Had this annoying thing with the power icon on my old Dell Vostro 1500 that showed "12%, plugged in, not charging". Googling the issue didn't have much of help, neither removing the battery - yet I've found a temporary solution.
Seems that your charger is about to die. Meanwhile you can restart the machine and enter the basic menu (F2). In the menu go to the "battery" section, you will see the battery image with percentage and text line "AC adapter is not recognizable". Unplug the power cord and plug back in several time until you'll see the text changed to "AC adapter 90W". If there's still no effect try to flip the power cord it as in a picture below and repeat the plug/unplug procedure - may be some chargers are sensitive to electrical polarity.