Bafang middrive conversion kit malfunctioning

[marqtte]

• This is a kit that was installed 3 years ago and 6k miles on it. Up until now, zero problems.
• Bike is used in rain and snow occassionally.
• This kit was purchased through amazon and came with the BBS02B, 36V 500W motor. I can send a link if needed but most/all of the kits are the same.
• What works now: all buttons, wheel sensor, display (no errors shown), brake sensor, headlight, no unusually noises or problems
• What doesn't work: motor does not provide power to the sprocket (motor is not working) when either the throttle or pedal assist is activated. On occasion it does work for a few minutes and then it stops working. Turning the display off or disconnecting the battery sometimes helps but not usually.
• When it does work for a few minutes, it works fine. I get full power easily. No weird noises. No indication of a bad battery or a bad connection from the battery. All connections were checked.
• What I've tried: disconnecting brake sensor, checked all connections, disconnected throttle, tried a different battery, reset unit to factory settings.
• I suspect water got in the motor? Although there's no indications that seals are bad.

Any ideas? My next step is to take the motor apart and see if there's anything obvious. I don't want to buy a new kit and want to try and fix it first.

 

[E-HP]

• What doesn't work: motor does not provide power to the sprocket (motor is not working) when either the throttle or pedal assist is activated. On occasion it does work for a few minutes and then it stops working. Turning the display off or disconnecting the battery sometimes helps but not usually.

Just seeking clarification. By motor is not working, you mean it’s not spinning inside, and not that it’s spinning but the sprocket doesn’t move, correct?

 

[marqtte]

Just seeking clarification. By motor is not working, you mean it’s not spinning inside, and not that it’s spinning but the sprocket doesn’t move, correct?

Good question. I was trying to be clear but obviously wasn't . By motor not working, I mean that the motor is not giving me the extra power that I ask for it. For example: When the bike is stationary (or moving) and I engage the throttle, nothing happens.

Or when I am pedaling and turn on the assist, I get no help from the motor.

 

[E-HP]

Good question. I was trying to be clear but obviously wasn't . By motor not working, I mean that the motor is not giving me the extra power that I ask for it. For example: When the bike is stationary (or moving) and I engage the throttle, nothing happens.

Or when I am pedaling and turn on the assist, I get no help from the motor.

When you say all connections were checked, do you mean external to the motor (or connection between the controller and motor inside as well)? Seems controller related, but maybe something got loose internally.

 

[marqtte]

When you say all connections were checked, do you mean external to the motor (or connection between the controller and motor inside as well)? Seems controller related, but maybe something got loose internally.

Correct. All connections external to the motor were checked. I have not started to tear anything down yet to get inside the motor housing so nothing inside the motor housing has been checked.

 

[gromike]

Does the motor spin, but not output power, or is it dead? Did you lift the rear wheel and use the throttle and listen?
Regardless, you have an excellent opportunity to open the thing up and look. If nothing else, it's time for some corn head grease.

 

[hillslayer@]

I would check all battery connections I have pulled my hair out when this was the problem. Carefully check the battery shoe ,if it has one if you see anything that looks like arcing is going on that's probably it.

 

[marqtte]

Does the motor spin, but not output power, or is it dead? Did you lift the rear wheel and use the throttle and listen?
Regardless, you have an excellent opportunity to open the thing up and look. If nothing else, it's time for some corn head grease.

When i lift the rear wheel and hit the throttle nothing happens: No sound, no noise, no clicks. The motor still turns, it just doesn't seem to be getting power.

If I hit the power and release about 20 times, I may get one out of those twenty that the motor gets power and turns the rear wheel.

 

[marqtte]

I would check all battery connections I have pulled my hair out when this was the problem. Carefully check the battery shoe ,if it has one if you see anything that looks like arcing is going on that's probably it.

I completely agree with you on this point. I've had many occasions with e-bikes and cars where there was a bad battery connection and/or ground and this causes problems.... I checked all wires and connections again and can't seem to find any abnormalities but I'll keep an eye out. FYI: I have a direction connection to the battery which is a good electrical connection with minimal resistance.

 

[hillslayer@]

I completely agree with you on this point. I've had many occasions with e-bikes and cars where there was a bad battery connection and/or ground and this causes problems.... I checked all wires and connections again and can't seem to find any abnormalities but I'll keep an eye out. FYI: I have a direction connection to the battery which is a good electrical connection with minimal resistance.

I completely disassembled my Bbso2 when it was a battery problem. Your problem sounds like maybe the controller I have a spare controller because thought that was my problem before.

 

[aae34]

Is that bbs02 with a shift sensor? I suppose that(or more likely the light wires!) might eventually lead water
into the controller - if unused/unprotected.

If it has it, it is a 3pin connector(like brake or throttle, but i don't remember which) directly on the controller.

edit: with a display that does show when the brake is on this might be easier to "debug", but kind of sounds
like either brake or gear sensor is stopping it. Battery power cuts are more unlikely if it's working only 1/20
while standing still and display never shutting either.

 

[marqtte]

it does have shift sensor capability but i don't have it connected and i have the exposed cable taped so it won't corrode.

I connected my third battery directly to the motor and the same problems continued so it's unlikely a battery issue.

It can't be the brake sensor as it would likely show the icon that the brake is being applied. And I don't see any corrosion or issues with the cables.

I opened up the area where the controller is located and there's no obvious signs of corrosion or broken wires. everything looks clean and new. I really think i just need a new controller. Looks like I can buy one at amazon or similar site for about $100. probably worth a try.

 

[aae34]

Yeah, not all displays show information about the brake, but if you remember seeing such icon,
your likely does, and there goes my best guess. Another option to try would be flashing it with
bbs-fw, and see what it does think about the voltages/sensors. The adapter used to flash does
cost like <5eur/usd, and nothing to loose except maybe a bit of time if you first wait to get the
"adapter"(usb uart w/display plug) to find out it is really gone, so would still have to order the
spare controller anyway, but that is only if the use of bbs-fw doesn't help fixing it, as it really
might not help at all.

GitHub - danielnilsson9/bbs-fw: Open source firmware for multiple electric bike motor controllers.

Open source firmware for multiple electric bike motor controllers. - danielnilsson9/bbs-fw

github.com

 

[docw009]

That's one problem with midmotors. Not easy to plug the motor into a working controller to determine whether its the motor or the electronics.

Wheel sensor flashes and the controller sends speed data to the LCD which shows a reading? I believe you can get a probe on the hall connector to see if they are working.

I'd gamble on a $100 controller from amazon fixing it.

 

[marqtte]

I received the controller today. I connected the new controller to the kit and everything worked fine. But for kicks, I reconnected the old controller to see what would happen and everything is working fine with the old connector. huh?

Here's my theory. The old controller is just fine. I suspect that there was poor connection with one of the connectors on the controller to the motor. The one i show in the photo here was somewhat stuck in silicone/epoxy and appeared to have strain on it. I never disconnected these connections and reconnected before ordering the new controller. Only after connecting the new controller did i first break and make the controller connections (today).

To repeat. Everything seems to be working fine now with both the old and new controller.

So I might just reassemble with the old controller and use for a few days before returning the new controller.

Only working once out of 20 times supports a poor connection theory.

THoughts?

 

[marqtte]

put the old controller back in and later in the day it exhibited the same failure mode as earlier so I put the new controller in so we'll see how that goes.

 

[marqtte]

almost 100miles on the new controller with no issues so far. Doesn't 100% rule out other issues but seems to be faulty controller as of now. I will report back in a few weeks.