The phone has an on board charger. The battery itself has its own controller which will disconnect the battery from the charger if it goes over voltage, under v

The phone has an on board charger. The battery itself has its own controller which will disconnect the battery from the charger if it goes over voltage, under voltage, or over temperature. The "percentage charge" of a lithium cell isn't really any measure of its safety. Even at 0% charge the cells can still auto ignite, there's an incredible amount of energy in them when they're considered to be empty.