Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
I'm concerned about the problem you describe, but I'm not sure at this point whether the charger is at fault, or the battery, or something else in the device.
When you use the charger, does the charger and the Nook both give indications of actual charging taking place, by indicator light(s) etc. ?
Examine the charger, whether the cord is sharply creased anywhere, etc. ? or are there any other signs of damage or wear to the charger and its cord(s) ?
How old is the Nook in question? if older than 1 1/2 years, the battery may possibly have begun to fail, or failed suddenly.
Examine the jack on the Nook, that the charger plugs in to... is it loose or damaged?