Comment 167 for bug 22336

Steve,
Perhaps you can remove the "battery charging" aspect of your observation by
removing the battery and running directly from AC w/o a battery present?
(not every laptop will run in this mode, but most will)

It is possible that your laptop enables some power savings modes when on DC
that it is not enabling when on AC. Eg. most laptops boot in low-frequency-mode
when on DC, but some boot in high-frequency-mode when on AC...
You'd be able to tell pretty quick by comparing the bogomips from the AC vs DC
boot messages.

While sometimes these difference are hidden in firmware, sometimes they
are exposed to ACPI. Please attach the output from "acpidump" so we can
figure out what the laptop exposes. Also, the output from dmesg -s64000.