I have a Latitude E6420. My charger is not charging the battery, and it's gone through a few stages in the last few days. If you tl;dr, just look at "Second Problem" since that's the current state.
Conjectured possible cause of this whole mess: I used somebody else's charger a few days ago, only for ~30 min. The computer did its standard response; it recognized that the adapter was wrong, did not charge the battery, and ran a bit slow. This may or may not be related, I'm just putting it out there.
First problem: Maybe a day or two later (perhaps the next time I ran the computer while not plugged in), when I tried charging the laptop with my own correct adapter, the adapter powered my computer but would not charge and gave me the "plugged in not charging" message on the power icon in the taskbar. However, on two occasions, the battery did receive a charge, at least for a limited time. (I don't really know what I did special those two times. Crazy machines.) The battery ran fine when the adapter was not plugged in.
During this time the battery light above my keyboard (with the lights indicating power, wireless activity, etc.) would light up for a second or two when I plugged in the charger, and then would stay off.
Second problem: Now an hour or two ago, I decided to update the BIOS. Suddenly the computer cannot run with only the battery in. The AC adapter must be plugged in or else the computer instantly turns off. The computer still recognizes that the battery is in: the taskbar power icon still says the battery is in and power is plugged in but not charging. (It also recognizes when the battery is not plugged in but still works fine.)
The battery light above my keyboard (with the lights indicating power, wireless activity, etc.) is rapidly blinking in orange.
I also briefly checked 'under the hood', and on a cursory look everything seemed to be in order. But I should mention, after doing the BIOS thing on the startup setup screen, it told me something along the lines of Battery Is Functional But Degraded. I think all it meant was that my battery was too old to last for too many hours. However, on 100% battery (as of last week) my laptop could still easily last up to 5 hours.
Help! I realize this may be a common problem (hopefully with a common solution!), so even linking me to someone else's case would be appreciated.
Thank you,
Funti Mepperson