Galaxy Note 9: How to use the Note 9 to charge other devices?
With your Galaxy Note 9 having 4,000mAH battery capacity, you may have the convenience to use it as charger for other devices.
Use the USB connector(USB type-C) to charge another mobile device with your device’s battery. Plug the USB connector(USB Type-C) into your device’s multipurpose jack, and connect your device and the other device via the other device’s USB cable.
When charging start, the battery charging icon will appear on the other device’s screen.