my phone is little hot on back while charging the phone, but if it reaches 80% or 90% while charging, then it starts to cool down. is it normal?
each battery gets warm while charging
Hi, as indicated in the Manual, chapter 1 "Basics" :
While charging, your ASUS Phone can become warm. This is normal, however, if your device becomes unusually hot, disconnect the USB Type-C cable from your device and send the device, including the AC power adapter and cable to an ASUS-qualified service personnel.
To prevent any damage to your ASUS Phone, AC adapter, or USB Type-C cable. Ensure that the USBType-C cable, AC adapter, and your device are connected properly before charging.
OK, now I understand. I thought my phone has problem, cause it gets little hot back while charging.
If you don't want the phone to get hot while charging, use a 5V/1A adapter. If you still think that your phone is getting hot when charging (it's a problem/not normal), take your phone and adapter to the service center for testing.
If you room temp is 26 Celsius or below and you're not using your phone while charging, then it shouldn't need to cool down.