[Just go Play]

Up front I admit to being somewhat clueless about the detailed workings of electric motors so please excuse me if I'm missing something.

Originally Posted by SpEEdyBL

Although power loss is rI^2, the resistance of the motor increases by the square as kv increases. So a 1515 1.5y on 6s is theoretically going to create the same amount of heat as a 1515 1y on 4s at the same power level, because the 1.5y has 2.25 times the resistance.

The spec sheet that I have for Neu 1515 motors shows the 1Y rated at 110 max amps with an internal resistance of .006 while the 1.5Y is rated 70 max amps and .011 internal resistance. This equates to the 1.5Y having 1.83 times the resistance of the 1Y.

Based on the spec sheet the 1.5Y would have a power loss of 53.9 and the 1Y 72.6. While they are close the 1.5Y appears to be noticeably more efficient. Like I mentioned it is entirely possible that there are other considerations that make this not as simple as I think it is.

Originally Posted by SpEEdyBL

Benefits of running 4s vs 6s are:

1. Bigger lipo cells holder ther voltage better C wise. So a 6000 mah 4s pack made up of 6000 mah cells is going to hold a higher voltage per cell at 60 amps than a 4000 mah 6s pack at 40 amps.

Based on user experience this sounds right but I cannot find any reliable documentation that proves it. (for that matter who has 6000mAh cells available today?) The discharge graphs proved by many pack builders seem rather questionable if there are any available at all. Whats worse is that there does not seem to be any standards when it comes to testing or rating lipo cells from one brand to another. Could you point me to any reliable data on cell discharge rates that confirms this claim?

Originally Posted by SpEEdyBL

In the end, you really do only need 6s for power. Is it better to have two motors or two packs? You can charge one while running the other if you do have two packs. I can only see the 1515 1.5 being absolutely necessary if the 1y is already too much on 4s.

I really don't think that this is a valid argument. Both motors are capable of creating almost the same amount of power at simular RPM's. I also don't think that anyone can reasonably argue that low voltage high current is more efficient than high voltage low current setups. If this was the case then everyone would be building rc's with ultra high kv motors to run on 7.4v packs right?