I had the same problem. It turns out you need to enable
drivers -> Power supply class support
(either built in or as module) to get ACPI AC/Battery support.
I must say that having these relatively top-level ACPI settings depending on something that is relatively buried away is not very intuitive!
Especially not since at first glance you don't really seem to need that option except for some weird hardware.
CC'ing ACPI mailing list for other opinions.