Undersized Controller ??

[dannydibbert]

I am looking for help to determine if my new off-brand fat tire bike has an issue because I get intermittent "chatter/scrape noises" when the hub motor is engaged.

The Bike:
Motor: Bafang, 750 watt fat tire rear hub bike motor, Part Number G060.750.DC
Controller: Lishui, 48V Rated Voltage, 22A Max Current, 11A Rated Current, Part Number LSW1238-31-1F
Battery: Reention Dorado, 48V, 16Amp-hrs, Part Number unknown, UPC Barcode DBSKYJY48V16AHP1805080020

While riding, my display shows the Watts in real-time and I am usually above 500 Watts when the Bafang chatters/scrape noise starts and I am thinking my controller may be causing instability. The max Watts I have ever seen on my display is ~970 Watts and it's usually 600-900 Watts with an annoying scrape sound above the normal whine noise.

My thought process is that because I have a 750 Watt Bafang hub, with a 48 V controller rated at 11 Amps and using the rated numbers (11 × 48 = 528 Watts) the "as designed ideal" nominal is 528 Watts to the motor without undue motor heat stress.

I realize that design parameters allow for rated and max. The 48 V controller max is 22 Amps, therefore, the motor can be "sent" 1056 Watts (22 x 48). The bottomline is that I am usually above the controller rated parameters in Watts (lots of hills) and have accepted the scrape noises, for now.

The 48 Volt 16 Amp-hr battery is pretty hefty but I do not know what the "Rated Amps" nor BMS are. Similar google searches indicate that the BMS max may be 30 Amps but I cannot confirm it. The seller is no help.

I think it is either undersized controller, an undersized Bafang 750 motor (Bafang has been known to have 350/500 Watt internals inside a 750 Watt motor) or maybe some loose internal magnets (they are glued). I tried and failed to open my motor to check.

WDYT ?

 

[E-HP]

Sounds like something is wrong with the motor, not a ratings issue. My guess is you'll need to open it up, even though your hypotheses would be less work.

 

[Sunder]

Without seeing or hearing it, I'm going to take a wild stab that it's a badly tuned sensorless start. If it is, it will judder and hum a bit while lurching you forward a little, then be perfectly smooth and fairly quiet once you've moved more than about 1/3rd of a rotation of the wheel. I went to the Lishui site, but can't find your exact model, but all their eBike controllers support both modes, so it's possible that it was designed for a sensored start, and hence the sensorless settings were never set up, but the hall sensors aren't working so it's falling back.

If it makes the chatter/scrape noises while you're cruising on partial throttle, you can completely rule this out as the problem. However, if it also occurs while you're moving, and change from a closed throttle to an on-throttle, it's still a likely candidate.

 

[amberwolf]

Without seeing or hearing it, I'm going to take a wild stab that it's a badly tuned sensorless start.
<snip>
I went to the Lishui site, but can't find your exact model, but all their eBike controllers support both modes, so it's possible that it was designed for a sensored start, and hence the sensorless settings were never set up, but the hall sensors aren't working so it's falling back.

FWIW, the tiny 6 and 9 FET LS controllers I have here, have a little hall emulation board mounted on the hall sensor pads of the controller inside, and no hall wires outside teh controller. They don't do startups very well, and sound a lot like the OP describes, especially with geared hubs (where they often run the motor back and forth until they finally try to startup forward).

 

[dannydibbert]

Without seeing or hearing it, I'm going to take a wild stab that it's a badly tuned sensorless start. If it is, it will judder and hum a bit while lurching you forward a little, then be perfectly smooth and fairly quiet once you've moved more than about 1/3rd of a rotation of the wheel. I went to the Lishui site, but can't find your exact model, but all their eBike controllers support both modes, so it's possible that it was designed for a sensored start, and hence the sensorless settings were never set up, but the hall sensors aren't working so it's falling back.

If it makes the chatter/scrape noises while you're cruising on partial throttle, you can completely rule this out as the problem. However, if it also occurs while you're moving, and change from a closed throttle to an on-throttle, it's still a likely candidate.

It never happens at the start under throttle only or pedal assist. It's during pedal assist when going up inclines and hills with the displayed watts increasing (ie. more current). It then comes and goes almost randomly although I have been trying to document specifically when. I'd say it is most prevalent when my display reads >750 watts up to the ~970 watts max I've seen on the display going thru my 750 watt motor. If I stop pedaling, it stops (0 watts).

 

[amberwolf]

Turn off the motor system, and pedal up the hill. If it still makes the noise, it's the freehub bearings. (or freewheel, but the freehub in my Fusin motor had a disintegrated outer bearing that made a hell of a racket I've never heard from a freewheel. )


Otherwise, it could still just be the way the controller sends power to the motor, not timed properly, either because of design (if it has always been this way), or because of a problem (if it just started).

 

[Sunder]

Yeah, you've ruled out my first suggestion.

I think Amberwolf's suggestion is your next best bet... The only thing I can think of after that is a dodgy clutch could *possibly* do what you're describing, but to be honest, I've never opened up (or owned for that matter) a Bafang geared hub, so I have no idea if it even has a clutch. I'm basing that guess off the roller bearing clutch that the very similar Q100 series motors have (of which I've rebuilt several)

It just seems unlikely from what you describe that you could get the noise due to insufficient power. It could be coincidental that it happens when you are applying high currents, and hence also high torque - hence the guesses about checking the freewheel/freehub/clutch. If you stripped the internal gears, the noise would be on constantly.

 

[amberwolf]

The only thing I can think of after that is a dodgy clutch could *possibly* do what you're describing, but to be honest, I've never opened up (or owned for that matter) a Bafang geared hub, so I have no idea if it even has a clutch. I'm basing that guess off the roller bearing clutch that the very similar Q100 series motors have (of which I've rebuilt several)

That's what's been in every geared hub I've opened up so far (fusin, ezee, tongxin, unbranded, or seen pics of here on ES, except for the GMAC and the old Fusin that had a fixed connection from gearing to shell, and maybe one other like taht one around here somewhere. I have not yet opened up the Bafang hubs from batterywarehouse deal, or the Bafang fatbike hub I've got, but they all freewheel one way and not the other, so they probably do too.

The only clutch i have broken so far (on a Fusin) wouldn't transmit any motor power at all, until I put a radiator hose clamp around the cracked clutch housing, which at least got me home.

 

[Sunder]

The problem of worn springs not letting the clutch engage properly has been well known, and given I drive my Q100Hs up to 1100w, it was a almost considered a consumable.

But I've had one where the spring didn't exactly wear, so much as tangle and get crushed under the roller. I couldn't see what was actually happening - this was a post mortem when I pulled it apart, but it appeared to be making the clutch intermittently engaging and disengaging suddenly, which was horrible on the gears, and making a crunching/grinding noise. The thing is, it would happen both when I did strong starts and up hills.

I've since done the "cut spring, add ball bearing" mod to one motor, and not had the issue again - even after several years - but I want to build another one, and I am having nightmares about how fiddly it was.

Anyway, I guess OP will have to do the old eliminate and keep hypothesising until he finds the issue.

 

[dannydibbert]

Thanks for all the suggestions. The bike is new. It was bought from a small business who works out specs with China and sells out of his house. He has now sold his business. He told me that the occasional scrape noise is normal. His tech specs do not indicate anything about the controller so I suspect it is a cheap one. I will try to record the noise later today.

https://www.perryspowerbikes.com/product-p/f2-ppb.htm

 

[markz]

It was bought from a small business who works out specs with China and sells out of his house.

Sounds to me like the owner just has an Aliexpress/Alibaba and an ebay account, because there are no specs to work out. You work out specs when you purchase 500 qty of something, not 5. New owners, yeah could very well be. I would be wary especially if the old ownership had any kind of negative rating. It wouldnt surprise me if the son, neighbor or friend owns it now. But thats all "who knows", its like the "owners" of an ebay store with multiple stores showing the same image, but I am tangenting.

The problem could be misaligned hall sensors, or a motor that got very hot and was on the verge of smoking but didnt, or just a very jittery controller when you first start off which is common for very cheap controllers.

 

[dannydibbert]

So I did some test runs.

1. From a stop I accelerated with full throttle only on level ground and everything was basically OK, maybe a slight scrape noise but nothing that was record-able.

2. From a stop I accelerated with full throttle only on a decent incline and the scraping started when my display showed ~960 Watts and I recorded it. 960 Watts is the max I ever see which calculates to 20 Amps (960 Watts / 48 Volts = 20 Amps). I continued riding and noticed that the vast majority of the scrape noise occurs at the 900+ Watt display. Also, when I then released the throttle the scrape noise remains for a couple of seconds and then goes away. Partial throttle of less and much less than 900 Watts does not cause any scrape noise. This was all done without peddling. At the end of the 6 mile run the Bafang 750 was warm to the touch, not hot at all especially with a 90 deg F day.

The file is an MP3 file and I had to change the extension to JPG to get it to attach to the post. Just change the extension back to MP3 and you should be able to hear it. The first 20 seconds is my accelerating with various road noises but the scrape noise is very audible for the next 7 seconds and then I released the throttle.

Some of my research indicates that a slightly loose rotor permanent magnet (they are supposed to be rock solid glued to the rotor) could be "bounced" around when the electromagnet windings of the stator are under high current. 20 Amps is also at the max end of my controller (11 Amps rated) and poorly designed control loops can get unstable at the limits.

I also ordered an oversize bore Shimano cassette removal tool from feedbacksports.com (item 17143) which I hope will let me remove my rear cassette so I can get inside my Bafang 750. The nut/washers are too big to go thru the standard Park tool and too small to slide over the Bafang 750 connector. My bike also has a 10 speed cassette which blocks the Bafang 750 torx screws.

Having trouble attaching the file -- stand by .....

 

[dannydibbert]

My Bike

 

[dannydibbert]

The mp3 recording of the noise at 20 seconds

https://drive.google.com/file/d/1ogwRKmNJDOAxhCVXV3dL2p0M5niQ3Ywo/view?usp=drivesdk

 

[markz]

The mp3 recording of the noise at 20 seconds

https://drive.google.com/file/d/1ogwRKmNJDOAxhCVXV3dL2p0M5niQ3Ywo/view?usp=drivesdk

Almost sounds like bearings or a wheel out of alignment and catching V-brake pads or boss mount.

 

[MadRhino]

IMO it has nothing to do with the controller.

I too, find it sound like a mechanical friction. Could be bearing, freewheel, disc screws... or any other component rubbing.

 

[GodsWarrior]

That my friend is a mechanical noise...it sounds right at the start(you can barely hear it) and gets louder as u pick up speed.... Dont know what it is but its mechanical.

 

[E-HP]

Are both axle nuts tight? Do you have torque arms?

 

[dannydibbert]

That my friend is a mechanical noise...it sounds right at the start(you can barely hear it) and gets louder as u pick up speed.... Dont know what it is but its mechanical.

Everything is tight. Brake pad clearances good. Initial noises are different and very minor. The grinding noises occur only when the motor starts drawing >800 watts and is very repeatable. No noises at all when running motor with bike upside down although the motor only draws 250 watts max when bike is upside down (no load basically).

 

[goatman]

id try taking the chain off, noise goes away its probably freewheel/cassette

 

[999zip999]

Nice-looking bike.

 

[Sunder]

That my friend is a mechanical noise...it sounds right at the start(you can barely hear it) and gets louder as u pick up speed.... Dont know what it is but its mechanical.

Everything is tight. Brake pad clearances good. Initial noises are different and very minor. The grinding noises occur only when the motor starts drawing >800 watts and is very repeatable. No noises at all when running motor with bike upside down although the motor only draws 250 watts max when bike is upside down (no load basically).

Wait, what? 250W no load? You have a phase order issue. Unless you're trying to turn a truck tyre, no wheel should need 250w under no load. Unless you mean just for the first second or so, to get the wheel spinning?

The no load power for most ebikes should be 50-80w once it reaches a stable top speed.

 

[fechter]

I've had strange motor noises when my spokes were loose in spots. Check the spoke tension.

 

[amberwolf]

No noises at all when running motor with bike upside down although the motor only draws 250 watts max when bike is upside down (no load basically).

There's either something seriously wrong with the wattmeter, or the phase/hall wiring combination is wrong. It shouldn't draw more than around 1-2 amps max for no load, which would be at most about 100w (which would still probably be pretty high). If you're getting twice that (more like four to five times as much as would be typical), and the wattmeter is accurate, either you have a physical problem causing drag on the motor somewhere, or you have the wrong combination of phase and hall wires (a "false positive").

 

[GodsWarrior]

Have you opened up your hub motor yet? Just keeps sounding like something is rubbing espcially under load....maybe something inside miss aligned or needs a little shaving somewhere....