changed usb sister board now no signal and battery dies fast

My galaxy s4 died about a week ago... and when I went to plug it in as I do every night a grey battery showed up that I had never seen before. The next day I ordered a new sister board USB port. After I installed it charged right up and was working great! Until I realized that after two hours of not being on the charger the battery went down to 60%. finally I realized My signal was at one bar and on edge service I don't know what to do I'm stumped can you guys help me out thanks!!