DAPU Rear Hub motor do not run.

[RikardLandi]

Hi,

I am new in this forum, but it really seem to be a great place to find information!

I´ve bought a used box-bike from a Swedish Company called Cargobike. I seller told me the battery was broken but otherwise everything should work.
I bought a new battery to the bike, but unfortunately the motor does not run. :-(

It has a DAPU controller, Display and DAPU rear hub motor (M123 RS) together with a PAS-sensor.

The display is working correctly, but is constantly showing 0,0 km/h independent of my speed.

I checked the PAS sensor because the magnet disc was a bit loose, but it seems to work OK. (+5V, GND supplied from Controller and signal from PAS is pulsing when pedaling , measured with volt-meter)
I checked the motor windings, which also seems to be OK, see below.

I disconnected the three feed cables from controller to the Hub motor.
- Turning wheel backward- Easy
Connected two of the motor-cables together
- Turning wheel backward - More Hard
Connected all three motor cables together
- Turning wheel backward - Harder

The motor is sensor less, means it has no Hall-sensors. It only have 3 feed lines + additional 3 small cables to the motor.
The additional 3 small cables to the motor seems to be +5V, GND and signal which I believe is a speed signal.
Measuring this speed signal (with volt meter), I could not see that it was toggeling. (constant 5V between GND to Speed signal)

I therefore believe that the problem is with the speed sensor inside the Hub Motor.
If the speed sensor does not provide any value, maybe the controller will not fire up the MOSFET¨s to the motor?

I now wonder how i could resolve this issue.
To disassemble the Hub motor seems difficult....

My current idea is to install a throttle to the controller. (It seems to have an option to do this)
Maybe with the throttle attached, the controller will not care about if there is any speed signal from the Hub motor and will fire anyway.
What do you think?

Regards
Rikard

 

[RikardLandi]

Update:

I temporarily bridged the speed sensor input (originally coming from Hub motor) with the PAS output and yes, now the speedo shows speed.
Unfortunatly the motor does still not turn. :-(

 

[Nealh]

Hi,



I disconnected the three feed cables from controller to the Hub motor.
- Turning wheel backward- Easy
Connected two of the motor-cables together
- Turning wheel backward - More Hard
Connected all three motor cables together
- Turning wheel backward - Harder

Regards
Rikard

It sounds like there may still be a short on the phase wiring, with and without the three phases connected the result should be similar and the wheel should rotate backwards with only slight resistance and a whirr as the internal gearing engages.
As you have easy wiring for diagnosis carry out a resistance test of the controller mosfets to rule out any failure.
Without any power on place Black probe to V- controller wire and then in turn Red probe to each motor phase wire, set ohms setting to dc 200. You should get three readings the pretty much the same (7 -15 ohms) if one is far out then a mosfet has failed. Also test the other side of the mosfet Red probe to V+ and black probe to the three phases, again readings should be the same but likely different you may just see a reading of 1 which is good, if a reading of 0 shows up then the mosfet has failed.
If any of the above reading differs then the controller is faulty.
If readings are fine then the issue is with the phase wiring to the motor and may be a short within the motor so look for any kinks or suspect wire damage esp as it enters the hub axle.

The hall sensor (speed) has failed or the feed wire is broken if 5v dosen't register on and off as you slowly rotate the wheel backwards.

 

[RikardLandi]

Hi Nealh,

I turned off battery power, unplugged the three phase wires to the motor and measured the phase wires by the Controller.

V- to:
Yellow: 116 KOhm
Blue: 116 KOhm
Green: Infinite

V+ to:
Yellow : 411 Ohm
Blue: 411 Ohm
Green 0,5 Ohm

Strange or?

I know it is not correct, but I also took a small external pwr supply and applied directly voltage on the three phase lines to the motor (without controller attached). The motor turns as it should so I believe the motor windings are ok.

 

[Nealh]

The controller phase readings aren't what I was expecting , the V+ reading on the green Green phase looks to be a failure meaning mosfet/s is bad.

When ever I carry out phase testing I get about 9 ohm's on the V- side & 1 on the V+ side.
I don't disconnect the motor phases and poke a probe down the bullet sheath.
Are you sure you measured using dc scale and not Ac ?

 

[RikardLandi]

The controller phase readings aren't what I was expecting , the V+ reading on the green Green phase looks to be a failure meaning mosfet/s is bad.

When ever I carry out phase testing I get about 9 ohm's on the V- side & 1 on the V+ side.
I don't disconnect the motor phases and poke a probe down the bullet sheath.
Are you sure you measured using dc scale and not Ac ?

I believe measuring resistance is the same in an AC-circuit as in an DC-circuit...but anyway I will double check on my volt-meter. I would assume that maybe the result is also different if you have the motor phases connected to the motor. I can try that again.

But as you say, since the green line differs so much from the other two, I also think there is a MOSFET problem in the controller. I will buy a new one and afterwards post the result here. Thanks again

 

[Nealh]

If motor phase is sound then the results connected or not will be the same.

 

[RikardLandi]

I just wanted to give a feedback, that my new controller (ordered from China) together with a new Display was received and installed. The motor is now running smoothly both with GAS (Throttle) and PAS (Pedal Assist)

I think even the performance is now better than before because I can now also disable the speed limit, I can make the motor go reverse and some other nice features.

My next project will be to install some nice headlights / rearligths and horn on the bike which you can switch on and off from the handlebar.

Thanks for the help on this issue.

Regards
Rikard

 

[Nealh]

Pleased you are back up and running, the controller resistance test is a simple one to undertake to find any erroneous reading, testing does help to save wasting money some times.

 

[badaboum]

Hello

New to the forum.

I am in Paris and owe a cargo bike with DAPU M123 front engine.

I did a simple tyre change today (bike was running great yesterday) had to unplug the front motor and now front engine is not turning and the display is very dim...

Any idea what could have happened?

Battery has 41V on it.
I can see the speed on the display (coming i guess from the pedal sensor)

Controller is hidden within the cargo bay for the battery so quite a pain to remove...

Thanks

 

[Nealh]

Have you double checked the multipin hub motor connection is pushed to and is fully home.
The two parts of the connector have an arrow to align correctly (as I expect you have seen) and there is a raised embossed line to which the male part of the connector push's up to, one should feel a slight click when it is pushed in far enough. It only needs 1 -2mm of not being fully pushed in to create a false /bad contact.
Aslo I see in the pic the motor wheel is upside down and the motor cable should ideally exit form underneath otherwise the way it is currently enables mositure/rain to run down the cable in to the hub motor, this eventually will rust and seize up the hub.

 

[badaboum]

Hello
Thanks for the swift response and advise. I will apply it

I have used silicone spray to make sure both connectors are in. I don't think I can get it much further. You can see the pic below.

The weird thing is that even when I unplug the motor, the display still behave strangly so I am assuming the controler or the display are somehow dead?

See the video below:

YOUTUBE
https://www.youtube.com/shorts/1dq2Qs87ZEQ?feature=share

 

[Nealh]

Yes it pretty much looks like it is fully home.
Did the spray get in to contact with the pins at all ?
If so then a false contact may be your issue with a thin film of silicone between the two metal surfaces.
It might be best to use a cotton wool bud and some and alcohol wash/isopropanol to clean the male pins, clean the female holes will be difficult.

 

[badaboum]

The silicone spray is made specifically for electrical contact (help the the connector in but avoid conductivity)

If there was a false contact within the front connector can this explain the situation? I though the front connector is only a 3 PIN getting the front whirring of the engine?

 

[Nealh]

Most modern hubs are sensored so are multi pin (x 9), Only you will know if yours is or isn't multi pin.
It is strange that the hub should stop working after a simple operation of disconnection unless of course a pin has been bent. I have never encountered an issue when disconnecting and reconnecting.

 

[badaboum]

Ok, so i dismantled the controler.

Turns out (beleive it or not) there is a short circuit on the PAS sensor. When I unplug the PAs sensor the display goes back to full brightness.

I am going to start by replacing the PAs sensor tonight and see if the problem stays. I have not been close to the PAS sensor during my tire change so quite funny

The cable coming from the M123 has 5 cables. I assume 3 for the 3 whirring and 2 for the hall sensor, right?

 

[Nealh]

What is the M123 ?

 

[badaboum]

Sorry,

It's the engine from DAPU

Dapu｜bicycle drive systems

www.dapumotors.com

 

[Nealh]

Hall sensor requires three wires and the motor needs three phase wires.

 

[badaboum]

Yes sorry you are right. I miss typed it. 6 = 3 + 3

I'll change the PAS sensor cable tonight and will update with I hope good news