Setup: I have a Lenovo T440s running Windows 10 which requests 20V and 2.25A/3.25A and a charger providing 20V and 2.25A.
I have been having this problem for a while. Essentially, when I plug in the charger the laptop is charging, however, it tends to stop charging and then start again at random times as if the charger is unplugged and re-plugged. Sometimes this happens multiple times in a row. Also, sometimes, after one of these unplug and re-plug episodes the CPU is throttled to 29%, but it often goes back to normal after some of those episodes. And yes, I have tried different power plans. However, I have noticed that it does not have that many episodes when on the power plan called "powersave".
Also, I noticed the charger getting pretty hot, so at first, I thought it was a problem with the charger so I tried another Lenovo charger with the same properties and it showed no problems. However, after 2 months it has started to also cause these episodes. Therefore, I thought the issue was because of the charger having a too low current, as I read it could lead to a hot charger or the charger not being able to "keep up", which this looks like, or the problem was caused by the laptop.
Here is the twist. I was just about to order a new charger that supplied 3.25A, but first I wanted to see if the same issues were present on Ubuntu. So, I created a live CD with Ubuntu 19.10 and booted from that. Then, I plugged in the charger and to my surprise, there were no problems. It charged normally with zero of these episodes, the charger did not get that hot either, and the CPU did not throttle at all.
What I have tried so far is to "reset" my laptop, meaning that in Windows I used the "Reset this PC" option where I said it should keep my personal files but reinstall Windows. However, the problems are still present.
Does anyone have any suggestions on what might be the cause or things I could try to fix the problem? And nonetheless, thank you for your time.
Additional information (added after original post date)
I have had this laptop for around 1.5 years without a problem. Then in late January 2020 it started. And in mid October 2019 I installed a new fan in the laptop, but I don't think that is the cause.
What I have tried so far: I have tried to update BIOS, Chipset Driver, and PM Driver, but the problems persist. Also, there were some error with the disk and they have been fixed, however, still not the cause. I have been running Lenovo Diagnostics Tool on motherboard, CPU, etc., and none of them solved the problems.
I booted Windows in safe mode and there the problem was gone, and both the Lenovo PM device and ACPI drivers were enabled, so I don't expect them.
I saw another one post about having the problem of the CPU throttling to around 28%, which is similar to mine. He said it was caused by the Lenovo PM device (seen in Device Manager), however, he was not able to remove it nor am I. He said he solved the problems by making a clean install of Windows, so that is what I will do next.
Update
As mentioned above, I found a post where the one asking the question said that the problem was solved by performing a clean install of Windows. I did that and my computer worked flawlessly for a couple of days. Then, when I opened League of Legends to play, the episodes started to happen again, and a lot of them happened, repeatedly. I Google'd if anyone had similar problems when gaming, and there was. They all said that the cause was that the charger were not providing enough power to both charge the battery and power the laptop. Before buying a new 65W charger, I wanted to test if this was a problem om Ubuntu, so I did a clean install of Ubuntu and the problem was still there. However, when I reinstalled Windows 10 afterwards, the problem disappeared and I were able to play League of Legends for more than 6 hours in a row without it having any of those episodes. And I were generally able to play games for the following days without problems. That made me believe that the issue was not the charger, however, I could be wrong. After 5-6 days of using my computer for 10-12 hours a day without problems, some of the hours used playing games, it started again, and it started on the same day I performed a full scan using MalwareBytes (which turned out negative, i.e. to problems) and synchronizing with my OneDrive. So, once again, I made a clean install of Ubuntu followed by a clean install of Windows 10, and the problem seemed to disappear once again, until I downloaded Adobe XD. However, after going to my powerplans and setting the minimum bound for CPU to 100% on all powerplans the problem haven't occured for around 4 hours now, but the fact that it happened indicates that the problem is still there.
So yeah, at this point I am not sure if the problem is hardware or software.
This is also going on in a Lenovo forum, see here, however, they have not found a general solution (as far as I see).
