First build advise (450 equivalent power)

[222built]

Over the past couple months I’ve done countless hours of reading and research to build my first electric bike.

I've been a licensed electrician for 14 years and a few years ago to opened my own metal fabrication business. So I can’t think of anything more in my wheelhouse than fabricating an electric bike.

I grew up racing motocross and have recently gotten into flat track. I had been racing the 450pro and openpro at the local ice races.

I want to build a bike that’s equivalent or possibly a little faster than a 450 so I can run the e bike in the open class.

I'm looking for advice on a setup. I’ve asked on many FB pages and it seems to be alot of false information on there. I think alot of people have built respectably fast bikes but don’t realize how much faster a 450 is compared to there e bike.

Starting with a motor. It seems like the more research I do the more curve balls get thrown my way.

Originally I was looking at motenergy me1507. I believe there a replacement for zero motor 75-7. Which I have seen perform very well. When I mention this motor in FB groups everyone tells me to too big and heavy and point me in the QS138 direction.
According to the rating of the qs138 it’s no where near as capable as the me1507 but everyone says you can push past the ratings of the qs138 but what’s the limit?
Then there’s the qs165 with gear reduction. I only need the bike to go between 50-60 so a gear reduction would be great but then again the qs165 rating is still very low. How far can you push them?
Then there’s the qs180?
After all that there a shwin motor that’s been proven to make power.
Also see some people mentioning a golden hyper torque?
Man I’m lost. Any help would be greatly appreciated. I think I’m leaning towards the gear reduction qs165v3. is it possible to push up to or past 40kw does anyone know?

 

[dominik h]

QS advertises constant power, minimum for 1 hour or even more.
Their peak power ratings are also very conservative.
There is no real limit for peak power, the limit is only efficiency and heat.
The more power you put in the motor the lower the efficiency will be and the more heat will be generated.
Probably a QS138 can give you 35kW , but efficieny will be around 75-80% , so you will heat your motor with 7-10kW. How long does it take to get the windings to 150C?

There are currently no builds with a QS165 with gear reduction here on ES.
I was also thinking of ordering one, but I want +40kw for a motorcycle, and I'm not shure the QS165 can do this.

The golden motor hyper tourque is a different concept, as it doesn't need an extra gear reduction, probaly it can also give much more power than advertised, but no one knows that for shure.

 

[222built]

With the qs165 v3 having a much higher power rating then the qs138 90h. would it be say to assume that the 165 can handle more power than the 138??

 

[dominik h]

If I read read your datasheet from the QS165 correct, it says long time operation at 10kW and 20kW for less than a minute.
So maybe 40kW for 10 seconds will be ok, but I would go for a higher battery voltage than 72V nominal, to be shure to get the needed peak power from the motor.
The QS165 is heavier, has bigger phase wires (30mm²) has higher continious power rating, so it should also generate higher peak power levels. But only the manufacturer knows exactly how the engine is built and which peak power levels the motor and the reduction gears can survive.

 

[E-HP]

How much battery is needed to make it through a race?

 

[222built]

How much battery is needed to make it through a race?

It’s only about 10 laps. Twice a day with plenty of time to charge between races.
I’m still learning how all this works but from my understanding I’m more concerned with a higher voltage and higher max amp discharge rather than amp hours. So I think I would build a battery from cells like jp40 or p45b?

 

[j bjork]

Here is some info I picked up from someone at facebook who actually dynoed a qs 138 90h:

• 
  It seems the 90h starts saturating at 800A, but still gives pretty good extra torque at 900A, and higher voltage should help with extra rpm :
  
  QS 138 90h V3 - verification of parameters and limits
  
  
  
  I have prepared some facts regarding this motor, based on laboratory measurements on the motor dynamometer and several years of experience working with it. The most important information to consider when designing your motorcycle:
  • The maximum power at the motor shaft that I achieved is 40HP.
  The supply voltage under load at this maximum power is 87.6V - a highly efficient li-ion source 24s, measured at the controller terminals.
  It is IMPOSSIBLE to achieve greater power at the motor output based on a pack with a nominal voltage of 72V (20s), regardless of the controller used.
  I achieved this power with a maximum efficiency of 86%, resulting in a source power of 34kW.
  • The maximum phase current during tests is 460ARMS (800A), allowing for a maximum torque of 80Nm.
  This is the recommended current limit; higher current significantly changes the value of the torque constant Kt [Nm/A], and additional current has little effect on torque increase (600Arms generates 100Nm).
  • The rotational speed for this maximum power is 5010rpm, much higher than the rated speed of the motor.
  Increasing losses start to have a greater impact on total losses, particularly losses related to the frequency of stator magnetization (eddy current losses and hysteresis losses). Powering the motor above 24s (100.8V) is economically unjustifiable; the power losses alone amount to several hundred watts converted into heat.
  • The continuous power of this motor is 8kW at an ambient temperature of 20°C.
  This value is much lower than the peak value of maximum power lasting a few seconds, due to the effectiveness of heat exchange with the surroundings. Depending on the application and the average load value, controller settings should be adjusted accordingly.
  
  Best regards
  
  

 

[j bjork]

I picked it up from this thread, I am not sure if I posted it elsewhere:

Best controller for QS138 V3 70

If 150 battery amps were a limit for the motor .. why not 1500 amps at 10% duty cycle? For an oversimplification, you're not entirely wrong. This is why motors (and batteries) often have continuous power ratings as well as peak power ratings; my 8000w rated hub motor can output 14,000-16000w...

endless-sphere.com

So I think 450 power or more can be difficult on a qs 138, but maybe possible at higher voltage.
3 shul has a controller that can do 1000pA and something like 170V, the cc1000. Something like that would probably be my best guess how to get the most out of a qs 138.
It will be hard to get good gearing, and it would probably overheat pretty fast if you ride it hard.

A problem with going for big motors like zforce 75-7, qs 180 90h etc. is the weight and that it takes up room that you would need for the battery.
You seem to have thought it over pretty well, but a common mistake is that people get a big motor that can put out a lot of power.
Then they need a controller, so the go for something mid powered.
They also need a battery, things already has gotten expensive so they go for a cheap Chinese one..

The result it that the controller cant deliver the phase amps to get max torque, and the battery cant deliver the amps to get the power the motor can deliver. They would have gotten better results with a smaller motor and a better battery.

 

[SlowCo]

The answer is: Stark Varg

Bit of an odd idea: use a 25-50kW scooter racing hub motor as a mid drive:50kW motor
Done sometimes in DIY ebike frames. Build a steel swing arm with that motor in/on it just in front of the rear tire. Put the pivot point to the frame just behind the hub motor axle. So the motor will move with the swing arm. Put Statorade in de motor for cooling and use a custom sprocket on the disk brake flange (reinforce or custom mill side plate). Run between a 1:1.5 to 1:2 gear ratio for correct max speed needed.

 

[222built]

The answer is: Stark Varg

Bit of an odd idea: use a 25-50kW scooter racing hub motor as a mid drive:50kW motor
Done sometimes in DIY ebike frames. Build a steel swing arm with that motor in/on it just in front of the rear tire. Put the pivot point to the frame just behind the hub motor axle. So the motor will move with the swing arm. Put Statorade in de motor for cooling and use a custom sprocket on the disk brake flange (reinforce or custom mill side plate). Run between a 1:1.5 to 1:2 gear ratio for correct max speed needed.

That is an odd idea. lol

 

[E-HP]

Would 28s be too much voltage on a 72v motor?

Motors aren’t rated for voltage. The motor will spin 40% faster than at 20s. Provided you can supply the current, torque increases across the rpm range as well.

 

[j bjork]

28s can be a good choice, there are some controllers to choose from in that voltage range.
I wouldn't go lower than that, maybe higher to be able to get more rpm and power out of the motors.
But it gets harder to find controllers. 3shul has their CL1400 that will take 126V (30s) or as I said before the CC1000. I dont really know of much else, maybe some kellys. But I am not sure they are a very good choice.

Motor ratings seem to be more or less made up. For example qs has their 165 35h that is rated 5kw, and is proven to be a lot less capable than the 138 70h rated at 3kw..
But I think you are right to go for something bigger than a 138 90h if you want at least 450 power for more than a few minutes.
(I have no personal experience running those motors at those powers though, maybe they can take it for a while, maybe they overheat in seconds)
Sotion has some interesting motors, but not as much tested as some of the qs motors. There is one that is called gtx 35 or something that could probably be interesting.