Bafang PMGR analysis - updated 9/17/08

shinyballs

1 kW
Joined
Sep 29, 2007
Messages
327
Location
Pacific NW
Created for Bafang PMGR related discussion only. Let me know if findings need changes. Post what you love and also hate about this motor. Will be updated as more data is received.

Speediest model: ? :arrow: calling seller Knuckles
Torquest model : ? :arrow: seller, do you know??

Motor specs, pics - (link upated, thx voicecoils)
http://endless-sphere.com/forums/viewtopic.php?f=3&t=4892&start=0#p72825

Compatible controllers:
Infineon Controller
Shenzhen 72v 30Amp - with 24mhz resomator mod
Kelly BLDC 72v - with current limited to 30Amp thru software
Crystalyte analog 72v 35Amp
Crystalyte analog 72v 20Amp - some problems

Features:
front or rear mounted
Can use Regen?
low cost, "for now" :roll:

Known issues, limitations
Should not be run over 72v, 30Amps at ___% efficiency
Hollow shaft on left side, not suited for heavy loads, max load limited to _____lbs

Must have parts/upgrades
disk brake mounting holes
replacement gears (nylon, steel)
other gear ratio, if higher rpm is desired

Road Test results:
over 500 miles -
Nogwin: I got to say this is the most efficient motor I have even owned. It has ZERO wheel resistance, which means pedaling 20mph on the flats is not too hard... It pulls real hard at 66V (NiMH) and performs similar to a 408 at 72V or a 503 at 36V.

1000 miles -
3000 miles -


More test results:
Voicecoils: I tried some more no-load testing with my power supply with the 36v 26" Bafang PMGR front hub motor. Then I used excel to create a linear trendline of speeds above the max voltage of my power supply (54.8v). I assumed that road speed (26" wheel) would be 20% lower than no load speeds:
noload_chart.jpg
 
Knuckles said:
I suspect that the Bafangs all have the same mass of copper but are wound differently to produce these PMGR models ...

24V - 200W
36V - 250W
48V - 350W

I also suspect that they will all run fine at 72V and 30 amps. The 24V will run fastest (and hotter). The 48V will run slowest (and cooler).
Just different motor constants (K rpm/v). That's my guess. Gotta love testing!
Has anyone tried the 48v Bafang? Knuckles have you?

The 48v model is still limited to 72v/30Ah right? cause its the same physical size. It can only handle beyond 72v and still 80% efficient, by making it bigger.
 
I have NOT found the Crystalyte 36-72 volt 20 amp analog controller to be compatable with the Bafang PMGR! If anyone has successfully run a Bafang on that X-lyte Controller please respond??????!!!!!!!
otherDoc
 
I now have almost 400 miles in 2 weeks and average ~9whr/mi. 200whr per 24 miles. Avg load is ~200w over 66V.
I got to say this is the most efficient motor I have even owned. It has ZERO wheel resistance, which means pedaling 20mph
on the flats is not too hard. Compare that to a 408 which has so much more resistance, it's pretty amazing.
It pulls real hard at 66V (NiMH) and performs similar to a 408 at 72V or a 503 at 36V

I run a Xlyte 36-72 35A model, and that combo is excellent. I hear the 20A model has some problems with high unloaded amps.

It was bought from Knuckles and built it up myself several weeks ago.

Could not be more pleased :D

Nog
 
Ditto Nogwins claim! With the Infineon it is quiet, powerful and smooth. It dont get no better than this!
otherDoc
 
Nogwin,

How much do you pedal for that 9ah/mi? All flat or a few hills? At what voltage and speed? Maybe I just need 2 Bafangs and a big 40" wheel on the front for really high speed. With my 1100wh pack I might even be able to make the 80mi to the Pacific without recharging if I pedal hard to get over the mountain. That efficiency is great news, as is running at high voltage.

John
 
I just had to do the math, and assuming Nogwin isn't pedaling (food costs a lot for the energy to pedal), using the prices of gas and electricity down here, that 9wh/mile equates to over 2,200km/liter or over 5,300miles/gallon! Staggering! (though it does exclude amortization of your batteries).

John
 
shinyballs said:
Features:
Can use Regen?

I thought that this was a freewheeling motor like the BMC/Puma, so regen isn't possible.

-JD
 
Thanks for the results.
Which model has the highest rpm for 20" or 26" wheel? Based on there list here, is this the one...
 

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I've analyzed the data in this table. There are some typos.
And it the same motor weight of 3.0 kg (just two different windings maybe).
Motors tested at two voltages and two currents.
It's almost pointless data IMHO.
Bafang_Data2.jpg
Gosh.
Same motor. Two available windings.
More volts and more amps.
Give more torque and more rpm!

Who would have thunk it! :roll:

Now if Bafang would only test it at 48V and 30 amps.
That would be nice. But heck. Just ride it and decide for yourself!
 
From what I can tell, Bafang has narrowed their brushless geared motor line down to just 2 basic motors, the 250W lighter weight one and the 350W one that we have. Then it's just a matter of which shaft and covers for front drive use and rear options of single speed freewheel, cassettes, disk brake. If anyone has info about other models, please do share.

John
 
From the data I provided, I did pedal. Using the CA reading, it was around 100watts pedal effort to about ~200W motor so 300W in all.
I commute 50 miles RT every day, so range and efficiency is top. I battle a 12 mile headwind along the dumbarton bridge (Norcal SF bay area)
With 300W, the whr/mi =~12-13. Not bad IMO

I'll take a screenshot of the bike. It's designed for light off road use and weighs about 60lb with battery. 650c front slick and 700c rear 23c wheel. Very efficient.

Like I said about the same power as my old 408 at 72v - but with added bonus of motor freewheeling efficiency and good low end torque.
 
Here are the speeds on the road for a given voltage (Xlyte 36-72v analogue, 35A)

48V - - 22.5mph flat no pedal
60V - - 27.5mph flat no pedal
66V - - 30.0mph flat no pedal

At around 10mph and more, the accel is excellent. The highest load over the ride is 30A for a few seconds. Mostly I use the CA to limit the Watts to around 200-300, and pedal the rest. I get a decent 22mph at 200-300W and that is ok for me. I do not go for hi speeds, but for safety sakes, prefer 30mph top speed.

I can attest how good the motor feels, and how much power 300W is. I ride a Cervelo P2C tt bike, and 22mph is pretty hard to manage for 24 miles

Nog
 
Nogwin, Fantastic results!
btw, what model Bafang are you using?
 
I tried some more no-load testing with my power supply with the 36v 26" Bafang PMGR front hub motor. Then I used excel to create a linear trendline of speeds above the max voltage of my power supply (54.8v). I assumed that road speed (26" wheel) would be 20% lower then no load speeds:
noload_chart.jpg
 
Thank you voicecoils! will post this in summary page, I like the conservative 80% load speed, leeway for heavy loads, strong headwind, etc... you think running dual motors would increase it to 85-90%?

Knuckles said:
I've analyzed the data in this table. There are some typos.
And it the same motor weight of 3.0 kg (just two different windings maybe).
Motors tested at two voltages and two currents.
It's almost pointless data IMHO.
What is your data that's NOT pointless?
 
Just a brief update. On 42 sad volts, I run 25-30 w/hrs/mi. My system and me together weigh about 310 lbs, or 141 kilos :oops: I truly believe that when I get better batts I can reduce this wh/hr use since it will be faster off the line, and need less holding open of the throttle! Soon, Grasshopper!
otherDoc
 
When I run the Bafang at 72V (nominal) I easy get 30 MPH (48 KPH)
 
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