Bafang motor upgrade comparison

[Altema]

I went ahead and bought the "upgrade" motor for my RadMini. It wasn't a need, and I bought it partly out of curiosity, but it provided a nice opportunity for testing and comparison.
If you spend any time on e-bike websites and forums, I'm sure you've heard the claim that Rad motors are not "true" 750 watt motors, and you need to buy an upgrade. This idea started in an online forum, then became popular through YouTube. Oddly, most opinions on this are based on looks, and while there are many things you can determine by looks, electrical specifications are not one of them. That being said, I do like the motor and will be keeping it. It's a high quality unit and worth the money, depending on your needs.


Side by side comparison



The Rad and upgrade motors do have some differences in design. Most notable is the magnet shell. This is narrower on the Rad motor, and wider on the upgrade. What does this mean? It means the shell is wider. What seems to throw people off is that the Rad motor has this empty space between the stator windings and the mounting plate. The upgrade motor does not have this space... or does it? It turns out the upgrade motor also has an empty space. It's just in a different location.





Although it seems the upgrade motor has bigger windings, in reality, it does not. The stator coils are the same size, as are the magnets.

The installation of the new motor itself went fine, with only one hitch: I was using a cast bit to remove the T-20 Torx head screws with anti-tamper pins, and the bit shattered. To avoid that, I purchased a forged Craftsman folding driver set, and used a butane mini-torch to soften the Locktite for the screws. The only settings changes required to the controller display was changing the speed pulse sensor (P2) from five to six.

Doing the math

I was a bit surprised when I could not get the motor specifications, so I had to do some testing on my own. Below are the results.

Stock Rad motor
Top speed: 23 mph
22 inch wheel RPM at 23 mph: 351.592
Motor RPM at 23 mph: 1757.96  (351.592 x 5)
Motor rating:  32.55 kV (approximate - electronically limited)
-------------
Bafang upgrade motor
Top speed: 27.4 mph
22 inch wheel RPM at 27.4 mph: 418.85
Motor RPM at 27.4 mph: 2094.26  (418.85 x 5)
Motor rating: 38.78 kV

The Rad kV rating is an estimate because it has a built-in limiter that starts reducing power electronically, so the motor is not free to reach it's natural RPM. The Bafang upgrade motor does not have this limiter, and this was one of the reasons I wanted to try it out. You can see the difference on the wattage being used at top speed: The Rad motor is only pulling a couple hundred watts at top speed, even though over a thousand watts is available, while the upgrade motor actually is pulling over a thousand watts at top speed.

Acceleration and hill climb tests

Tests with both motors were done on a RadMini 4 with dual batteries and a 35 amp controller, battery voltage at 54.3 volts, and the tires at 12 PSI. Performance would be better with more air in the tires, but since the first tests were done at low pressure, I kept them the same.

Original Rad motor 0 to 20 mph: 4.9 seconds
Bafang upgrade motor 0 to 20 mph: 4.9 seconds

Wait, what? You read that right, and I ran the tests multiple times. The motors had the same acceleration times. They are both a blast to ride with the 35 amp controller, with the Rad motor pulling ahead off the line and the upgrade motor catching it.

The hill climb test was a bit more subjective, but basically I drove up an absurd 28% grade berm for a freeway overpass. The Rad motor seemed to have a bit more low RPM torque, getting up without me touching the pedals. The upgrade motor had a little harder time, and although it made it, it was not as confidence inspiring.

In top speed, there was no comparison. The Rad motor can hit 23 mph if you change your settings, but the power starts being electronically reduced above 20. If you are already riding at 20 mph and go full throttle, the response is like "Well, ok, give me a minute" as it gradually gathers momentum on the restricted power. With the upgrade motor, it's prime time, and giving the throttle a full twist at 20 mph responds with the attitude of "Hold my beer!". Yes, it does top out at 27/28 mph because kV x voltage = RPM, but it gets you there decisively.

In conclusion, if you have off road or private areas where you can safely use the extra speed, the Bafang upgrade motor is worth every cent. If you need to keep it locked to 20 mph though, the Rad motor will do the same job and can handle the 1,600 watt power levels fine.

[TDR]

Nice analysis. Thanks for sharing.

[Tony]

Good report, thank you. I've been following your upgrades. Very informative. 

[George3]

Thanks very much for your comparison and analysis.  Helps me to decide to leave well enough alone.

George

[fin_rad]

Thank you for sharing this info! Do you know what Bafang model the 750W hub motor is? Curious to see its specifications. And in which part (motor, controller) the power limitation is made that causes the stock 750W motor not giving the full power?

Edit: also are there somewhere photos / videos how the upgrade motor looks inside?

[fin_rad]

Cannot edit my previous post, so let's write a new one then..

Found an interesting conversation:
https://electricbikereview.com/forums/threads/misleading-motor-information.34104/
There they say the Rad's 750W motor is actually a 350/500W motor that is just over-volted to the 750W peak power. Someone checked the real model by emailing Bafang directly with the motor's serial number and Bafang answered it to be the 500W version.
My wild guess is that the motor used by Rad is this one: https://bafang-e.com/en/oem-area/components/component/motor/rm-g060500dc/
So the nominal power is 500W and the peak power up to 750W (which I have never reached according to the bike's display, but around 730W).

Here are good details about the RadRhino 750W EU version (L1-eA) if someone needs: https://electricbikereview.com/rad-power-bikes/radrhino-750w/

[Altema]

Thank you for sharing this info! Do you know what Bafang model the 750W hub motor is? Curious to see its specifications. And in which part (motor, controller) the power limitation is made that causes the stock 750W motor not giving the full power?

Edit: also are there somewhere photos / videos how the upgrade motor looks inside?

The Bafang model number is RM G060.750.D 06
Rad controller limits the motor power. The Rad motor internal RPM limiter limits the speed.
Photos showing inside both motors through the openings on the gear side are below.

[Altema]

Cannot edit my previous post, so let's write a new one then..

Found an interesting conversation:
https://electricbikereview.com/forums/threads/misleading-motor-information.34104/
There they say the Rad's 750W motor is actually a 350/500W motor that is just over-volted to the 750W peak power. Someone checked the real model by emailing Bafang directly with the motor's serial number and Bafang answered it to be the 500W version.
My wild guess is that the motor used by Rad is this one: https://bafang-e.com/en/oem-area/components/component/motor/rm-g060500dc/
So the nominal power is 500W and the peak power up to 750W (which I have never reached according to the bike's display, but around 730W).

Here are good details about the RadRhino 750W EU version (L1-eA) if someone needs: https://electricbikereview.com/rad-power-bikes/radrhino-750w/

I've seen those same threads. I would hesitate to dis an entire company based on one email from a service rep.
Especially when we have the physical motors in hand.
The thing is, you can have a ten thousand watt motor in your Rad, and do you know how much power you'll get when you twist the throttle? 730 watts. The peak power is set by the controller in this case, not the motor.
The Rad Power Bikes controller output is 15.625 amps. At 48 volts that's 750 watts, and when you factor in electrical resistance and voltage sag from the battery, 730 watts is normal.

So my question is; if the maximum power of the Rad motor is indeed 750 watts, why does it so easily handle 1,641 watts? That's how much power I've run through mine, frequently for mile after mile, for 600 miles. The motor has never gotten above barely warm, which is something I'm sure Lectric XP owners would be jealous of as they sit in the middle of a long hill waiting for their 500 watt motor to cool off.

The Rad motor has the exact same power capabilities as the Bafang upgrade motor. As a matter of fact, for startup torque, the Rad motor is BETTER than the upgrade. The only benefit to the upgrade motor is the higher top speed due to not having the electronic limiter.

[Tony]

I know nothing about this type of thing, but can the limiter be removed/disabled from the motor ?  Tony

[vudude]

I read your comparison with interest. Thanks for testing them. Is there any difference in weight?

[fin_rad]

Thank you @Altema, that was a clear explanation how these things work.

Not sure if it would be possible that the RPB has used different types of Bafang hub motors under their 750W label? Because the hub motor I got in my RadRhino 750W EU gets so warm on average 350W (PAS 3) and on a 20 km average trip that it can melt snow around it. Until the gears got frozen when melted water turns into ice... So it surely gets warm enough even on some minus degrees (between 0 - -10 C).

[Altema]

I know nothing about this type of thing, but can the limiter be removed/disabled from the motor ?  Tony

That would require replacing the circuit board inside the hub, and soldering all the power, sensor, and stator coil connections. I'm not sure where you'd get the board, but if I had a free one sitting on my work bench, I'd rather spend the $249 to avoid all that work!

[Altema]

Thank you @Altema, that was a clear explanation how these things work.

Not sure if it would be possible that the RPB has used different types of Bafang hub motors under their 750W label? Because the hub motor I got in my RadRhino 750W EU gets so warm on average 350W (PAS 3) and on a 20 km average trip that it can melt snow around it. Until the gears got frozen when melted water turns into ice... So it surely gets warm enough even on some minus degrees (between 0 - -10 C).

Based on that, it seem to me that the EU motor is different. I have a road near me with a 96 foot elevation gain. I rode my RadMini up it on throttle only, and the motor was barely warm. Same thing after 12 minute rides on mountain bike trails, and I was actually hoping the motor would be able to warm my fingers up, but it wasn't!

[Altema]

I read your comparison with interest. Thanks for testing them. Is there any difference in weight?

There's a few ounces more on the new motor because of the magnet shell being wider. Both are very heavy, and when I carried them both at the same time, I didn't notice the difference.

[fin_rad]

Thank you @Altema, that was a clear explanation how these things work.

Not sure if it would be possible that the RPB has used different types of Bafang hub motors under their 750W label? Because the hub motor I got in my RadRhino 750W EU gets so warm on average 350W (PAS 3) and on a 20 km average trip that it can melt snow around it. Until the gears got frozen when melted water turns into ice... So it surely gets warm enough even on some minus degrees (between 0 - -10 C).

Based on that, it seem to me that the EU motor is different. I have a road near me with a 96 foot elevation gain. I rode my RadMini up it on throttle only, and the motor was barely warm. Same thing after 12 minute rides on mountain bike trails, and I was actually hoping the motor would be able to warm my fingers up, but it wasn't!

I recall checking the hub motor and controller when it was summer time here and over +20 C degrees - both did not feel even warm after a long trip on PAS level 3-5. More likely the motor is the same than yours and just generates enough heat while riding in winter temperatures that it can melt the snow.

Good though it is possible to upgrade the components. Not so easily done if you had a Bosch, Shimano etc.