RadRover Bafang Motor Issues...

[Panama Vic]

I am seeing on other posts some issues with the Bafang 750 watt hub motors using Pedal Assist mode. People are saying, when in pedal assist and at a stop the bike wants to move forward without any cranking of pedals. Do rad rover owners have simular issues?

 

[Tars Tarkas]

Not me.

TT

 

[AHicks]

What you're seeing is common to many, if not most cadence PAS systems. MOST people prefer a minimum amount of pedal travel to get some power to the bike's motor. Not a lot, but a start. Having to turn the crank 2-3 turns previous to that happening is not a very desirable trait, especially if you don't have a throttle.

So, the way this is done is with a ring that has 6-12 magnets mounted in it fastened to the crank. There's also a sensor (PAS sensor) mounted to the frame, that tells the controller when these magnets are moving past it. When the magnets are moving past the sensor, the controller supplies power to the motor. Stop pedaling, the magnets are no longer moving past the sensor, and the controller stops supplying power to the motor. Easy, right?

Now, to your question. What's going on is that occasionally, one of those magnets moves past the PAS sensor (because the rider bumped a pedal just right for instance), the PAS sensor reports that motion to the controller, and the controller gives the motor a LITTLE bit of power, which the rider did not expect - and it's not hard to imagine the rider might be a little startled. The bike will lurch noticeably, but nothing that might be dangerous. Just one magnet moved past the sensor, then it stopped. The controller responds to that motion and supplies a little shot of power to the motor - just enough to get your attention if you aren't expecting it.

There's nothing wrong here. Everything is working as designed, and nearly any brand bike or motor that's using cadence based PAS will do this. -Al

 

[EBJ]

If an e-bike is applying power to the motor based on a single errant sensor count, then something is broken or some component manufacturers logic implementation is terrible.

On a Rad, with the bike turned on in any PAS Mode, you can spin the pedals backwards until you're blue in the face and nothing will happen. You can also raise the rear wheel and turn the crank forward very slowly and nothing will happen. If you slowly increase the crank speed, at some point the controller will apply power to the motor.

Therefore it would appear to be safe to assume that there are several individual and sequential Hall Effect sensors in the PAS sensor assembly to be able to determine direction of rotation and provide input for the controller to make an educated guess as to whether any sensed rotation is purposeful or just a random blip (to be ignored).

If you want to align your pedals at a stoplight for takeoff, if you do so by turning them backward with the brakes on you'll be fine. On the other hand, if you attempt to align them by letting the bike drift forward while putting pressure on them you'd better do it VERY slowly or you might get a blip of power that could move you forward a few inches. Could this surprise someone to the point they panicked and jammed a pedal down or rolled on the throttle, propelling them into an intersection, maybe...

 

[Gordon71]

I have a 2020 Rover step through and have never had that happen.

 

[AHicks]

If an e-bike is applying power to the motor based on a single errant sensor count, then something is broken or some component manufacturers logic implementation is terrible.

On a Rad, with the bike turned on in any PAS Mode, you can spin the pedals backwards until you're blue in the face and nothing will happen. You can also raise the rear wheel and turn the crank forward very slowly and nothing will happen. If you slowly increase the crank speed, at some point the controller will apply power to the motor.

Therefore it would appear to be safe to assume that there are several individual and sequential Hall Effect sensors in the PAS sensor assembly to be able to determine direction of rotation and provide input for the controller to make an educated guess as to whether any sensed rotation is purposeful or just a random blip (to be ignored).

If you want to align your pedals at a stoplight for takeoff, if you do so by turning them backward with the brakes on you'll be fine. On the other hand, if you attempt to align them by letting the bike drift forward while putting pressure on them you'd better do it VERY slowly or you might get a blip of power that could move you forward a few inches. Could this surprise someone to the point they panicked and jammed a pedal down or rolled on the throttle, propelling them into an intersection, maybe...

Turning the pedal/crank backwards will have no effect on ANY PAS sensor. They're designed to function in the forward direction only.

Never tried seeing if I could sneak a magnet past a sensor undetected. That might be true...

" If an e-bike is applying power to the motor based on a single errant sensor count, then something is broken or some component manufacturers logic implementation is terrible. "

Here's something else to consider. When you get further into this, you'll see that magnet rings with 6 magnets are popular, as well as those with 12. I've always preferred those with 12 as the crank won't have to turn as far to get a magnet past the sensor and get power to my motor. Over the last couple of years, I have experienced this "errant sensor count" causing the bike to surge maybe twice. If that were of any concern to me (not!), I might be tempted to seek out a bike with a 6 magnet sensor ring, knowing that it will need to travel a little further (depending on where it was parked) to provide that same signal.

Point being, I wondered why somebody might choose a 6 magnet ring over a 12. That could very easily explain it. My thought anyway, FWIW. -Al

 

[PortPerryBob]

I am seeing on other posts some issues with the Bafang 750 watt hub motors using Pedal Assist mode. People are saying, when in pedal assist and at a stop the bike wants to move forward without any cranking of pedals. Do rad rover owners have simular issues?

Hello, there is a fellow who does a lot of videos of his rides on his RadPower bikes, (he has three of them). In one of his videos he deals with a problem which he calls "ghost throttling" and it has to do with an error message that appears on his display screen. In the video he demonstrates how the bike jumps ahead on its own and how he fixes the issue. It is a simple fix and just involves replacing the throttle cable. The issue appears in the first three minutes of the video which you can view here.

Hope this helps.