Bafang Ultra Max, the new big dog on the porch

January 14, 2019



Bafangs内贴标系统调用的MM G510.1000这一点,它的设计使得在我最喜欢的车程多次改进,该BBSHD。该BBSHD是一个工具包,滑入几乎任何你喜欢的框架,但超最大需要专有的外壳安装它(见下文)。

The first thing that pops out at the casual observer is that the Ultra has a larger diameter motor. This increases the amount of leverage that the magnets exert onto spinning the rotor, without any additional watts applied to it, compared to the same watts being applied to a smaller diameter motor with the same copper mass. The other thing that this helps is the efficiency, since the “tangential magnet speed” is faster for a given RPM.


这意味着…控制器将apply higher amps to the electromagnets in the stator until the permanent magnets in the rotor are spinning fast enough to reach the motors’ top-speed, the so-called “Kv” of the winding (点击这里了解“电机技术,了解这些条款”)。



Another thing that is worth noting is that the BBS02 in the picture above uses what’s called “Surface Permanent Magnets” / SPM on the rotor, and the Ultra (along with the BBSHD) uses a style that inserts the magnets a small distance away from the surface of the rotor. This style is being seen more often these days, and it’s called an “Interior Permanent Magnet” motor / IPM.

This design allows the magnets to run cooler, which is important because one of the limitations on how many amps a motor can use is the heat that is generated by “eddy currents”. The stator core is made from a stack of very thin steel plates in order to reduce eddy currents, which are generated anytime a ferrous metal is rapidly passed through a magnetic field.


With an IPM, the permanent magnets will “magnetize” the slim section of steel between them and the electromagnets in the stator. This keeps the magnetic field strength in the air-gap at an acceptable level, while still placing the actual permanent magnets a short distance away from the air-gap. Permanent magnets can lose their magnetic power if they get too hot, so…by doing this, you can use more “temporary peak” amps without overheating the magnets.



Square taper spindle on the left, and a 10-spline ISIS spindle on the right.

The BBSHD also uses a square tapered spindle, which I believe was simply chosen to save on costs. When comparing the BBS02 to the BBSHD, it was obvious to me (years ago) that the larger BBSHD would be the drive of choice for off-roaders (off-road is where there are no power limits in many countries).


For instance, when it comes to a “street legal” electric bike, the USA has a 750W power limit. Then…Canada, Switzerland, and Austria have a 500W power level, and many other countries have a ridiculously low 250W power level. The Bafang label claims a 1000W power level, but they are actually being run at over 2000W, and THAT…is not street legal anywhere!








The pic below shows that the factory controller for the Ultra uses 12 MOSFET’s. A Field Effect Transistor / FET is an “on-off” switch that controls the amps that are fed to the three phases of the motor.

The controller for the Ultra Max. Notice the “63V” capacitor. This drive can use the 58.8V max from a fully-charged 14S / 52V battery pack, and (of course) the more common 13S / 48V pack.

质量和FET的效率,并且还FET的大小对多少总最大放大器可以通过它们流过的效果(没有任何过热)。即便如此,12个场效应管是很多!如果你只运行52V 20A X = 1000W(如标签),它会勉强得到温暖......

Side note…the fact that the controller is not “potted” (not covered in a firm waterproof goo) means that it wouldn’t be too hard to upgrade the FETs to higher efficiency (meaning less waste-heat for the same watts), or higher voltage (along with higher voltage capacitors). That being said, it would be easier to splice-in an external controller to use 20S / 72V, if you wanted to experiment…

Gear Reduction


转子驱动器具有9齿,其从动齿轮具有23T(均为斜齿齿轮,其使用高RPM的时运行更安静),用于减少2.5:1。第二螺旋齿轮组是66T / 25T为2.6:1。第三齿轮组为2.7 46T / 17T:1(以及在驱动器的低RPM的最终用途实惠直切正齿轮齿)。


This builder has removed the stock controller and is trying to fit a controller model called a “Phaserunner”. If you don’t have a grease preference when re-assembling, Mobil-28 synthetic is my go-to option. Pic courtesy of ES member Daxxie.


The benefit of a conventional mid-drive kit is that it can slide into the “bottom bracket” of almost any bicycle frame that you like. The drawback is that it limits the arrangement and sizes of various components inside the drive. Proprietary drives have much more design freedom.

最流行的工厂中期驱动器是Bosch, Yamaha, Panasonic, Continental, and others

This builder found a titanium frame that uses the Bafang Ultra Max mounting shell. Welding aluminum to titanium requires experience and a TIG-welder. Pic courtesy of Daxxie.

红月周期(南加州)的零售价月神先端具超最大的车程,但他们也愿意卖在八方超最多由它自己专有的外壳沿(点击这里),so custom builders can weld it into an aluminum frame of their choice. Do your homework before purchasing the shell. I believe it is aluminum, which may restrict the frames that can accept it…



What ebikes have it?

The Bafang Ultra Max was first shown at the Taipei bicycle show in 2017, and it was marketed as being more powerful and less expensive than the popular Bosch mid drive.

The 27.5-inch tire version of the Frey full suspension frame.

Frey was an early adopter of the Bafang Ultra Max drive, as seen in the pic above. They also have a hardtail version, and a fat tire version too. The Ultra is reported to allow the use of 1600W of power in the factory-authorised high-powered versions. It is reported to provide160-NM的扭矩,并且还提供了功率高达28-MPH(45公里/小时),这是巧合在美国街道法律功率应用限制。

(The most powerful Bosch mid-drive is listed as providing90-Nm扭矩,以及最近的“TQ”中驱动被列为120-NM


Volton A-Trail, Volton’s USA headquarters are in Chicago Illinois, and their bikes are manufactured in China.



“瓦货车”,使一个高档的钛荷兰风格的城市自行车与盖茨皮带代替链(to see it, click here)。

Luna Apex


我最喜欢的作家是卡尔从。Here is a link to his impression of the Luna 2500W Ludicrous Apex

Over time, I believe more retailers will begin carrying a model of ebike with the Bafang Ultra Max mid-drive, and as I find them, I will add some to this list. Below is a teardown video showing the insides of the Bafang Ultra Max…

Written by Ron/spinningmagnets, January 2019

在加利福尼亚州洛杉矶,从1977年至1981年/美国圣迭戈海军潜艇机械师长大。在1980年的液压技工/洛杉矶。重型设备操作员在1990年/前往不同地点。自卸车司机在2000年代/ SW犹他州。目前,由于2010 / NW堪萨斯州水厂运营商


  1. “举例来说,当它涉及到一个‘街头合法’电动自行车,美国拥有750W功率极限”

    This is not true. In Virginia the max for an ebike is 1000W. That law you keep quoting is a consumer product safety recommended max for sale. Each State sets its own limits for use on it’s roads.

    • I thought 750 was the federal limit.

  2. 没有!每个国家将它自己的极限。在VA它的千瓦特和35英里每小时与1500W电动自行车和35英里每小时的e-滑板车

  3. Georgia has a 1000W limit as well but only a 20 mph speed limit

  4. 谢谢你的更新内容非常丰富。我把Befang BBSHD 1000 Watt with a 52 volt battery pack on a old Giant mountain bike and am enjoying it very much. 45kmph is a piece of cake

    • 如何是一个古老的帧兼容安装电机?

  5. As the title of this article implies, never take this sucker out. Leave it on the porch.


    This thing is illegal in many states and gives ebikes a bad name. Especially since you can’t get assistance when something breaks unless you’re up at 1am and are fluent in Chinese.

    Besides the fact that they feel the need to crest over 1500w due to the fact that their motor is inefficient and doesn’t output as much torque as some 250w mid drive systems.

    This type of motor system is damaging to the municipal acceptance of ebikes nationwide and should be covered as such.



    steps off soap box

    • Or people like you will unleash their authoritarian way of life and try to control us.. Your laws are meaningless. I will take this out and ride it wherever and whenever I wish. I will go fast if I wish, just like I have control and you don’t over what I do with my car. I know you would like to control that too but sorry..

    • Laws are made to limit ctivity and give “rights” to certain people to make money if they bribe the politicians enough, like PHANTOM DRONES who sold out to Gov to allow access to their data to log every flight wherever you fly.

      • When the power goes down,and there is no electricity for 18 months, no one will care what power you are running on your bike.

  6. 车电机可以做这样的方式wayyyy超速但能力是存在的,我们需要对自行车强大的马达柜面我们拖小型车像Holdens的出水沟,甚至移动已经越过道路倒下的大树干,所以,,,电源偷看!

  7. 明尼苏达州的电动自行车限制也是千瓦特。明尼阿波利斯是专为独立的车道,街道和公园路的街道之前耕种的雪地自行车交通。下车气体和不判断。

  8. I just bought a MOAR ebike with this motor and the nylon gear failed immediately. I checked the blog for the bikes and there have been many failures, so it isn’t a minimal issue. Bafang, however, sent me a new motor. Must have 16 spline 44mm deep socket to remove bottom bracket locknut which is almost impossible to find. So, good luck!

  9. 好。但你在哪里买八方M620在欧洲???

  10. 一对夫妇挑剔的。你永远不能焊接铝钛与任何类型的焊机。至于电容器的额定电压应作为一个经验法则运行双系统电压。因此,一个48或52V系统应具有100V额定上限。这样做是为了使瓶盖不会死的早。

    • You CAN In fact weld these two metals together!

  11. Incredible review, thank you so much for all the effort put into this post!

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