Technology3 min read
Windows 11 and Lenovo laptops: why KB5121003 'unplugs' the power
Windows 11 update KB5121003 makes Lenovo Legion and some HP Victus laptops report being unplugged while the adapter is connected and the charge light stays on. A Reddit user traced the cause to the ACPI and battery driver chain and confirmed the fix: removing the update.
What the problem looks like
The laptop runs on mains, yet the system periodically reports switching to battery: the backlight dims, performance drops, a notification appears. Nothing is physically disconnected and the charging indicator stays lit. Most complaints come from Lenovo Legion owners, with similar reports on HP Victus.
A good example of diagnostics: measure instead of guessing. A script polling every 50 milliseconds gave more than a week of driver reinstalls. Website problems deserve the same approach: logs and metrics first, hypotheses second.
What the user found
The author of the Reddit analysis wrote a script that polled the power state every 50 milliseconds and saw short dips that Windows interprets as the adapter being removed. The battery is not at fault; the issue is how Windows talks to the laptop's embedded controller through the ACPI power stack after the update. The drivers battc.sys, CmBatt.sys, acpi.sys and CAD.sys are involved.
What to do
The proven fix is to uninstall KB5121003: after rolling back the author saw 15 hours without a single dip. Steps below. Lenovo driver updates and power plan resets did not help affected users.
- Open Settings, Windows Update, Update history, Uninstall updates.
- Find KB5121003, uninstall it and reboot.
- Pause updates for a week so the patch does not return automatically.
- Watch for a fix from Microsoft and Lenovo before installing the update again.
Summary
This is an update regression, not a hardware failure. If a laptop 'unplugs' after KB5121003, roll back the update and wait for the fix.
Sources
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