So I seem to have the same problem as some other users out there. I've had this notebook for about a month and a half now. It was working fine until recently. When I plug in the AC power adapter cable, a message pops up saying that the AC adapter type cannot be determined, and that my system will operate slower and battery will not charge. It then tells me to connect a Dell 45W AC adapter, which it already is. I can confirm that it's not charging by hovering over the battery icon in my system tray. This is the second time that this has happened. The first time I simply switched to a different power outlet and that seemed to do the trick, but this time it isn't doing it.
Basically, I've been following the instructions on this post: http://commweb-ps3.us.dell.com/support-forums/laptop/f/3518/p/19511058/20387444.aspx#20387444
I've checked my battery health by hitting Fn+F3 to pull up the Battery Meter and it tells me nothing is wrong with the battery. I can't enable Desktop mode because it's greyed out. I confirmed that the battery was fine by going into the BIOS as well. Another thing was that in the BIOS, "Unknown" shows up beside AC Adapter on the main page. While in the BIOS, I unplugged and replugged the AC adapter, and it still comes back as "unknown." Therefore, I've tried resetting to defaults, and still no results. I've also performed an ePSA diagnostic and my notebook passed all the tests. Currently power passes through the cable as the white light on the plug still lights up and it's continuing to power my notebook. I looked in at the pin and there aren't any damages that I can see. Something else I also tried was go into Device Manager, and under Battery, uninstalled the Microsoft AC Adapter, and replugged in the power adapter, but that didn't do anything.
The last thing I have yet to try is to update my BIOS as I'm currently running A02. However, I can't do so since my battery is currently at 7%. But it's been working before so would doing a BIOS update solve the problem? It seemed to do the trick for the other user from the post I linked, but then again, his adapter actually shows up as 45W in the BIOS whereas mine shows up as unknown.
What options do I have? I still have warranty coverage. Thank you in advance.