iPod classic 5th gen; charges half way but now it won't charge at all

I suppose my first mistake was buying a used iPod, oh well. If worked fine when I got it but had a weak batery which I replaced. It worked perfectly. A few weeks later the right channel went on the fritz; had to jiggle to make it work. However when I replaced the the jack (fyi, the jack and hold button are on one ribbon cable) it stopped charging to 100%. Now it's been two days and my iPod hasn't charged. Whether I plug it into my PC or a wall outlet, the screen while continuously read "very low battery please wait". Any theories? They'd be much appreciated.

iPod Classic Video 5th Gen, 30Gb