Hi. I am making a small bipedal robot with 9 servos, listed below. How much power would I need to sustain this for about 30 min?
3 arm servos : http://www.robotshop.com/hitec-hs311-servo.html
6 leg servos : http://www.robotshop.com/hitec-hs422-servo-motor.html
Batteries are rated in amp/hours. You need to know your amperage.
Lets make a wild guess.
The servos would be busy almost all the time for the balancing.
They are 150mA no load to 700mA stall current.
Lets assume 400mA at 75% of the time during 30 minutes.
Lets assume 9 servos total (not 3 servos per arm).
That makes 2.7A. So we need a 6V battery of 1350 mAh.
If using a 12V battery, and a DC-DC converter to 6V, and a loss in the circuit of 20%.
We would need a 12V battery of 1000mAh.
I suggest a balanced battery pack as used with RC of at least 2000mAh and a balanced charger and a DC-DC converter to make 6V.