Changed screen now battery won't stay charged

Got in iphone 6 plus, screen is smashed, changed the screen out and moved over the home button. Comes on, display works properly, Touch works, home button works. It will show 100 percent charged then go to 1 percent and shut down. Try to turn back on and it goes to the screen with the battery with a red line. Plug it in let it sit for a minute phone comes back on, and it shows that its charging. Battery life shows 97 percent. If i disconnect it and use the phone in only a few minutes it will go to 1 percent and shut down again. I got a new battery on the way. Anything else it could be?