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BBS02 Speed Sensor

Old 08-21-23, 07:57 PM
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dotyj
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BBS02 Speed Sensor

Hi all:

I've been converting an old Pacific Cycles Handy handcycle to an ebike with a Bafang BBS02 kit.

I ran into a problem which might be my fault. I noticed I no longer have a working speed sensor. Testing with a magnet has no effect.

I removed the sensor and tested all three pins with an ohm meter and they all seem to be open, so maybe the speed sensor is dead?

I checked the pins on the cable with a volt meter with power on and I see 5 volts available.

I get an error 21 on the display.

The speed sensor had initially worked. I hadn't noticed but I hadn't tightened the motor enough on the bottom bracket and the speed sensor cable was very tight, so I corrected the issue and really tightened the motor to the bottom bracket. I don't see any damage at all on the speed sensor cable. I don't know of a way to test the pins on the end of the speed sensor cable though to verify that I've not damaged a wire.

My throttle and assist seem to still work, of course the motor now has no idea how fast I'm going.

Is it safe to use the bike without the speed sensor? Is it possible to test the speed sensor cable without taking the whole motor apart? If I do have to take the motor apart do I have to remove it from the handcycle?
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Old 08-21-23, 09:31 PM
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AFAIK, the "speed sensor" you refer to is the PAS sensor. There's a small bulb on the unit, and if this lights up when the system is activated, it's operational FME. If not, you need to discover whether it's the sensor or the wire at fault (might be easiest to just replace the $10 sensor and determine whether that solves the problem), then act accordingly. I'm pretty sure you'll need to remove the motor from the cycle if you need to disassemble it. Also, you might call or email Luna Cycle; they have been very helpful to me in the past.
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Old 08-21-23, 10:23 PM
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I tested the sensor while it was plugged in and the bike was turned on, the LED doesn't light up.

I have another sensor ordered, just waiting for it to come in.

On assist level 1 I was still getting assist from the motor while hand pedaling, and could use the throttle, but yeah no MPH indicated and an error 21.

I didn't initially notice the speedo wasn't working and quickly wheeled back to my powerchair because at the time I didn't know what error 21 was and didn't want to get stuck away from my powerchair and having to call for help. I can pedal the handcycle unaided but not very well and only on flat ground.

I'm considering installing a 23 tooth hub gear to give me more torque so I can possibly pedal unaided a bit easier.
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Old 08-22-23, 09:12 AM
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I would concur with you about a "lower" gear so you'll be able to operate the cycle without motor assistance, even though it reduces the top speed.
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Old 08-22-23, 11:04 AM
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I'll see if I can get help with changing the hub sprocket.

I've done all the rest of the work myself but I don't have the hand and finger strength to remove the snap ring holding the sprocket on then put it back on again.
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Old 08-23-23, 07:24 AM
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This link has a diagram of what is inside the sensor

Looks like you need to apply power than test with the magnet while monitoring the voltage out of the other two pins.

Simply taking resistance measurements at the pins may not tell you anything.
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Old 08-23-23, 08:45 PM
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I installed a new speed sensor, that didn't resolve the issue.

I just ordered a replacement controller.

In the meantime I am able to use my handcycle, but the unit times out every few minutes and shuts off because it's not detecting use.
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Old 08-23-23, 10:54 PM
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The very early BBS02's had a controller which failed frequently (I have one and was fortunate since it hasn't had the problem after eight years). They changed the controller very quickly. Hopefully you ordered the correct one and they send what you ordered.
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Old 08-23-23, 11:23 PM
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I bought it on August 3rd. I bought the controller for the BBS02 so with luck I'll get the right one.

I'm really not looking forward to all the work it's gonna take to remove the motor, replace the electronics and put the motor back on.
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Old 08-24-23, 09:18 AM
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Was this a new motor? It should have some sort of warranty. Also, Bafang seems to have a pretty good reputation. This is the first instance I've heard in which the failure occurred in such a short time.
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Old 08-24-23, 10:19 AM
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It was new, bought at the beginning of August. I'm sure this is my fault, because the speed sensor used to work. Here's why I think this is my fault.

I failed to properly tighten the motor to the bottom bracket, this caused the motor to rotate under load until it hit the frame of the bottom bracket, and this did two things. It caused my power cables to be pulled out at their connectors and it pulled the speed sensor cable really hard.

I went back and really tightened the motor to the bottom bracket so it will no longer rotate. Then I plugged the power back in, but I forgot to turn the battery pack off and when I connected power there was a significant spark and arc.

I either damaged the speed sensor cable when it got pulled, or I blew the circuit plugging the power back in.

None of the other cables were pulled, and everything else seems to work just fine.
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Old 08-24-23, 10:20 AM
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This is the handcycle I mounted my motor kit to.
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Old 08-24-23, 02:45 PM
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Nice job with the assembly. There are sheaths (or my favorite since it's functional - a frame pack) that contain the "extra" wires and keep them from getting snagged. You might check the connectors to insure there was no damage when they were pulled out. It's very difficult to secure the motor so it won't move FME; I used a Hozan "wrench", which retains the locknut very well and a hammer to secure mine (I know, I'm a hammer mechanic).
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Old 08-24-23, 03:15 PM
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I'd be interested on the sheaths. Cable ties look tacky.

I ended up using my one pound mallet with the stock Bafang tool. I hammered until it quit moving.

Routing the sensor cable was a pain, it had to lie where it wouldn't cause the brake cable, and itself from getting wrapped up. Also the brake and shift cables can no longer be run through their stay welded on right behind the bottom of the motor, it required too much of a bend and I damaged my cables and had to replace them.
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Old 08-24-23, 05:08 PM
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Before you go through the effort to disassemble your system, you might ask the same question(s) at endless sphere. There are at least a couple of very savvy individuals who might help you. For instance, it seems to me (after you explained the problem more thoroughly) that some connectors are faulty, and they might be able to help you repair the wires without taking the whole thing apart. If you pose your questions, and I see they don't answer, I'll send them a PM and ask for help.

For "sheaths" go to Amazon and insert cable sleeving protector or wire loom protector and you'll see a myriad of options.
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Old 08-24-23, 08:53 PM
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I'll do that. Probably tomorrow though, I'm pretty wiped out, it's been a busy day at work.

I'd still have to remove the controller to test the wires.

But I did find out I can remove the controller without taking the motor off the handcycle. Just remove the right crank and chainring, then the dust cover, then three bolts to remove the controller to get at its cables.

I'll still have to disconnect a few things and cut some cable ties off, but that won't be so bad.

I'd already ordered a new controller which is due tomorrow. I think I'll go ahead and install it then I can repair the original controller at my leisure, it would be nice to have a spare.
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Old 08-24-23, 09:35 PM
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As I said, it would be nice to know the controller is the problem before doing all that work.
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Old 08-24-23, 10:04 PM
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True, but I can't test the wires without taking it apart.

Well, actually, maybe I can. I'll check out the other site to see if there's a pinout showing what signals I should expect to see on the end of the speed sensor cable when the unit's turned on. That would be pretty easy to do.
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Old 08-25-23, 06:22 AM
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They sell torque arms for Bafang motors. I installed one on my conversion, motor hasn't moved.

BSB-1 Stabilizer Bar for BBS02 and BBSHD - Luna Cycle

BTW a definitive source on all things Bafang related

****** - Dive into anything

(looks like one can't link directly to www.r e d d i t .com. Google /r/ebikes/wiki/bbs_faq/ to find the page I tried to link above)

From what I have *read* replacing the controller is not a difficult task. IIRC there is a link in the repository above
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Old 08-25-23, 08:04 AM
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That's clever! I'll check it out.
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Old 08-25-23, 11:17 PM
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I tested the cabling using a volt meter. I had 5 volts dc between the signal pin and the ground pin, but I had no volts between the 5 volt dc pin and the ground pin. The cable itself and the connector seemed okay.

So I ended up swapping out the controller. that fixed it. My handcycle is working again.

I want to diagnose the old sensor, anyone know the best way to get the pot material out? What's the melting point? If it's low enough I would put the thing face down in the oven on a cookie sheet covered in aluminum foil and let the potting stuff drip off. I have an old cookie sheet I can sacrifice.
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Old 08-26-23, 01:34 PM
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Good job getting it repaired, especially without needing to completely disassemble the system.
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Old 08-26-23, 01:55 PM
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Yeah, this in no way was Bafang's fault, I'm taking full responsibility for the damage to the controller.

I was very happy to not have to remove the motor from my handcycle, swapping out the controller wasn't trivial but it wasn't all that hard either. At least I got the opportunity to re-organize my cabling, it's much better this time.
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Old 08-27-23, 07:14 PM
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Yesterday I grabbed my cell phone in case I got stranded, put my bike helmet on for the first time, then took a ride around the neighborhood.

My Handy has a Shimano 7 speed gear hub and I actually got all the way up to 7th gear. I kept the assist level at level 1 and really had a good time. I doubt I hit more than 10 miles per hour, at least not for very long. I rode around 1.5 miles so not very far. I used the throttle to get going from a stop but otherwise I was pedal assist only.

I have a rhythmic rub someplace that I couldn't see from the seat and I'm not very stable in the seat because my legs are too short for my feet to rest on the foot rests but overall I had a great experience.

I didn't ride today, I really want to do something about the foot rests so I don't lose my balance and fall of the handcycle.

I live in a small town and drivers were courteous where we met up. One driver actually wave, I managed a smile and nod but my hands were too busy to wave back.
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