Bafang m420 doesn't turn on without removing battery first

[schierisfier]

Dear forum members,

I hope you can help me out with this issue

Cortina bike with m420 bafang motor doesn't seem to turn on anymore without removing battery first. So when I turn the bike off I can only turn it on again by shortly unplugging the battery first (or by unplugging display cable ). Is this a controller issue or is there maybe another explanation for this weird behaviour.

I do have to admit that I did remove the speed limit with the help of a Alibaba bafang 600c display not too long ago (set the speed limit to 50km/h). Maybe if I use this 600c display the bike will work perfectly again?

If someone can give me some idea what could be the problem here that would be super helpful!

 

[Chazmo]

If a spare display is what you have on hand, I’d certainly try substituting that in, @schierisfier . Is there any reason why you wouldn’t want to use the spare?

In my limited (but growing) experience, electrical weirdness like this usually ends up being the controller. But on the surface, it sounds like your display (where you power-on the bike) is at fault. Of course, if you see the same problem with the substitute display, then it’s elsewhere.

 

[schierisfier]

Thanks for the quick reply.

The Alibaba display was borrowed by a family member. We discovered that by plugging this display in the parameters of the motor are changed so there is no 25km/h speed limit anymore. After this tuning I did use the original display again for a while but I now got this issue with not starting up. I will try the other Alibaba display again and see if this causing the problem. But just wondering if there is something else I could try. Maybe oxidation somewhere?

The battery is not at fault. I tried another new bafang battery and I got exactly the same issue.

I got the suspicion that the controller could be at fault here.

 

[Chazmo]

Thanks for the quick reply.

The Alibaba display was borrowed by a family member. We discovered that by plugging this display in the parameters of the motor are changed so there is no 25km/h speed limit anymore. After this tuning I did use the original display again for a while but I now got this issue with not starting up. I will try the other Alibaba display again and see if this causing the problem. But just wondering if there is something else I could try. Maybe oxidation somewhere?

The battery is not at fault. I tried another new bafang battery and I got exactly the same issue.

I got the suspicion that the controller could be at fault here.

You’re welcome. Even if you have a spare controller then make sure you first inspect all the wires and connectors before you pull the old one and install it. Could be you’ve broken/bent a pin or that one of the cables got damaged.

Yeah, as I said, most of the time weird behavior is due to the controller. If you don’t have a spare and you’re maintaining the bike yourself try to get one.

 

[Gionnirocket]

Dear forum members,

I hope you can help me out with this issue

Cortina bike with m420 bafang motor doesn't seem to turn on anymore without removing battery first. So when I turn the bike off I can only turn it on again by shortly unplugging the battery first (or by unplugging display cable ). Is this a controller issue or is there maybe another explanation for this weird behaviour.

I do have to admit that I did remove the speed limit with the help of a Alibaba bafang 600c display not too long ago (set the speed limit to 50km/h). Maybe if I use this 600c display the bike will work perfectly again?

If someone can give me some idea what could be the problem here that would be super helpful!

Did the issue start immediately after making the changes with the 600c display?
If not it may be coincidence.
But as suggested you might as well try the 600c since it is accessible.

 

[schierisfier]

Not sure what exactly happened, it is my brothers bike. Tomorrow I will install the other display and I will let you know if it solves the issue. My guess it is the controller but it is still worth a try.

 

[Gionnirocket]

Not sure what exactly happened, it is my brothers bike. Tomorrow I will install the other display and I will let you know if it solves the issue. My guess it is the controller but it is still worth a try.

If my assumptions are correct the m420 is a CANbus motor. Is the battery a Bafang as well?
There maybe be some communication error between the battery/controller/display that the reboot fixes.
That said.... let's hope it's the display as that's the easiest

 

[Mjones49]

Not sure what exactly happened, it is my brothers bike. Tomorrow I will install the other display and I will let you know if it solves the issue. My guess it is the controller but it is still worth a try.

Were you able to get to the bottom of this?

I have a bike with an M420, and have just bought a 600c display as I read that it can remove the speed limit,
…Then I discovered this thread and am worried about using the new display in case it causes this issue!

 

[schierisfier]

connected the 600c display again but unfortunately still got the same issue. Bike is not being used anymore anyways so we are not supermotivated to dig deeper into this. My guess is that the controller is at fault which might be coincidence as well; don't think removing the speed limit should burn out the controller (?).

 

[Gionnirocket]

connected the 600c display again but unfortunately still got the same issue. Bike is not being used anymore anyways so we are not supermotivated to dig deeper into this. My guess is that the controller is at fault which might be coincidence as well; don't think removing the speed limit should burn out the controller (?).

Well I don't think the controller is burnt out as it still works once reset.
I'm still leaning towards a communication error or some type of firmware incompatibility issue
Try putting everything back to stock?
Try contacting Cortina?

 

[schierisfier]

Ok I'll try contacting cortina. Probably best thing to do is to plug in a besst bafang diagnosis tool. But thanks for the advice.

Moral of the story is to get a bosch ebike whenever possible

 

[stompandgo]

Ok I'll try contacting cortina. Probably best thing to do is to plug in a besst bafang diagnosis tool. But thanks for the advice.

Moral of the story is to get a bosch ebike whenever possible

For drive units with full diagnostic capability, you have many choices.

 

[Gionnirocket]

Ok I'll try contacting cortina. Probably best thing to do is to plug in a besst bafang diagnosis tool. But thanks for the advice.

Moral of the story is to get a bosch ebike whenever possible

Try removing the speed limit or using a 3rd party display on a Bosch or any other for that matter.
Perhaps the moral is to finish your education before you attempt an organ transplant.