a bafang mid drive motor

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In this Bafang BBS01 250w review, I will be going over the pros and cons of this popular mid-drive conversion kit – this is the only variant I can recommend for road legal use in the UK,  EU and Australia. The more powerful variants of the Bafang motor are covered in separate articles.

The Bafang BBS01 has been with us for a few years now and continues to be popular with DIY e-bike builders the world over. It’s particularly popular in the UK and EU countries, where e-bike laws are more restrictive (than in the US). I have personal experience installing dozens of these motors over 5 years, and I still think it’s one of the best road-legal options for converting your bike to electric assist.

Bafang BBS01B Specs

Motor PositionMid-Mounted (Bottom Bracket)
Motor Compatibility68-73mm BSA Threaded Bottom Bracket
Rated Motor Power250-watts to 350-watts
Motor Peak Power540-watts to 648-watts
Max Torque120Nm
Motor Rated Voltage36-volt
Controller Current 15-18-amps
IP RatingIP65
Motor Weight3.8 kg
Price $350 – $450
AvailabilityVarious online retailers


  • Road legal in the UK and EU (if the speed limit is set)
  • Plus and play design
  • Very smooth and quiet
  • Can be programmed (with optional USB lead)
  • Efficient
  • Good parts availability – easily serviceable


  • Lacks the ‘get up and go’ of the more powerful variants
  • Only compatible with 68-73mm bottom brackets
  • Controllers can be unreliable
  • Not completely waterproof


Bafang is currently the global leader in plug-and-play mid-drive electric bike conversion kits and has been for several years. Earlier versions were plagued by reliability issues, and although these can still be an issue, the problem isn’t as bad as it was four or five years ago.

I have personally installed over a hundred of these kits on various bikes, ranging from low-step commuter bikes to full-suspension mountain bikes.

bafang bbs01b 250w fitted to mountain bike
Bafang BBS01B installed on a Carrera MTB

The main criterion for installation is the size of the bike’s bottom bracket. It needs to be a standard 68 mm-73 mm wide bottom bracket with an inside diameter of approximately 33.5mm. It must be noted that these kits are not intended to be installed on bikes that use a pressed-fit bottom bracket, as the dimensions are not compatible with the motor unit. There can be a way around this if a special shim and mounting plate are machined by a professional engineer.

If your bike has an eccentric bottom bracket as fitted to tandems and bikes with internally geared hubs like the Shimano Nexus, installation is still possible but may be problematic.

What’s included in the Bafang BBS01B 250w Kit?

  • The motor unit with integrated controller
  • LCD Display
  • Wiring loom
  • Inner and outer lock-nuts
  • Chainring
  • Chainguard (BBS01 and BBS02)
  • Thumb throttle – I do not recommend fitting this, as it is unnecessary and will increase the risk of controller failure if used inappropriately.
  • Brake levers with cut-off sensors (only compatible with cable brakes)
  • Speed sensor and wheel magnet
  • A bag of various Allen bolts and screws
bafang bbs01b 36v 250w electric bike kit

Unlike the Bafang BBS02B 750w, the 250w version would be perfectly legal to use in the UK, EU (and Australia). But, you will need to check the speed limit is configured out of the box to no more than 25km/h (15.5mph). Some sellers in the UK and EU do this by default, but you will need to check beforehand if you’re concerned about legality.

Most displays have an advanced settings menu which can be accessed via a 4-digit pin code. It is possible to alter the speed limit, but this would render your bike illegal to use – Please consider the laws in your country before changing the speed limit. 

Is the Bafang BBS01B Easy to Install?

If you’re looking for a nice and easy conversion to do yourself, but you have little or no experience with bicycle mechanics or using tools, I would recommend getting a friend or bike shop to help with the installation.

Certain aspects of installing the BBS01B can be challenging and it’ll help if you are mechanically minded. See my guide on how to install a Bafang BBS02 This also covers the BBS01 which is physically the same.  The installation will need to be carried out by someone who is fairly competent. Removing the bottom bracket can be a right pain, and you will require a lot of patience!

Motor Technical Data

These motors have an internal cadence sensor, and give assist based on pedalling cadence. The controller will reduce the power at any given power level based on pedalling rpm. This is called the keep current, and depending on the way your particular controller is programmed, this can reduce the power by up to 60%. The logic behind this is the higher the cadence, the less help you need, this is somewhat counter-intuitive as electric motors work best when spinning at a high rpm.

One great thing about these motors is they can be programmed with a Bafang programming cable and software (which you can download for free here). I will be writing a separate post about programming the Bafang. PLEASE NOTE: Reprogramming the 250w motor to any higher than 15A and 15.5mph (25km/h) would make it illegal for road use in the UK / EU / AU.

The motor itself works through a series of gears and drives the rear wheel directly through a single front chainring. The benefit of this is the motor is using the bike’s gear ratios for maximum efficiency and torque. The downside of this is you have to make sure you are in the right gear when hill climbing as excess load on the motor can cause controller failure.

The 250w motor is very quiet and smooth, and you have up to 9 levels of pedal assist to choose from.

bafang bbs01 250w review
A Bafang BBS01B 250w installed on a hybrid bike with Shimano Nexus 8 geared hub

Is the Bafang BBS01B 250w reliable?

As with all things electric, problems can and do occur from time to time. I have installed many BBS01B 250w Bafang motors and to date, have only had a handful of issues reported – these are mainly confined to the more powerful variants. Having said that there are several things to consider.

  • Controller failure is rare on this model nowadays, especially since Bafang upgraded the MOSFETs in the controller.
  • You will need a Bafang lock-ring spanner – these motors do sometimes need to be re-tightened periodically.
  • The speed sensor can be easily knocked out of alignment with the wheel magnet – this will throw up an error code and the pedal assist will stop working.
  • In my experience, the C965 display is the most reliable but has limited functionality. The available colour displays are great but I have had the occasional fault with these in the past.
  • Increased wear and tear on the bike chain and gear components – this can be mitigated by fitting a Bafang gearshift sensor.

Riding a Bafang-Powered Electric Bike

The 250w motor is very quiet and smooth, and you have up to 9 levels of pedal assist to choose from, so you really can fine-tune the power output to suit your needs. When climbing steep hills you will need to make sure you are in a low gear (as you would be in a car or on a motorcycle) this is especially important as trying to climb a hill in a high gear will put the motor under excess load and could overheat, causing controller failure.

The pedal assist is responsive, and works well, although, on some of the older units, there was always a slight over-run noticeable when pedalling stopped. This was down to one of the controller programming parameters being set too high. I always reprogrammed the unit to stop this issue.

The main downside, in my opinion is the extra pedalling resistance this motor has when the power is on ‘0’ or the motor is switched off altogether. It is not too bad on the flat, but it is noticeable when going up a slight gradient. This is the main reason, I tend to prefer small geared hub motors.

If your bike has a double or triple front chainset, then you will be sacrificing that for a single steel chainring. Bafang only offers 44t, 46t and 48t options. This in my opinion is high gearing, especially if you are climbing lots of steep hills. There are however a couple of alternatives – you could fit a 104BCD chainring adaptor or buy one of the many aftermarket chainrings available.

If you want to fit the brake levers with cut-off sensors, then bare in mind these are only suitable for cable-operated brakes. If your bike has hydraulic brakes, you may want to purchase hydraulic brake cut-off sensors or completely new hydraulic brakes with the sensors already built in.

The Verdict

The Bafang mid-drive motor is not for everyone. Installation can be challenging and the motor will need periodic maintenance. It is nonetheless an excellent option, and the result will be a bike that looks more like a factory-produced e-bike.

bafang bbs01 250w fitted to a ladies mountain bike
Bafang BBS01B 250w installed on an Orbea MTB

For a 250w motor it produces a lot of torque, I have done a side-by-side hill climb comparison of the Bafang 250w vs a 1000w hub motor and the Bafang outperformed the larger, more powerful hub motor. The large direct drive hub motor was only rated at 35Nm of torque compared to the Bafang’s 80Nm.

If you are comfortable with your ability to install it, and you have an appropriate donor bike, then as long as you can live with some of the compromises, this is still one of the best electric bike kits available.

Where can I buy the Bafang BBS01B 250w?

The Bafang BBS01B 250w is available globally through e-commerce websites like eBay, Amazon and Aliexpress. The latter is usually cheaper, but returning a faulty item isn’t always so straightforward. My recommendation would be eBay or Amazon as the returns process is usually more straightforward, although the initial purchase price will be slightly higher.

Thanks for reading, if you have any questions please leave a comment below – I usually reply within 24hrs.

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  1. I am considering buying a Koga F3 with beltdrive as a donor to convert to ebike using Bafang BBS01. I just love the beltdrive. Only thing is, all the information and sets offered I see is with conventional chain. What is your experience with this, or is it just not advisable?

    1. Hi Marcel,

      There are chainring adapters available for the Bafang mid-drive, so you can fit a gates belt drive ring. It’s not a conversion that I’ve personally done, but there’s lots of info online and it looks fairly straightforward. One thing to remember when converting a bike with internally geared hub is to use a gearshift sensor – this reduces stress (to the hub) when shifting under load. The only other issue I can see is if your Koga has an eccentric bottom bracket (to adjust belt tension), then fitting the motor may still be possible but you wouldn’t be able to adjust belt tension (unless the motor is removed).

      I hope this helps. Let me know if you have any more questions.


  2. Hi Tony,

    I have a 500w Bafang drawing on a 48 v 15 ah carrier battery. I use it at the basic level 1(Ive set the range measurement from 1 to 10) to get up hills and there a lot of steep ones around here!

    If I change the motor to 250 w will that extend my range by 100% ( I suspect that that the calculation is not as simple as that)? I presume also that since I am using the current one at the basic level that the performance of the 250 w motor will not be that different at basic level 1.

    Btw the motor has changed my life at 73 as I can get out into the hills again….

    Your site and advice/comment column are outstanding…thanks for creating them and for your obvious generosity of spirit when it comes to cycling and giving advice. Frank

    1. Hi Frank,

      Your best course of action would be to buy a USB programming lead and download the free opensource software. The Hackers Guide to Programming the BBS02 will give you detailed instructions on how to modify the controller parameters on the pedal assist. You can configure each level to produce just the right amount assist for your needs. Plus, you can change the characteristics and feel of the assist. If you dial back the current in the lower levels you should be able to see significant range improvements. I used to get about 100 mile range from a BBS02B running a 48v 17.5Ah battery (in Cornwall which is very hilly).

      Swapping the motor out for a 48v 250w version would be an unnecessary expense as you can achieve the same results by doing the above. It’s fairly straightforward and as long as you follow the instructions. Limiting the maximum controller current settings to 12A will effectively turn your 500w in to a 250w motor.

      I hope this helps, if you have any more questions, please let me know.


  3. Hello Tony. You have a really great website with a lot of usefull informations. Thanks a lot for the time you spend for it!
    I would like to ask you what are maybe some dumb questions, but I couldn’t find any answers about that… And I would like to be sure…
    You write in this review about thumb throttle “I do not recommend fitting this, as it is unnecessary and will increase the risk of controller failure if used inappropriately”.
    You also write in the comments “Brake cut-off sensors are only really necessary if you’re going to fit the throttle, I used a Bafang for about a year and never had any cut-off sensors fitted and it never caused any problems”.
    I’m working on installing a Bafang mid motor at the moment, and I think I don’t need the thumb throttle.
    Is leaving the throttle cable unplugged ok, maybe protected by some sort of cap? I guess it won’t affect the motor/controller, am I right?
    Bonus questions (!): Do you confirm (2 years later) that without any throttle, brake cut-off sensors are not necessary?
    Especially if the motor cut off is correctly tuned, of course.
    Same as the throttle cable, these brake sensor cables can be left unplugged?

    1. Hi Victor,

      You can leave the thumb throttle and brake cut-off sensors unplugged without issues, but I would recommend retaining the small caps that cover the ends of the connectors. I usually cable tie the redundant connectors out of the way.

      I’ve covered well over 2000 miles on a Bafang (BBS02B 750w) and not having the cut-offs hasn’t caused any problems. I always dial back the ‘time of stop(x10ms)’ to 10 – it’s usually set to 25 and this causes a slight overrun of the motor when pedalling stops.

      I hope this helps and best of luck with the conversion.


  4. Hi Tony

    Excellent website and in particular the install video for the Bafang kit. 👍 I’ve just lost the use of my first ebike conversion which was powered by a 46v 1000w rear hub motor. Sadly after one or two issues with the rear wheel (maybe not HD enough for the supplied motor ?) I found the dropouts wore to a point where the motor drive pins didnt seat properly thus preventing the motor driving the rear wheel. So now Plan B is to use a Bafang mid drive motor instead (via one of your links) to see if I experience a new set of issues or if I can enjoy e bike life once again ???

    I have three questions in advance of the purchase of the kit and would appreciate your input.
    1.If I purchase a 250w mid drive motor – so it’s street legal in the UK – will I notice a considerable lack of performance from my previous 1000w rear hub motor bike ? When it worked, my first bike was pretty nippy up steep hills albeit with additional pedal power. Will a 250w mid range motor suffer by comparison ?
    2. The bike I intend to convert is a Carrera Vengeance 26″ wheel frame. Have you any experience of installing a Bafang on that particular bike ? I ask as I’m concerned about the issue of fit ?
    3. Assuming the kit fits and, in an effort to avoid the issues I had with my first ebike conversion, is there anything else I need to check before ensuring there is compatibilty with the motor and my MTB ?

    Thanks so much

    1. Hi Chris,

      I have converted several Carrera Vengeance MTB’s in the past. If it’s an older 26″ wheel version it should be a doddle. The only thing to remember is to use the correct Shimano BB extraction tool on a long breaker bar, and when you unscrew the bottom bracket both sides unscrew towards the front of the bike. If your rear shifter cable is routed underneath the BB shell, you may need to re-route it as there’s never a lot of clearance with the motor.

      Regarding performance – the Bafang can be configured to produce more power using the free opensource software and USB lead. You can set the maximum current to 18A safely which will give peak power of around 648w. I’ve done lots of 1000w hub conversions over the years and I always felt a properly tweaked 250w felt better on hills – not so much at higher speeds though.

      I would be inclined to buy from one of the eBay sellers as there’s better comeback if you have any problems.

      I hope this helps. Let me know if you have any more questions.


  5. Grazie mille delle informazioni. Vorrei montare questo motore o più grande su un tandem Power Twin 2. Sapresti indicarmi quale batteria usare e se fosse possibile installarlo su questo tandem? Grazie mille e buona giornata

    1. Ciao,
      Non sarebbe possibile montare un mid-drive Bafang su questo tandem a causa della configurazione della pedivella anteriore (è sul lato destro). Dovresti montare un motore con mozzo anteriore o posteriore. Consiglierei di guardare i kit motore mozzo Yose Power, in quanto sono affidabili e hanno un buon rapporto qualità-prezzo. Spero che questo aiuti.
      Cordiali saluti,

  6. Beste Tony,
    Mijn bafang 250 w motor doet niks meer . Het display geeft code 21 aan verder werkt het display goed.
    De speedsensor werkt volgens mij ook goed als het magneetje er langs gaat brand het rode lampje.
    Ik heb duimgas maar deze werkt ook niet .
    Nu is mijn vraag kan dat aan de controller liggen en zijn er mogelijkheden om dat te controleren, ook vraag ik mij af of dit veel voorkomt.
    Bedankt voor je medewerking.
    Hans Lassooy

    1. Hallo Hans,
      Foutcode 21 duidt op een probleem met de snelheidssensor. Eerst zou ik de verbindingen controleren en ervoor zorgen dat de magneet niet verkeerd is uitgelijnd en dat er een opening is van minder dan 5 mm. Als al deze dingen in orde zijn, dan zou ik de sensor vervangen omdat dit het goedkoopste onderdeel is. Als het probleem aanhoudt, kan er een storing in de controller zijn of een probleem met de bedrading van de controller naar de connector. Laat me alsjeblieft weten hoe het met je gaat.

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