Raspberry Pi released an official 48W (8V DC, 6A) Power Supply, designed for use with the Raspberry Pi Build HAT. Similarly, it can also power the Arduino and Raspberry Pi via the BuildHAT.
Power your Arduino Pi Build HAT projects with the Arduino Pi Build HAT Power Supply
48W power supply will power the Build HAT and connected LEGO Technic motors, as well as your Arduino/Raspberry Pi computer.