KV question?
 

Does a lower KV motor with higher voltage = less current and longer run times?

Just wondering if a 4s2p LIFE running a 2650kv motor will be different then running a 5s2p LIFE on a 2000kv motor,speed can be compensated with gearing to be roughly the same as I only need around 40mph but what benefits are there to the lower kv/higher voltage?longer run time?heat?

Is the extra cell worth the weight gain from a 4s2p to 5s2p as in a noticeable difference.

The takes approximately the same amount of power to make the same vehicle go the same speed. So take that power as a constant, and P=VI (Power = Voltage x Current), so if voltage goes up, current goes down. With less current consumption comes more runtime and less heat because current generates heat. That's the simple way to understand it.
Is it worth the weight difference?...the weight between the packs probably isn't huge so probably yes. If the higher voltage pack is double the weight and the lower voltage is already heavy, than that may be a toss up as when vehicle weight goes up, the power needed to push it to the same speed goes up also.
In general though, the weight differences between lower voltage and higher voltage packs isn't that big.

Thanks for the reply,it would add 130 grams to go to 5s from 4s.I need to make 15 min in runtime.So at the end of the day with the higher voltage my runtime would be longer.

Look at it this way. With the step from 4s to 5s, you are getting more battery mass. The more battery mass you have, the longer your runtime will be.

If you were to go from a 4s 5000mah pack to an 8s 5000mah pack and set up your truck accordingly, you will get about twice the runtime even though you are running the same mah.