DIY Fix for BBS02/BBSHD Pedal/Throttle Issue

[Rassy]

EDIT: 4/20/21; After 3 years my fix described in this post quit working. I didn't try to figure out why, simply removed it to make sure everything worked as originally shipped from Bafang. Also, I had another fix I wanted to try which is simple and requires no electronic parts. I completed and tested this alternate fix today and I'm planning a simple enhancement to make it's use completely transparent. First I cut the grey PAS sense wire in the middle, which effectively shuts down the PAS. Then I spliced a wire onto each of the grey wires and ran the wires out of the controller through a small notch cut into the rubber wire entrance area. I used a small two wire conduit long enough to reach the handlebars where I connected them to a toggle switch. Now if the toggle switch is closed the circuit between the grey wire ends is completed and the PAS works, but with the original throttle problem. When the toggle switch is open the PAS does not work but the throttle works properly whether or not you pedal.

My enhancement thought during my test ride is to install a small normally closed momentary button switch right where your thumb goes on the throttle. Then when you choose to use the throttle the button switch will open the circuit and the throttle will work properly. Here is a link to the type of switch I am talking about:

https://www.aliexpress.com/item/32954763027.html?aff_platform=true&aff_short_key=UneMJZVf&isdl=y&src=bing&albch=shopping&acnt=42005546&isdl=y&aff_short_key=UneMJZVf&albcp=373871275&albag=1308419064071836&slnk=&trgt=pla-4585375808811125&plac=&crea=81776241344382&netw=o&device=c&mtctp=e&utm_source=Bing&utm_medium=shopping&utm_campaign=PA_Bing_customlabel1_US_PC&utm_content=customlabel1%3D7&utm_term=small%20momentary%20normally%20open%20push%20button%20switch&msclkid=117b23028d211ccd8153437dfba5b14b

I have decided against any modification to the throttle because of possible negative effects on the throttle. I have started a new thread for discussions concerning this simple fix here:

https://endless-sphere.com/forums/viewtopic.php?f=28&t=111469

EDIT 5/29/19: There is finally a possible programming fix for this problem. Here is a link to a thread that you need to read (BOTH PAGES) if you are experiencing this problem: Update on 10/13/19, there is no confirmation that these firmware flashes fix the pedal/throttle issue. I will leave the following link in place, since there is a lot of information there pertaining to firm ware flashes:

https://www.endless-sphere.com/forums/viewtopic.php?f=28&t=100064

EDIT: Fechter has completed and tested a simpler fix for this issue. See his solution five posts down on this page.

In August of 2017 I purchased a new BBS02 and something seemed to be wrong with it. It did not operate the same as the previous five BBS02 kits I had purchased and installed over a period of four years. Since then there have been many threads addressing this problem, but the dealers I have contacted could not offer a fix, (LUNA did exchange the “faulty” controller for an older good controller), and Bafang did not even respond to my questions.

THE PROBLEM:

While pedaling, in any PAS level, 0 through 9, the throttle would not work, unless you went to full throttle. This resulted in lots of jerking and stress on the drive train, etc. In PAS 0 you were unable to use partial throttle and pedal at the same time. Although the hardware and firmware versions were unchanged, Bafang apparently made an internal change to the controller that caused this problem. All of the BBS02 controllers manufactured after 2016 apparently have this problem and perhaps some of the BBSHD controllers also have this problem.

I.e., in the older controllers, when the throttle is used the PAS system is disabled and in the newer controllers, when the pedals are rotating the throttle is disabled.

EDIT: There are a couple of technical details concerning the above simple statement, just so the accuracy of this statement does not become the focal point of any further discussion: First, in the older controllers whichever was greater, either throttle or PAS dictated which input controlled the motor. The result is the same, since there would be no reason to use the throttle when using PAS and also pedaling unless you wished to override the PAS system and speed the motor up, and; Secondly, in the newer controllers when I say the throttle is disabled, I am aware that the throttle still cuts in when you reach the full throttle position, but the full range of the throttle is disabled, and a throttle that just works like an on/off switch and only gives you full throttle is a disabled throttle IMHO.

THE FIX:

Recently on another thread concerning this problem a discussion ensued between Alan B and fechter on possible DIY fixes. I joined the discussion and with a lot of patience and guidance from fechter, have now completed and road tested the following fix on a faulty 2017 controller. This fix interrupts the PAS signal when the throttle is used so that the controller does not know that the pedals are turning. This fix is delicate and would void any warranty you might have.

With the controller off the BBS02 I very carefully removed some of the potting where the external wires entered the controller area, back to where the individual wires came out of the outer sheathing. The only wire I was after was the blue throttle signal wire so I carefully removed about the last inch of the outer casing from the main wiring harness that leads to the display and brakes. This was the most difficult part of the fix. If I were to do it again I would gain access to the blue wire at an external point and run the lead into the controller through a new hole drilled on an upward angle near the top of the grommet. Then there would be no need to further disturb the potting or other wires in that immediate area.

Next I exposed about 1/8” of wire within the insulation of three wires by first making a small cut in the insulation and then pulling the insulation back with my fingernails. The three wires are the blue throttle wire previously mentioned, the grey PAS sense wire, and the black PAS ground wire. The PAS wires were already exposed in the controller area and are two of the four wires on one of the mini plugs.

With the three wires bared a lead wire was attached to each. You could do this with good solder skills, but I used Silver Conductive Epoxy. Then these taps were coated with liquid electrical tape.

One end leg of a 100K trimmer resistor, Mouser part # 652-3296W-1-104LF, was attached to the blue throttle lead, the middle leg of the resistor was attached to the base leg of a transistor, Mouser part # 610-2N5550, using a short wire for flexibility, and the other end leg of the resistor was attached to the black PAS lead. The collector leg of the transistor was attached to the grey PAS lead and the Emitter leg of the transistor was attached to the black PAS lead.

Then all the connections were coated with liquid electrical tape and everything was wrapped with electrical tape with just the adjustment screw end of the resistor showing.

Final adjustment was made by trial and error testing with the controller uninstalled but all wires connected.

This diagram was copied from a post by fechter on another thread:





IN CONCLUSION:

IMHO the need for this fix should not even exist. Bafang made a manufacturing mistake and even when the dealers were alerted to the problem by their customers, instead of working with Bafang to find a solution, they just continued selling the kits.

Even though I am happy with my BBS02 kits, I can no longer recommend them. It’s been eight months since I came across this issue and AFAIK every new BBS02 currently for sale still has the faulty controller in it.

If anyone can provide any rationalization why making the throttle inoperative when pedaling was an improvement or had any value to anyone I would like to hear it.

 

[bhaaf]

I wouldn’t buy another Bafang kit until this problem is fixed and they replace my faulty controller. My BBSHD controller was also faulty. Great work on finding a remedy to the problem. Congratulations.

 

[Alan B]

I have no idea why Bafang would make this change.

Glad fechter was able to find a fairly simple fix.

My early 2016 BBSHD doesn't seem to have this problem, I haven't tried my partially completed BBS02 setup yet. I think I will convert them to PhaseRunners anyway and retire the Bafang electronics. Perhaps they'll show up in the for sale section later on.

 

[LowkeeRider]

I think i am going to run into this problem too, I bought a bbs02 two month ago but not yet installed. Is this circuit small enough to fit inside the bbs02 or is it external? Looks challenging, I don't know much about electronic to make the modification.

 

[Rassy]

Yes, the finished circuit did fit within the controller case. I have no electronic experience or knowledge, but was able to do the modification explained above with guidance from fechter.

The biggest problems I see is that this modification would void your warranty, and it would be very easy to destroy other wires, etc. when gaining access to the little blue throttle wire. If I ever do another modification like this I would possibly gain access to that blue throttle wire by cutting into the wiring before it enters the controller. That way you would have more wire length to work with and would not have to dig into the potting at all, except you would have to run the lead from your tap into the controller area through the grommet and a bit of potting, probably drilling the hole near the top of the grommet on a slight upwards angle. You would still have to work very carefully and you would also be voiding your warranty.

Edit: There is also more work being done be fechter and another expert to define a better fix that isn't dependent on guesswork using a trimmer resistor and transistor. It also wouldn't be subject to failure due to temperature fluctuations. Might require more parts making it more difficult to fit into the controller area:

https://endless-sphere.com/forums/viewtopic.php?f=28&t=91306&p=1376704#p1376704

I still think the best fix is the one that Bafang needs to supply.

 

[fechter]

There are a few variations of the circuit that will work. I chose the Darlington one, as it was the easiest to build and install.
The one in the picture below used a 2N5308, which has a different pinout than the ones recommended. I just happened to have it around. Sealed in adhesive lined heat shrink it is waterproof.


The circuit diagram looks like this:


When the throttle voltage reaches about 1.1v, the transistor turns on and grounds the PAS sensor signal, disabling it.
Ideally, we would want it to turn on right at 1.0v, but it takes a bit more complex circuit to do that. We can compensate by tweaking the throttle min voltage in software.

There are many alternate parts that would work. KSP13BU is the least expensive and readily available from Mouser
Alternate Darlingtons are: KSP13TA, MPSA12, MPSA13, 2N6426, 2N6427

Resistor R1 is not critical. Anything between 20k to 100k will work. I used 100k from my junk box. A similar part from Mouser is part# 71-RN55D-F-100K

I trimmed the legs of the transistor to about 6mm length and tinned them. The resistor goes to the base leg (center). I found some blue and black wire which is nice to match the controller, but any color will work if you label them.


Small heat shrink tubing over each leg will keep them from shorting:


Next, a larger heat shrink over the whole thing strengthens the wires and prevents breakage


I installed the fix on my BBSHD. Digging into the potting and tapping into the skinny throttle wire is challenging and best done by someone with some electronics experience.

The first step is to disconnect the battery from the controller. Then press and hold the power button to drain the main capacitors. We don't want to blow up anything by accidentally touching it.

Next remove the 3 bolts holding the controller on and carefully pull it away from the motor. It will be attached by a bunch of wires. I disconnected the 3 phase wires and unplugged the PAS sensor and the hall sensor. The hall plug was glued in with potting stuff, but I was able to dig it away with a small screwdriver.

Controller removed from motor


Next I used a small straight blade screwdriver to dig away the potting around where the wires enter the housing. The one we're after is buried pretty deep. Once I got where I could see the top of the display cable (the thickest one), I pushed the cable in from the outside and got a loop of slack inside.

Display cable looped up


Next, I used some small wire cutters to carefully split the cable jacket in the loop. It's easy to damage the little wires inside so be careful. It may also work to use a sharp blade and only cut half way through the jacket, then spread it until it splits open.

Jacket spit open


Next, I located the blue throttle wire and pulled it away from the others

Blue wire


Now the hard part, exposing the copper without damaging it. You could use some kind of stripper or blade, but I tried a new approach; I used a hot soldering iron to heat the spot I wanted to expose and the insulation sort of melted apart. Once I could see copper, I scraped away the melted insulation plastic so it would solder well.

tap spot


I tinned the spot, then wrapped the wire going to the circuit around the spot and soldered it.

soldered tap wire


Once it was connected, I wrapped a small piece of electrical tape around the joint.

The wires on the PAS sensor are silicone and you can part the insulation just by using your fingernails. Spread apart a spot, and solder on the wires to the grey and black wires, then tape them up.

Ready for assembly


Carefully reconnect all the wires and try to stuff them in the same way they were originally. There is plenty of room for the correction circuit, but just try not to pinch any wires.

Once everything is back together, I used the Bafang Software Config Tool to change the Throttle Min voltage from 1.0 to 1.1. This ensures the circuit kicks in before the motor. It would probably work fine with the stock 1.0v setting but there would be a tiny range at low throttle where you might get some of the original behavior. In practice, it seems to work fine either way.

 

[espresso]

Thanks to all concerned for the fix!

 

[jeffcrilly]

I recently installed a BBS02 motor and throttle.
Purchased new in April 2018.

I've been following this thread a bit, and have been observing the throttle & "PAS" behavior on my 22 mile roundtrip commute.

When pedaling (and actually applying pressure/torque) and applying, maybe, 50% throttle I do feel a bit more assist than just with pedaling.
So.. I ~think~ it is working, but I do not have experience with the "older" BBS02/BBSHD Pedal/Throttle behavior.

Now.. this is probably a completely different issue...
PAS with the BBS02 is more like "pedal de-assist" imo.
For example, when I apply pedal force -- i.e. exert energy, it seems that the motor backs off.
If I apply less pressure (ghost pedaling), then the motor applies more power.
To be honest, the best way to get around seems to be apply as little pressure to the pedals as possible.
My understanding is this is just the nature of the "cadence" sensing BBS02. (its not torque sensing, which would give the opposite behavior.)

-Jeff

 

[fechter]

Now.. this is probably a completely different issue...
PAS with the BBS02 is more like "pedal de-assist" imo.
For example, when I apply pedal force -- i.e. exert energy, it seems that the motor backs off.
If I apply less pressure (ghost pedaling), then the motor applies more power.
To be honest, the best way to get around seems to be apply as little pressure to the pedals as possible.
My understanding is this is just the nature of the "cadence" sensing BBS02. (its not torque sensing, which would give the opposite behavior.)

-Jeff

The BBS02/HD PAS system is pretty crude compared to torque sensing. What you are feeling is the motor is trying to stay at a fixed speed, so when you try to pedal faster than this speed, it cuts power in an attempt to maintain that speed. You can change this behavior by reprogramming the PAS settings. Kepler's profile has the speed set at 100% for all the settings but changes the current limit. With this profile, the motor will keep assisting no matter how fast you pedal. If you have the setting too high, the motor will start going faster than you are pedaling. I sort of prefer this kind of profile.

 

[Rassy]

jeffcrilly said:

When pedaling (and actually applying pressure/torque) and applying, maybe, 50% throttle I do feel a bit more assist than just with pedaling.

Thanks for posting this. When this issue first cropped up the BBS02 units were being shipped out with whatever settings that dealer had been using and jerking to the point of distraction was a big issue. Now that the dealers are aware of the problem I think they have changed some of the settings to reduce the sudden jerk when "full" throttle is applied.

It would be great if you could do the following tests and report your results. That would be the only way I could tell if the issue is actually fixed.

PAS 0 Test: With your bike in low gear use the throttle only, with no pedaling, to get the "feel" of the full throttle range. Then do the same test while turning the pedals but not applying any pressure. Do you experience the same full range of the throttle? If not, what seems to be different?

PAS 1 Test: While riding at the slowest speed you can and also turning the pedals at a comfortable cadence, but not applying any pressure, try using the throttle while you continue pedaling. Does the throttle cut in smoothly at a fairly low application and then allow you to speed up and hold different speeds using the throttle while maintaining the same comfortable no pressure cadence? If not, what does happen?

I know these tests don't duplicate any "normal" riding style, but they do show whether or not the pedal/throttle issue is working "correctly".

Thanks,

 

[jeffcrilly]

It would be great if you could do the following tests and report your results

I'll test this weekend when I get a chance.
(btw, when you say "PAS 0" and "PAS 1" test, you do mean PAS Level 0, and PAS Level 1, correct?")

Fwiw, I occasionally use throttle for to get some boost from stopped at an intersection/light, etc., or if I'm bored pedaling on a long flat.
In general tho, my normal riding is usually w/o using the throttle.

On yesterday's commute I did a bit more experimentation -- this was at like 15mph and Assist 9, so not the same as the test you suggest.

One thing I did notice (that I had not previously noticed) is this (which may just be noise, so take this with a grain of salt):

1) Pedaling , apply 50% throttle => noticed subtle increase in power
2) Keep pedaling, Increase throttle to 100% => noticed a bit more power but subtle (I believe the power indicator was at max, like ~900 watts)
3) Keep pedaling, REDUCE throttle to 50% => noticed power dropped to ZERO -- this was on the display, and indeed the pedaling got harder.

I think it stayed at zero for a couple seconds, then recovered up again.
This behavior was difficult to reproduce, but I managed to do it a couple times.

The "drop to zero" was quite unexpected.
Many times I have been pedaling, apply 100% throttle , then 0% throttle and don't notice any dropping of power to zero.
It seemed related to the 50% throttle... but this is totally anecdotal and unscientific.

I'll try out the other test you suggested.

 

[Rassy]

Yes Jeff, when I said PAS 0 or PAS 1 I did mean PAS level 0 and PAS level 1.

Another interesting note, in another thread, forum member unclejemima has a fairly new BBS02 and is getting some strange behavior. Also, he has a programming cable and his firmware version number is different. Read here, and perhaps you could also post your controller manufacture date:

https://www.endless-sphere.com/forums/viewtopic.php?f=3&t=94202&p=1379572#p1379572

 

[Alan B]

The original behavior of the PAS/Throttle system with the BBSHD was that a tiny bit of throttle would shut off the PAS, essentially the throttle "took over" from the PAS when the throttle was used. Then it worked like throttle only regardless of PAS. The throttle was "dominant".

The new behavior seems to be the opposite, where the PAS takes priority over the throttle if I understand what folks are experiencing. Perhaps the newer behavior is better. I have not hooked up my "newer" BBS02 yet so am getting this from ES threads, just to be clear.

 

[fechter]

The new behavior seems to be the opposite.

That would suck.

It's important to make sure the issue isn't just with goofy settings in the software configuration. Some of the settings are still a little cryptic.

 

[bhaaf]

I hope we get some positive results and the new motors are fixed. I’m holding off buying a new BBSHD.

 

[fechter]

I've been out for several rides since fixing my BBSHD and really like how it turned out. I still need to dial in the PAS settings a little more but so happy I can simply hit the throttle anytime and it doesn't try to throw me off. For real technical trail stuff I can just go to PAS 0 and have throttle only.

 

[bhaaf]

Great news that a fix has been found. I have one of the bad controllers and my friends have a few. I’m hoping that someone could fix our controllers for us for a fee. I’m not capable of doing this myself but I’d be happy to pay someone that can do it. Anybody?

 

[fechter]

Great news that a fix has been found. I have one of the bad controllers and my friends have a few. I’m hoping that someone could fix our controllers for us for a fee. I’m not capable of doing this myself but I’d be happy to pay someone that can do it. Anybody?

Where are you located?

 

[bhaaf]

South Orange County. I have a spare BBSHD controller that needs the cure. I would be happy to mail them. I have a few to take off the bikes to do also.

 

[expomm]

What was the issue, just the controllers? I want to buy a BBSHD what do I need to get within the kit to make sure the throttle works fine?

 

[fechter]

South Orange County. I have a spare BBSHD controller that needs the cure. I would be happy to mail them. I have a few to take off the bikes to do also. Thanks bhaaf@yahoo.com

If you were close enough to pick up, I might offer. Shipping anything for me is a complete PITA due to issues with the post office and distance to UPS. It is also pretty time consuming to dig out the potting and cut into the throttle wire and I am backlogged with many other projects.

What was the issue, just the controllers? I want to buy a BBSHD what do I need to get within the kit to make sure the throttle works fine?

Yes. The first post describes the problem. We are not sure which production dates/ software rev. are affected. You can always just unplug the PAS sensor and use throttle only like I did for a year.

 

[Rassy]

bhaaf wrote:

Great news that a fix has been found. I have one of the bad controllers and my friends have a few. I’m hoping that someone could fix our controllers for us for a fee. I’m not capable of doing this myself but I’d be happy to pay someone that can do it. Anybody?

I also lack experience and equipment required to do a neat job like fechter does, however my fix is functioning perfectly so far. I am exploring the use of small tapping and splicing connectors that could eliminate the need for both cutting into wires and soldering the connections. However, it will be a while before I have anything to report, or if I even come up with a satisfactory solution. Here are a couple of the items I am planning to test:

https://www.superbrightleds.com/moreinfo/wire-connectors/28-12-ga-lever-lock-quick-connect-terminal-blocks/1372/

https://www.superbrightleds.com/moreinfo/wire-connectors/clear-24-18-awg-t-tap-wire-splice-connectors-single-dual-channel/4157/

Particularly since you have multiple controllers to "fix" I would encourage you to make one of the fixes outlined in this thread. I plan to try a fix using the parts that fechter listed in his fix outlined in this thread.

Good luck with whatever you decide to do, and keep us informed.

 

[thetrevdev]

I just installed my first BBSHD yesterday. While a blast I am finding it difficult to control speed.
Can you describe how it is supposed to work?
I haven't installed my disc brake sensors yet so I am avoiding PAS > 0.
I am pedaling in PAS 0 and trying to manually control the assist but it is jerky and feels like 100% throttle.
I assumed this is just the way it is. Is this related to the issue you are discussing here? I have nothing to compare this to and don't know how it is supposed to work.

 

[Rassy]

Your brief description using PAS 0 sounds like the issue that we attacked in this thread. The earlier BBSxx models allowed pedaling and modulated throttle usage at the same time. Try using the throttle in a low gear, without pedaling. You should be able to go from a slow speed to full throttle, and anywhere in between. Then try the same experiment while you are pedaling, even fake pedaling without applying any pressure.

I'm going out of town for the next week, but the results of the above tests would help us determine if you got stuck with a problem controller. Then we can talk about your options based on you riding style, etc.

 

[thetrevdev]

I am able to modulate the throttle when not pedaling. If I start to peddle the motor turns off until I turn the throttle high.

My riding style is I want to peddle and get something like 50% assist. I haven't tried fiddling with the the max speed setting. I will try that on my commute tomorrow but it is not ideal if I want a burst of speed. I have the Bafang C961 display if that helps. Just reading through the forums is it easiest to just disable PAS if I am fine with controlling power with the throttle? Are there different programming options that can help mitigate the issue? I am not excited about opening up the brand new motor the first week.

Thanks so much for input.
-Trev