Today my phone died after four hours and it was charging all night. I started to charge it again (turned on) and a half hpur later the battery was hotter than all holy hell. I took the battery out to let it cool. A few hours later I put it back in, left my phone off, started charging it, and left my case and back cover off, and laid it face-down. I checked ten minutes later and the battery was a little warm. What's going on?