[SpEEdyBL]

Why don't you just get more 4s packs you can interchange them and still have enough for each vehicle? The CC2650 will do fine on 4s geared way down (like an 11-12 tooth pinion), but it will still draw a lot of amps and give you short runtimes. I personally have switched to the Tekin T8 1900 kv buggy motor which is much more suitable for racing on 4s. But if you want to save money, the 2650 combo is cheaper than buying an esc and motor separately and 3s is the most suitable for racing with that motor.