Mxus 3k vs Qs205

Im planning to buy new motor for my ebike and I would appreciate if somebody could tell me the difference between Mxus 3k V3 4t (kv 8.9) and QS205 V3 5t (kv 9.03). Im searching more acceleration and performance because I believe my Mxus even with statorade cant use all that current that my controller is feeding.

Battery is 20s, controller Sabvoton 72150 unlocked, 175 batteryA/400 phaseA, wheel 26" semi fat tire.

If looking ebikes.ca simulator, there is no difference between those in practise. Graphs are almost identical but in higher speed QS205 sucking battery some more so it looks like there is no reason to make swap.

How about real world, what is the saturation point for those motors, I dont know if simulator pay attention for that? Probably not so other calculations are meaningless if using overkill current like I do. I would love to buy QS273 but it is so heavy for my bikes frame that it could act dangerous in some situations.

I hope comments should I buy that 205 for performance or is there any other options?

Assuming that you have enough battery amps to feed the controller your best bet would be to get a QS205 v3 3.5T. Acceleration is fantastic with lots of amps. I've used up to 325a in bursts on mine, it will get hot if you rag the nuts off it though. The mx is a weak by comparison (I've burnt 2 out).

Changes that I've made to my EEB

5000 watt hub + infineon 84 volts- pants
MX + Sabovton 84 volts - ok
Cromotor V3 + sabvoton72150 84 volts - v good
QS205 V3 +sabvoton72150 84volts - v good
QS205 V3 + APT96600 118 volts - blisteringly good but heavy
QS273 + nucular electronics 24f 84 volts - on another level just awesome

Latest build - QS138 mid drive + nucular electronics 24f 84 volts + Aprilla MX50 -
Should be interesting

Jonno

So it seems that you have lot of experiences with ebikes :thumb:

What I have understand if I put lot of current for fast speed winding motor it is getting stronger in lower speed yes but best improvement happen in best efficiency area which is higher speed area in 3t motor. So in my mind if I want accelerate 0-50mph as fast as possible best option is 5t motor and lot of battery/phase current because that way acceleration start from zero with high power and there is still power left near the 50mph at least that I want to believe. Also 26" rim need lot of torque vs 18" or 19".

I have noticed that there is two group, one group say that big kv value and huge current is best for acceleration and others say that low kv and medium current is way to go. I dont know what is the right way, thats why Im asking here. I want go from zero to top speed as fast as possible and I can use flux weakening at the end.

How about this:

If I using QS205 v3 with kv 11.39 and little smaller rim I can get more acceleration from start to stop even if low rpm torque is smaller?

I cant get 3.5T version like Jonno recommend because of my small battery so this might be compromise.

How accurate is that simulator vs real life?

If they havent changed anything since I looked at them...the MXUS has a 45mm wide stator and magnets, the QS has 50mm.

The QS seems to have a greater variety of Kv's available, but if the MXUS has the KV you want, its not an issue. The QS has thicker phase wires from the factory, but if the MXUS phase wires are thick enough for the watts you'll run, it's not an issue.

For either one, check to see if the model you want has the pressed steel core, or the cast aluminum one. The pressed steel is lighter and less expensive. The cast aluminum core absorbs heat spikes and dissipates them over time.

If you plan to use ferro-fluid, the steel core might be better due to how heavy both brands are, so you can save a lot of weight in one of the only places where its possible.

If you plan on super-hard acceleration (high amps) then the extra weight and cost of the aluminum core might be a better choice, maybe even add ferro-fluid to the aluminum core for the ultimate heat protection. There might be others...

I don´t think half turns is the way to go. According to qs it leads to uneven heating. I suspect it also leads to less copper fill, but I am not an expert.
I would go 4t or 3t. 3t can make the most power at the same voltage (the same torque up to higher rpm) but needs more amps to get there.
I think your controller is a little weak for the 3t if you want max performance. The 4t can take more too, but will give good performance at max settings.

Yes Mxus is 45mm and QS 50mm so there is little torque benefit with QS wider stator. I also believe that Mxus 4t will saturate with current I use. I say "believe" because there is no test results to see what is the real limits of the motor. QS might also saturate but later than smaller Mxus so I can go further with it. More performance with same current. That steel/aluminum core thing is new for me but Im afraid I dont have possibility to choose if I want to use 205 version 3 motor, it is one or the other. I need to make researchs.

I also believe that my controller and battery is too weak for 3T version like j bjork said and other think is that 3T is not so fast from stationary acceleration which is also important for me so best way in my case is QS 205 4T and little smaller rim. That way I can get improvement the whole area with same controller and battery.


QS 205:
5t kv9,03
4t kv11,39
3t kv16,32

Mxus 4t kv8.9

All based on the simulator so if it dont show right everything is going to be wrong?

I have a 4t myself, in a 16" motorcycle wheel. I am using 500 phase and 300 battery A and 20s lipos.
I think at the 300 phase A that qs specify it is not that exiting, at 400 things start to happen.
I can´t really say if the differens from 4-500 is the same as from 3-400, but with my 500 phase and 300 battery A it wheelies or spins.
I have to really lean over the handlebars to keep the front wheel down.

It goes about 80km/h without field weakening, and accelerate good up to 70km/h or so. I guess it starts to loose power somewhere in the 50-60km/h range, but you cant really tell until you almost reach top speed.
Here is my build if you want to see:
https://endless-sphere.com/forums/viewtopic.php?f=6&t=98723&p=1513508#p1513508

That is powerfull and good looking build!

Torque must be insane with 16" rim and those current levels. Usually that current is used with Qs273 I think but it is good to see that smaller 205 will survive also. At this point it seems that 4t is best option for me.

Big weight of motor is little problem and will need strong rim and spokes. Of course it is how and where you drive. I drive most of my trips in normal road so it is not so hard for wheel and will forqive a lot.

Has anyone experienced this:

https://nexun.pl/pl/p/QS-205-v3-3000W-30x4-Ferrofluid-Tyl/382

Kv about 10 and ferrofluided from factory, I have never heard that and also Google does not regocnize that?

"It depends" on what you want...a 10T MAC has more acceleration than a Cromotor/QS205 (Kv~9.6) until you reach about 12 mph. Any Kv QS205 motor will accelerate just as quickly as any other QS205 motor with a different Kv "if you feed both the same battery amperage". Potential acceleration is determined by the motor design...mainly the diameter but the stator width is a secondary factor. The QS273 50H motor will give you a lot of acceleration but fitting it in your bike may not be possible and it is also heavy. Usually a QS205 is as large as most people can fit. Just check the dimensions and compare them to what you have available. IMO the MXUS 4500 series would be a good compromise of everything...45 mm stator and a well designed/built motor. It is in the Grin Tech Simulator so you can compare it to other motors. If you select the Cromotor and change the Kv, you basically have a QS205 motor so you can compare the QS205 motor to other motors. I mentioned the 10T MAC being an awesome motor and it is for acceleration BUT it doesn't go as fast and it will overheat quicker than a big hub motor. The MAC is a different design...it is an internally geared hub motor. Stator diameter and width are still the biggest factors determining torque but with the MAC the torque gets multiplied by 5 because of the 5:1 internal gear reduction and the top speed gets decreased by a factor of 5 because of the internal gear reduction . The MAC also has 16 pole pairs...great for torque but that is also one reason the losses stack up in a hurry if you run it on higher voltages (16 pole pairs X 5:1 gear reduction means 80 pole pairs are passed per rev of the wheel where a hub motor with 16 pole pairs passes 16 pole pairs per rev of the wheel...so like I said in the beginning, "it depends" :lol: .

I like to plug two motors in the Grin Tech Motor Simulator and I look at four things...compare the blue lines because they represent acceleration, look at the battery/phase amperage to see if my battery/controller can provide the required amperage, compare top speeds, and look at the "Final Temp" to see how easily the motor will over heat. You can increase the Grade to see how the motors respond to hills and higher loads and grab the vertical line with your cursor and slide it left and right to see how the amperage requirements change.

j bjork said:

16" moto
I think at the 300 phase A that qs specify it is not that exiting, at 400 things start to happen.
I can´t really say if the differens from 4-500 is the same as from 3-400, but with my 500 phase and 300 battery A it wheelies or spins.
I have to really lean over the handlebars to keep the front wheel down.

It goes about 80km/h without field weakening, and accelerate good up to 70km/h or so. I guess it starts to loose power somewhere in the 50-60km/h range, but you cant really tell until you almost reach top

Click to expand...

It really takes that many amps? I got one that wheelspins and wheelie at 100A battery... On about 7500w.... Violently, 8 mi/ h / sec/ sec average acceleration... 120 ftlbs... Up to half loaded speed, max being 40 mph on a 24"... Seems like A lot less than what you run? I also have to lean down or wheel pops up... Never start off w full throttle... Smoke tire rolling on pavemend at 5 mph holding brake... ?

j bjork said:

I have a 4t myself, in a 16" motorcycle wheel. I am using 500 phase and 300 battery A and 20s lipos.
I think at the 300 phase A that qs specify it is not that exiting, at 400 things start to happen.
I can´t really say if the differens from 4-500 is the same as from 3-400, but with my 500 phase and 300 battery A it wheelies or spins.
I have to really lean over the handlebars to keep the front wheel down.

It goes about 80km/h without field weakening, and accelerate good up to 70km/h or so. I guess it starts to loose power somewhere in the 50-60km/h range, but you cant really tell until you almost reach top speed.
Here is my build if you want to see:
https://endless-sphere.com/forums/viewtopic.php?f=6&t=98723&p=1513508#p1513508

Click to expand...

Are you sure you have a 4t? That sounds a lot more like a 3t to me. I have a 4t in a 16" as well, which is why I ask.

Bullfrog said:

our things...compare the blue lines because they represent acceleration,

look at the battery/phase amperage to see if

e how the amperage requirements change.

Thank You

Click to expand...

Blue line alone is not representative acceleration. Mi/H/Sec is clearly listed in the lower right. No?

Weight and wheel dia, other factors play. I thought. Lol.


I like to move the throttle to sane man realms.. The black cursor bar only shows the instant that speed is crossed at full ( or chosen by slider) throttle. Rare that you accelerate full throttle off the star, I would flip instantly. Cant really compare full throttle to real world use case stuff... I thought.

Many people overlook the fact that there is a throttle slider and only bother looking at the full throttle output, and come to incorrect conclusions related to 'efficiency' and 'sweet spot'. If you want to see how a system behaves at slower speeds, which is achieved in practice by backing off on the throttle, then move the throttle slider to less than 100% or choose the "auto" checkbox and then click on the graph at the lower speed you want to simulate.


If you have "auto" checked by the throttle slider, then on moving the cursor to a new location, the program will recomputed the simulation at a throttle setting that results in a predicted steady state speed at the cursor.

Click to expand...

DogDipstick...you are correct.

Forgot to mention I select "Thrust" as opposed to "Torque". Torque is constant throughout a system where Thrust changes depending on gearing (wheel diameter for a hub motor). I mainly use the blue lines (thrust) for a relative comparison so I can quickly see how two motors compare over the speed/rpm range. As you said, the acceleration can be read in the lower right for wherever you position the vertical lines.

Thanks for catching my error :wink: .

Anybody know the Kv for a QS205 motor with a 3T winding? I have read different values in different places so not sure which one to believe and none of the values I could find were from QS :lol: .

eCruiser3k...where did you find your numbers?

QS 205:
5t kv9,03
4t kv11,39
3t kv16,32

Thanks

HK12K said:

j bjork said:

I have a 4t myself, in a 16" motorcycle wheel. I am using 500 phase and 300 battery A and 20s lipos.
I think at the 300 phase A that qs specify it is not that exiting, at 400 things start to happen.
I can´t really say if the differens from 4-500 is the same as from 3-400, but with my 500 phase and 300 battery A it wheelies or spins.
I have to really lean over the handlebars to keep the front wheel down.

It goes about 80km/h without field weakening, and accelerate good up to 70km/h or so. I guess it starts to loose power somewhere in the 50-60km/h range, but you cant really tell until you almost reach top speed.
Here is my build if you want to see:
https://endless-sphere.com/forums/viewtopic.php?f=6&t=98723&p=1513508#p1513508

Click to expand...

Are you sure you have a 4t? That sounds a lot more like a 3t to me. I have a 4t in a 16" as well, which is why I ask.

Click to expand...

Yes, I have a 4t. To me it seems right. 11,39kv x 82v about 934rpm (no load) Wheel is about 1,69meter circumference if I remember correct. That is 1,578km/min x 60= 94,7km/h. I think it is about right. I dont have the controller on now, so I cant check. The 3t should be something like 140km/h I think, and I sure dont get that.
You dont reach 80Km/h?

DogDipstick said:

j bjork said:

16" moto
I think at the 300 phase A that qs specify it is not that exiting, at 400 things start to happen.
I can´t really say if the differens from 4-500 is the same as from 3-400, but with my 500 phase and 300 battery A it wheelies or spins.
I have to really lean over the handlebars to keep the front wheel down.

It goes about 80km/h without field weakening, and accelerate good up to 70km/h or so. I guess it starts to loose power somewhere in the 50-60km/h range, but you cant really tell until you almost reach top

Click to expand...

It really takes that many amps? I got one that wheelspins and wheelie at 100A battery... On about 7500w.... Violently, 8 mi/ h / sec/ sec average acceleration... 120 ftlbs... Up to half loaded speed, max being 40 mph on a 24"... Seems like A lot less than what you run? I also have to lean down or wheel pops up... Never start off w full throttle... Smoke tire rolling on pavemend at 5 mph holding brake... ?

Click to expand...

I'm not sure if there was a question for me there, but I dont have any acceleration numbers. I did get an app for my phone, but I haven't tested it. I don't really understand your numbers, I planed to just get 0-60km/h or something.
The smoke tires thing, you mean go slow and use front brake and throttle? I haven't tried, but as long as I could get enough grip on the front wheel, sure
I have tried from standstill in my garage, but then it just spins a little and lifts or skids the front wheel. It may be possible if I sit really close to the handlebars, but it is difficult to control the bike then.

Yes, it is a lot less then I run. My display usually shows that I have used 21-22kw

j bjork said:

HK12K said:

j bjork said:

I have a 4t myself, in a 16" motorcycle wheel. I am using 500 phase and 300 battery A and 20s lipos.
I think at the 300 phase A that qs specify it is not that exiting, at 400 things start to happen.
I can´t really say if the differens from 4-500 is the same as from 3-400, but with my 500 phase and 300 battery A it wheelies or spins.
I have to really lean over the handlebars to keep the front wheel down.

It goes about 80km/h without field weakening, and accelerate good up to 70km/h or so. I guess it starts to loose power somewhere in the 50-60km/h range, but you cant really tell until you almost reach top speed.
Here is my build if you want to see:
https://endless-sphere.com/forums/viewtopic.php?f=6&t=98723&p=1513508#p1513508

Click to expand...

Are you sure you have a 4t? That sounds a lot more like a 3t to me. I have a 4t in a 16" as well, which is why I ask.

Click to expand...

Yes, I have a 4t. To me it seems right. 11,39kv x 82v about 934rpm (no load) Wheel is about 1,69meter circumference if I remember correct. That is 1,578km/min x 60= 94,7km/h. I think it is about right. I dont have the controller on now, so I cant check. The 3t should be something like 140km/h I think, and I sure dont get that.
You dont reach 80Km/h?

Click to expand...

I guess you're right, just that those amperage numbers are higher than I'd ever expect to be able to get away with without encountering thermal rollback or landing flat on my back. Maybe my bike and I are just fatter, lol.

Sure it will overheat fast at max output, but I can only use that for a (very) few seconds before I reach top speed anyway.
To be able to use that longer, you would have to pull a trailer or something. And as I said, it is hard to keep the front wheel down. It works if I sit on the frame, in front of the seat.
I have tried the landing on my ass part too :wink:

I usually drive in the woods, and I cant really use the full power there. Maybe sometimes for a second or two. But usually I'm probably using more like 10-15kw peak. It is not very hilly around here, and even if it was I would not be able to keep the front wheel down at the kind of hill that would require that power and still have grip on the rear wheel.

j bjork said:

Sure it will overheat fast at max output, but I can only use that for a (very) few seconds before I reach top speed anyway.
To be able to use that longer, you would have to pull a trailer or something. And as I said, it is hard to keep the front wheel down. It works if I sit on the frame, in front of the seat.
I have tried the landing on my ass part too :wink:

I usually drive in the woods, and I cant really use the full power there. Maybe sometimes for a second or two. But usually I'm probably using more like 10-15kw peak. It is not very hilly around here, and even if it was I would not be able to keep the front wheel down at the kind of hill that would require that power and still have grip on the rear wheel.

Click to expand...

Lol, did I forget to mention the trailer with my kid, charger, NY noose, etc etc etc that are trailing behind me 90% of the time? Point taken, haha. (Not that I'm doing 80 under such circumstances, to be clear.)

The offroad part makes a lot of sense too. Unless I'm climbing something stupid-steep it's hard for me to overheat offroad, even in boost with my controller maxed. On road it becomes much easier, especially if I'm in stop/start traffic.

I was thinking of something heavier, but you would probably be able to scare tour kids :wink:
Anyway, for the non believers I connected the controller and got some statistics:

j bjork said:

I was thinking of something heavier, but you would probably be able to scare tour kids :wink:
Anyway, for the non believers I connected the controller and got some statistics:

Click to expand...

WOOT !

24kW is a lot of power for that motor. What type of riding do you do ? Is there much hill-climbing ?

serious_sam said:

j bjork said:

I was thinking of something heavier, but you would probably be able to scare tour kids :wink:
Anyway, for the non believers I connected the controller and got some statistics:

Click to expand...

WOOT !

24kW is a lot of power for that motor. What type of riding do you do ? Is there much hill-climbing ?

Click to expand...

Question is for how long was it at 24kw.