HelpMe69:
Do I need to supply above 20 volts as they require 4.8-6v and I am using 6 of them?
No you connect them in parallel, as shown in the pic attached.
I know the UNO won't have enough power
In fact, it's unwise to power even one servo from the Arduino: forum wisdom is to allow 1 Amp per servo. So if it's likely that all 6 of yours will be maxing out at the same time, even that 4A supply that CR linked may be stretched.
That particular servo at 6V is quoted as 0.37Nm and 7 rad/s (converting
imperial units to something sensible), so the mechanical power can be
estimated:
power = torque x speed = 0.37 x 7 = 2.5W
Allow for loss in the motor, gears, circuitry and it ought not to
take more than about 1A (6W electrical) during operation. Servos
only draw full power briefly when accelerating or when moving against
a heavy mechanical load, so with 6 servos its not clear how many
amps you need without knowing how many are going to move
simultaneously.
Give the servos about 6V, common only the GND with the Arduino, all should be well if
the batteries provide enough current, else the servos will underperform, the battery
will struggle, but the Arduino's only sending PWM signals so its safe.
