Controller actively brakes when wheel speed goes over different RPM limits

[randunel]

I have an ebike with pedals, a rear hub motor and an 8 speed cassette.

I replaced the controller with this kit BuyWeek Elektrofahrrad Brushless Motor Controller Kit, 36V 48V 250W 350W 17A 3 Modus Sinuswelle Controller T5S LCD Display Meter 130X Daumengas Kit für E-Bike Elektroroller : Amazon.de: Sport & Freizeit. I kept the original motor, which is a Jinhua Vision Industry https://www.decathlon.de/p/vision-motor/336228/c1m8668416, while the original controller was rated 20A 48v.

This new controller is 17A 48v with OMD2 over UART protocol (JN compatible). I have configured it with multiple possible speed limits, lower and higher, including the highest possible setting during tests.

The controller applies motor braking when the motor's RPM exceeds some constant limits. This is not a speed limit, but a RPM limit, because the speed limit for motor braking varies in accordance with different wheel dimensions, but the RPM appears to stay the same.

For example, with a 20" wheel setting, the limits are:

Level 1 - 16km/h
Level 2 - 22km/h
Level 3 - 26km/h
Level 4 - 32km/h
Level 5 - unknown

When going 25km/h (level 2), when I lower the assistance level to 1, the controller uses the motor to brake pretty hard until the speed reaches 16km/h. If I change the assistance level to 0, the controller does NOT brake at all, so I can pedal faster, as fast as I can go.

Setting the controller's speed limit to 0km/h results in the controller always actively braking the motor. Setting the controller's speed limit to 100km/h results in the controller applying varying speed limits depending on the selected level as above.

Is there a way to deactivate the controller's motor brake behaviour? I could not find such a setting in the menu.

 

[stancecoke]

Is there a way to deactivate the controller's motor brake behaviour? I could not find such a setting in the menu.

no, this is a very basic controller, that simply sets a fixed duty cycle per assist level. With a direct drive, this leads to the behaviour, you are describing. With a standard geared motor with a freewheel, this behavior doesn't matter, as the wheel can spin faster than the motor due to the freewheel.
You will have to buy a controller that is suitable for a direct drive.

 

[randunel]

What keywords should the non-direct-drive controller have? I can't even find "direct drive" controllers on amazon or other websites. Is there a name or some specs I need to look for to not get the wrong one again?

 

[stancecoke]

Is there a name or some specs I need to look for to not get the wrong one again?

These "Brainpower" style controllers you have bought are a mystery—you never know what firmware they have installed or exactly how they'll behave.
You can search for the keyword "regen". The cheapest choice will be a Kunteng, there you will know what you get. The Kunteng controlles can be set to "torque simulation", so they don't just set a constant duty cycle, but control the battery current. So they won't brake at a certain speed, but just adjust the duty cycle to get the wanted battery current. They can do very basic regen, too.
Of course there are much better controllers available, the Kuntengs are quite outdated and can't do FOC. In my opinion, Lishui controllers offer the best value for the money.

 

[AdR]

@stancecoke -Where can I buy a lishui controller that does regen and FOC. The lishui website don't seen to sell to individuals. I don't understand their naming convention. Thx.

 

[stancecoke]

Where can I buy a lishui controller that does regen and FOC.

Lishui sells to OEMs mainly, but you can find them on AliBaba or AliExpress or at some Conversion Specialist shops like EBS Heidelberg also.
Buying at Ali is some kind of Roulette, as Lishui taylors the firmware to the customers demands and you will not know, how it is configured.
As I always use the open source firmware, the original firmware doesn't matter for me

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[morningsun]

That sounds like the controller firmware is enforcing an RPM limit for each assist level , rather than a normal configurable speed limit. Since level 0 lets wheel freewheel normally, motor itself probably isn't the issue.