It is normal for fast charger to heat up. Inside the charger, when the electronic components are overcharged, some of the electricity is converted into heat. This is a normal phenomenon. The amount of heat is related to voltage, current and resistance. If the voltage and current output of the charger is relatively large, the relatively hot point, and the charging time will be shortened. So it is normal for the charger itself to heat up.
Fast charge mobile phone heat proves that this model is not very matched, has a certain impact on the mobile phone, it is recommended not to.