Help! Bike is always on full throttle after changing motor

[elishia]

Hi folks!

I had issues with my previous e-bike motor (dgw07-20j) and bought a new one to replace it. I think the only difference is that the old motor is 36V 250W and the new one is 36V 350W. The new motor Seems the same for me (Dgw07-md) and what I did was open both motors, take off the main part, and put the new one in the older 'shell' - so no connections need to be made again, I don't have to redo my bike rim spokes to the new motor shell.

All good? All good. The new motor fitted perfectly, motor plug fitted perfectly with the same number of pins, so let's go and ride.

Then the issue happened: The new motor works but is always on full throttle. I turn it on, start to pedal, and then it is like I am on a motorcycle. I have a basic display, with pretty simple 3 buttons: On/off, change speed (low, medium, high), and assist mode, which makes the wheel turn alone without pedaling (like when I am out of the bike and need an extra hand to push it).

If the display is turned off, the motor is also off - this is working normally
If the display is turned on, and I don't select any speed in the control, the motor is still off - this is working normally
If I turn on the assist mode, the motor turns on and the wheel turns without pedaling - this is working normally
If I select any - low, medium, or high speed and start pedaling, the motor turns on and works at full (high) speed. If I change the speed, nothing happens.

If I stop pedalling the motor stops. Also, it stops when I hit the brakes. So this also works as it was supposed to.

My bike is a White Velocity Energy Boost, rear wheel motor.

I would really appreciate if you have any idea on how to fix it.

Cheers
Tati

 

[Sturmey]

A quick and wild guess/possibility but I am not familiar with that motor, is that there is some problem/difference with speed sensor wire or magnet (should be fourth hall sensor /usually one magnet fitted to sidecover?)

 

[saneagle]

Changing the motor can't change the way the control system works. If you didn't change anything else, then, as said, the only possibility is that the controller is using the speed sensor in the motor to get the speed, your old one had 6 magnets in the hub and the new one has one magnet. The only way to be sure would be to either measure the pulses on the white wire in the motor cable or take the side-plate off the motor to see how many magnets are in it.

Normally, I'd be surprised if that were the issue because I didn't think controllers with those dumb LED control panels used the speed sensor. Instead, they get the speed from the commutation pulses.

 

[elishia]

Hi guys, thanks for your comments. I don't have a hub tester, so for now I think I'll just open the front hub side so I can check the connections.

In my case, I think the white wire was never connected (or at least seems to be like this by how the conector ir placed) and I had only the black/red/green/yellow/blue (thin cables) plus the 3 green/yellow/blue hall power cables connected to the controller coming from the motor cable.

The previous motor had 3 hall sensors placed near the motor magnets + one in the internal motor PCB.

Well, I'll open it and check if I can see anything different. Maybe this one needs the white one connected, so I'll also check if I can plug it somewhere

 

[saneagle]

Hi guys, thanks for your comments. I don't have a hub tester, so for now I think I'll just open the front hub side so I can check the connections.

In my case, I think the white wire was never connected (or at least seems to be like this by how the conector ir placed) and I had only the black/red/green/yellow/blue (thin cables) plus the 3 green/yellow/blue hall power cables connected to the controller coming from the motor cable.

The previous motor had 3 hall sensors placed near the motor magnets + one in the internal motor PCB.

Well, I'll open it and check if I can see anything different. Maybe this one needs the white one connected, so I'll also check if I can plug it somewhere

If you can see the wires at the controller end, you don't need to open the motor. There is nothing in there that will help you other than counting the magnets on the side-plate, but that's quite difficult to get to for your motor. Instead, put a voltmeter on the white and black wires and count the number of 5v or zero volt pulses it gives for one rotation of the wheel. Depending on your controller and the hall sensor, the voltage will be 5v and dip down to zero when a magnet passes, or it'll be zero volts and jump up to 5v when the magnet passes.

You then need to compare that with your other motor. In fact, if you have the old motor disassembled, all you need to do is count the magnets on the side-plate. If it has 6, it's almost certain that's what is giving the problem.

Alternatively, you could solve your problem by getting a controller with an LCD.

 

[Ajax]

if it has a throttle, or pedal sensor acting like a throttle, you should have a least 3 lines. A ground, a VCC power, and a sensor. It could be the vcc and the sensor are swapped.

 

[thelarkbox]

Then the issue happened: The new motor works but is always on full throttle. I turn it on, start to pedal, and then it is like I am on a motorcycle. I have a basic display, with pretty simple 3 buttons: On/off, change speed (low, medium, high), and assist mode, which makes the wheel turn alone without pedaling (like when I am out of the bike and need an extra hand to push it).

Fyi My bike also accelerates at full speed regardless of the pas level selected from a standstill when i start to pedal, the difference between the modes is the speed at which the assistance cuts out, at the highest level the assistance cuts out when 15.5mph is reached and at slower speeds for lower levels. But the power delivery upto the cut off speed is full pelt, thats just how it works..

Perhaps your old motor was geared differently delivering less initial torque so the power delivery was less pronounced??

Or is your bike responding differently are you hitting speeds of 15mph with assistance with pas level 1 selected??

 

[elishia]

Hi folks!
After some time I finally had time to open it all and check for your advice. And today, I took some pics
As far as I can see, connections are the same. Both hubs have just one magnet, the new hub uses the same PCB as the old one and the connections are in the very same place.

The new motor arrived with its own cable (the one we connect to the controller) and just in case some pins had a different color cable, I did a test connecting the new cable to the controller. The same behavior happened, the motor went full speed, no matter the speed selection.

Then, something that saneagle said comes to my mind, and well.. my old motor was a 36v 250w. The new motor is a 36v 350w. I took the controller off the bike to check and my current controller is a 36v 250w.

So, before I spend more money on a new controller.... could it be that my controller is not handling the new motor power?

Some pics:
pic 1 - the old motor opened - I did not full open the new one because for that I need to remove the cassette and the small motor holder which is a pain to remove and put back again. So I just opened the new one and lifted it until the mentioned holder, was enough to see it internally and the magnet. PCB is the same, including components.

pic 2 - The lid magnet from the old motor - 6 holes, 1 magnet in place, same as the new motor.

pic 3 - Controller connections - All other connected cables but the motor. No swapped or twisted cables here. The yellow disconnected cable has been like this since I opened it and doesn't seem to be connected anywhere.

pic 4 - motor connections - Also everything seems to be ok. 5 cables are connected, but the white one seems to be disconnected purposely.

pic 5 - controller - The controller itself (the name could be a pun but is not). As you can see, 36v 250v.

BIG thanks!! I am a total newbie in this stuff and your advices helped a lot <3

 

[saneagle]

It's very significant that the white was isn’t connected because it carries the speed signal. That wire needs to be connected to the controller's speed signal input for the controller to know how fast you're going. Without a speed sensor input, the controller gets the motor's speed from the hall sensors. If I were you, I'd chuck that crappy controller and get a decent one with an LCD.

The motor's being 250w and 350w means nothing. They don't give or have that power. It's just a number stamped on the casing. It's the controller that decides how much power is given to them. Any normal motor will work with any normal controller.