I have the latest 2018 MacBookPro 13" connected to the G-Drive TB3 (10TB). Sometimes, the HD charges the laptop, but more often, despite showing the “charging” icon in the menu bar, it doesn’t charge. Hovering on the icon either gives “battery is not charging” or an unreasonable charging time: “More than 10 hours”. I tried both the TB3 cable that came with the HD and the original Apple usb-c cable. It’s the same. What may be the problem?
There isn’t a problem it is just that the charging isn’t as much as what the actual Apple adapter will be providing. It basically gives enough so that you don’t drain the battery down to 0 while using it. It is enough to maintain. If you want to actually charge your laptop you will want to use the Apple adapter.