SUMMARY STEPS TO REPRODUCE 1. Drain battery to critical 2. Sleep/suspend 3. Charge during sleep/suspend 4. Unplug, computer still asleep/suspended 5. Wake, log in.* 6. Set screen brightness. 7. Drain battery to critical again.** OBSERVED RESULT *: the battery critical notification is not cleared **: The screen brightness isn't changed as the Battery Critical notification is shown again. EXPECTED RESULT *: The battery critical notification is cleared/revoked **: The screen brightness is set to what's set in the battery critical power setting. SOFTWARE/OS VERSIONS Linux/KDE Plasma: Arch Linux KDE Plasma Version: 6.x (Currently 6.3.5) KDE Frameworks Version: 6.x (currently 6.14.0) Qt Version: 6.x (currently 6.9.0) ADDITIONAL INFORMATION Due to the time consuming nature of testing this, I'm unable to provide more information on how this behavior... behaves, in a timely manner. This may or may not be important: The "On battery" power state has the option that sets the screen brightness disabled.
Pretty sure I've seen this myself. Sounds a bit like Bug 471636. It would appear we need to re-evaluate the battery percentage when waking from sleep.
Additional information and accidental discovery: turns out, if you sleep during the hibernate timer, it will force hibernate even with a mostly full battery. This went from a minor inconvenience to a rather loud bug.
*** This bug has been marked as a duplicate of bug 507203 ***