Bafang question

[Steady]

Hi,
I've seen a Bafang BPM 36V500W Rear Driving Hub Motor E-Bike Kit. Code: 8, RPM: 393
at BMS Battery. Im not interested in high speed, would prefer higher torque but it seems this isn't an option with this kit.
Does anyone know if this drive would give me enough torque. I should add I'm about 12 stone trying to get fitter (59years old ) and its quite hilly around here. I would be fitting the kit on my ridgeback with 26 inch wheels

 

[flecc]

That's a very high speed option Steady, it will give 30 mph at the full revs at the cost of torque for climbing. I'm not familiar with all the available SB motor options, and it would be best foryou to re-post this in the main e-bike forum where more will see it and you'll get the necessary advice.

Here is the link to the main electric bike forum where you can enter the query in a new thread.

(admin - thread moved)

 

[Steady]

Thanks for the info flecc. 30 mph is too fast for me, I sent an email to BMS and they told me they're getting the high torque version in 3 weeks. I have fitted a bafang to my wife's Dahon and was impressed with the torque so thats why I opted for another bafang albeit a slighter higher power version.

 

[NRG]

Go for the BPM motor, a number of forum members have bought this motor and had good results with it.

Some info on ES here:

Endless-sphere.com • View topic - Bafang BPM Pics and Specs - Large 3.9Kg Sensorless Geared

 

[mechaniker]

hi steady,

if you want high torque, then order the BPM 36V-500Watt with 195rpm , in result you get 25km/h but very high torque. The Bafang motors you can order from 150rpm up to 400rpm in around 20rpm step´s

ahh... all Bafang motor you can order with Hall or in sensorless version but if you want higher as 250Watt motor, i reconment Hall-Motor and of course Hall-Controller

regards
frank

 

[Steady]

Hi, Frank
I'm definitely going for the Bafang. what the advantage would there be in opting for the hall sensor version.

Thanks
Steady

 

[Steady]

Hi,
I followed the link its really useful to be able to get this info before I actually order the BPM. I'm surprised BMS don't give more information on their products. I should have joined the forums earlier and saved some cash.

Thanks
Stead

 

[mechaniker]

Hi steady,

the Hallsensor version save a bit energy (around 10%) and have a better start behaviour.
On the otherside the hallsensor have a problem with overheating on a hill if the driver know only position full throttle on high Ampere.
Motor with high Watt, more as 250, i suggest to use the Hall version because the sensorlesscontroller sometime have problem with this power and on start they give a big kick to the gearbox and sooner or later the sprocket get toothage. Sorry for my english, explain is not so easy but i hope you understand what i want say with my easy words ;-)
If a sensor go brocken you can drive further with a sensorless controller as a repair suggest.

have good day
frank

 

[JuicyBike]

We have a few in stock... Here

 

[jerrysimon]

Bob,

Nice to see a UK supplier stocking DIY parts

Regards

Jerry

 

[banbury frank]

Hi

I can recommend bobs kit what you get is Support Support Support


Sorry to repeat myself

If you want more power the BMS kit Email them they will do the motor you need

But with more power you need larger capacity battery

36V16Ah Li-Ion Alloy Shell EBike Battery Pack - BMSBATTERY

Total cost about £450 including Kit battery delivery

Remember to pay by PayPal to protect your Money also 4/6 weeks delivery


Frank

 

[Scottyf]

A few of the forum members have the motors the bpm version is a a decent geared hub drive. Plenty of torque. Mine is a code 12 wind which allows up to 22mph in a 700c wheel. @ 48v it would be good eos about 28mph. Even with my standard battery it climbs hills very well and quickly using a 20th amp controller.

I think even with the high speed version you have it will still be stronger than the 250 watt motors. BUt you'll have to pedal a lot to keep it in tif torque band at roughly 15mph. IF not the motor will labour become inefficient and heat up.

ON the flat tthough it will be very quick if not a little slow to get there providing you pedal and its not to windy.

 

[Steady]

Hi Scotty,

I'm going to have to stick with 36volt as I already have a 15amp lifepo4 from Ping. 15 to 20mph would be fast enough for me as long as there is enough torque to help me up those hills. Would the speed be limited to the chosen motor wind even when putting plenty of effort in myself

 

[Scottyf]

once you get to anything over 20mph it becomes hard to beat the wind resistance with your own pedalling unless you start using a race and lowring your own drag. YOur own pedalling will only add a few mph on top of the motor itself and weight.

Current wind that I have is plenty quick at 20ish mph and doen't drop that much up most hills. But I only ride road and have thin tires and a hybrid bike so the rolling resistance is very good and rolls forever it would seem.

15mph to 20mph is quick enough for a push bike though. In comparision I travel my work commute in the same time I can drive to work at rush hour... Sometimes quicker when traffic is really bad.

 

[jbond]

if you want high torque, then order the BPM 36V-500Watt with 195rpm , in result you get 25km/h but very high torque. The Bafang motors you can order from 150rpm up to 400rpm in around 20rpm step´s

When SB quote these RPM values, are they no-load RPM or something else and if so at what actual voltage? Is it possible to relate the motor quoted RPM to an actual road speed with a specific rim and tyre circumference?

From what I've seen and actually measured against a GPS, the quoted rpm seems a bit low compared with what I'm observing with the BPM motor I've got. But then perhaps this is caused by a nominal 36v motor being driven by a nominal 36v battery when the battery is actually ~40v

 

[Scottyf]

They would be rpm speed at the nominal voltage or rated power for that given motor.
You start monkeying about with the voltages and the rpm no load speed changes.

You have to really take No load speeds as there are so many other varibles to consider when on the road. You should generally take no load speed x 0.8 (To give 80%) should give you a rough on the flat speed.

 

[jbond]

They would be rpm speed at the nominal voltage or rated power for that given motor.
You start monkeying about with the voltages and the rpm no load speed changes.

You have to really take No load speeds as there are so many other varibles to consider when on the road. You should generally take no load speed x 0.8 (To give 80%) should give you a rough on the flat speed.

I understand that. The question is what it actually means when SB quote (say) a 36v 250w motor rated as 195rpm. Is that a no-load rpm at 36v? So on my fresh fully charged 36v battery which actually has 40v I'd expect a no-load rpm of 216rpm?

Working the other way. I've got a BPM marked as 36v350w 26(11) which I take to be a code 11 designed for a 26" wheel. I've measured a no-load speed of 23.5mph (cycle computer calibrated against GPS). Typical flat out top speed is about ~20mph.

23.5mph
2045mm circ
23.5mph = 37.819584 kmph
= 0.6303264 kilometers per minute
= 630326.4 mm per minute
630326.4/2045 = 308 rpm
Compare this with
Endless-sphere.com • View topic - Bafang BPM Pics and Specs - Large 3.9Kg Sensorless Geared where a chart appears to say the code11 should have a noload rpm of 285 +-10%. 285*40/36 is 316rpm. So it's all circling around, and does suggest that quoted rpm are no-load rpm at exactly 36v.

 

[Scottyf]

Is that a no-load rpm at 36v?

Yes thats what is quoted. There would be no other way in which to quote the No load speed.
It has to be at the rated power / volts and usually a set amperage to get the specific figures.

Else you could fiddle all sorts...

Mine is a code 12 but In a 700c wheel which is probably a similar top speed in mph as your bike due to the larger radius of the wheel (However it would have a lower RPM wind of say 265rom +/- 10%)