Motorola Droid 4 :: Battery Became Hot

Today I left my D4 unplugged at work to see how long it would last. After about 7.5 hours, the battery had dropped to 30% with minimal use and next to nothing running in the background. When it hit 30%, the temp spiiked to 107F, and the battery decay accelerated (despite a battery extender Smart Action engaged). The battery was at <5% by 8:30hrs and still just as hot. This is very unusual behavior in my brief 3 week experience with this phone, although I have seen it a couple of times. I usually charge at 50%, and only see the overheating at the lower %. The heat continues when the charger is eventually plugged in. It got so hot today that I decided to reboot the phone, and it seemed to run cool after that.