RE: Planing to Buy Futaba 4PK But Scared :(
I think HarisKhoso referred to an electric car with just one battery powering the ESC plus the motor and with the Rx powered by the BEC built-in to the Electronic Speed Controller. If this is the intended setup, then HarisKhoso just need to make sure that the BEC is capable of delivering the current to drive the steering servo and that BEC voltage is set properly, if it's configurable. Battery type would not matter as it would not connect to the Rx directly, but only through the ESC's BEC. Sorry for jumping in while not being a Futaba support person, maybe that will be still useful..
Cheers,
Smok