What's Wrong With My Battery?

Alright, i've had my HTC One since 2013, but I burned the charge port late 2014. Phone wouldn't charge anymore, so I got a new phone. I eventually came back to my HTC One, bought a new charge port, and replaced it. Great! It kind of charges? It shows the battery filling up for a few seconds, the red light is on, and then it just shuts off. 10 seconds later, it comes back on, it seems like it charges for a couple seconds and then stops, removing the ability to charge my phone. Also, if I turn my phone on, it only has a couple percent of battery, and doesn't charge while on. I can only assume it's my battery, but maybe there is a simpler answer? I assumed replacing the charge port would fix it. The charger I use works on my other phone fine, so it's 100 percent the phone. I've tried the proximity sensor light crap, the battery recalibrate stuff, and i'm stuck. It seems no one else on the internet has my specific problem.