 The pouch batteries in your cell phone are really thin, and if they break or crack open, they'll start to spark and go off. They'll start to self-oxygenate, turn into a little torch. One way in preventing that is, of course, not charging a lithium-ion battery when you're not around, but also taking care of your devices and replacing a battery. When you notice you're getting less run time, any swelling of the battery,