What is the meaning of a large battery symbol with exclamation point in its center?

[WPCentral Question]

Phone won't turn on. I tried to start the phone with the volume down & power on but didn't work. Also tried charging the phone and one time on the charger the battery symbol briefly came on. Am I needing a new battery?

 

[hotphil]

Change charger and cable, let it charge for a good few hours and see if it powers up. Otherwise it's probably a hardware issue.