Smart Pie with external controller growls and vibrates at low speed?

[Herkell]

I just set up a front smartpie with an external controller, and the motor vibrates the handlebars a lot at low speed. Beyond about 8mph it smooths out and works fine. It's a 26" wheel, so that translates to rpm of less than about 100.

I have another smartpie controller, and swapped it out - same issue. I've checked all connections - especially phase connections - and all seems good. I shorted each of the phase wires together, and the motor is difficult to spin with each combination - so I guess that means those wires are connected all the way through.

What do you think? Does the smartpie w/ external controller simply do this? Or is this a real issue?

Thanks!
Henry

[Bikemad]

Hi Henry,

The Smart Pie is quite noisy when loaded at slow speed and this is caused by the sudden magnetic pulses which take place between the stator and the magnets within the hub assembly.

When I first tested my Smart Pie, the internal controller was pre-set to 15 Amps continuous 45 Amps max from the factory and it was reasonably quiet, but with the controller reprogrammed to 30 Amps continuous 70 Amps max it suddenly became much noisier:

I was eager to see how powerful this motor was, so I decided to reprogram the controller for maximum Amps, to see how much difference it would make to the performance.
I noticed the additional assistance straight away, which was also accompanied by a much harsher  "growling" noise when the motor was working hard at slow speed, but this noise soon diminished as the speed began to rise.

Mine is a rear Smart Pie and on full current settings the vibrations resonate right through the frame causing different items to rattle at different frequencies (Mainly the pedals and the brake levers).

If you have the USB programming lead, it should become much quieter if you reduce the current setting, but you'll need to try it out and see how much difference it actually makes.

The Smart Pie is not very efficient at high current settings, so your range should also be greatly improved by reducing both the maximum and continuous current settings.

Alan
 

[Ron Burgundy]

I also have the Smart Pie. When you change these settings higher does that increase your max speed? Is there any chance you can damage anything by doing so?

[Bikemad]

Increasing the current will only affect the torque being produced at lower speeds and should not affect the top speed, as the current being drawn at full throttle will automatically reduce as the motor's speed increases.

Motors run very inefficiently when drawing high current at low rpm, and a large portion of the energy being supplied to the motor is simply converted into heat.
If an internal controller becomes too hot due to sustained high load at low speed, it will eventually cut out completely to prevent further heat being generated and will only start working again when the temperature of the controller drops back down to a safe level again.

I don't think you would damage anything by increasing the current of an internal controller, but I won't guarantee it.
However, with an external controller, there would be no temperature protection whatsoever for the motor, and I suspect that the insulation on the stator windings could be permanently damaged if the motor overheated due to being constantly overloaded.

If you want to increase your maximum speed (and the controller is already set for maximum rpm) you will need to upgrade to a higher voltage battery and a throttle control to match.
However, if you're already using a 48V battery, you would also need to use a higher voltage external controller as well. 

Alan