# Bafang Mid-Drive Installation



## simon.r (6 Apr 2020)

I’ve already got the bike and the postman’s delivered everything else I need (I think). Let’s see how it goes. 







I’m not planning to post a blow by blow account, but I’ll update this thread with the major points (don’t hold your breath, I’m in no rush to get it finished).


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## simon.r (6 Apr 2020)

Step 1 - remove BB, cranks etc.


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## simon.r (6 Apr 2020)

2 - fit the motor.


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## Nibor (6 Apr 2020)

Where did you get your kit from it looks a very neat solution?


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## simon.r (6 Apr 2020)

Nibor said:


> Where did you get your kit from it looks a very neat solution?



The kits are widely available, this particular one came from https://eclipsebikes.com/index.php?cPath=26_27&osCsid=b8d94d67d1b31f90864c2655c6cab2ef , the battery from eBay.


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## simon.r (6 Apr 2020)

3 - Fit the speed sensor. I’m going to have to move this somehow, as the cable is too close to the tyre.

I want to get it up and running to prove the concept, then I’ll spend some time tidying everything up and tweaking the fitting.

Also worth mentioning that I’m going for a fully UK road legal system - 250W, motor cutting out at 15.5 mph, pedal assist only (no throttle) and motor cutting out when the brakes are applied.


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## simon.r (6 Apr 2020)

4 - Fit the display and and control pad.

Bafang make numerous different display units. My preference would have been for a more discrete unit (the SW102), but for various reasons I’ve ended up with this one (C965).


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## simon.r (6 Apr 2020)

5 - Install chainring. The motor means the chainring is much further out, so the chain line is horrible. May try reversing the chainring at some point, but as mentioned before, I want to get up and running, then I’ll start tweaking.






Edit - the chainring is fitted incorrectly. See later post.


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## simon.r (6 Apr 2020)

6 - Cranks fitted and new chain. The supplied chainring is 46t - with a 36t largest sprocket I needed the full length of the new chain. This bike was fitted with a 36t chainring, so this is going to be a large jump in gearing. Time will tell if the motor makes up for the higher gearing...

There is a plastic chainguard supplied with the kit, which I’ve not fitted at this stage, pending tweaking the chainline (and possible gearing changes).






(Yes, I will make sure that cable’s moved before riding it!)


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## jowwy (6 Apr 2020)

simon.r said:


> 6 - Cranks fitted and new chain. The supplied chainring is 46t - with a 36t largest sprocket I needed the full length of the new chain. This bike was fitted with a 36t chainring, so this is going to be a large jump in gearing. Time will tell if the motor makes up for the higher gearing...There is a plastic chainguard supplied with the kit, which I’ve not fitted at this stage, pending tweaking the chainline (and possible gearing changes).
> 
> View attachment 513026
> 
> ...


Why not put the sensor on the non drive side, which will remove some cable slack and move it from the chain and chainring


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## simon.r (6 Apr 2020)

jowwy said:


> Why not put the sensor on the non drive side, which will remove some cable slack and move it from the chain and chainring



That sounds like a plan. Thanks.


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## simon.r (6 Apr 2020)

7 - Fit the battery. The base plate doesn’t line up with the bottle cage bosses, due, I guess, to the non-standard bike I’m fitting it to. One bolt will hold it securely enough for a test run up and down the road, then another problem to sit and think about!


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## simon.r (6 Apr 2020)

8 - Connect the battery. I don’t have anything to hand to fit what the motor is supplied with. I have some ‘quick release’ connectors on order, so, with apologies to any electricians reading I’ve done a temporary job.


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## simon.r (6 Apr 2020)

9 - A very short test ride😄. There’s obviously quite a lot of work left to do, but I’m pleased to report that, basically, it works.






To be continued...


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## shingwell (7 Apr 2020)

simon.r said:


> with apologies to any electricians reading I’ve done a temporary job.


When you tidy up I would suggest a fuse inline with the battery unless you know the battery has one built in, you really do not want to accidentally short one of those babies. A modern car "blade" type works well.

I had the same bottle holder/battery problem, an M5 Rivnut did the job very nicely https://www.cyclechat.net/threads/variation-on-a-nano-conversion.251868/


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## simon.r (7 Apr 2020)

10 - Speed sensor repositioned. Thanks @jowwy


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## simon.r (7 Apr 2020)

11 - Remove chainring and refit the right way round This improves the chainline and means the screws supplied are now long enough to fit the chainguard.


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## simon.r (7 Apr 2020)

12 - Tidy up the cables, refit battery and test ride.


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## simon.r (7 Apr 2020)

13 - Set the wheel size / max speed through the display.


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## simon.r (7 Apr 2020)

Thoughts, in no order of priority after a brief test ride round the block:

The kit isn’t difficult to fit - I’d say that if you can remove a bottom bracket you’ll be OK fitting this kit. 

A longer, hillier test ride is needed to check whether the gearing is low enough.

Given that this bike is almost exclusively used for fairly local shopping trips (< 15 miles) I think I’d look at a lower capacity, physically smaller and lighter battery if I was starting again.

I haven’t fitted the throttle, brake sensors or gear sensor. I didn’t plan to fit the throttle, I can’t foresee a situation on this bike when I’ll be braking and pedalling at the same time and it seems to work well enough without the gear sensor.

I don’t think the brake sensors (where power is cut when the brakes are applied) are a legal requirement - https://www.gov.uk/electric-bike-rules 

I need to finish off the battery / motor connection, but can’t do this until the postman brings me the right bits. Apart from that and probably a bit of further cable tidying, the job’s done.


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## CXRAndy (7 Apr 2020)

Add extra rivnuts to the battery bracket. Also you might find the battery holder needs to have some washers under a couple of points. Its not totally flat


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## simon.r (7 Apr 2020)

shingwell said:


> When you tidy up I would suggest a fuse inline with the battery unless you know the battery has one built in, you really do not want to accidentally short one of those babies. A modern car "blade" type works well.
> 
> I had the same bottle holder/battery problem, an M5 Rivnut did the job very nicely https://www.cyclechat.net/threads/variation-on-a-nano-conversion.251868/





CXRAndy said:


> Add extra rivnuts to the battery bracket. Also you might find the battery holder needs to have some washers under a couple of points. Its not totally flat



I need to do something to secure the battery better, but I don’t like the idea of drilling holes in the frame. I may resort to that, but I’ll see if I can think of another way first (which may involve cable ties). The battery holder came supplied with some spacers shaped to fit the downtube. 

Thanks for the comment about the fuse, I’ll look into that My electrical skills are minimal, so will be good to do a bit of research and up my knowledge.


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## shingwell (7 Apr 2020)

I didn't want to drill my bike either, but cable ties did not stop the battery slipping around, and I was worried about theft, batteries are expensive. In the end there was no drama, it was easy, and I bought some stainless steel rivnuts from eBay.

If it is a (legal) 36V 250W motor a 10A fuse should do it. Try "inline fuse holder" on eBay, many are water resistant and even come with a suitable fuse.


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## CXRAndy (8 Apr 2020)

If you wrap the frame where the speed sensor is in a couple of layers of electrical tape. re cable tie the sensor, it will be more secure, less likely to move


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## Ananda (10 Apr 2020)

simon.r said:


> I need to do something to secure the battery better, but I don’t like the idea of drilling holes in the frame. I may resort to that, but I’ll see if I can think of another way first (which may involve cable ties). The battery holder came supplied with some spacers shaped to fit the downtube.
> 
> Thanks for the comment about the fuse, I’ll look into that My electrical skills are minimal, so will be good to do a bit of research and up my knowledge.



If you remove the cover of the battery base plate (where the connectors are) you will see an aluminum plate. Drill this to secure the battery on the frame. You may also want to put some form of rubber between the frame and plate.

Also, on my bafang installation on a bike with hydraulic brakes, I used one of the supplied vbrakes (the left one) as an 'electric clutch' for when I change gears. It works very well. It also gives the ability to cut power during certain maneuvers. 

The one and only fly in the ointment with bafang drives is the way they are programmed. You get too much current even at the min assistance level. It can be changed though. But mine is a 750w so yours may be different. As far as the electric throttle goes, I do use mine, especially when starting from traffic lights until I clip to my pedals and also when offroading technical sections. 

Your chainring is too large. The motor can turn it, but not without unecessary stress. Lekkie has produced a 40t model that goes with a bling motor cover that helps it fit with correct chainline. What range cassette do you have?


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## simon.r (10 Apr 2020)

Ananda said:


> If you remove the cover of the battery base plate (where the connectors are) you will see an aluminum plate. Drill this to secure the battery on the frame. You may also want to put some form of rubber between the frame and plate.
> 
> Also, on my bafang installation on a bike with hydraulic brakes, I used one of the supplied vbrakes (the left one) as an 'electric clutch' for when I change gears. It works very well. It also gives the ability to cut power during certain maneuvers.
> 
> ...



Still waiting on the electrical connectors to arrive, then I’ll sort the battery position out. Thanks for the point about drilling the base plate, will look into it.

Interesting idea about the ‘clutch’. Again, I’ll look into that. How have you positioned the lever? Any photos?

After a couple of rides I have come to the same conclusion as you about the chainring. I have a 38t ring on order. Cassette is 11/36. Prior to the conversion I had a 36t chainring. This bike’s obviously not designed for speed, so I think the 38t will be OK.


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## CXRAndy (10 Apr 2020)

The Bafang is a pedal assist system. It gives you set amount of extra power per level.

The Tongscheng TSDZ2 is a torque sensing system. It has multipliers of power at each level of effort put in by the rider.
That means setting off is smoother and not a sudden acceleration

The gear selector switch, cuts power momentarily to the Bafang motor allowing a smoother shift. They have two types of switches one for derailleur the other internal geared hubs


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## Ananda (11 Apr 2020)

simon.r said:


> Still waiting on the electrical connectors to arrive, then I’ll sort the battery position out. Thanks for the point about drilling the base plate, will look into it.
> 
> Interesting idea about the ‘clutch’. Again, I’ll look into that. How have you positioned the lever? Any photos?
> 
> After a couple of rides I have come to the same conclusion as you about the chainring. I have a 38t ring on order. Cassette is 11/36. Prior to the conversion I had a 36t chainring. This bike’s obviously not designed for speed, so I think the 38t will be OK.



I hope this helps. Its a convenient place to be despite what it looks in the pic.
The 38t chainring will mess your chainline. The smallest chainring that has a decent offset is 42t. However, it is possible to fit a suitable spacer on the inner side of the freehub and take out one of the smallest sprockets of the cassette. In this way you will bring the biggest sprocket one position out and loose one gear.


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## Bonefish Blues (11 Apr 2020)

Just by way of an enquiry on a relevant thread, are there any suppliers who will do this type of conversion on your existing bike for you?


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## CXRAndy (11 Apr 2020)

Bonefish Blues said:


> Just by way of an enquiry on a relevant thread, are there any suppliers who will do this type of conversion on your existing bike for you?


Any decent bike shop could do it. 

It really isnt difficult though, with a few tools for bottom bracket. I used heat shrink to keep the excess cables tidy, a bit of insulation tape and cable ties. 

I took about an hour to swap over to a motor kit. It took a couple more hours to tidy all the cables up and make it a cleaner install.


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## simon.r (11 Apr 2020)

Ananda said:


> I hope this helps. Its a convenient place to be despite what it looks in the pic.
> The 38t chainring will mess your chainline. The smallest chainring that has a decent offset is 42t. However, it is possible to fit a suitable spacer on the inner side of the freehub and take out one of the smallest sprockets of the cassette. In this way you will bring the biggest sprocket one position out and loose one gear.



I’ve not received it yet, but it looks to me as if this set up will give a very similar chainline to the Bafang supplied chainring:

https://www.ebay.co.uk/itm/352870426326

I’ll let you know when it arrives.


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## Bonefish Blues (11 Apr 2020)

No, I understand that, but at the moment I simply don't have the time - I'm doing stupid hours sorting out the CJRS for a company and I'm just knackered by way of icing on the cake!

It also fails my 'can I be *rsed?' test, if I'm being frank!


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## simon.r (12 Apr 2020)

14 - Battery base plate re-fitted. New hole drilled and existing slot extended slightly, so it *just* fits. Spacers added so it’s parallel with the downtube.


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## Bonefish Blues (12 Apr 2020)

simon.r said:


> 14 - Battery base plate re-fitted. New hole drilled and existing slot extended slightly, so it *just* fits. Spacers added so it’s parallel with the downtube.
> 
> View attachment 514427
> 
> ...


Drilling holes? That's engineering


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## simon.r (12 Apr 2020)

Bonefish Blues said:


> Drilling holes? That's engineering



 Only in plastic and aluminium though!

This level of ‘project’ is just about right for me. A few minor difficulties to overcome, but nothing too taxing for someone with limited practical engineering experience!


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## simon.r (12 Apr 2020)

15 - Realise that new position of battery base plate is no good as the battery just touches the motor, making it difficult to seat properly Take battery base plate to bits and discover slot that can be used to put a bolt through. Reposition battery base plate.











Cross fingers that it’s 3rd time lucky


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## CXRAndy (13 Apr 2020)

simon.r said:


> 15 - Realise that new position of battery base plate is no good as the battery just touches the motor, making it difficult to seat properly Take battery base plate to bits and discover slot that can be used to put a bolt through. Reposition battery base plate.
> 
> View attachment 514460
> 
> ...



I drilled and added two more riv-nuts to make the battery mount as secure as possible. They weigh a fair bit. I too had to carefully place the holder to clear chain ring and allow removal of battery


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## Ananda (13 Apr 2020)

I used rubber grommets between the base plate and the frame. I also drilled the holes on the aluminum plate where the screws go through quite a bit larger, to allow some vibration absorption. It works well (so far!).


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## simon.r (14 Apr 2020)

16 - Tidy up the wiring.


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## simon.r (14 Apr 2020)

17 - Ride to the supermarket, load a trolley full of shopping onto bike and marvel at how easy it is to cycle home


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## simon.r (28 May 2020)

18 - As is the way with these things a few miles under the wheels and you start to think ‘what if...’. This is, I think, the finished article.

Changes:

Battery changed for rack mounted. Looks neater and the bike feels more normal with the battery in this position.

44t chainring. I underestimated the motor assistance and don’t need anything smaller.

Smaller display fitted.

Gear change sensor fitted, which cuts out power when changing gear. This has made the ride significantly less jerky.

Wiring tidied. I can live with the wiring bundle around the headtube as I always have a large black bag fitted to the bike (as shown in previous photos) which obscures it to some extent.


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