Bafang BBS01 changing RPM

Deere John

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Hi all, I have long been disturbed about the BBS01 low speed. Only rated 78 rpm at 36V/250W version.

Personally I like riding at about 80-100 rpm or something like that.

So the BBS01 cuts out just when beginning to reach the sweet spot.

How to fix this?

I guess you can't change this through programming because it has to do with winding/voltage.

But then I came by this great comparison of different versions:

Spec comparison.png
https://www.elecycles.com/bafang-bbs01b-bbs02b-bbshd-250w-1000w-mid-motor-conversion-kit.html

That makes it very interesting. IF I would have a BBS02/36V/500W version, program it for 250W. Suddenly I would have the same bike, legal. And with 113 rpm instead.

That would be fantastic!

But then I came up with another idea? Wouldn't this only be a winding issue? And thus... is it possible to change the stator to this one?
(can be found here: https://www.greenbikekit.com/bbs01-bbs02-kit-core-stator-rotor-for-replacement.html)
Maybe it doesn't physically match and/if some other issue?

Any ideas?
 

Fordulike

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Feb 26, 2010
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Personally I like riding at about 80-100 rpm or something like that.

So the BBS01 cuts out just when beginning to reach the sweet spot.
Have you had a look at your programmed parameters with the programming cable and software? Even though the RPM appears to max out at the lower end of your preferred cadence, a low 'Keep Current', lower than 100% speed limit or lower than 100% current limit, could mean the assistance fizzles out too low in the RPM range. If you get what I mean :rolleyes:
 

Deere John

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Have you had a look at your programmed parameters with the programming cable and software? Even though the RPM appears to max out at the lower end of your preferred cadence, a low 'Keep Current', lower than 100% speed limit or lower than 100% current limit, could mean the assistance fizzles out too low in the RPM range. If you get what I mean :rolleyes:
Yes, I get what you mean. When I first got the bike this issue was a real disaster. The stock parameters was really bad. But now I have changed them. I have tried with both at 100% and it gets "almost ok". But still I always wish it would assist higher up.

Found a great thread on Endless...
http://52.25.253.50/forums/viewtopic.php?f=28&t=58780&start=575



It is an issue with the BBS01. One good thing though is that it is probably better battery time :)
 

KirstinS

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Apr 5, 2011
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And just a note on legal, don't shoot the messenger , if it ain't stamped 250w by the factory it ain't legal. So a 500w or 750w still isn't legal if detuned to 250w settings

Yes, I know.

Don't shoot the messenger
 

Fordulike

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If it were me, I wouldn't risk changing the internals to try and get what you want to achieve. I would just go for the BBS02/36V/500W and flog the 250w to cover some of the costs.

BTW, the messenger has been shot, you may never see KirstinS again :D:p:D
 

anotherkiwi

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Get a GSM from Woosh and a 48v battery would be the cheapest legal sollution. I only need 44.4v :)
 

Deere John

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And just a note on legal, don't shoot the messenger , if it ain't stamped 250w by the factory it ain't legal. So a 500w or 750w still isn't legal if detuned to 250w settings
The stamp is on the BBS-chassi. Stator and controller are spares. So that would not be a problem. And I should use the same controller, probably with same programming also, so no tuning at all :)

If it were me, I wouldn't risk changing the internals to try and get what you want to achieve. I would just go for the BBS02/36V/500W and flog the 250w to cover some of the costs.
Mine is so used it would be pointless trying to sell :) changing stator is easy. I had it removed a few weeks ago, too bad I didn't think of this then :( I'm only worried about some compatibility issues between BBS01 and BBS02 parts.

Get a GSM from Woosh and a 48v battery would be the cheapest legal sollution. I only need 44.4v :)
GSM, that is an interesting motor. Wonder if it is improved somehow compared to Bafang. So what is the RPM of that one?
 

Deere John

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Now I have found drawings of the two. Have read that BBS02 is bigger, just didn't understand exactly what dimension is changed. Seems it is only the "axial" length of the motor. 6mm more protruding to the crank arm. No problem.

Also, the rotor can be found in various spec so I guess a new rotor is also necessary.

Would be great to find pictures on the stators to see if some mechanical attribute is changed so it does not physically match.

size_comparison.png
 

anotherkiwi

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GSM, that is an interesting motor. Wonder if it is improved somehow compared to Bafang. So what is the RPM of that one?
I should have said external controller GSM - 85 RPM loaded like the Bafang @ 36v so about 110 at 48v. It is BBS01 clone (BBS01 parts fit), the only distinguishing feature is the external controller version.

Oh and 64.5 mm chainline from technical drawing not measured on bike.
 
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Deere John

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I should have said external controller GSM - 85 RPM loaded like the Bafang @ 36v so about 110 at 48v. It is BBS01 clone (BBS01 parts fit), the only distinguishing feature is the external controller version.
mkay... but if you change connector on the BBS you can use external controller also. If you want. But I like the programming capabilities of the stock controller so I don't wanna change :)

Oh and 64.5 mm chainline from technical drawing not measured on bike.
Is that the dimension that is 50mm on above BBS drawings? strange if so
 

anotherkiwi

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mkay... but if you change connector on the BBS you can use external controller also. If you want. But I like the programming capabilities of the stock controller so I don't wanna change :)

Is that the dimension that is 50mm on above BBS drawings? strange if so
Yes but I am calculating for a double chainring, the single dished one supplied is about 50.3 mm like the BBS01. Remove the dishing and add half the space between the two chainrings you are at about 58-59mm, add 5mm for maximum derailleur reach...

Where I live a double chainring is mandatory, not an option for the most interesting rides. And yes, I am talking about on the road :eek:
 

Deere John

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Yes but I am calculating for a double chainring, the single dished one supplied is about 50.3 mm like the BBS01. Remove the dishing and add half the space between the two chainrings you are at about 58-59mm, add 5mm for maximum derailleur reach...
Ok, then I understand. The standard ~50mm is not great either so I was worried there :)

Where I live a double chainring is mandatory, not an option for the most interesting rides. And yes, I am talking about on the road :eek:
I just put an order for a new 11-46T cassette for mine :)
 

Deere John

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One good thing though is that it is probably better battery time :)
I was thinking about that. Is it really good for efficiency to pedal near motor max rpm? This max rpm that it has, is it the physical maximum rpm or is it some limited rpm? I mean, isn't this kind of motors most efficient in the 65-85% range of top rpm or something like that? In that case it would be bad for the efficiency if going on 95-100% mostly.

This BBS02 with 113 rpm would give some head room so you might even tune down max speed a little, then you might be at some lower %. Would be more efficient.

I find it a little odd that all these models have so different rpm. From 78-140! Wouldn't the goal be to have a particular cadence and then a correct wind (or gearing) to get there.

Or... I am just way off the track with my thinking and the BBS01 just performs best at 78 rpm!?
 

anotherkiwi

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I get back EMF when I spin over about 85 rpm at 36v and closer to 100 rpm at 44.4v (nominative) so the correct rpm is an issue. I wrote last week in another thread that after using my trike - no motor and my preferred cadence is quite high - getting back on to the pedelec the motor cut out immediately on the first hill because I was spinning too fast.

You also see the Watts go down on the LCD Watt meter as you spin faster. I have a tendency to change down to maintain cadence so I really have to think about slowing down the rpm to keep the motor working on steep hills.

So if you spin like me one of those high rpm motors will help or... get a cadence meter and adapt you spinning to the motor. As battery voltage goes down so must cadence, don't forget!
 
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Deere John

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...ok, yes, I am about pulling the trigger here. But I can't get wise about the rotor. Some stores list the BBS01/BBS02 rotor as same article no (68mm). While the BBSHD has both 68 and 72mm. Kind of strange. Need to investigate more.

Meanwhile I made a Photoshop comparison of a BBS02 to my BBS01 :) have stretched the photo a little so that nuts is on the same place (and then moved it to the right to see). Looks very same.

BBS_comparison.jpg
 

Deere John

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Got reply from Green Bike Kit. They just say it is different and not gonna work :) but when I asked about what is different I got this pic. Seems rotor is also different. Still I am not 100% sure about this but I felt that I can't really know until I've tried myself so I ordered the stuff :) will be most interesting!

bbs01 and bbs02 core different.jpg
 

vfr400

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When the BBS01/02 first came out, Bafang told me that the 02 had thicker wire in the windings and the motor was slightly wider.

Regarding efficiency, it's true that as any electric motor approaches its max speed, the efficiency drops off, but so does the power, so you're wasting a higher proportion of a very small amount It's nothing compared with how much you waste at the point of maximum efficiency.
 
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Deere John

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mmm, yes, maybe it's not worth worrying too much about this. It was just a little interesting :)

Found this graph of a standard BLDC-motor.

BLDC-performance-graph.jpg

http://www.mellorelectrics.co.uk/BLDC-MOTOR-EN.html

Maximum power is delivered way before the efficiency peak.

Because of that I have actually two different settings:

MTB mode: Here i want top torque but not top speed: so speed limited to 72%.
Road mode: Top speed (with better efficiency also). Not speed limited.
 

Woosh

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the usual method of changing the noload RPM is to change the battery's voltage. The other two methods are changing the winding (fewer spires = faster Noload RPM) or changing the back EMF with a Field Weakening controller (weaker magnetic field= higher speed).
Changing the voltage is by far the most popular approach but there is no free lunch, the risk of damaging the controller goes up exponentially with the voltage. Using an external controller does not change the motor's constants. Changing winding code (lower= faster =less maximum torque at low speed) may be possible if you can order in bulk, FW controller wastes more energy in heat.
 

anotherkiwi

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Which is why I would always recommend an external controller, heat is easier to evacuate. I have finally found a supplier of a 15 Amp KT sine wave controller that is 36/48v and which has waterproof plugs to boot. All that needs to be done is to add an external speed sensor connector which is really easy because there is a useless light connector coming from the controller.
 
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