AC Adapter Type - Unknown device Installed

Hi,

I've got a XPS 15 (L511Z) which recently stopped charging the battery. It says plugged in but not charging when I hover the mouse over the battery icon.

Luckily I've got an extended warranty and on contacting Dell they sent out a new charger. I plugged that in and the same result. In fact now when I boot the laptop it gives me an "The AC adapter plugged in cannot be determined" message.

Dell then asked me to buy a new battery since batteries are not covered in the warranty. Did that but still no luck. Am thinking that the original battery was ok to begin with anyway!

Dell then asked me to update the BIOS but when I tried to with the update they gave me it failed, saying incompatible with the current hardware. 

I then ran the DELL Support Center utility which identified another BIOS update which updated successfully but then I noticed that it changed the Product to L501X now. The charging issue still persists though.

I've sent a response back to Dell but based on what I've been reading on the forums it looks like the motherboard would have to be replaced.

Has anyone else had this problem and if so what was the fix?