Galaxy Note 9: How to use fast charging feature
The device has a built-in fast charging features. You can charge the battery more quickly while the device or its screen is turned off.
To increase the charging speed, turn off the device or its screen off when you charge the battery. While charging the battery when the
device is turned off, the charging icon appears on the screen.
If the fast charging feature is not activated, On the Home screen, Tap Apps → Settings → Device maintenance → Battery → More option → Advanced settings → Activate Fast cable charging option
• You cannot use the built-in fast charging feature when you charge the battery using a standard battery charger.
• If the device heats up or the ambient air temperature rises, the charging speed may decrease automatically. This is a normal operating condition to prevent damage to the device.