it is the original battery. I use the original charger when at home , not a usb. My car charger is a generic one from walmart. it is not hot in the least when it has done this. as i said it is usually always on the charger when i am at home as i have it on and use it as my primary phone when at home. have also been having a strange random reboot every now and again...not sure if it is related. backing up my files and going to try a reflash to see if it solves any problems.