[suicideneil]

The Kv rating (rpms per volt) will determine the voltage you use, for example:

2200kv = 4s
1700kv = 5s
1500kv = 6s

Ideally, you dont want to excede 40,000rpms on whatever voltage and motor combo you come up with (feigao type motors), but better quality motors like Neus, Lehners etc will happily run at a higher speed without issue- upto 50~60,000rpms say.