Question about performance at different voltages

[scoob]

Let's say I had a 380c-6t (6760 kv) on 2s lipo and a 380c-9t (4565 kv) on 3s. The rpm of either setup will be almost the same. They should have the same top speed at the same gearing. Will the higher voltage setup out accelerate the low voltage? In other words will the high voltage setup run stronger dew to higher voltage and better efficiency? Will it have better torque?

I realize it will draw less current and be easier on the ESC, as well as better runtime. I understand this advantage but I've wondered if this is the only advantge.

So will a low kv motor on high voltage be more powerful than a high kv motor on low voltage with equal total rpm?

[kufman]

I believe they will be about the same. Torque is proportional to Amp-Turns in the field winding. the fast motor will draw more amps, but it has fewer turns. The slower motor draws fewer amps, but it has more turns so the number ends up being similiar. the only real way would be to dyno some motors. you can look on Lehner's webpage since they have a lot of motor data.

http://www.lehner-motoren.de/motordia.php

look at these two

http://www.lehner-motoren.de/diagramm/basic-24.13v_liste.txt

http://www.lehner-motoren.de/diagramm/basic-42.7v_liste.txt


They are not quite the same, but you can still comepare them if you pick equal power levels. one thing that I notice right away is that the higher voltage system is more efficient. Take a look and see what you think.

[scoob]

Thanks Kufman. Good data.

[tcolesen]

This also depends on the batteries. A 2s Lipo running the 6t will require a good amount of amp handling capability, whereas the 3s Lipo on 9t will require less. If you were to use the same cells in a 2s and 3s pack (where the 3s pack would be heavier), you would get more overall power because there is an extra cell, and also because the voltage drop will be lower due to the lower amp draw. Efficiency with slower motors and higher voltage will also be higher, so a higher output power can be attained from the slower motor, but with the same amount of heat as the faster motor on lower voltage would put out.

[OptimaMan]

In theory yes, they are the same... however, practically speaking, they are WORLDS apart!!!

A 6s vs. 12s on 2s lipo vs 4s lipo is totally different. The acceleration is completely different, the overall efficiency is at least 20-25% greater and everything stays cooler and the controller doesn't overheat and the motor is cooler, and the gearing can be taller.

I had/have both 6s and 12s motors and running 2s2p lipo vs 4s1p lipo using the same gear ratios and vehicle and U Force 75.

Exact numbers? I don't have them, but they are extremely different in performance.

[Key]

The smoothness from start to low speed on higher voltage is also an area that cannot remain unnoticed!!

Don't get me wrong a UF-75 for example running on 7.4v is very very smooth on low speeds but it gets even better as voltage increases especially when you know at the back of your head you can almost outrun anything that moves :D

[kufman]

I had/have both 6s and 12s motors and running 2s2p lipo vs 4s1p lipo using the same gear ratios and vehicle and U Force 75.

you can run the u-force on a 4s lipoly?

[tcolesen]

Yes, you can.