robots use 7.4V for servos so some servos can handle 7.4V as well some recievers. have a look into its specs. if not you will have to usevoltage regulator (UBEC will do nicely)
Radek
V4 D8 - RX8, XERUN 4168SD
F1-09 - Tekin RS Pro, 17.5t Redline, 2S LiPo
Sakura Zero S - LRP, Saturn 20T, 2S LiPo
*EX-10 Eurus*