# Help needed - powerful scooter, little low end torque



## Ziggythewiz (May 16, 2010)

Does it have any gears? It sounds like it is just geared for higher speed, which means the low end would suck. That's the same behaviour I would see in my bug if I started out in 4th gear, instead of 2nd like I do.


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## alfbo (Sep 2, 2012)

Ziggythewiz said:


> Does it have any gears? It sounds like it is just geared for higher speed, which means the low end would suck. That's the same behaviour I would see in my bug if I started out in 4th gear, instead of 2nd like I do.


I do not think it has any gears. The motor is a hub motor (which I unfortunately do not know anything about except it is supposed to be 8kW) and aren't those usually direct drive? 

But thanks for the suggestion - I have been thinking along those lines myself. However, the new scooter has a vastly inferior low end compared to a lead battery 3kW scooter that was only slightly lighter. That scooter had a top speed of about 50 km/h. I am thinking that with a properly dimensioned 8kW motor/battery/controller I should not get a terrible low end even with the higher top speed of 100+ km/h. If I read the Kelly controller settings correctly, max motor current is set to 60% which I understand should be 300A which sounds like a lot of current to me, but I guess I am missing something...


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## alfbo (Sep 2, 2012)

I tried adjusting the controller max motor current setting from 60% (300A) to 90% (450A) and that made a MAJOR difference in low end torque. I have not noticed any adverse side effects so far but I would think the original setting was 300A for a reason. This leads to three new questions:

What is the short term and long term effect of supplying too much current to an electric motor?
(My understanding is that heat buildup is the primary concern and that this in turn is affected by the duration of applying high currents, heat dissipation capability and ambient temperature)
Is it reasonable to assume that an 8kW motor will sustain currents of 450A for short durations (ie 10 seconds)?
Is it likely that the Kelly controller will supply close to 450A given a software setting of 450A?
(I seem to recall that someone mentioned that actual current was a lot less than the nominal capacity of the controller and with 450A on a 500A controller, this effect may come into play. Reading/measuring the actual motor current is not that trivial since I would have to break up existing cabling which again would require some disassembling of the scooter)
Thanks in advance for any input you may have.


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## dutchlincoln (May 6, 2012)

Hi,
I'm almost sure it's all in the settings, even though i havn't looked at them.
Do you have the regulation on torque mode?

Current setting is a factor of the controller capability, not the motor. i.e. a 400A controller set to 50% will output 200A...(max. Regardless of the connected motor.

How does the motor eventually work?
I have a Escooter with 1500W motor and a big kelly controller, but it lacks power. It is faster as most 50cc mopeds however...
So, i ordered this exact 8Kw motor for it. Not to have it run at 100km/h, but to have bulks of whoppy torque  (thats more fun 

Let me know.
I may even be interested in the motor, in case you would like to sell it.

thanks.


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## alfbo (Sep 2, 2012)

Thanks for your input. 

I do have the controller set for torque mode and as mentioned I have experienced a major increase in torque by upping the motor current setting. The scooter works fine now, but I am a bit concerned about the consequences for the motor considering the major increase in the controller current setting. I have not seen any adverse side effects related to the motor so far but I am using some caution and common sense. I have noticed that the controller cuts the power for a second or two when applying full power at 30-40 km/h. I guess it represents some kind of overload condition, but am uncertain why it should happen as I was under the impression that the controller would limit motor and battery current rather than cutting the power.

Btw, I am not interested in selling the motor as it is a rather important component of my scooter .


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## electro wrks (Mar 5, 2012)

The cutting-out is probable the low voltage cut-off (step 2 in the Kelly config.) trying to protect the batteries. You could try to adjust it lower, but try to keep it above the per cell min. as recommended by the batt. manufacturer.

Unfortunately, the parts that overheat are deep inside most hub motors and the heat has a long way to go to dissipate out. By the time you could feel the excess heat on the outside of the motor, it might already be cooked. Your motor probable has a temp sensor tied to a controller cut-off or power reduction. Make sure it works. Maybe add a temp. gauge, if it doesn't have one.

Even at 8kw, your scooter still only has the power equivalent of ~ a 125cc gas bike. You wouldn't expect a 125cc bike to have the performance of a more powerful bike. Likewise your bike.


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## alfbo (Sep 2, 2012)

I doubt that the cutting-out is due to the low voltage cut-off. The volt meter indicates only a moderate voltage drop when the cut-off occurs. I have a no load voltage of around 80V and at the time of the cut-off the voltage is in the low to mid 70s. If accelerating a bit more carefully and then applying full throttle, I will see the voltage drop to high 60s and no cut-off occurs. I do have a BMS and perhaps a single battery experiences a temporary low voltage and signals this condition to the controller. I will try to get hold of the wiring schematics to get a better understanding of the setup and also check with Kelly.

As for overheating the motor, I am sure you are right. The controller settings show that a temperature sensor is in use, but I have not confirmed that it works correctly. I am not applying full throttle at low speeds for more than a couple of seconds and I would think that this together with low ambient temperatures makes overheating less probable. No problems experienced so far after about 1000 km running on this elevated motor current setting.


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