I have good news and bad news....

The good news is that with code from this morning, I'm no longer seeing
battery charge errors or battery state errors.  I haven't run the tests
as long as my earlier ones, but in the 1.5 hours I've been polling the
batteries, I've seen zero errors.

The bad news is that the system also isn't seeing ACPI events.  It
doesn't detect line power coming or going, it doesn't detect the lid
switch, it doesn't even detect the sleep button.  I can suspend by
running a manual script, but not in any of the usual automated ways.