Bafang Bpm, how many RPM?

General Discussion about electric bicycles.
Herrsprocket   100 W

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Re: Bafang Bpm, how many RPM?

Post by Herrsprocket » Jul 11 2012 11:46am

Greetings all,

I'm not sure if BMS battery itself understands its own code ratings and voltages for the BPM motors but simply passes along the information as given to them from managerial marketing. Regardless, many months ago I too wanted to de-confuse the code ratings so I could better understand exactly the performance values and code reasoning for any particular motor. So I began a communication directly with Bafang and they were extremely informative, courteous and helpful. The coding actually from Bafang is quite simple. It seems however, that BMS battery tends to muddy the waters by simply filling in different market needs with a variety of voltages, windings and wheel sizes. This marketing ploy from BMS battery is understandable and does help satisfy a wide spectrum of performance values, but unless you know the basics of how the motors are coded directly from Bafang, you'll be scratching your head like most of us have.

Firstly, the two BPM models and the new CST cassette hub model are all rated at 36 V. The coding applies to a 36 V input and all the values I will be giving you are in unloaded conditions. Let's begin with a code 16 motor and work our way up to the code 8 motor.

The code 16 motor is rated at 192 RPM. The code 15 is 205. The code 14 is 215. The code 13 is 230. The code 12 is 250. The code 11 is 280. The code 10 is 300. The code 9 is 335. And the code 8 is 378. That's right, the code 8 at 36 V is not 393 RPM but is 378. Again, mind you all of these specifications are directly from the engineers of Bafang.

And thus the game begins. The closest proximity I can muster for the difference between a 36 V and a 48 V system is simply to take the code rating at 36 V and multiply it by a factor of 133% for an approximate unloaded speed at 48 V. This is not an exact science but it's fairly close for our unloaded guesstimations. As an example, you will see that BMS battery lists a 48 V BPM model with a 393 RPM output. This is simply a 36 V rated motor with a code 10 winding that is being over volted to 48 V and will now spin at an unloaded speed of approximately 399 RPMs, or as they list, 393 RPMs. The number they list prior to the code value (which is the first number listed on the motor) is a suggested wheel size in which to put this rated voltage and coded motor into to reach a particular miles per hour value. This is confusing. You simply need to know how fast your motor is spinning with its particular voltage and code rating and then figure out how fast in miles per hour it will go with the particular wheel size that you select. Obviously, the higher code windings will give you more torque and less RPM unloaded speeds and might be better suited for larger wheels. However, it's up to you to decide whatever blows your skirt up to get the performance you want.

As TD says," have a nice day".
Last edited by Herrsprocket on Aug 26 2012 1:41am, edited 1 time in total.

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Re: Bafang Bpm, how many RPM?

Post by cwah » Jul 11 2012 6:23pm

Is the BPM code 8 equivalent to the Mac 8T?
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Re: Bafang Bpm, how many RPM?

Post by Samd » Jul 11 2012 7:08pm

Good point Russell.

Outrunner motors are sold as RPM per volt (or a KV rating).

Makes sense for us to do same...
http://ballaratebikes.com/

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Re: Bafang Bpm, how many RPM?

Post by Herrsprocket » Jul 12 2012 9:04pm

cwah wrote:Is the BPM code 8 equivalent to the Mac 8T?
Equivalence with regard to unloaded rpm's at 36 volts is as follows: BPM code 8 is 378 as per Bafang, and the MAC 8T is listed as 360 rpm.

Yep, it would make comparisons for performance values much easier if the manufacturers would list them wih KV ratings. Perhaps the "math" of then figuring out the final speeds would be too much for the general public, or so the manufacturers may think. :?

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Re: Bafang Bpm, how many RPM?

Post by phproomer » Jul 13 2012 7:29am

Herrsprocket, man thats a clear and great explanation! wish I new that before getting my engine. does bafang have a website ?, one more quastion if P put a 48volts battery to my engine 36 volts 500 watts 16(10), would it harm the engine in the long term ?

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Re: Bafang Bpm, how many RPM?

Post by motomech » Jul 13 2012 8:05am

Above poster, yes you can run that motor on 48V.

Herrsprocket, great work! I tried to decifer BMS Battery's BPM coding a while back and almost had a mental breakdown :roll:

I think I do have a handle on the mini-geared motors, at least the 36V versions. The "slow winds" are 230 rpm @ 36V and the "fast winds" are 270 rpm @36V. Except the MXUS, which is 250 RPM.
Not sure how the 24V versions play out though.
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Re: Bafang Bpm, how many RPM?

Post by miuan » Jul 13 2012 3:30pm

phproomer wrote:one more quastion if P put a 48volts battery to my engine 36 volts 500 watts 16(10), would it harm the engine in the long term ?
it's not the voltage that kills the motor. it's the heat and excessive current for long periods. you can model your motor (10 turn) in ebike.ca simulator, just choose the BPM500 motor from the list. I ride this very motor in 28 inch wheel at even higher voltage and it copes very well, so you should have no problems unless you climb some long steep hills.

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Re: Bafang Bpm, how many RPM?

Post by Marc S. » Jul 29 2012 8:05pm

Herrsprocket wrote:Greetings all,

I'm not sure if BMS battery itself understands its own code ratings and voltages for the BPM motors but simply passes along the information as given to them from managerial marketing. Regardless, many months ago I too wanted to de-confuse the code ratings so I could better understand exactly the performance values and code reasoning for any particular motor. So I began a communication directly with Bafang and they were extremely informative, courteous and helpful. The coding actually from Bafang is quite simple. It seems however, that BMS battery tends to muddy the waters by simply filling in different market needs with a variety of voltages, windings and wheel sizes. This marketing ploy from BMS battery is understandable and does help satisfy a wide spectrum of performance values, but unless you know the basics of how the motors are coded directly from Bafang, you'll be scratching your head like most of us have.

Firstly, the two BPM models and the new CST cassette hub model are all rated at 36 V. The coding applies to a 36 V input and all the values I will be giving you are in unloaded conditions. Let's begin with a code 16 motor and work our way up to the code 8 motor.

The code 16 motor is rated at 192 RPM. The code 15 is 205. The code 14 is 215. The code 13 is 230. The code 12 is 250. The code 11 is 280. The code 10 is 300. The code 9 is 335. And the code 8 is 378. That's right, the code 8 at 36 V is not 393 RPM but is 378. Again, mind you all of these specifications are directly from the engineers of Bafang.

And thus the game begins. The closest proximity I can muster for the difference between a 36 V and a 48 V system is simply to take the code rating at 36 V and multiply it by a factor of 133% for an approximate unloaded speed at 48 V. This is not an exact science but it's fairly close for our unloaded guesstimations. As an example, you will see that BMS battery lists a 48 V BPM model with a 393 RPM output. This is simply a 36 V rated motor with a code 10 winding that is being over volted to 48 V and will now spin at an unloaded speed of approximately 399 RPMs, or as they list, 393 RPMs. The number they list prior to the code value (which is the first number listed on the motor) is a suggested wheel size in which to put this rated voltage and coded motor into to reach a particular miles per hour value. This is confusing. You simply need to know how fast your motor is spinning with its particular voltage and code rating and then figure out how fast in miles per hour it will go with the particular wheel size that you select. Obviously, the higher code windings will give you more torque and less RPM unloaded speeds and might be better suited for smaller wheels. However, it's up to you to decide whatever blows your skirt up to get the performance you want.

As TD says," have a nice day".

Thanks Herrsprocket!

I just ordered the 'wrong' code 8 BPM motor from BMSBattery and could swap it because of your info to the 'right' code 10 motor before they ship it out.

I'm quite anxious to see how the new Bafang BPM in 26" rim will drive my ICE trike instead of the little Bafang SWXH in 20" rim (at 36V and 48V) I'm used to.

Marc

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Jeremy Harris   10 GW

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Re: Bafang Bpm, how many RPM?

Post by Jeremy Harris » Aug 24 2012 7:41am

Marc S. wrote:
Herrsprocket wrote:Greetings all,

I'm not sure if BMS battery itself understands its own code ratings and voltages for the BPM motors but simply passes along the information as given to them from managerial marketing. Regardless, many months ago I too wanted to de-confuse the code ratings so I could better understand exactly the performance values and code reasoning for any particular motor. So I began a communication directly with Bafang and they were extremely informative, courteous and helpful. The coding actually from Bafang is quite simple. It seems however, that BMS battery tends to muddy the waters by simply filling in different market needs with a variety of voltages, windings and wheel sizes. This marketing ploy from BMS battery is understandable and does help satisfy a wide spectrum of performance values, but unless you know the basics of how the motors are coded directly from Bafang, you'll be scratching your head like most of us have.

Firstly, the two BPM models and the new CST cassette hub model are all rated at 36 V. The coding applies to a 36 V input and all the values I will be giving you are in unloaded conditions. Let's begin with a code 16 motor and work our way up to the code 8 motor.

The code 16 motor is rated at 192 RPM. The code 15 is 205. The code 14 is 215. The code 13 is 230. The code 12 is 250. The code 11 is 280. The code 10 is 300. The code 9 is 335. And the code 8 is 378. That's right, the code 8 at 36 V is not 393 RPM but is 378. Again, mind you all of these specifications are directly from the engineers of Bafang.

And thus the game begins. The closest proximity I can muster for the difference between a 36 V and a 48 V system is simply to take the code rating at 36 V and multiply it by a factor of 133% for an approximate unloaded speed at 48 V. This is not an exact science but it's fairly close for our unloaded guesstimations. As an example, you will see that BMS battery lists a 48 V BPM model with a 393 RPM output. This is simply a 36 V rated motor with a code 10 winding that is being over volted to 48 V and will now spin at an unloaded speed of approximately 399 RPMs, or as they list, 393 RPMs. The number they list prior to the code value (which is the first number listed on the motor) is a suggested wheel size in which to put this rated voltage and coded motor into to reach a particular miles per hour value. This is confusing. You simply need to know how fast your motor is spinning with its particular voltage and code rating and then figure out how fast in miles per hour it will go with the particular wheel size that you select. Obviously, the higher code windings will give you more torque and less RPM unloaded speeds and might be better suited for smaller wheels. However, it's up to you to decide whatever blows your skirt up to get the performance you want.

As TD says," have a nice day".

Thanks Herrsprocket!

I just ordered the 'wrong' code 8 BPM motor from BMSBattery and could swap it because of your info to the 'right' code 10 motor before they ship it out.

I'm quite anxious to see how the new Bafang BPM in 26" rim will drive my ICE trike instead of the little Bafang SWXH in 20" rim (at 36V and 48V) I'm used to.

Marc
Just for info, BMS seem to be shipping the Code 10 motor when you order a 36V, 500W, 393 RPM one. I double checked with them before ordering that the motor I wanted was the 393 RPM at 36 V version (a Code 8 ), and they still sent me a Code 10, which isn't any use to me.
Please ask questions on the forum, rather than by PM, as it helps others and you'll get a better range of answers.

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Re: Bafang Bpm, how many RPM?

Post by Marc S. » Aug 24 2012 8:24am

Jeremy Harris wrote:
Marc S. wrote:
Herrsprocket wrote:Greetings all,

I'm not sure if BMS battery itself understands its own code ratings and voltages for the BPM motors but simply passes along the information as given to them from managerial marketing. Regardless, many months ago I too wanted to de-confuse the code ratings so I could better understand exactly the performance values and code reasoning for any particular motor. So I began a communication directly with Bafang and they were extremely informative, courteous and helpful. The coding actually from Bafang is quite simple. It seems however, that BMS battery tends to muddy the waters by simply filling in different market needs with a variety of voltages, windings and wheel sizes. This marketing ploy from BMS battery is understandable and does help satisfy a wide spectrum of performance values, but unless you know the basics of how the motors are coded directly from Bafang, you'll be scratching your head like most of us have.

Firstly, the two BPM models and the new CST cassette hub model are all rated at 36 V. The coding applies to a 36 V input and all the values I will be giving you are in unloaded conditions. Let's begin with a code 16 motor and work our way up to the code 8 motor.

The code 16 motor is rated at 192 RPM. The code 15 is 205. The code 14 is 215. The code 13 is 230. The code 12 is 250. The code 11 is 280. The code 10 is 300. The code 9 is 335. And the code 8 is 378. That's right, the code 8 at 36 V is not 393 RPM but is 378. Again, mind you all of these specifications are directly from the engineers of Bafang.

And thus the game begins. The closest proximity I can muster for the difference between a 36 V and a 48 V system is simply to take the code rating at 36 V and multiply it by a factor of 133% for an approximate unloaded speed at 48 V. This is not an exact science but it's fairly close for our unloaded guesstimations. As an example, you will see that BMS battery lists a 48 V BPM model with a 393 RPM output. This is simply a 36 V rated motor with a code 10 winding that is being over volted to 48 V and will now spin at an unloaded speed of approximately 399 RPMs, or as they list, 393 RPMs. The number they list prior to the code value (which is the first number listed on the motor) is a suggested wheel size in which to put this rated voltage and coded motor into to reach a particular miles per hour value. This is confusing. You simply need to know how fast your motor is spinning with its particular voltage and code rating and then figure out how fast in miles per hour it will go with the particular wheel size that you select. Obviously, the higher code windings will give you more torque and less RPM unloaded speeds and might be better suited for smaller wheels. However, it's up to you to decide whatever blows your skirt up to get the performance you want.

As TD says," have a nice day".

Thanks Herrsprocket!

I just ordered the 'wrong' code 8 BPM motor from BMSBattery and could swap it because of your info to the 'right' code 10 motor before they ship it out.

I'm quite anxious to see how the new Bafang BPM in 26" rim will drive my ICE trike instead of the little Bafang SWXH in 20" rim (at 36V and 48V) I'm used to.

Marc
Just for info, BMS seem to be shipping the Code 10 motor when you order a 36V, 500W, 393 RPM one. I double checked with them before ordering that the motor I wanted was the 393 RPM at 36 V version (a Code 8 ), and they still sent me a Code 10, which isn't any use to me.

I received my motor and the 900W charger yesterday from BMSBattery.
I've ordered the (silver) Bafang BPM 48V/500W/393rpm/Code 10 kit and got a black BPM II 48V/500W/Code 11.
Close but no cigar.

On top of that the 900W charger isn't charging but really good in blowing 250V/16A fuses.
Opened it and a big blop of solder fell out... Chinese quality at its best.
Last edited by Marc S. on May 04 2013 1:01pm, edited 1 time in total.

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Re: Bafang Bpm, how many RPM?

Post by Jeremy Harris » Aug 24 2012 9:54am

Marc S. wrote:I received my motor and the 900W charger yesterday from BMSBattery.
I've ordered the (silver) Bafang BPM 48V/500W/393rpm/Code 10 kit and got a black BPM II 48V/500W/Code 11.
Close but no cigar.

On top of that the 900W charger isn't charging but really good in blowing 250V/16A fuses.
Opened it and a big blop of solder fell out... Chinese quality at its best.
Sorry to hear that, but if it's any consolation you're not alone. I'm in the midst of a debate with them about sending me the wrong motor, and am pretty annoyed as they did this after I'd double checked with them that the motor they were going to send was actually the one I'd ordered.

BMS Battery are clearly a bit of a lottery, you don't know if you'll get what you've ordered or whether it'll work when it turns up...............
Please ask questions on the forum, rather than by PM, as it helps others and you'll get a better range of answers.

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Re: Bafang Bpm, how many RPM?

Post by miuan » Aug 27 2012 8:27am

It seems asking BMS Battery any product information is futile.
I start feeling guilty of spreading good feedback some time ago when I had a string on 5 straight orders without a single problem or breakdown. It turned out later some chargers bit the dust and people on ES would receive different motor codes without warning.
Jeremy, I still have a spare code8 sitting at my garage and would gladly exchange it for your code10, but I keep it as a spare for my 2WD project. I should have ordered 5 more at that time.
Jeremy did a mistake of leading his question to a YES/NO answer. Never ask a chinese merchant such questions, you will always get a YES answer. A better way is asking them to replicate exactly what was written between the spoke flanges. This has 2 advantages. Firstly, you know what you get. Secondly, you see if it's in stock so you don't waste your time placing the order. I did this back in spring 2011 when ordering for the first time.

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Re: Bafang Bpm, how many RPM?

Post by Jeremy Harris » Aug 27 2012 8:47am

miuan wrote:It seems asking BMS Battery any product information is futile.
I start feeling guilty of spreading good feedback some time ago when I had a string on 5 straight orders without a single problem or breakdown. It turned out later some chargers bit the dust and people on ES would receive different motor codes without warning.
Jeremy, I still have a spare code8 sitting at my garage and would gladly exchange it for your code10, but I keep it as a spare for my 2WD project. I should have ordered 5 more at that time.
Jeremy did a mistake of leading his question to a YES/NO answer. Never ask a chinese merchant such questions, you will always get a YES answer. A better way is asking them to replicate exactly what was written between the spoke flanges. This has 2 advantages. Firstly, you know what you get. Secondly, you see if it's in stock so you don't waste your time placing the order. I did this back in spring 2011 when ordering for the first time.
I think you're spot on about the YES/NO thing, looking back on it now. With the benefit of hindsight I should have done as you said, and given them the exact part number I wanted.
Please ask questions on the forum, rather than by PM, as it helps others and you'll get a better range of answers.

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Re: Bafang Bpm, how many RPM?

Post by Beagle123 » May 03 2013 2:18pm

Hi Everyone. Thanks for the info. Here's my contribution:

I just purchased a 48v 500w BPM kit from BMSBattery, I selected the 201 RPM option. And here's what they sent me.
DSCN1514.JPG
It has the inscription BPM 48v 500W (14) on it, So I guess its a code 14. There's a green circular sticker that says QC 03.
DSCN1513.JPG
DSCN1512.JPG
It doesn't look like any of the pictures I've seen of it online. They're all shiny chrome with the 8fun logo on them. This one is all matte finished. I like the pretty chrome one. I don't know if this is a real 8fun motor or a clone. WHy would they make two different silver varieties? Its a little fishy.
DSCN1511.JPG
The diameter is exactly 7 inches, so its the right size.
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Re: Bafang Bpm, how many RPM?

Post by Beagle123 » May 03 2013 4:38pm

Also, now I've discovered that there are no bolts or washers included in my kit. When I received the wheel, the axles had nothing on them. No bolts, washers, or torque washers.

I've screwed on a 7 speed freewheel, but now I've discovered another problem. The freewheel protrudes so that if I placed the wheel in the bike and tightened the bolts on the axle, the bike's frame would smash against the freewheel. On the original bike hub, there's a bolt on the axle that protrudes further than the freewheel so it is clear from the frame:

DSCN1515.JPG
Does anyone know how this is supposed to work?

I will ask BMSBattery about the bolts and washers and report back on their customer service. I'm a person who doesn't value customer service, but I can't be missing crucial parts.

Eric
Avoid BMSBattery like the plague. (I read that somewhere :)

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Re: Bafang Bpm, how many RPM?

Post by friendly1uk » May 04 2013 11:56am

My 500w CST came last week. They were going to tell me what was sent to them when they got it, So I could accept it or cancel. Next I heard it was on it's way to me. Upon arrival I tried to relieve my sunken feeling by reading the label. It's cast with the 8fun logo, and the text printed on goes..
CST 36v500w 26
1304 0933

Nothing in brackets

The bill has something scrawled across it. " HScode871,42000 " Although the 4 could easily be an X

I have asked, but since they shipped they no longer talk to me. I also wrote another note about the bms getting broke as it had no packaging, but it was fine as I ordered two expecting this. Also a note about the spokes they advised me to get being too short to get over a turn on each nipple. They are in fact 186mm and the calcs say 189mm, but that was not based on erd but simply the hole being 531mm face to face. So add a couple more mm, and suddenly the spoke threads are actually within the nipple, not hanging out 4mm

I really need the proper size for ordering spokes. I measure 165mm but that was using a compass. Not really the way is it...
bmsbattery sent me broken and incorrect stuff, and won't even talk to me about it.

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Re: Bafang Bpm, how many RPM?

Post by d8veh » May 05 2013 10:31am

The speed of your motor is 270 rpm like it says on their website.

You have to use a spoke calculator algorithm to determine spoke length. You need 210mm for 2 cross.

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Re: Bafang Bpm, how many RPM?

Post by friendly1uk » May 05 2013 5:22pm

There is no such thing as a 270
I have an over sized frame and tyres, so the skinny bms wheels are scrap. I'm getting some sun mammoths and going 1x. That actually puts the angle the spokes enter the rim further off 90 degree's than a typical 3x. I reckon that ought to do it. I'm not happy about having 1x on the other wheel to match, but it's the front and a big strong rim, I should be able to look after it.
bmsbattery sent me broken and incorrect stuff, and won't even talk to me about it.

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Re: Bafang Bpm, how many RPM?

Post by ShoGinn » May 11 2013 4:03pm

Found this post on google, and wanted to do a cross ref to a nice table here in another post

http://endless-sphere.com/forums/viewto ... =2&t=43106

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Re: Bafang Bpm, how many RPM?

Post by -dg » May 11 2013 6:03pm

For future reference:

I ordered a 36V 500W BPM from greenbikekit.com near the end of April 2013. I selected 216 rpm from the webstore drop down selector (the other choice was 312). I received a code 10 BPM (not BPM2) with sensors.

I measured the no-load speed using a lipo pack, a greenbikekit CON61 controller and a cycle computer set up for a 700c/32 tire. This tire size works out to be 8 mph per 100 rpm. My measurements appear to be a couple percent slow compared to Jeremy's chart for BPM speeds. My cycle computer only reads in 0.5 mph steps which may account for this.

For the greenbikekit.com 36V 500W "216 rpm" BPM I measured a no-load speed of 33 mph @ 49.3 volts as 33 mph at 49.3 volt. This is just over 24 mph or 300 rpm at 36 V which correlates fairly well with Jeremy's chart for a code 10 BPM.

I also have a Bafang SWXK "201 rpm" from greenbikekit.com ordered in November 2012 and a Bafang SWXH 36V "305 rpm wheel size 26" ordered from elifebike.com in April 2013. These two motors are both slower than the BPM but have the exact same no-load speed as each other. I measured 27 mph at 49 V using the same setup as for the BPM. This works out to 19.8 mph at 36 V or about 250 rpm at 36 V. I'd say this is most similar to a code 12 BPM.

I will update this thread when I get another motor. But maybe we should have a thread for keeping track of what you order from random Chinese vendor vs what you actually end up with. Then perhaps we would be better able to make sense of it all and order with some idea of what we might get.
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Re: Bafang Bpm, how many RPM?

Post by ShoGinn » May 15 2013 12:03am

We need to debunk the cycle computer variable.


Also what calculations are you using to get your numbers?

I'm sure we could make a nice google doc to ensure proper calcs.

Mine was well within limits. I'd be curious also to see the discrepancies these vendors have.

Or if the controller is truly giving you 100% throttle.

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Re: Bafang Bpm, how many RPM?

Post by -dg » May 15 2013 1:47am

ShoGinn wrote:We need to debunk the cycle computer variable.
You talking to me?

What do you mean by this? Debunk is a fairly negative term, what is wrong with using a cycle computer? What would you suggest instead?
ShoGinn wrote:Also what calculations are you using to get your numbers?
What do you refer to, the calculation of speed at 36 volts vs 49 volts, eg S2 = S1 / V1 * V2. Or some other calculations?
ShoGinn wrote:I'm sure we could make a nice google doc to ensure proper calcs.
Be my guest, I'm sure "we" are all interested to "ensure proper calcs".
ShoGinn wrote:Or if the controller is truly giving you 100% throttle.
I did not mention it, but I tried 3 different kinds of controllers from two vendors. They were all variations on the KU63 (6FET) or KU93 (9FET) style controllers in both 36 and 48 volt versions. I also tested with three different throttles and all the various positions of the "3-speed switch". The results were consistent across all the controllers and throttles.

I did all the extra testing to: a) weed out any defective throttles or controllers, b) to see if any of the controller flavors were measurably better than the others. At no-load I observed no significant differences between the controllers sourced from greenbikekit.com or elifebike.com.
If simplicity worked, the world would be overrun with insects.

tronne   10 mW

10 mW
Posts: 21
Joined: Dec 09 2013 4:59am

Re: Bafang Bpm, how many RPM?

Post by tronne » Dec 09 2013 12:35pm

Hi, after reading all the post, I'm still unsure about the motor, what is quicker in terms of kmh/mph overvolt a 36v 500W 201rpm to 48v or building my own 48v 500W 328rpm to 26" wheel?? what are the seeps in each case? which one is the most efficient?

I'd like it for the city (going quick) but also for the country (uphill)

I've opened a discusion here about the options and the kit I'm ordering

Is it true that overvolting 36v 500W icreases 33% rpm?
http://ebikes.ca/simulator/ After doing some simulations seems the speed increases around 22%
When you run a code 11 at 48v, you get 33% more RPM than the same motor at 36v
Regarding speed
BMSBattery only do 201 RPM or 393 RPM. The 393 RPM won't be very efficient as it's meant for small wheels. You'll waste a lot of battery, which will compromise your range. Your best bet is to use a 36v 201 RPM at 48v, which will give about 35 kph and very good climbing power. Only use the 393 RPM if your journey is flat. Other suppliers do the other versions of the motor. I would say the one you want is code 11 or 12. You might be able to get one from Cell-man. I know EVassemble were doing them, but you have to get your own rim and spokes.
Thanks in advance :)

d8veh   100 GW

100 GW
Posts: 5503
Joined: Dec 10 2010 10:45am
Location: Telford

Re: Bafang Bpm, how many RPM?

Post by d8veh » Dec 10 2013 5:37am

Top no-load speed is directly related to voltage. Speed on the road depends on torque and power. Efficiency drops off rapidly when you have full-throttle at less than half the max no-load speed. Because of that, when you increase the voltage, it also changes the efficiency curve. When choosing a motor, you should aim for one that has a max no-load speed about 25% higher than your normal cruising speed. It needs enough torque to maintain your cruising speed, which depends on your all-up weight,how hard you like to pedal and how hilly your rides are.

You can calculate the no-load speed from this. Average battery voltage is about 10% higher than nominal:

No load speed = Motor rpm/201 x ave batt voltage/nominal motor voltage x wheel size/26 x15

So for a 328 rpm 36v motor with a 48v battery in a 26" wheel, you get:
No-load speed = 328/201 x 53/36 x 26/26 = 36mph

The speed on the road up to which you get meaningful assistance is about 10% less

In the example above, you'd have to pump at least 30 amps to reach that 36mph.

Cees   10 mW

10 mW
Posts: 27
Joined: May 10 2019 12:57am

Re: Bafang Bpm, how many RPM?

Post by Cees » May 10 2019 1:01am

What is the nominal power of this Bafang motor and the max rpm ?
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