Asked
— Edited
Do the 3 servo wires have to be connected to the EZ-B v4, or can the power wires of several servos be connected to a common power source with only the signal wire connected to the controller?
You can connect to a different power source, the only thing to remember is to use a common ground.
Great, thanks. That's the same as Arduino then.
can you explain how to common the ground?
A common ground is when all grounds are joined together, therefore common.
The easiest method is usually to link all grounds of the batteries/power supplies together.
Like in this diagram
All ground connections are connected at some point throughout the circuit.