Mxus 3K v2 45H - 3 turn on 27.5 inch rim

[bruno4500]

Hi Everyone,

This summer, I got my first e-bike hub motor. It is the MXUS 3K 3000W V2.
I didn't know much about the different winding options, and the seller decided to ship a 27.5-inch rim along with a 3 Turn version hub.
This configuration on paper gives me 120 km/h top speed on a Li-ion 20S battery, which is just too much.
The most I could handle was 80 km/h before letting off the throttle.
I'm running it with a Flipsky FSESC 75200 Pro at 200 phase amps and 80 battery amps. I'm pretty happy with how it runs, and I'm pushing around 8,000W peaks.
The motor is smooth, and statorade is helping me to not overheat it too quickly when pushing lots of current.

I was happy with it until I tried the CYC mid-drive kit my friend got today. The thing lifted the front wheel at only 3.5kW, and with 5000W, it was not possible to keep the front wheel down. So, I was wondering, should I change my MXUS for a higher turn version? 5T or a 6T? I don't mind being limited by 70-80 kmh if that would give me the extra torque. I feel like my system is pretty inefficient, and it produces a lot of heat for not that crazy torque.

Thanks!

 

[neptronix]

You can use a higher turn version or up the amps.
27.5" wheel is working against you. use the smallest wheel you can get away with and i'd recommend a 4T or higher.
3T is more ideal for a 22" wheel or below. Or lower voltage than you're running, ha.

A winding change can only move the efficiency of a motor +/- 3% once you adjust for wiring gauge and things like that between different windings.

This is not a mid efficiency hub motor and it doesn't have great copper fill, it's no QS motor.
That CYC is a super efficient mid drive.
The best comparison to a CYC is a very efficient DD hub like a cromo or grin all axle max45.

 

[bruno4500]

You can use a higher turn version or up the amps.
27.5" wheel is working against you. use the smallest wheel you can get away with and i'd recommend a 4T or higher.
3T is more ideal for a 22" wheel or below. Or lower voltage than you're running, ha.

A winding change can only move the efficiency of a motor +/- 3% once you adjust for wiring gauge and things like that between different windings.

This is not a mid efficiency hub motor and it doesn't have great copper fill, it's no QS motor.
That CYC is a super efficient mid drive.
The best comparison to a CYC is a very efficient DD hub like a cromo or grin all axle max45.

Damn that was a quick reply! Thanks.

I would love to push it past 200 phase amps but at this point I’m wondering at which current I will see smoke coming out of it. i’m afraid to burn it. Currently it overheats in around 10 minutes if I really push it to the 8kW peak I have set. Otherwise, riding normally I never reach my 90C temp limit.

I could try a 26” rim but anything lower than that and the bike would look goofy. I’d love to try it with a 5T to see the difference. Another motor is also an option but I’m limited by a 135mm dropout.

And also, this is how the bike looks like, if anyone is interested

 

[neptronix]

Yes the sad thing is that the power level isn't really above the leaf 35mm stator. It has more width but less copper proportionally.
it's more like a 2.25kw continuous motor.

If you have the coin, sometime in the next 6 months we should see grin's all axle 45mm fit into a 140mm space. That motor has higher efficiency and the extra ~5% of input energy going into heat production makes an enormous difference as the speeds climb.

 

[ZeroEm]

Hi Everyone,

This summer, I got my first e-bike hub motor. It is the MXUS 3K 3000W V2.
I didn't know much about the different winding options, and the seller decided to ship a 27.5-inch rim along with a 3 Turn version hub.
This configuration on paper gives me 120 km/h top speed on a Li-ion 20S battery, which is just too much.
The most I could handle was 80 km/h before letting off the throttle.
I'm running it with a Flipsky FSESC 75200 Pro at 200 phase amps and 80 battery amps. I'm pretty happy with how it runs, and I'm pushing around 8,000W peaks.
The motor is smooth, and statorade is helping me to not overheat it too quickly when pushing lots of current.

I was happy with it until I tried the CYC mid-drive kit my friend got today. The thing lifted the front wheel at only 3.5kW, and with 5000W, it was not possible to keep the front wheel down. So, I was wondering, should I change my MXUS for a higher turn version? 5T or a 6T? I don't mind being limited by 70-80 kmh if that would give me the extra torque. I feel like my system is pretty inefficient, and it produces a lot of heat for not that crazy torque.

Thanks!

One thing to watch for. Not all windings will have the most copper fill. Getting a higher wind motor may give less copper. Chao clamed the Leafmotor 6T had the most and never researched it.

Put your motor in the simulator in a 27.5 vs 26" and or 24" wheel and no torque was gained. To get more you will need to get a bigger controller and the gains are small.

 

[neptronix]

The gains in torque are small minor when reducing the wheel but the gain in continuous current handling and efficiency is much higher. This translates to higher continuous speeds and better hill climbing.

The MXUS 3kw is rated in a 20 inch wheel as 3kw continuous, which is true.
In a 26" wheel, it's a 2.25kw continuous motor
In a 29" it is probably more like 2kw or less continuous.

Gear down ( in terms of wheel size ), volt up, is how you get great power density out of DD hubs.

 

[bruno4500]

The main thing I'm still trying to wrap my head around is the current limit with higher-turn motors. I know I can safely push my 3T motor with 200 phase amps, but for example, the 5T motor has a much lower current limit. It may give me more torque per amp, but I'm not sure if I would be able to hit an overall larger torque if that makes sense...

 

[neptronix]

I understand what you mean.
Start with the assumption that a 3T -> 5T = will take 33% less amps and tune from there.
I always have my hand on the motor at stops when i am pushing the power to levels i haven't before.

Too hot to touch fore more than a minute? it's too hot inside.
Ideally you have a temp sensor but i've tuned dozens of motors the flinstone way.

 

[bruno4500]

I do have a temperature sensor inside the hub. I connected it to my VESC, and I set a 90 °C temperature limit. At 90 °C, the motor power reduces to approximately 250W, and the temperature usually drops to around 70 °C in just a minute or two. So I guess I can be pushing even more current? increasing it by, let's say, 25 phase amps and riding each setting to see how it performs... This can be done because the temperatures outside are around 3 °C right now, so I can play with higher currents without the motor overheating

I'm still trying to figure out if I should stick with the 27.5-inch rim and go for a higher turn motor, or do I have to get a smaller rim too. I think a 24-inch wheel would still look okay on this setup, but sticking to 27.5" would be most convenient for me. 200 phase amps is totally fine right now, but in the summer, with outside temperatures of around 35 °C, the motor overheats quickly if I'm really pushing it.

 

[Ls6s]

I do have a temperature sensor inside the hub. I connected it to my VESC, and I set a 90 °C temperature limit. At 90 °C, the motor power reduces to approximately 250W, and the temperature usually drops to around 70 °C in just a minute or two. So I guess I can be pushing even more current? increasing it by, let's say, 25 phase amps and riding each setting to see how it performs... This can be done because the temperatures outside are around 3 °C right now, so I can play with higher currents without the motor overheating

I'm still trying to figure out if I should stick with the 27.5-inch rim and go for a higher turn motor, or do I have to get a smaller rim too. I think a 24-inch wheel would still look okay on this setup, but sticking to 27.5" would be most convenient for me. 200 phase amps is totally fine right now, but in the summer, with outside temperatures of around 35 °C, the motor overheats quickly if I'm really pushing it.

Have you ever used a controller other than VESC? And can you compare them? I was also considering installing a VESC on my 3k turbo, but I've often heard they're somewhat weak compared to typical e-bike controllers. I myself ride an MXUS 3k, but with 17.9 kV, so it spins much faster than yours and should have significantly less torque than your 3T, but in a 20-inch BMX rim with only 48V and 60A, using a KT controller, it has a lot of torque and the acceleration is strong

 

[E-HP]

The Put your motor in the simulator in a 27.5 vs 26" and or 24" wheel and no torque was gained. To get more you will need to get a bigger controller and the gains are small.

There should be no torque gain by changing tire sizes. We say/imply that it does, but torque is measured at the axle and not affected by tire sizes. Thrust however is directly related to tire size, and affects climbing and acceleration. So it has the effect of increasing torque.

 

[bruno4500]

I didn't try any other controllers but the VESC, but as long as I can push the required current, I think another controller would not help me much. Since the outside temperatures are below 5°C at the moment, it's impossible to get the motor hot, so I tried pushing over 200 phase amps, and I'm slowly getting to the instant wheelie torque, but riding like this in the summer would overheat it in just a few minutes.

I guess I could get similar torque with a higher-turn motor, but at less current and with less heat. The heat seems to be my biggest problem at the moment. Without Statorade, in summer conditions, the motor would overheat at 150 phase amps in less than 10 minutes.

The 5-turn version seems the most appealing to me. On 72V with a 27.5" rim, the top speed would be around 67km/h, and with a 24" rim, 58.8km/h. Then there is the option to enable field weakening, which would give me a little bit more, which is totally fine. I don't have a reason to go any faster...

I'm interested in what setups people usually use on these 26-29-inch MTBs with the 3K MXUS. I've seen a lot of 72V ebike videos on IG, but no one seems to have the same issue. Also, a bit weird that the factory sold me a 27.5" rim with a 3T laced into it. They didn't even ask me about the turns, and it is the factory that manufactures them in China. I told them that the speed is too high and the torque too weak, and the response I got was to limit the speed in my controller

 

[E-HP]

3T going from 27.5" to 24" tire. Small difference in torque and speed, huge difference in motor temps.


Same wheel size, going from 3T to 4T. Loss in performance/torque past 22 mph, huge difference in motor temps.


Going from 3T to 4T and decreasing wheel size. More loss in performance, super low temps.

 

[neptronix]

The most important aspect of being in a smaller wheel is that by down gearing the motor and volting up, you can get substantially higher continuous power, which means more torque and higher top speed potential.
With this you can see a notable increase in efficiency too.

VTEC on 90's Hondas is kinda similar: spin the motor way faster, gear it down more.. and now your 1.8L engine is performing more like a 2.2L

MXUS 3kw is 3kw continuous rated in a 20" wheel and 2.25kw continuous in a 26". Maybe 2kw rated in a 29".

 

[bruno4500]

I finally kinda understood how the simulator works. Here is my current setup on the left and a 5T + 24" on the right. I chose the MXUS 3005 + Statorade for the motor as I don't have any hubsinks. On the 5T, the torque is much higher at start, but drops quicker than on my current setup. Did I run the simulation correctly? Also, my current consumption after a 3hour ride around the city is around 20 wh/km, which is much lower than the sim say,s but my average speed was only around 18 km/h. On my 72V 20Ah battery, my range is around 100 km.

 

[Hummina Shadeeba]

Is there a thread in which someone opened the motor and drilled the side plates? I vaguely remember seeing one and they’d added a bright red protective winding paint to the stator side. Theres a lot of threads on this motor to weed through

 

[E-HP]

I finally kinda understood how the simulator works. Here is my current setup on the left and a 5T + 24" on the right. I chose the MXUS 3005 + Statorade for the motor as I don't have any hubsinks. On the 5T, the torque is much higher at start, but drops quicker than on my current setup. Did I run the simulation correctly? Also, my current consumption after a 3hour ride around the city is around 20 wh/km, which is much lower than the sim say,s but my average speed was only around 18 km/h. On my 72V 20Ah battery, my range is around 100 km.
View attachment 381968

At 18km/h you're using 6.7Wh/km

 

[neptronix]

Example with a 45mm stator of mostly identical stator dimensions. In this case, we are not saturating the motor.



By the way, if you adjust KV instead of voltage/amperage first, you will probably see inaccurate results because other parameters that change with motor design do not change along with the kv ( you used to be able to change these )



When comparing two motor systems, it's very important to also eliminate for the difference in what battery would would optimally need for each. Otherwise battery efficiency will become an uncontrolled for variable.

For example since we are pushing a lot of power here i've equalized the battery's resistance to close to nothing so that the interference with motor efficiency and torque is reduced just a few %

If we want to talk about potential power for a given motor, then the discrepancy in power output is large

 

[bruno4500]

Is there a thread in which someone opened the motor and drilled the side plates? I vaguely remember seeing one and they’d added a bright red protective winding paint to the stator side. Theres a lot of threads on this motor to weed through

Two pics I took while installing Statorade. 3 turn motor

 

[bruno4500]

Example with a 45mm stator of mostly identical stator dimensions. In this case, we are not saturating the motor.

View attachment 381971

By the way, if you adjust KV instead of voltage/amperage first, you will probably see inaccurate results because other parameters that change with motor design do not change along with the kv ( you used to be able to change these )

View attachment 381970

When comparing two motor systems, it's very important to also eliminate for the difference in what battery would would optimally need for each. Otherwise battery efficiency will become an uncontrolled for variable.

For example since we are pushing a lot of power here i've equalized the battery's resistance to close to nothing so that the interference with motor efficiency and torque is reduced just a few %

If we want to talk about potential power for a given motor, then the discrepancy in power output is large

Thank you for the explanation!