Pico’s Projects: eBike Conversion Kit Installation

I like to have fun on my bike. However, my new home is in a river valley and every path leads up steep punchy hills which makes my heart rate max out and my legs and lungs scream. Coupled with my loss of cycling fitness due to back pain it means I am not cycling other than on my bike trainer. That is not fun! I mean, I’m fine with a hard ride on the weekends, but after work I don’t want to have to crush it. There are some nice trails in my area, but I don’t like to drive my bike to go for a ride. The round trip includes 30–40 minutes of driving. Something needs to change! So, I started considering an eBike.

Bafang eBike Conversion Kit

My wife has a Rad City eBike and it is fun to ride, but it is too small to be comfortable for me. Looking at new eBikes gives me pause as those I was interested in were starting around $2500. That is more than I am willing to spend right now, so I looked at eBike conversion kits. I searched `wirecutter ebike` and found this New York Times article on conversion kits. There are some reputable places online which anchored the price at around $1200 for a conversion. Which was still more than I wanted to spend. As part of the search, I found Schematix and his experience installing a Bafang eBike conversion kit on YouTube. He seemed to be pleasantly surprised with his experience, so I clicked on his affiliate link (you’re welcome, Schematix!) and began my first experience with what I consider one of the more sketchy places on the internet, aliexpress.

I have been avoiding aliexpress, because I don’t want to spend money on low quality items that may have been misrepresented (I’m thinking of the kiddie pool boxes you see on the store shelves that have 10 grown men playing volleyball in the pool that is literally 5 ft wide) or deal with misuse of my credit or identity information. If there are issues with the transaction, I want some kind of support or return policy without a language barrier. Looking at the price, the eBike conversion package was less than $700, which is less than $1200, which is a lot less than $2500. Since I was price anchored at $1200 that $700 seemed like a really good deal so I decided to risk it. If it all goes sideways at least I’ll have a story to tell. The combination of NoScript and uBlock plugins in my web browser makes the aliexpress website non-functional, so I removed restrictions, created an account, and pulled the trigger.

As a safety precaution, I use Capital One Eno to generate single use credit card numbers that are linked to my main account, that way if my information gets improperly used I know the source of the data breach (I’m looking at you CA glasses). The transaction went through and here comes the first snafu. The seller contacted me saying that the controller I had specified was out of stock. It is evident that English is not their first language (but kudos to them for communicating in more than one language). The gist was that I could get the better controller for an extra $10.60 and it is in stock and would ship immediately. In for a penny, in for a pound. I agreed and they sent me a request for another $10.60.

Now, this is the sticky part. Aliexpress, I’m sure, has to deal with a lot of fraud. They requested that I submit photographic evidence of the credit card (which is kind of hard to do for a virtual credit card) and a credit card statement. I tried my best, I wrote a note describing my situation, took an image snapshot of the number and downloaded a credit card statement and tried to upload it. However, they do not accept PDF uploads, only tiff, jpeg, and png. Does adobe allow saving as a jpeg? Oh no… that is an upcharge. I found a website conversion from pdf to png and with fingers crossed that they don’t steal my personal information (I am violating a lot of personal internet usage rules for this transaction) I converted image formats and submitted the documentation. The next day, I got the same message about missing information, so I sent another note with the information…. and I got the same message about missing information. It appears that I will not be dealing with any humans today and Aliexpress does not handle virtual credit card numbers well. I contacted the seller and they said that I should try a different payment method. I ended up using my paypal account (which is tied to a Capital One virtual credit card number!) and paid the $10.60. By the time this was completed, the seller messaged me that my original controller came into stock and they had shipped the package to me. I’m considering that $10.60 a gift instead of trying to request a return. It took about 5 days from start to finish, but I did get a message that my order has shipped.

The box arrived with those large flammable materials stickers indicating that there was a Lithium Ion battery enclosed. I unpacked the kit and everything seemed to be in order. I kind of panicked when I couldn’t find the controller, but it was in there after some digging. The thing that seemed to be missing was… instructions! This didn’t turn out to be a big deal. Every search for things like ‘Bafang motor installation’ or whatever came back with a useful result and a video to watch.

The project came with a lot of ‘firsts’ for me. I have never: replaced a chain; replaced a derailleur; aligned a derailleur; replaced cranks; or replaced a bottom bracket. This also means I had to purchase some new tools: A crank puller (and then I found out there is a universal crank puller! I should have gotten that one); bottom bracket removal tool; derailleur alignment tool; master link chain tool; chain wear measurement tool.

The Installation Plan

Bafang Motor BBS02B 48V 750W Mid Drive Motor 8fun Electric Bike Ebike Conversion Kit 52V17.5AH

1. Remove chain; pedals; cranks; bottom bracket
2. Slide in motor, bafang logo presents to the left side of the bike
3. Secure the motor with the Y bracket with the ridges toward the bike, install with M6 screws do not fully tighten
4. Install locknut (grey with 4 indents) on crank threads. The arrow should point clockwise
5. Tighten the m6 bolts from step 3.
6. Install and tighten the M33 lock nut (black, many indentations)
7. Install the speed sensor on the rear triangle. The speed sensor magnet needs to be within 1–2mm
8. Route wiring
9. Install Display, controller, throttle, lamp
10. Install chain ring with m5 bolts, sprocket faces out from the bike
11. Install chain guard
12. Install crank arms
13. Install pedals
14. Install chain
15. Test

Speed sensor; Motor; Controller

Derailleur Detour

The bike that I am installing the bike conversion kit is the one I had an accident on a couple of years ago (and I won’t post pictures of the 33 stitches in my knee). The front fork needed to be replaced and it hasn’t really shifted well since then. The motor install went pretty smoothly, so I decided that before I add power, the bike should really be shifting well. I spent hours and hours trying to get the rear derailleur indexed, but it just wouldn’t happen and I messed up a lot of things in the process.

1. Before messing with the chain, I did use the chain wear checker and it said the chain was still good, but I know I put a lot of miles on the chain so I was going to replace it.
2. I didn’t have a set of chain pliers to separate the master link, so I used my chain tool to push out a rivet. That should only be done in an emergency and you’re not supposed to push the rivet all the way out. I had a master link in my emergency bag that I tried to install but it was too wide. I’m not sure what kind of chain that it is meant for, but definitely not for any of my bikes, so I spent hours getting that pin back in and learned that was a bad idea. I ended up buying a new chain with new master links (that were the right size).
3. Did you know you should count the number of links in your chain before you buy a new one? My chain had 125 links which is non-standard for a 9 speed because it has a big climbing gear in the back. The chains I bought were 116 links. I ended up splicing two of them together with master links to get back to 125. I did learn how to properly size a chain, so that is good. You wrap the chain around the largest sprockets and then add two rivets and that is how long your chain should be.
4. The new chain didn’t help with indexing my gears. The next step in troublingshooting is to check the derailleur hanger. Since the accident, the hanger has not been replaced. I thought that perhaps that might be the issue so I purchased a new hanger and installed it. There were numerous issues reinstalling the derailleur but I’ll address those in a bit. The indexing of the gears still didn’t work, so I took off the derailleur and used my new derailleur alignment tool to check that it was good. It was good, so that was not my indexing problem.
5. I had recently replaced my shifter cable, but I had torqued it too much trying to tighten it and ended up breaking it, so I had to replace the shifter cable (again).
6. The barrel adjuster was not able to be hand screwed into the derailleur for adjustment. I had to use pliers, but this caused the plastic casing to deform and it had to be removed. The derailleur’s threads for the cable adjustment were messed up. While turning with pliers, I also destroyed the little spring that is underneath the plastic barrel adjuster. I failed again to index the gears.
7. I messed up installing the derailleur in multiple ways. The first major issue I had was when I replaced the hanger and I missed that there was a nub on the hanger that the derailleur needed to rest behind. So, it was too far forward and not allowing proper shifting and I wasn’t able to get the tire and rim back into place. Once, I figured that out, I felt kind of foolish because it looked obvious. The second major screw up I made was routing the chain through the pulleys. There was a little metal piece that looked like it made a channel for the chain to ride through. This was completely wrong and caused the chain to bind multiple times (which is scary when it locks up!). It turns out the chain needed to ride on top of that metal plate. None of my other bike’s derailleurs had that bit of metal. Once I finally got everything correct I tried to index my gears… and still failed.
8. I went to the bike store and bought a new derailleur since I tried everything except for replacing my shifter. This isn’t supposed to happen. The derailleur hanger is supposed to bend and save the derailleur from damage. The guys at the bike shop told me this and were dubious. I ordered the derailleur anyway and fortunately they had one in stock at another one of their locations and I had it in hand that day.
9. Wow! The errors and hard earned knowledge really came together. I disconnected the shifting cable, separated the chain, installed the new derailleur, set the high and low set screws, reconnected the chain, connected the shifting cable, indexed the gears and it worked perfectly. It took like 15 minutes. The best tip I learned for initial cable tension is to get the shifter and derailleur into gear 3. Then release the tension on the cable and shift to gear 1 then pull the cable snug. Tighten the cable down and turn the crank and it shifts into gear 1 and little additional cable adjustment is needed.

I basically replaced my entire drivetrain. I may have been able to save myself a little work if I had better knowledge upfront, but the things I learned will definitely help in the future.

On with the Show!

I wired up all the components, charged the battery, and began testing. I was really thinking that things were bad because I could not send any power with the throttle. It turns out, the power cutoff sensors were not close to their magnets and once they were the crank turned all by itself! First success! After this most of the other elements installed easy enough, the light, the speed sensor, and the controller all came together. I had to disconnect the motor cutoff sensors and took a powered ride down the drive. I learned that those motor cutoff sensors are really important because when you hit the brakes you do not want to have the motor keep driving you forward!

The most finicky step was setting up the power cutoff switches on the hydraulic brakes. These magnetic switches have very small tolerances. I really wanted the power to cut off when I touch the brakes even a little bit. I ended up designing and 3d printing a small arm to mount the magnet and used a small shim under it to tune the distance. I spent a lot of time on the design as I had to take little steps to get it closer and closer to correct. Even the ‘final’ build was wrong but it was fixed with the shims. The setup on the front and rear brake are slightly different due to differences in the switches (or magnets).

Taking measurements and designing the cutoff sensor arm

Success! After the cutoff switches were installed, I did some cable organization and tested out the bike and some of those steep punchy hills. The motor helped tremendously, but it still needed my leg power but I think this is going to work out well. I’m looking forward to having some fun biking again.

eBike controls; wiring; and headlamp