ORIGINAL: seanreit
Were you just told that the speed controller had a regulator, or was it published somewhere? If published, can you show me where?
Go to the Tower Hobbies website and search for speed controllers.
Some of the car controllers specify the receiver voltage and current. It's also known as B.E.C. voltage.
Some were 5.0 V and others were 6.0 V. I found one that specified the current as well (3.0 A).
Some of the lower power aircraft speed controllers also have BECs. Typically these BECs are rated at 5.0 v at 1 or 2 A. Since aircraft go way beyond the six or seven cells found in cars the dissipation in the regulator can become quite high, so separate receiver packs are common once you get over ten cells or so. Aircraft BECs are typically rated for two or three mini or micro servos and up to eight or ten cells.
RC cars with spring type battery holders expect you to use alkaline cells. The cell voltage is 1.5 V, so a four cell battery will give you 6.0 V. Car servos are typically specified at 6.0 V, with expectation that user will use four Alkaline cells, or five NiCd cells.