Currently, I'm running Ubuntu 12.10 on a MacBook Pro 8,2 with kernel version 3.5.0-21-generic, but this bug also happens with the same kernel and OS on a MacBook Pro 2,1. Furthermore, it also happens with Fedora 17 with Kernel 3.6.x. Also doesn't matter what DE I'm using. I can confirm the behavior with KDE and Gnome Shell. Expected Behavior: battery meter should report accurate charge Actual Behavior: battery meter drops to low, inaccurate percentage remaining at seemingly random times. Time remaining calculation remains correct. upower reports incorrect stats. acpitool reports correct percent. acpi reports no battery found.
Have also seen bug reports on Ubuntu's tracker that appear to be the same issue, but affect non-apple hardware.
Suspend & Resume cycle will sometimes temporarily alleviate the issue.
Your problem is "upower reports incorrect stats, acpitool reports correct percent. acpi reports no battery found." ? Most these user-space tools' information are from "grep . /proc/acpi/battery/*/*" or "grep . /sys/class/power_supply/*/*". You can check these directly. And their values call come from bios. ACPI battery driver just exposes them.
ping...
Since no response more than one month, close the bug.