Turnigy 9225-90 Motor Specifications

Hi all,

So I've just had my new motor arrive, a Turnigy 9225-90 kV motor which is much smaller than the previous motors used (Rotomax 50cc and SK3-149 kV) and will help me reduce my iron losses.

Here is a short video of the motor unboxing, some specifications and a partial disassembly of the motor:

https://www.youtube.com/watch?v=5Qf1oq0gNsA&feature=youtu.be

Haven't yet tested the motor but I will in the coming days. If anyone wants any further specs. I'm happy to provide them.


James

Here is a short video of the first bench test of the motor:

https://www.youtube.com/watch?v=OYUR-T0EoE4

No Load Current more than specified on Hobbyking but not substantially more, especially given I was running it at 32V and they test no load at 10V.

Additionally here is the code for the Arduino that was used in the video:

#include <Servo.h>

Servo esc;

int pos = 1000;

void setup() {
pinMode(7, OUTPUT);
esc.attach(7, 1000, 2000);
esc.writeMicroseconds(1500);
delay(50);
esc.writeMicroseconds(1000);
delay(50);
}

void loop() {
for(pos = 1000; pos <= 2000; pos += 1)
{ // in steps of 1 microsecond
esc.writeMicroseconds(pos);
delay(15);
}
for(pos = 2000; pos>= 1000; pos-=1) // goes from 1000 microseconds to 2000 microseconds
{
esc.writeMicroseconds(pos);
delay(15);
}
}

Thanks James,

I have to say that, looking at the specifications on the Hobby King website, the 9235 looks to be a better buy than the 9225, for most people. Why did you get the 9225?

Hi Miles,

Our electric efficiency vehicle uses around 900Watts to accelerate it to it's cruising speed of 40-45 kph, once there it really only consumes a few amps. The decision to go for the 90 kV 9225 are as follows;
- We have a fixed battery voltage (10S LiPo) so lower kV means lower gearing ratio to rear wheel.
- We needed a more with enough torque, 9225 has a higher kT than the 9235.
- We really were looking to lower our iron losses in our stator for higher efficiency and so tried to find the smallest motor that still has the torque and RPM required for our application. The 9225 supposedly has half the iron losses of the 9235.

Thanks for sharing your reasoning, James.

The goal is maximum efficiency at a given cruising speed. Right?

So, the question is. Which motor would be most efficient when run at the shaft speed & torque required for 40-45 kph?

9225 has a higher Kt but this can only be assessed in relation to the phase to phase resistance (Rm). Bear in mind that the shorter stator will have proportionately greater end turn losses.

The 9225 should have iron losses of 25 / 35 or 0.7 times those of the 9235.

What is your Cd and frontal area? Or, your power requirement at 45 kph?

Yeah that's the goal.

I was using the motor efficiency calculator here http://www.bavaria-direct.co.za/constants/ (bottom of that page) with the most accurate values I could find about different motors to determine the efficiency.

Our Cd is about 0.24 and FrontalA is 0.35 m2. At 40 kph, our required power is 154 W which is 4A. So from the calculator above we were expecting around 85% efficiency. Optimal efficiency is at 10A which spurred my discussion in this thread of mine https://endless-sphere.com/forums/viewtopic.php?f=7&t=75893.

CoulombMotorsport said:

Optimal efficiency is at 10A which spurred my discussion in this thread of mine https://endless-sphere.com/forums/viewtopic.php?f=7&t=75893.

Click to expand...

Sorry, I missed that thread! I'll read through it.

Ok. You need a torque output, at the motor, of around 0.5 Nm at cruising speed. So, you definitely made the right choice

I've done a provisional comparison between the two motors, on this spreadsheet, in case it's of interest:

Are you going to add Hall sensors, or run it sensorless?

If sensorless how do you start from a stop? I have had issues with that in the past.

@Miles, thank you so much for the effort you've put into that motor comparison. Fantastic to see the different options. Really appreciate it!

@Drewjet, we've always run our motors sensorless as we use sensorless controllers. To help initially we usually push off on the e-Bike which is fine as the motor then spins and works out where it is. Or with our previous car we'd get a push wherever possibly or suffer some maybe stutter.

I'm very tempted at the moment to build my own sensored motor controller and put some hall effect sensors in this motor though.

Thanks.

I used an Astro 3220 and Castle HV110 controller once on my electrathon. It would stutter badly, but get going. Once moving no issue. I always was afraid of blowing up my controller and ended up removing it.

Drewjet, I've had a watch of some of your electrathon videos. Very cool!

I'm seriously considering building a Lebowski V2 controller without the hall sensors or putting some sensors in and running it sensored so I no longer have to worry about the start up. Going to do another efficiency test this weekend with our old drivetrain (friction drive with outrunner) before I get this 9225 working with the new drivetrain

Update:



Well we've now had the motor on the car for the last month or so and it's performed pretty well in the tests we've conducted. It does get rather hot under acceleration but we have a computer fan sitting behind the motor bracket I constructed that cools the motor.

Unfortunately we haven't had the best luck with weather on testing days with a large amount of wind and/or rather hot days (although it's now cooling down substantially here in Perth, Australia). Our best efficiency achieved over a single lap has been just less than 6 wH/km which beats our past friction drives efficiency of 7.63 wH/km, although that figure of 7.63 wH/km was set over 10 laps rather than just one. Also positive is that without the friction drive, we've been able to run the rear tyre at a much higher pressure which has helped handling and rolling resistance a lot.
Enjoy a short video below of the car doing 60 km/h using only 550 Watts!

[youtube]ijVNx1nD53k[/youtube]

James,
If you use the YouTube tags, only include the actual video identifier.

Thanks Miles, I've fixed it now