What's the deal with ordering from QSmotor?

MJSfoto1956

10 kW
Joined
Jul 28, 2010
Messages
960
Location
Boston, MA
So I'd like to upgrade my Chinese QS 205 2000W 12" hub motor to a more modern motor from QS. For example: 8000W 13" QS273. Easy peasy -- just go to their AliExpress site and select their QS273 13" hub. So far, so good. But then there is the fine print:

  • What's your scooter weight?
  • Voltage & RPM? or Voltage & max speed?
  • Wheel size? Tire size?
  • Climbing performance requirement?

My concern is not how to answer the above (easy) questions, but rather what happens if you make a change to your ride AFTER the sale? Do they actually ship slightly different motors depending on your specs? For example, what issues might arise if I initially specify 84V but only start out with 72V? Or vice versa (i.e. specify 72V but later upgrade to 84V)?

Curious minds want to know.
M
 
Hi qs motor are not to bad to order from only they are slow to reply some times but they do want to sell you stuff they get to be a pain in the ass when you have a problem with anything you have bought as i have discovered. Besides that tho I would say it's to do with the T count of the wire in the hubs they are selling as far as I remember a low t count is fast and a high t count has more tourqe so say they are trying to gauge what it is they should send you for your needs
 
Ammo1 said:
as far as I remember a low T count is fast and a high T count has more torque, so say they are trying to gauge what it is they should send you for your needs

That makes sense. Still leaves the question: if I were to start my build with a 72V battery pack but eventually upgrade it to 84V should I list my requirement as 72V or 84V? Or put another way: does it make sense to over-volt a motor (eventually) or under-volt it (initially)?

M
 
Definitively overvolt :twisted:

Undervolting a Motor will make it run slower and it won't be in it's best efficiency range anymore.
 
eee291 said:
Undervolting a Motor will make it run slower and it won't be in it's best efficiency range anymore.

Fair enough.

But what if the question were modified slightly? i.e.:
  • If I initially only have a 72V battery but within three months of installing the motor I would have upgraded to 84V is it not better for the motor to be "tuned" by QS initially for 84V rather than 72V in such a situation?

M
 
That really depends on the speed and power you are planning.

Overvolting makes more sense to me with 36/48 Motors
A lot of people (like me) overvolt 48V motors to 72V for a few reasons:
  • 48V Motors are more available and Cheaper
  • Lower turn count is good for large currents
  • High current 72V Controllers are relatively cheap compared to 84V
  • Flux weakening 8)

But since you are going with 84V then I think a 84V Motor makes more sense.
Voltage doesn't even define all Motor characteristics.
You need to tell QS what speed you are trying to achieve in order for them to choose a turn count.
 
eee291 said:
But since you are going with 84V then I think a 84V Motor makes more sense.
Voltage doesn't even define all Motor characteristics.
You need to tell QS what speed you are trying to achieve in order for them to choose a turn count.

Yeah that is the conundrum. I will be happy with 100kph when all is said and done. Not looking for top speed but reliability, battery life, and distance. Seems I should tell them 100kph + 84V + 13" rim + 7% grade max. as that would be the ultimate goal.

Thanks!
Michael
 
I would agree wit eee291 go with the most economic one price wise and just overvolt most motors can take a much higher voltage and ampage than rated just for shorter periods so if your being charged twice as much for an extra 12 v just get 72 v and overvolt with the controller
 
Ammo1 said:
...so if your being charged twice as much for an extra 12 v just get 72 v and overvolt with the controller

AFAIK, QS doesn't charge more for the same motor with different specs.
But perhaps they do -- can anyone confirm that?
Need to find out.

M
 
Most if not all of qsmotor inventory is now on AliExpress and Alibaba, descriptions are a bit weak as to what you get motor and controller and maybe the swingarm also. Saw a $50 difference from one to the other as one had high shipping for the kit and the same shipping for just the motor ,$150 extra either way.
 
QS just want to help customers to find the right spec, all motors can be overvolted within reason and with some limitations

Core losses go up with the frequency squared so overvolting a 48V spec motor to 72V can be problematic.. since core losses will be more than doubled.

I'd take a motor winding that will provide the speed you want under load plus some 20-30%.

Why? The acceleration drops off quite a bit towards your top speed so if you really want to use for example 60mph and get there in an ok time then you need higher top speed.

Noload speed would then be 60*1,2/0,85=85 mph, that's with 20%extra and 15% lower loaded speed than unloaded
 
The plot thickens. Let's say I have a generic 120A BMS from China. To be on the safe side, I probably want to run it at no more than 100A. Fair enough. But let's also say I'm running a 72V battery pack. Now my choices from QSmotor get murky:

  • 8000W V3 273 (8000W/72V = 111A)
  • 7000W V2 273 (7000W/72V - 97A)

The calculations suggest one should probably go with a 7000W motor. But QS only offer 7000W with the older V2 design. What would happen if one were to run a QS 8000W V3 with such a setup? Would the 7000W be more performant? Or the other way around?

M
 
I don't really understand your question..

BMS current does not define your max system power in that you need a safety margin there - max power out will be roughly 10kW from a 72Vx120A battery on full charge.

8000W is always more than 7000W.
The motor rating is also very loosely defined. I run a "3000W" motor to 15-20kW currently.

The question is more what kind of weight, dimensions of motor you can accept and what your typical use case is. If you run a large motor at low loading then it could be inefficient due to the unloaded losses that are always there and increase with the motor size.
 
larsb said:
BMS current does not define your max system power ...

Well, as part of a system, is indeed involved in calculating the system amps. I took this quote from a fellow forum member to heart:

wesnewell said:
If you plan on normal use, I'd get an 80A minimum bms for a 60A max controller.

In my example, I have used the above "rule" to suggest a 120A BMS + 80A (programmed) Controller would be ideal, which is precisely what I plan on using.

However, it still does not answer my question regarding ordering a 7000W V2 vs. 8000W V3 from QS.

Michael
 
I had to check which motor you're referring to.. It's a QS 273 50H? I got this from QS site:
image.jpeg
The basic difference between 273/50H 7000W and 8000W motor is better materials and winding which gives higher efficiency, longer range, lower heat, more power and torque for the same amps.

I would get the 8000W v3 motor, it is simply a better motor and worth the slightly higher cost. That does not necessarily force you to get a higher amp bms or controller - but you can if you want to use all the available power :D This is a simple choice.

Controller power, battery, bms is really dependent on budget, your power goal, range and how you will use your bike so not easy to say something about without more info.
 
larsb said:
Controller power, battery, bms is really dependent on budget, your power goal, range and how you will use your bike so not easy to say something about without more info.

I ordered a custom-made battery pack from an AliExpress vendor today. My specs were: 120A BMS, 20s17p layout, 72V 57Ah (4.1kWh), (340) LG 3350mAh F1L 18650 cells, with package dimensions of 330mm x 220mm x140mm to fit nicely into my scooter's existing battery tray. The LG cells are rated for 1.5C continuous which is slightly more than 80A. They said they can deliver it in a few weeks. Price with shipping to the USA was $1692US

I understand this pack as-is cannot drive an 8000W motor at full power (i.e. 8000W/72V=111A). But in the future, I may double things up with a 2nd identical pack. Run in parallel, I'd have more than enough Amps to drive it. As such, I'll likely go with the QS 8000W 273 V3. (Note: I notice that QSmotor have developed a V4 model which tests much better than their V3 models. Sadly it doesn't seem to be available retail yet...)

M
 
Looks ok at max 7A discharge per string:
https://lygte-info.dk/review/batteries2012/LG%2018650%20F1L%203350mAh%20(Purple)%20UK.html

But it will be getting hot built into a large pack at that current, it'd be good to use a heat exchanger plate to move the heat to free air. 8)
 
I think the pack needs to be stripped to get a better heat path out. It all depends on how it's built if it's possible.

But possibly you will only use high current in bursts if you're not going freeway speed for longer time, then it'll be ok anyway.
 
Well I bit the bullet and just ordered a V4 QSmotor.

I told them about my use-case (very hilly region, 130kg bike weight, 72V @ 57Ah, 150/70-13 rear tire) and they suggested a winding that would provide 95kph real-world top speed. So instead of a "fast wind" I have ordered a "moderate wind".

They started fabricating it today. Here's the receipt:


QSinvoice.1200.jpg
 
I also found QSmotor's customer service / pre-build info-intake to be very good. Responsive and well-informed.
 
Reviving this thread. Can anyone comment on their experience with QSmotor, in terms of general quality, reliability etc? Considering using them for an upcoming motorcycle project.
 
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