Critical Battery Trigger Met, System Entering Sleep?

I am running a Dell Lattitude E6440 01, laptop, 8gb memory, 500gb HD.
This happened twice now. Last night watching a movie streaming, with microsoft edge, after about 1 hour, system apparently shuts down, screen goes black..? hit the power button comes back quickly, and resumes where I left off.
Checked temp of cores, 51 c max.
Then ran intel diagnostics for chip, no errors, also checked temp hit 57 c, but system never shut down. Ran HD diagnositics, no problem
Then checked windows logs, and found this:
CRITICAL BATTERY TRIGGER MET
SYSTEM ENTERING SLEEP.
Evidently my system entered sleep mode.. why?
Also, battery is not charging holding at 5%.

So where is the problem here?

Thanks,