T450s charger repeatedly connecting and disconnecting

[Sultan_of_Sass]

I've had my T450s for a little over 2 years now with no issues, however last night while working I noticed that the green power indicating light was repeatedly flashing for no reason. My first thought was that the power connector had become frayed so I grabbed my spare but it too exhibited the same problem. I then removed both batteries (internal and external) and connected the AC adapter to see if it was the cable. The laptop then booted up no problem to my surprise. I then left the internal battery unplugged and connected the external to see if I could figure out which battery was causing problems and repeated with the internal. Both of them on their own exhibited no problems at 100% charge (have not tried completely discharging yet). To then check if it was a faulty AC port I connected it to my dock at work through the bottom port and the problem still remains.

The problem also persists in BIOS and other Operating Systems, in Windows it briefly connects and states that it is "Plugged in and charging" then after about 5 seconds, then "Battery in use", then "Plugged in, not charging" and then repeats the cycle ad infinitum.

The batteries are not hot too the touch and diagnostics show that they seem to be in good condition and pass the tests. Any insight would be helpful.

[RealBlackStuff]

Most likely it is Windows 10 to blame.
Get an external CD/DVD drive or USB stick with bootable Life Linux, and run that (without installing).
If the charger still mopes, you might have a motherboard problem.
(Go have a pint of Murphy's).

[RecTech]

It seems it is not Windows to blame, as you have tried different versions and also within the BIOS and if you have tried two ac adapters and the docking station it looks like it may be the internal charging circuit unfortunately

[Elmer Fishtwanger]

I had this problem with a T420, so might be similar or not.

In my case it was both a bad adapter /AND/ a bad battery. It would go back and forth between charging and not charging about once a second. There was an IDE I would load up that causes high demand on the processor. With adapter, or battery, or both together, there was not enough current available and the computer would shut off while it was loading. It was fine as long as there was smaller current demand. It was pretty confusing. I suggest holding the power button down for a minute with all power disconnected before trying the new known-good parts.