Wireless charging is roughly 70-80% efficient versus 95% for a cable, and the lost energy shows up as heat -- normal, and rarely something to worry about.

Deep discharge, heat and a bad charger all break down a battery's electrolyte into trapped gas. Here's the actual chemistry, the real fire risk it creates, and how to stop it in a device sitting in a drawer.

A powered-down phone isn't on pause. Self-discharge, a clock circuit, and a storage habit worth breaking all quietly chip away at its charge.