You can use the Samsung DeX multimedia dock only when you connect it to a charger and need to use only Samsung-approved chargers(9 V/1.67 A, 9 V/2 A, 12 V/2.1 A). Charging of device connected with Samsung DeX station may not work properly depending on type of connected charger.
For example, if you want fast charging of Note8 device while connecting DeX Station, use only Samsung-approved chargers that support fast charging based on *12V/2.1 A (*Note : This is a charger supplied for Samsung Tablet devices).
If Samsung DeX station is connected to Samsung-approved Adaptive Fast Charger in-boxed with Note8, fast charging do not operate and general charging is only possible.
Lastly, charging device itself is not supported if Samsung DeX station is connected to standard Samsung-approved charger, not Samsung Adaptive Fast Charger.