Sorry I didn't see this earlier. There is something you can try.
Shut down the laptop; remove the ac plug and then remove the battery.
Hold the power button for at 20-25 seconds; Then reinstall the battery, plug the AC charger back in, then power it up and give it a go.
From what Dell has told me (sometimes) the bios can get stuck into not "seeing" the battery enough to recognize that it needs to be charged, and when you hold the power button it's like resetting the CMOS on a desktop.
As for mine. I don't go to a computer shop. I usually know more than they do. and since I am still under warranty, I'm going to let Dell replace it for free.
IF by some chance that fixes it, please make sure you update your bios to the latest one for your laptop.