It depends on the motor you are using, but generally speaking for a solid 15 minute main with a few warm up laps you will need
4s 5000 (2000-2200kv motor)
5s 4000 (2000-1700kv motor)
6s 3300 (1700-1400kv motor)
Those batteries should give you right around 17-20 minutes of race time depending on gearing, track, and driving style.
Perfect
.... thanks again .... very much appreciate the quick and knowlegable response
... your info gives us a place to start