Anyone have any official info or unofficial on this?
I'm talking about the microusb port under the cover on the opposite side from where the standard power connects on the 3 battery charging hub.
Cant find documentation on this.  Assumed it would charge batteries just at a slower rate if connected to a powered microusb plug without the standard power plug connected.  This would be convenient to charge more then one battery at a time from a car.  I tried plugging in a Samsung note 5 charger that should support a high level charge for microusb, but I didn't get anything.   Anyone else have any luck or know about the port?

Thanks

Yes, it's tested and can be used to charge with a computer, in the car, or even portable USB power. Check out this video:

This doesn't answer the initial question. The question is in regards to the micro usb port on the charging hub not the drone

It's for updating the chargers firmware. Manual indicates hooking to pc to do so.

Yes it is for updating the charger, I have not tried it, but you can plug the charger into your computer and update it via DJI Assistant 2

its for the firmware update refer to battery charging hub manual