QS 205 vs QS 273 watts consumption

[MadRhino]

Logging and stats are not important to me. I am a rider, so everything I build is rider oriented.

I was collecting datas in the first years, trying to find what could be improved, what are the limits, how to achieve my goals. This period of ´builder oriented’ bikes is over. It was useful for some time, but soon became inconvenience.

I now feel my bikes instinctively, and my only monitoring displays are minimalist volt and temp. My handlebar is clear of any accessories, but half twist throttle and 2 toggle switches.

The monitoring displays are small and fitted under the stem where no crash damage could occur. I have replaced many handlebars and saddles because of crashes, but now I have found the best solution with very expansive handlebar and very cheap saddles. The same with every component, selected for quick maintenance and crash resistance.

 

[PeeHell]

Last summer, I built three ebikes using the enduro frame kits from em3ev. Two of them are powered by QS biggest hub motor that fits a 150mm dropout : the QS 273 40H v3. MadRhino kindly laced these two heavy motors in a 19" moto rim just like the one around which the third motor was built : the QS 205 50H v3. All three motors are fed by unlocked Sabvoton SVMC72150

Having read the entire thread, I totally agree with what has been said about the higher weight of the QS 273 being detrimental to the handling and acceleration. In the same manner, it is also obviously true that those motors can handle larger currents for longer due to their thermal inertia and larger surface area to shed heat. I've seen as much as 30 degrees (celsius) difference between both motors on similar riding conditions. But there are advantages to this motor over the QS 205 that are often overlooked.

I gathered a few key information on the table below of the differences between three well known hub motors for ebike (QS 273 50H and above are not suited for ebikes as they require a 200mm dropout)


As far as my understanding goes, the amount of torque per ampere also increases as the height of the stator (diameter) augments. It does so because the length between the road and the rotor is decreased, indeed shortening the lever. It is the same phenomenon as when you decrease the size of your wheel ; the smaller the wheel, the higher the torque.This is why despite having a similar stator width, the Crystalyte 5403 outperforms completely the old Crystalyte 408. A few years back, I asked Justin from ebikes.ca about the relation between the stator width vs height by comparing a Crystalyte HS35 (205mm height, 35mm width) to a Golden Motor Magic Pie (273mm height, 18mm width). He answered :

The total magnetic area is half as wide (35mm vs 18mm), so it generates only half as much linear thrust per amp. However, it is also 33% larger in diameter (273mm vs 205mm) so you have 33% more length of magnet, and that brings it to having 66% as much linear thrust as the magic pie. But, the thrust on the Magic Pie is also acting at a larger radius (33% larger again), so in terms of torque the magic pie ends up being about 89% as much as the HS35XX series. The larger diameter means that it can achieve 89% of the torque of an HS35 motor with just 69% of the magnets.

Please correct me if I am wrong, but my point is the same calculations applies to the QS 273 40H vs the QS 205 50H ; sure it's heavier but the thrust per ampere is higher too ! That means not only it can take more current, it generates more torque with it.

Edit: The QS 273 ebikes are running 18s 48Ah lipo @ 225A battery current limit good for 15kW nominal (as you cannot multiply battery voltage with max/peak phase current to calculate the ebike power because these are waveforms (square or sine) that don't get their current "multiplied" in a way that doesn't respect Watt’s law. The power you see on the cycle analyst/wattmeter is, minus small losses, the power your motor gets)

 

[MadRhino]

@PeeHell
I am happy to know that you are finally riding your bike. Thanks for your feedback on ES. I hope that we can ride together soon. I am curious to see how your build turned into. Must be a big change, compared to your first build.

 

[DogDipstick]

I am about to buy a V3. I am torn between the 4T and the 5T.

I have let the CA display rack up a few cycles, and my Wh/mile consumption on my 35H motor is steady at about 45Wh/mile. I have concern that the amps will eat up my pack with a 4T opposed to the 5T. I kinda want the 4T.. but people have told me to go 5T... but I want more than 45mph...

 

[MadRhino]

No doubt that faster will consume more, not because of the faster winding though. It would still consume more with the 5t if you’d use another mean of increasing speed, like larger wheel or higher voltage.

 

[Dragonsandfaeries26]

Same volt and amp, same power=same torque when all other factors being equal. If one has better torque when fed identical power, it is because some other factor is different: smaller wheel diameter, different winding kv, etc...

Then, something will be different if you build with a 273: weight.
More weight does mean that more power will be required to achieve the same performance, and more battery capacity for the same range. Now, if you plan building heavy already and need equal performance, the 273 is a solution but it will have to be fed more power than a 205.

The 273 is capable of better acceleration, because it can be fed more watts.

Top speed is another story. It is not about motor size. It is about voltage, motor winding, and aero drag especially.

I bought the 273 v3 8,000w 3.5t (speed version windings) yet I can only hit 51mph. How can I get more speed and torque without ruining the sabvoton 150a controller and motor? I have the advanced settings code(1801) and I can change amps and polls on the motor etc. But I don't want to do anything that will mess up anything. Could use someone experienced in upgrading this beast.

 

[Eastwood]

I bought the 273 v3 8,000w 3.5t (speed version windings) yet I can only hit 51mph. How can I get more speed and torque without ruining the sabvoton 150a controller and motor? I have the advanced settings code(1801) and I can change amps and polls on the motor etc. But I don't want to do anything that will mess up anything. Could use someone experienced in upgrading this beast.

Definitely don’t need the QS273 with 150 amp controller. The QS205 which is 20 pounds lighter can handle those power ratings. If you were running 300 or 400-ish battery amps, then you would need a QS273. This has been stated over and over on the site even the thread you posted in.

If you post pictures of your settings I can help you.

 

[MadRhino]

I bought the 273 v3 8,000w 3.5t (speed version windings) yet I can only hit 51mph. How can I get more speed and torque without ruining the sabvoton 150a controller and motor? I have the advanced settings code(1801) and I can change amps and polls on the motor etc. But I don't want to do anything that will mess up anything. Could use someone experienced in upgrading this beast.

Yep. You didn’t need that motor.
To make it go faster, you have only 2 solutions:
Either you lace it in a larger wheel, or you feed it more volts.

But, it could happen that your controller does limit the top speed, for one of 4 reasons:
- defective throttle.
- 3 speed switch not set to full speed.
- the top speed is limited in the software.
- the phase and/or halls are connected to a ‘false positive’ color combination, in which case the motor would be noisy and/or stuttering in acceleration.