours to drain from 95 % to 5%. However, it takes considerably longer to get from 5 % to 0 %, and even after ACPI thinks the battery is fully discharged and there is no juice left, the laptop stays on for about 30 minutes. That is, even though the battery should be empty, I can use my PC for another half an hour.

On the other hand, if discharging under load, the battery level polling goes all haywire. For example, when watching some youtube videos and such, the battery level dropped from 62 % to 0 % in one minute. At this point the charge left was supposed to be only 220 mWh, but after that it didn't drop a bit, at least not during the time I had patience to watch it. I suppose 220 mWh should be drained in few seconds. Then I just plugged in the power because I didn't want it to shut down.

I've tried to fully discharge, charge, discharge... to no avail.

I guess it could be a software issue. However, when Linux thinks my battery is out of juice, so does also my Thinkpad (the battery icon at the base of the screen is orange and blinking). Does this icon get its info directly from BIOS? If so, is this a hardware problem then? (Edit: Probably not. The module thinkpad-acpi makes it possible to command the leds so it's probably not BIOS related.)

I tried searching, but could not find anything helpful. I apologize if a similar topic already exists.