My HTC One M8 (Sprint) has worked fine, battery lasts all day mostly. But recently, about 1/2 of the time, the unit gets hot and the battery is just sucked dry! Like right now, after being off charger for 5 hours, I'm down to 42%. It doesn't happen all the time, but frequently. Sounds like maybe an app is running away with itself. How do I tell what's draining it? I looked in Settings-Power-Battery usage, and nothing looks too far out (mail at 21%, Google Play services 14%, FB at 11%, everything else less than 10%. So how do I find what's causing the battery to get hot and drain so quickly?