Bafang BPM Pics and Specs - Large 3.9Kg Sensorless Geared

This is my first post. I've spent many hours reading ES posts and have learned a great deal thanks to so many of you. I'm not going to ask questions, but post information about a Bafang motor I haven't seen discussed here in any detail. Hopefully some will find this interesting and post their thoughts and comments.

Let's see if this shows up with pictures and links. Let me know if I've posted this to the wrong forum, etc. --John

The source of my information is a German (?) site I found on Google. The link follows. The article also has details on Tongsin, Puma, and the Bafang BPM and SWXK. Interestingly, this is a sensorless motor.

http://translate.google.com/transla...h?q=Tongxin+-+Bafang+--+FWF+-+Puma&hl=en&sa=G


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I just saw this on ebay at ecity. The first retailer I've found listing it. http://cgi.ebay.com/Bf-350W-BPM-Per...1c0c4adaff&_trksid=p3911.c0.m14#ht_500wt_1173.

No, I'm not a shill for eCity, and Dogman doesn't work for Ping (LOL).

I'm curious about this motor. I was surprised no one responded to my initial post. As a newby, I probably put it on the wrong group or should have added it to the geared hub thread. Anyway, it is bigger than than the standard Bafang. Look at the size of the satellite gear bearing compared to that of the regular Bafangs. They look much larger. Shouldn't this give it more torque? It is also rated by Bafang at 350w and weighs about a kilo more. Could this be cheap competition for the BMC 400w?

It is sensorless. Most people seem to like hall equipped motors from what I've observed. Is this really a bad thing? Will Keywin fix me up with a proper controller for this.

Anyway, post some comments on this motor. I'm really interested in what you guys think. Bafang guys, Russell, Dogman, Docnjoj, Nogwin, Marshy, what do you guys think. Should I just keep my focus on the regular Bafangs? I am planning to make my first build. I'm not yet looking for a hot rod.

Thanks!

That larger bafang does look interesting.

Here's my comments:

* Still has plastic gears (hopefully better quality!)
* Still appears to have a cast aluminium case
* Gear side of motor core is not sealed from the windings. So, you can't put heaps of grease on the gears or it will sling all over the windings. But, open design may be better for heat transfer.
*In photo 'Internal 3' it almost looks like it's using a very large diameter bearing (that black ring). Interesting if it is...
*Looks like it has a higher winding density and a fair bit more copper then the small bafangs.

I think it'd be fun to play with, but it might still fry at higher power or get peanut butter gears like some have found the original bafang to do.

Thanks for the comments voicecoils. Can anyone tell if this is actually sensorless? Ypedal, I think, said that freewheeling motors can't be sensorless because pedaling doesn't make them spin. Do I have this right? (ypedal, my apologies for any misquote.)

I have a hard time deciphering the Bafang product line mostly because of their convoluted website and also because of the letter designations for their motors. After studying them for some time all I know is my original motor, one of the nicely polished front motors with the cable through the axle and not disc capable, is a QSWXB (‘Q’ being front, No-Q being rear). The motor only has a serial number on it with no other manufacturer information, probably because many are sold to OEM’s. The QSWXH (sensored, cable thru axle, disc) and QSWXK (sensorless, cable exiting case, disc) are even smaller than my QSWXB. The BPM is also sensorless and as you have shown is probably the biggest Bafang and just about 5-6mm smaller than a BMC or eZee. I’m not sure where the “Climbing King” falls.

The problem right now with the sensorless motors is finding a controller that works with them. I bought a mini-motor from GoldenMotor because it employs hall sensors and can be used with the controller(s) I already have. I thought it would be the same size as my QSWXB Bafang but judging by its dimensions it may well be a QSWXH though once again there is no information on the motor except for a serial number.

As you noted Ecitypower has the rear BPM and front QSWXK sensorless Bafangs for sale on eBay (as well as the rear SWXH sensored motors) but doesn’t list a controller for them. The biggest flaw however with the rear Bafangs is the cable exiting on the drive side which complicates maintenance and repairs. This is a deal breaker for me.

-R

Looking at the Bafang website it sure looks sensorless. Same scrawny phase wires though. Also, they have one called the BPM Climber, which weighs 4.6kg and is rated 750W at 48V. see http://www.szbaf.com/en/Product.asp?CategoryID=275 toward the bottom.

Ypedal, What's wrong with AL housings? The ring gear is a steel insert, and AL is lighter. Also, can grease cause a problem in a sensorless motor?

John

It is indeed a sensorless motor. The motor size is larger than the standard bafang, and it uses a different gearset that is made of the same nylon material. Uses the same 16awg wire as other bafangs. The "climber" version is just a slower wind.


The aluminum housing is just cast of unknown quality stuff. There are occasional voids in the material.

johnrobholmes said:

The "climber" version is just a slower wind.

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With more than a pound more of what? Are you going to be getting any of these in? Controllers for them? It seems like something I want to try without the housing or gears, in a non-hub setup.

John

Are there weight differences too? If the climber is heavier, maybe it is just larger all around. I doubt they would invest in another gearset and stator size personally.


I don't think I will be getting them in. I can't compete with the ebay and china vendors who are selling direct, it is the same price for me buying from bafang!

johnrobholmes said:

Are there weight differences too? If the climber is heavier, maybe it is just larger all around. I doubt they would invest in another gearset and stator size personally.

I don't think I will be getting them in. I can't compete with the ebay and china vendors who are selling direct, it is the same price for me buying from bafang!

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JohnRob,
If you still want to deal in motors, you may want to talk to Louis at Fusin. Their geared hub motors are significantly more beefy than the Bafangs. The planetaries are thicker, seem like a better material, and have a larger gear ratio. Plus the stator is 30% or so wider. Since Dogman's didn't melt in the desert over the summer, they've gotta be tougher than the Bafangs. My interest in the new Bafang is to get one cheap, and run it out of the housing with real wires and some real power.
John

You just want a bare bafang motor with no housing or gears?

I think he means run the wires out of the housing instead of the axle, so as to be able to use larger wires.

Ah, yes. Thats going to be a tough one. Maybe the front version they have that is non sensored?

johnrobholmes said:

You just want a bare bafang motor with no housing or gears?

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Absolutely, PM me a price including shipping to Miami 33122. The wiring harness can even be bad, just not blackened windings.

John

I will look around and see if I have one. I am pretty sure I do somewhere.

The intended use would be like a sensored RC motor with a single stage reduction mounted directly to a swingarm by the axle. A composite ventilated fixed housing will protect it from debris and the elements while allowing real phase wires to run directly to the stator. I'm doing this with a Fusin geared hub motor too, and I'd like to compare with a Bafang.

John

The usable power of a motor increases with the square of the stator diameter, and linearly with the width of the stator. Ignoring efficiency differences you can get a pretty good rough comparison based on these measurements alone.

Took the bike for a spin for the first time this arvo with the newly built rear wheel with the Bafang BPM code 13 @48V/25A.

First impression - its a beast, a raging bull! Sensorless works quite well. There is a slight delay at the startup, but so tiny that is prob not worth mentioning.

Pros: being able to spin the rear wheel on the gravel, being able to ride a downhill singletrack backwards i.e. uphill (if that makes any sense)

Cons: Top speed was ~36km/h (even though it only takes a couple of seconds)

Will write a more detailed review some time later..

full-throttle said:

Took the bike for a spin for the first time this arvo with the newly built rear wheel with the Bafang BPM code 13 @48V/25A.

First impression - its a beast, a raging bull! Sensorless works quite well. There is a slight delay at the startup, but so tiny that is prob not worth mentioning.

Pros: being able to spin the rear wheel on the gravel, being able to ride a downhill singletrack backwards i.e. uphill (if that makes any sense)

Cons: Top speed was ~36km/h (even though it only takes a couple of seconds)

Will write a more detailed review some time later..

Click to expand...

Nice work full-throttle!

At 60v nominal (lifepo4) should give about 48 km/h then which would be perfect.

Or 72v nominal (lifepo4) should give about 58 km/h

It looks like it might have enough copper to take take 60v25A reliably so that could be a good setup.

You won't go back to small underpowered hubmotors now!

Thanks for the post and welcome to ES! As best I can tell, you are the first BPM owner on the forum. I'll be looking forward to your future posts. What controller are you using?

I have one of these on order for a 26". Do you have advice on wheel build? Do you know the spoke length I will need? I'm thinking Sun Rhyno Lite with a Maxxis Hookworm.

Any advice is much appreciated.

full-throttle said:

Took the bike for a spin for the first time this arvo with the newly built rear wheel with the Bafang BPM code 13 @48V/25A.

First impression - its a beast, a raging bull! Sensorless works quite well. There is a slight delay at the startup, but so tiny that is prob not worth mentioning.
...

Click to expand...

Thanks for the report.
What controller are you using?

The controller is 12-mosfet Big Box from http://www.lsdzs.com/ (their site is down as I write this)
The reason I went for this particular one is that I've already had contacted them previously. They also have a PayPal account and were very helpful. The controller uses IRF1010E mosfets and is rated 48V 25A(peak)/12A(cont). Incl shipping it turned out to be AU$57 (less than US$50). Inside it has the main board with power supplies, mosfet drives and the main processor and a plug-in board with another processor that does phase-to-hall conversion. I had it powered in the lab at work and the CRO shows its doing the right thing - the waveforms are identical to the ones in the app notes for sensorless washing machine drive (a similar scenario to an ebike)

Spokes are from an online BMX shop that voicecoils found: 194mm black double-butted 14/15 (I use washers on the hub flanges), mated onto a Mavic F519 rim I already had. I think these choices could be quite personal, dep on budget, previous experiences and hype.

A quick update: last night I took the rear wheel off and noticed that the torque arm converters are having hard time coping with all the forces. Right now they are 4.5mm mild steel and no issues with the previous setup for over than 4,000km.

Following is a readable technical drawing of the BPM. (Can one read a drawing? ) I could not find a readable one online and Victor M. Dong at Suzhou Bafang Electric Science-Technology Co.,LTD was kind enough to send me the pdf.

Thanks for the initial review. This motor looks like a nice step up from Bafang's smaller motors - such as the SWXH which I've been enjoying lately, but find it gets too hot easily for my needs.

Full-throttle, you mentioned a "top speed of 37 km/h" for your code 13 wind. Is that on level ground without peddling? Does anyone else have experience with this or other codes (read winds) of the BPM?