My Samsung YP-T9J MP3 player

Question

My Samsung YP-T9J MP3 player stopped running after I had it on for about 3 hours. I had briefly uploaded 2 files to it the night before. The battery had just been charged a few days ago and was reading full, so I did not continue to charge it. Now, when I plug it in to charge it, it doesn't even come on. Is this the battery that needs replacing? Or something else that I don't understand.