Hub motor swap from Bafang to MXUS

[Binlo]

Hi All, Im new on this forum and new to the ebike world, but after doing 140 miles on my new bike looks like I have messed up my motor (Bafang 250w 36v). I was carrying my 10 year old son (27KG) on the back Pannier rack with a seat cushion I got off Amazon. We were having so much fun, that I think we over loaded the motor goign up on some small inclines etc.

The motor now just cuts out like after a few mins riding, or just seems to spin up and suck up current .. and on the display it come up MF intermittently (motor fault). Shutting it down for 10mins, gets it going again and is unable to climb any sort of incline , it is just a hit and miss now so I think I have over heated my motor or burnt it out.

Good news is that I managed to pick up another motor on ebay brand new MXUS XF15R one with the rim and tyre. So it is now just a matter of swapping it out!

The question I have is the 9pin motor wire just plug and play or do I need to mess around with the wires to get it to work. It looks like it just plugs in but I dont want to damage this new motor

Also any one know if I can fix this Bafang motor and have a spare wheel hub available ???

So any help on this would be appreciated, I have tried to provide as many pics as possible.

Thank so much in advance!

 

[vfr400]

Good news is that I managed to pick up another motor on ebay brand new MXUS XF15R one with the rim and tyre. So it is now just a matter of swapping it out!

The bad news is that you've probably ordered the wrong part. Motors are extremely robust and rarely give problems, especially considering what you've described. More likely, you've blown a mosfet or two in the controller.

Testing the controller is very straight-forward using a digital multi-meter. set it to measure resistance in the right range. Withe the controller completely disconnected, measure between the black battery wire and each of the blue, yellow and green main motor wires, then repeat between the red battery wire and each of the three motor wires. You should get three results round 7K ohms and three around 14K. the exact value isn't important, but each set of three should be the same as each other.

Your problem could be as simple as the 9-pin motor connector not in all the way to the marked line. Did you check that?

 

[Binlo]

The bad news is that you've probably ordered the wrong part. Motors are extremely robust and rarely give problems, especially considering what you've described. More likely, you've blown a mosfet or two in the controller.

Testing the controller is very straight-forward using a digital multi-meter. set it to measure resistance in the right range. Withe the controller completely disconnected, measure between the black battery wire and each of the blue, yellow and green main motor wires, then repeat between the red battery wire and each of the three motor wires. You should get three results round 7K ohms and three around 14K. the exact value isn't important, but each set of three should be the same as each other.

Your problem could be as simple as the 9-pin motor connector not in all the way to the marked line. Did you check that?

Hi, thanks so much for your advice and feedback. My initial gut feeling was the controller, I wish I posted first on here before getting the wheel. Anyways I now have a spare wheel with hub motor at hand.

I definitely checked the pins for the motor wire, both ends are firmly pushed in. I do have this ebike tester available once I work out how to use it, would that do the same job as your suggested test, or I need to use the multimeter.

If I do not get the readings you stated then does that mean I need to buy a new controller and any recommended ones for this sort of setup?

Thanks for all your help, really appreciated.

 

[vfr400]

Hi, thanks so much for your advice and feedback. My initial gut feeling was the controller, I wish I posted first on here before getting the wheel. Anyways I now have a spare wheel with hub motor at hand.

I definitely checked the pins for the motor wire, both ends are firmly pushed in. I do have this ebike tester available once I work out how to use it, would that do the same job as your suggested test, or I need to use the multimeter.

If I do not get the readings you stated then does that mean I need to buy a new controller and any recommended ones for this sort of setup?

Thanks for all your help, really appreciated.

I doubt that you'll be able to use that tester without going to a lot of trouble, and even if you can, it doesn't test the mosfets in the right way. Just do the tests that I detailed above and you will get your answer quickly.

Maybe time to build your own super ebike with the MXUS motor. I'd not seen that one before, but it looks pretty good. Does it have the cassette spline or the freewheel threaded boss? Has it got any markings on it?

To answer you question, it should be plug and play, but don't expect any more power. The power is determined by the controller and supplied by the battery.

Edit: I just checked a couple of listings, which showed it as 340 rpm at 36v, which might be too fast for your 15 amp 36v controller unless you're not very heavy.

 

[Binlo]

I doubt that you'll be able to use that tester without going to a lot of trouble, and even if you can, it doesn't test the mosfets in the right way. Just do the tests that I detailed above and you will get your answer quickly.

Maybe time to build your own super ebike with the MXUS motor. I'd not seen that one before, but it looks pretty good. Does it have the cassette spline or the freewheel threaded boss? Has it got any markings on it?

To answer you question, it should be plug and play, but don't expect any more power. The power is determined by the controller and supplied by the battery.

Edit: I just checked a couple of listings, which showed it as 340 rpm at 36v, which might be too fast for your 15 amp 36v controller unless you're not very heavy.

Im not that heavy,just around 80kg, tall slim guy .. lol. Will that new MXUS motor work with my existing controller then? I have a 36v 10.4amp battery to power it. I get around 25miles on pedal 4-5 assist.

Okay, I will run the tests you suggested and report back to you On my findings. If it is the mosfets can they be replaced or do I need a new controller and probably new display too to match the controller or can the existing one still work? I’m pretty good with electrics and soldering iron.

I did a bit of googling and It looks like the DMHC controller and display are the typical cheap OEM Parts used for most china made Ebike’s. So you could be right about the MOSFET‘S being burned out.

Im in the UK , so we limited to 250w anyways so I’m not that concerned with Increased power or speed but I just want to get the bike working properly again. I think it’s a free wheel one as cannot see any markings.

Time for me to order a multimeter now .. lol

 

[vfr400]

Im not that heavy,just around 80kg, tall slim guy .. lol. Will that new MXUS motor work with my existing controller then? I have a 36v 10.4amp battery to power it. I get around 25miles on pedal 4-5 assist.

Okay, I will run the tests you suggested and report back to you On my findings. If it is the mosfets can they be replaced or do I need a new controller and probably new display too to match the controller or can the existing one still work? I’m pretty good with electrics and soldering iron.

I did a bit of googling and It looks like the DMHC controller and display are the typical cheap OEM Parts used for most china made Ebike’s. So you could be right about the MOSFET‘S being burned out.

Im in the UK , so we limited to 250w anyways so I’m not that concerned with Increased power or speed but I just want to get the bike working properly again. I think it’s a free wheel one as cannot see any markings.

Time for me to order a multimeter now .. lol

If you use a motor that's too fast for the power provided to it, it'll take the maximum power that the controller can give nearly all the time. That's very bad for range and it'll overheat the controller. Your controller has 15 amps written on it, which is the maximum current that it can give. Its rated current is half of that. Also, the motor will be working outside of its efficient range a lot of the time, which will cause it to make a lot of heat and waste a lot of your battery.

If you normally go everywhere at 20 mph continuously, it's no problem. A high speed motor can work well for a fit rider on a light bike with high average speed, but definitely not for someone that wants the motor for hill-climbing.

 

[Binlo]

If you use a motor that's too fast for the power provided to it, it'll take the maximum power that the controller can give nearly all the time. That's very bad for range and it'll overheat the controller. Your controller has 15 amps written on it, which is the maximum current that it can give. Its rated current is half of that. Also, the motor will be working outside of its efficient range a lot of the time, which will cause it to make a lot of heat and waste a lot of your battery.

If you normally go everywhere at 20 mph continuously, it's no problem. A high speed motor can work well for a fit rider on a light bike with high average speed, but definitely not for someone that wants the motor for hill-climbing.

Hiya, okay I managed to get hold of a multimeter and performed the tests you said, here are my results.

Measuring between the black battery wire and each of the blue, yellow and green main motor wires I get the same reading of 8.64 on all 3 phase wires

Measuring between the red battery wire and each of the three motor wires I get nothing on any of the phase wires ???

So what conclusion do we come to on this?

Thanks again!

 

[Binlo]

If you use a motor that's too fast for the power provided to it, it'll take the maximum power that the controller can give nearly all the time. That's very bad for range and it'll overheat the controller. Your controller has 15 amps written on it, which is the maximum current that it can give. Its rated current is half of that. Also, the motor will be working outside of its efficient range a lot of the time, which will cause it to make a lot of heat and waste a lot of your battery.

If you normally go everywhere at 20 mph continuously, it's no problem. A high speed motor can work well for a fit rider on a light bike with high average speed, but definitely not for someone that wants the motor for hill-climbing.

Hiya, okay I managed to get hold of a multimeter and performed the tests you said, here are my results.

Measuring between the black battery wire and each of the blue, yellow and green main motor wires I get the same reading of 8.64 on all 3 phase wires

Measuring between the red battery wire and each of the three motor wires I get nothing on any of the phase wires ???

So what conclusion do we come to on this?

Thanks again!

 

[Nealh]

Black side readings are consistent and good.
Measuring the resistance on the Red wire to phases you don't always get the same reading as the previous reading or in the same ohm range, you must have got a reading of some kind. Usually infinity/0 means a failed circuit with the fet , a reading of 1 is good.

 

[Binlo]

Thanks for the reply, Sorry that was not correct what I said, I got a reading of 1 for all 3 phases on the red wire. So does this indicate that the controller is okay and mosfet's are all working. The issue could be the actual motor then?

I now have my new MXUS motor on the biked and will give that a try and see if I have the same issue which would then indicate that has to be the controller ?

 

[Nealh]

A reading of 1 means all is well.

It is possible you have over loaded the windings and caused damage or more likely you may have stripped partly the nylon planetary gears, opening the hub should tell.

 

[Binlo]

A reading of 1 means all is well.

It is possible you have over loaded the windings and caused damage or more likely you may have stripped partly the nylon planetary gears, opening the hub should tell.

Okay so the conclusion is controller is all good and working. You could be right, must have overloaded and burnt the windings, as once this issue happens and you turn off the battery and allow motor to settle all is okay until another incline comes. This is the cheapest range of motor that Bafang fit on OEM type bikes so I wouldn't be surprised at all. Also states. for light use only.

If it was the planetary gears, then I would have thought I would get like a grinding noise to indicate something is wrong in the motor etc.

I will try and open up the motor and see what I can find.

Thanks for your input.

 

[vfr400]

Your conclusion is wrong. A reading of 1 doesn't imply that everything is OK with the controller. You should get a reading in the range 12K to 22K. What scale did you measure on? Does your meter show 1 when you short the probes? If so, it means that one of the mosfets is shorted.

 

[Nealh]

Shorting the probes should produce a 0 reading in any of the scales., a fet showing 0 will be shorted other wise none of my bikes would work and that is how my meter's read.
Not all meters give a multi K reading some will just give a reading of 1 and if a short is indicated will read 0.

 

[Binlo]

Your conclusion is wrong. A reading of 1 doesn't imply that everything is OK with the controller. You should get a reading in the range 12K to 22K. What scale did you measure on? Does your meter show 1 when you short the probes? If so, it means that one of the mosfets is shorted.

I measured upto 20k, what do you mean by shorting the probes exactly. I am not familiar with using multimeter so learning as you ask me to perform the steps?

I have no put the controller back in the bike and all wired up with new MXUS motor, to see if I have the same issue or not. Worth checking this out I think.

 

[vfr400]

I measured upto 20k, what do you mean by shorting the probes exactly. I am not familiar with using multimeter so learning as you ask me to perform the steps?

I have no put the controller back in the bike and all wired up with new MXUS motor, to see if I have the same issue or not. Worth checking this out I think.

Measure again on 200k scale.

 

[Binlo]

Measure again on 200k scale.

Okay so on 200k scale, slightly different results
Measuring between the black battery wire and each of the blue, yellow and green main motor wires I get the same reading of 9.4 on all 3 phase wires

Measuring between the red battery wire and each of the three motor wires I now get very high readings starting at 90 and then climbs incrementally higher on all 3 phase wires.

Doing the same test 10 mins later I get the same on black but now back to 1 on red across all 3 phases? I have repeated this several times and only getting a 1.

Does this indicate normal behavior and controller is healthy?

 

[WheezyRider]

Hi All, Im new on this forum and new to the ebike world, but after doing 140 miles on my new bike looks like I have messed up my motor (Bafang 250w 36v). I was carrying my 10 year old son (27KG) on the back Pannier rack with a seat cushion I got off Amazon. We were having so much fun, that I think we over loaded the motor goign up on some small inclines etc.

The motor now just cuts out like after a few mins riding, or just seems to spin up and suck up current .. and on the display it come up MF intermittently (motor fault). Shutting it down for 10mins, gets it going again and is unable to climb any sort of incline , it is just a hit and miss now so I think I have over heated my motor or burnt it out.

Good news is that I managed to pick up another motor on ebay brand new MXUS XF15R one with the rim and tyre. So it is now just a matter of swapping it out!

The question I have is the 9pin motor wire just plug and play or do I need to mess around with the wires to get it to work. It looks like it just plugs in but I dont want to damage this new motor

Also any one know if I can fix this Bafang motor and have a spare wheel hub available ???

So any help on this would be appreciated, I have tried to provide as many pics as possible.

Thank so much in advance!

I doubt that the motor is the problem, you are using a stock 36V 15A controller for 250W motors and having a 27kg child on the back of the bike is not going to bother the motor much and you say it's only done 140 miles. I've carried much heavier loads on the back of my bike with my Bafang 250W 36V motor.

 

[WheezyRider]

Okay so on 200k scale, slightly different results
Measuring between the black battery wire and each of the blue, yellow and green main motor wires I get the same reading of 9.4 on all 3 phase wires

Measuring between the red battery wire and each of the three motor wires I now get very high readings starting at 90 and then climbs incrementally higher on all 3 phase wires.

Doing the same test 10 mins later I get the same on black but now back to 1 on red across all 3 phases? I have repeated this several times and only getting a 1.

Does this indicate normal behavior and controller is healthy?

Can you post a photo of the mutimeter reading, showing what settings it is on?

 

[Binlo]

I doubt that the motor is the problem, you are using a stock 36V 15A controller for 250W motors and having a 27kg child on the back of the bike is not going to bother the motor much and you say it's only done 140 miles. I've carried much heavier loads on the back of my bike with my Bafang 250W 36V motor.

Okay so the money is still on the speed controller , perhaps I should upgrade it with a 36v/48v and higher amps then as maybe the controller is unable to handle this additional load?

I now have the new MXUS motor mounted, so will see I have the same issues with this one, if I do then it has to be the controller.