plugged in not charging

[Dilum Wickramasinghe]

I worked with the AC current of the battery. Then it showed 20% is available. Then i connected it into DC current & laptop showed plugged in, not charging

 

[C12Friedman]

DC current of the battery, AC from the wall into the power adapter which then changes it to DC for the laptop.
I suspect what is/was going on is that the laptop was using all of the available power to run it's tasks leaving no extra to go into the battery. Does it show the same behavior when all programs are closed?