Public bug reported:
Affected system:
Laptop: Lenovo ThinkPad T490
Ubuntu versions tested: Ubuntu 24.04 LTS and Ubuntu 25.04
Battery condition: Moderate degradation (~36% capacity loss)
upower:
Installed: 1.90.7-1build1
energy-full: 32.35 Wh
energy-full-design: 50.5 Wh
capacity: 64.06%
On this system, when the battery level dropped to ~2%, the system
attempted to perform a shutdown as configured by UPower default:
PercentageAction=2.0
However, due to the degraded state of the battery, the voltage dropped
too rapidly at that level for the system to complete the shutdown
properly. This resulted in a system freeze with a blinking Caps Lock
LED, indicative of a kernel panic caused by power failure during a
critical system operation.
This issue occurred reliably and repeatedly on both Ubuntu 24.04 and
25.04.
Diagnosis:
1. The battery has significantly reduced capacity (~64% of design).
2. At 2% reported charge, there was insufficient residual energy to allow the
shutdown process to complete.
3. Increasing the threshold for the shutdown action to 5% resolved the issue
completely.
Solution:
I edited the file /etc/UPower/UPower.conf and changed the following lines:
PercentageLow=20.0
PercentageCritical=10.0
PercentageAction=5.0
I also restarted the service:
sudo systemctl restart upower
After this change, the system reliably enters CriticalPowerAction when the
battery reaches 5%, with no further freezes or panics.
Suggested change to default UPower configuration:
PercentageAction=5.0
** Affects: upower (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2112342
Title:
UPower default PercentageAction=2.0 is too aggressive for degraded
batteries — suggest changing to 5.0%
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