4th generation classic 20g iPod screen wont turn on after battery replacement

I bought a used iPod 4th gen classic a few years ago from ebay. It never worked long though. I put it away then recently decided to to replace the battery after coming across a video on youtube. I ordered a battery and did just that. I just put it back together, seem to work ( played a tune while on a radio/ipad charger but the screen shows nothing. Does that have anything to do with that it needs time charging first? I don't know since Ive never really actually used it as I guess the battery was pretty much done when i got it. Im not sure if I could have harmed the screen while replacing the battery or something else, i don't think so as I was careful and used a very good video to guide me, but who knows. I know the screen did work before tho. Just wondering if anyone has had this problem. I dont even know how long they take to charge.Thanks for any ideas anyone has.