Sorry if my question looks newbie, but I'm just starting to delve into robotics and electronics, and my first project was building a small arduino collision-avoidance robot with a ultrasonic range finder, one servo and two dc motors. Right now I'm using a 6V battery pack to power both DC motors, another 6V just for the servo, and a 9V battery for the arduino. But I'm in doubt if the power supply for the DC motors is enough. I'm using an L293D IC to control both motors, but the robot can barely move under load (and the total weight of the robot is not that much. I already reduced all the weight I could). So, how much power, typically, I should supply for the L293D to control those motors?