That's happened to me the last couple of days. I charge up my nook to 100% and then I read for about an hour. Then I get a warning saying my battery is about to be at 0% and then the screen goes dark as if it was turned off. It then boots itself back up and I check my battery status and it's about 91%.
I have no idea what the issue is.
This kept happening to me over a series of weeks.
I ended up calling customer service-they had me reset my Nook t the factory settings; that still didn't solve the problem.
They ended up sending me a replacement Nook.
No issues since the replacement a month ago.
Having same problem, where all of a sudden displays battery critically low; when I did turn off and back on battery power back to @ 45% where it was previously but than drained alot faster after that even with the Wi-fi turned off.