I'm building a bipedal robot and I'm using 7,4V servo motors that can consume 3.9A of current (Feetech FT5835M) and RPi4B, how can I control these servos? I'm thinking about using Adafruit 2327 HAT but I read that it can only operate at 5V, what should I do to control my servos? manufacturer's site I bought them here
Use an external power supply for the servo.
Connect a wire between the external power supply ground (-ve terminal) and a Pi ground. This ensures that the servo and the Pi have a common voltage reference.
Connect a wire between a Pi GPIO and the control line of the servo. The servo detailed specs says that the control line needs between 0V and 0.45V for low and between 2V and 5V for high. As the Pi outputs 0V for low and 3.3V for high the servo will work okay.
The servo you link appears to be a continuous rotation servo rather than a standard servo. Is that intended?