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ThinkPad released in 2011. This version of the T420 is thicker than the T420s and lacks integrated USB 3.0. The T420i uses the same chassis, so most T420 repair guides work interchangeably.

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Why won't my thinkpad charge if plugged in when already powered on?

I have been working on fixing up an older Lenovo Thinkpad T420. The laptop is working great, apart from a charging issue I have been having with it that I can't seem to figure out. The laptop charges with no issues whatsoever if it is plugged in before it is turned on. However, if I attempt to plug in the laptop after it has been turned on, the computer will not charge and instead beeps every few seconds. Even though it works as expected when plugged in before being booted, unplugging the computer while it is running will result in the same issue. The computer will run off of battery power and will not charge.


I cannot figure out what is causing this. So far, I've tried the following:

  • Replaced the original battery to determine if it was an issue with the battery. This was not successful.
  • Disconnected the CMOS battery in an attempt to clear any errors (with the main battery also removed). This was not successful.
  • Tried several other power adapters to see if the power adapter was to blame. It was not.
  • Powered on the laptop to see if an issue with the charging port was the problem (the laptop uses a barrel plug). It worked as normally when the computer is run without a battery.
  • Visually inspected the charging port with the back cover removed. Nothing looked out of the ordinary.

Does anyone have any other suggestions I should try that might resolve this issue?

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Hi @ck2445

Try uninstalling the battery drivers in Device Manager, then restart the laptop and allow Windows to reinstall them and check if this resolves the problem.

Go to Device Manager → Batteries → click on > to expand the list → right click Microsoft ACPI Compliant Control Method battery → uninstall and follow the prompts.

To get to Device Manager in Win10/11, press the Win key + x key (both together)m and click on the Device Manager link in the options box that opens

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My laptop is currently running Ubuntu 23.04. What would you suggest doing on a linux system?


Hi @ck2445

I don't know Linux systems but perhaps the following links may help you, at least to look for anything pertaining to power management etc

link 1 link 2


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Cole sera éternellement reconnaissant.
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