Comment # 28 on bug 1203748 from Stefan Dirsch

(In reply to Stefan Dirsch from comment #25)
> Created attachment 863066 [details]
> dmesg-bad-battery.log
> 
> dmesg - After switching to battery - in a bad/slow state (unfortunately no
> relevant difference in dmesg to good state)

Maybe I was wrong. There is at least this

-[ 2200.120064] perf: interrupt took too long (2540 > 2500), lowering
kernel.perf_event_max_sample_rate to 78500
-[ 2307.480111] perf: interrupt took too long (3242 > 3175), lowering
kernel.perf_event_max_sample_rate to 61500

Maybe that's related.