One way to tell whether or not your battery needs to be replaced is by doing a simple test. If the "plugged in, not charging" message pops up on your screen when you are using it without being plugged into a power source, then your battery most likely needs to be replaced. If the message pops up when you are using it while plugged in, then there is a possibility that your charger needs replacing or that there is an issue with its connection with the laptop itself.