Dell Latitude: Not charge but AC adapter plugged

Sometimes I uses Dell Latitude E7*** notebook and I found that it can stop charging before fully charged. Limiting battery charging is good for battery lifetime but Dell does not provides such a feature.

When I plugged not it not all the way seated as picture. The AC power provides power but note PC does not start charging!

(A PC on this picture is Thinkpad but it does not provides such features. This picture is just for describing how to plug.)