It still could be the charging system on your Nook.
(But you say that your old battery charges ok. What does the temperature say?)
It would be nice to figure out exactly what the problem is.
Do you have a meter to measure the yellow to black ...
XDA Developers was founded by developers, for developers. It is now a valuable resource for people who want to make the most of their mobile devices, from customizing the look and feel to adding new functionality. Are you a developer?