When I connect the USB cable to the bottom of the RC and the other end to the phone, it [the RC] becomes a charging port for the phone, that is to say, the phone is being charged by the RC. The USB cable is mine [not supplied by DJI].

Is this normal? Or the USB not compatible? I have to disconnect [take out the USB and reinsert] then the GO4 works.

DJI did not give me any other USB cable except the 3 small [short] cables.

I am using Andriod phone.

On the Mavic Pro you need to use the micro to lightning connector from the side of the controller.  If you connect a lightning cord to the bottom it will replicate your problem.

Papa Ski Posted at 2018-1-13 21:15
On the Mavic Pro you need to use the micro to lightning connector from the side of the controller.  If you connect a lightning cord to the bottom it will replicate your problem.

Papa ski

Sorry I did not mention I am using an Android phone.

CHEOLK Posted at 2018-1-13 21:50
Papa ski

Sorry I did not mention I am using an Android phone.

Yes its a standard "feature" for android devices connected to the RC's bottom USB port.  The RC battery is not very large and it can result in the RC being discharged before you run out of Mavic batteries.  

There are a few solutions and workrounds:

• Some newer android devices offer the option to turn off charging - or only charge when below a certain capacity.
• Its possible to make a data only USB lead.
• The RC itself can be charged while in use - using a USB power pack or a Mavic battery + adaptor.
  

This latter option isn't recommend by DJI

Or make sure that your phone is fully charged prior to setting out.

Simmo1 Posted at 2018-1-14 03:13
Or make sure that your phone is fully charged prior to setting out.

That I think is the best solution.
When the phone is fully charged it won't pull much energy from the RC.