Functions of iStick TC 200w's Micro USB Port

Charging:
The battery power indicator on the screen of iStick TC200W will keep flashing when the remaining power of the 18650 cells is less than 10%.

It is recommended to charge the 18650 cells with an external battery charger as it will take less time to give them a full charge. The cells can also be charged in the Eleaf iStick TC 200W through USB port via 1A wall adapter or a computer.

If the 18650 cells are charged in the iStick TC200W, the battery indicator on the screen will keep flashing during charging and the screen will go out when fully charged. 
Firmware Upgrading:
The firmware can be upgraded by connecting the device with a computer through the USB port via a micro USB cable.