Bafang BBS01b low power and low cutoff cadence

[marshall2389]

I've had this motor for 2.5 years and it's worked very well. In the last few days it has been acting funny. Half the time I turn it on I get no assist. The display reads full battery voltage, but no assist. The other half of the times the assist will kick in. However, it's only providing about half the power it normally does. My display doesn't show motor current or power, but the 3 amp setting is unnoticeable and the 15 amp setting feels more like 6 amps.

The battery connector looks fine. I would think if it was a connector issue then the voltage seen by the display would go way down when lots of current is being drawn by the controller. However, the voltage on the display doesn't change when the motor is powered.

I haven't noticed any funny noises coming out of the motor.

Any ideas?

 

[TomD]

Do you have brake sensors? Perhaps those could be cutting off power intermittently. Doesn't explain the low power though.

 

[Gionnirocket]

I would start with the Display.
Test with a second display.
If you don't have another display you can use the SPEEED APP and a programming cable.
Then I would double check the Battery
Double check/clean all connections
It may be possible to connect a voltage meter to the battery charge port for a more accurate reading of what's going on under load. But do not attempt this if beyond your comfort/skill level as short circuit is not good.
If you can, post a pic of your hardware.. Display, motor, battery.

 

[marshall2389]

Do you have brake sensors? Perhaps those could be cutting off power intermittently. Doesn't explain the low power though.

No brake sensors.

 

[marshall2389]

I would start with the Display.
Test with a second display.
If you don't have another display you can use the SPEEED APP and a programming cable.
Then I would double check the Battery
Double check/clean all connections
It may be possible to connect a voltage meter to the battery charge port for a more accurate reading of what's going on under load. But do not attempt this if beyond your comfort/skill level as short circuit is not good.
If you can, post a pic of your hardware.. Display, motor, battery.

I’m waiting on the tools I need to take the motor off then I’ll get to troubleshooting. Unfortunately I don’t have a second display or android phone.

 

[Gionnirocket]

I’m waiting on the tools I need to take the motor off then I’ll get to troubleshooting. Unfortunately I don’t have a second display or android phone.

Do what you think is best....
#1...but troubleshooting 101 is always eliminate the easy and more likely first.
#2 It can quite possibly be the the controller or wiring harness as well... But I would refer to #1

 

[marshall2389]

Do what you think is best....
#1...but troubleshooting 101 is always eliminate the easy and more likely first.
#2 It can quite possibly be the the controller or wiring harness as well... But I would refer to #1

I’ll ask around. Maybe I can borrow someone’s android phone.

 

[m@Robertson]

Yeah... not sure what taking the motor off will tell you unless you open it up and find no grease and a lot of rust inside, which is unlikely. I would follow the given advice and try to methodically eliminate the easy stuff.

 

[marshall2389]

Yeah... not sure what taking the motor off will tell you unless you open it up and find no grease and a lot of rust inside, which is unlikely. I would follow the given advice and try to methodically eliminate the easy stuff.

The fact that the power is low with a low cutoff cadence makes me suspect the controller. However, I don’t know much about controllers. I figured I’d use a multimeter to check the MOSFETs.

 

[m@Robertson]

The fact that the power is low with a low cutoff cadence makes me suspect the controller. However, I don’t know much about controllers. I figured I’d use a multimeter to check the MOSFETs.

Luna sells replacement controllers that will turn this motor into a 750w BBS02. Thats assuming the only diff between a BBS01b and 02b is the controller. I've always stuck with HDs for parts commonality across the fleet so no direct experience.

 

[Gionnirocket]

The fact that the power is low with a low cutoff cadence makes me suspect the controller. However, I don’t know much about controllers. I figured I’d use a multimeter to check the MOSFETs.

A faulty display can give you a myriad of issues as it speaks directly to the controller. Unless you've been abusing the controller, they are pretty robust.
I'm not saying I know what your problem is... I'm just suggesting do the least evasive first
Does your display give you the option of viewing error codes?

 

[marshall2389]

A faulty display can give you a myriad of issues as it speaks directly to the controller. Unless you've been abusing the controller, they are pretty robust.
I'm not saying I know what your problem is... I'm just suggesting do the least evasive first
Does your display give you the option of viewing error codes?

It hasn’t displayed any error codes. It’s a C961 display. There’s no menu region to observe error codes. The manual makes it seem like the error code will appear if triggered.

 

[m@Robertson]

It hasn’t displayed any error codes. It’s a C961 display. There’s no menu region to observe error codes. The manual makes it seem like the error code will appear if triggered.

Thats correct. But a faulty display or a bad wiring harness can still give you funky results. I do agree it sounds like the controller, but on general diagnostic principles - and having seen surprise results by swapping out seemingly extraneous bits - I would do the easy stuff first and work my way up.

 

[Gionnirocket]

It hasn’t displayed any error codes. It’s a C961 display. There’s no menu region to observe error codes. The manual makes it seem like the error code will appear if triggered.

I've never seen one in hand... But from what I can tell the C961 does not display voltage and only has a segmented bar graph... Not really accurate enough for troubleshooting.