Galaxy Note 9: How to utilize the fast charging feature?
The Galaxy Note 9 has a built-in fast charging features. You can charge the battery more quickly while the device or its screen is turned off.
Increasing the charging speed
To increase the charging speed, turn the device or its screen off when you charge the battery.
If the fast charging feature is not activated, follow this steps:
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.