6s vs. 4s?

[jsr]

The 15min runtime was just a number to make the math simple. Whatever runtime you get on your specific setup (which includes your motor, battery (capacity and discharge), vehicle weight, track size and design, and driving style) on 4s, if you want to keep that same runtime, then use the calculation I did in the previous post to find out what capacity you need in a 5s or 6s battery to make the same runtime.
Good luck and have fun!