Hey ***[link|https://www.ifixit.com/User/4533777/AnnabananaS|AnnabananaS|new_window=true],*** at the time of installation of the new battery, did you get a chance to hook up the battery to a capacity tester to ensure it was the correct model? I would potentially go to a repair shop if possible or someone you may know with a capacity tester to see if the battery itself is at fault rather than the device. Please let me know if this helps!