Building the Arduino Receiver. The whole board and micro weighs in at 22 grams. The supply will be a 3C Lipolly
The Xbee Vin (max 16V) and Arduino VIN (max 20V) hare both powered from the supply battery 11.1 V directly as the both have internal regulators. This helps isolate any noise from the Arduino and ore servos from being superimposed on the Xbee supply rail.
The Xbee need around 220mA and the Arduino say 100 mA driving the servo PWM signals, and not the motors. All up say 750mA in a 750mAh 3C