In my case with the Turbo, the would suddenly and prematurely drop to 0%-5% and shut down immediately. It wouldn't power at all until you plugged in a charger cable and then it immediately jump to ~50% battery. If you unplugged again, battery would tank immediately. When that happened I had to do the press & hold power hold button to complete reboot and reset the battery cal. Then leave the phone plugged in over night. The real pita with the Turbo and battery re-cal is that it would also wipe out all my BT pairings...so I had to go through that rigamarol every time it happened too.