Smallest controller available for a Q100 hub motor ?

Hello,
I'm looking for the smallest possible controller for a Q100C CST hub motor, 36V and 10A max.
I would like it to be less than 40mm in width/height (lenght doesn't matter).
Any advices ?
Thanks !

All the low power 6-FET controllers are about the same size(the size of a pack of cigarettes). Since you will be going so slow, I am assuming you will be using PAS(Pedal Assist Sensor)and the important question you need to ask is what type of pedal assist do you want. A sine wave with it's LCD display with it 5-speed "Torque Imitation" system or a more simple and stealthy square wave unit with LED display. At low speeds, it's likely the 3-speed square wave would offer enough flexibility.

Thanks momotech for this quick reply

Yes I will use PAS.

I don't know the difference bewteen 5-speed "torque imitation" and the standard controller.
I want to make a very light bike with a smooth assist up to the legal speed and power in Europe which are 25km/h (16 mph) and 250W.
Which one do I need ?

Sorry for the other "question for dummies", what does mean 6-FET ?

Do you know where I could find such controllers with max section of 40x40mm ?

I would just start looking at controllers on ebay. The low wattage ones are fairly small, but finding them much smaller is not likely, until you start looking at RC hobby type controllers, which tend to fail when hooked up to lower rpm hub motors.

Even the more medium size 6 fet controllers are easily mounted on bikes, small enough to hang or mount right under the back of the seat on almost any bike, with no problems at all. Good place, in the rain your ass keeps it dry as long as you have some kind of fender.

I'm curious why it has to be extremely small. There are controllers that are long and slim, that mount great on the seat post, or the other two bars on the frame. The one I know where to get it is 750w though, at E-Bikekit.com It comes with a display that can easily limit your power. But it might not be strictly legal, since you can also easily enable the full 750w.

dogman dan said:

I'm curious why it has to be extremely small.

Click to expand...

I'm guessing he wants to stuff it inside the bike frame somewhere.

Grin Technologies Phaserunner has a 34x40mm cross-section.

Note that if you go cutting holes in an existing bike frame, there will be stress concentrations and rapid structural failure. Bike frames are well optimized and don't usually have pieces that aren't required.

Thanks guys, it helps

You should be looking at a KT sine wave 6 FET controller with LCD (LCD often has to be bought separately). They're about the smallest normal controllers you can get and best for PAS. Don't get a cheap Ebay one because they usually have terrible PAS functions.

You can get one from BMSbattery, listed as the S06S or equivalents from PSWpower or Aliexpress. It's always best to get everything from one supplier if you can to kep shipping costs down.

Install the controller in an under the saddle tool bag, like show in the photo in your other thread.

Thanks