How can I tell if its a bad U2 IC?

I replaced a lightning connector on an Iphone 5s, when I connect the charger I get an image of a black battery with a thin red line on the left centered on the screen and at the bottom of the screen an image of the lightning connector and a bolt.

This was the first connector I replaced but I've worked on several phones for other issues with no problems so I'm 95% sure it wasn't the install. The phone's owner admitted that she had been using a charge cable she bought of Groupon. She said that when it was connecting that the battery was holding a normal charge over a normal period of time.

How can I tell if is a bad connector, bad battery, or bad IC chip? I have plenty of tools but I don't know the best way to diagnose which part is the culprit. I don't want to tell her to give me more money for a battery if I'm not sure if that will resolve the issue.