Why won't my iPhone charge?

I have had a problem with my iPhone 4 running iOS 7.1.2, jailbroken with Pangu. It was running fine one day then all of a sudden, it dies at about 50% while I was playing a game. I plugged it up and it booted just fine and went back to my game, then died again. I have replaced both my battery and dock connector. I have researched a lot and couldn't find any solution that I haven't tried previously. I was thinking it may be the logic board, but I hope not! Any help would be greatly appreciated.