Perhaps it is your customer who bought the phone used, but misuse or don't keep all the good phones, such as the omission of them in a car that was so hot, causing the blast.
Perhaps it is the customers themselves. But I bought the phone used to misuse or keep it as a place of torture in terms of the car is very hot. Thus causing an explosion
Maybe it will be of the customers. Buy phone use but abused or maintain good purpose, such as placing the phone in the car at the very hot, it caused the explosion.