By Paul Levett. All images courtesy of Paul Levett.
I am a cyclist who rides for transportation. I got into e-bikes after ten years of riding the Metro and decided to commute by bicycle to work in downtown Washington, DC. I needed a pedal-assist to cycle uphill to my home in Arlington, VA.
In fall 2016, I bought a Bafang BBS01 (also known as an M215 or G340.250) mid-drive kit motor and 36v battery.
Deciding on a pedal bicycle to convert
I wanted a step-through bike with an internal gear hub (IGH) to shift gears when stationary, with the ability to mount a mid-drive motor and carry the battery on the downtube to keep the weight low and central.
Frame type and assembly
The first-generation Breezer Downtown ST had the mid-step frame and internal geared hub I was looking for and the mid-step design meant I could mount a battery on the downtube. Breezer has since changed the design of the Downtown ST to a traditional loop frame step-through that does not work for conversion purposes.
Papillon Cycles of Arlington placed the order and assembled the bike for me with some modifications: I had them remove the bottom bracket so I could fit the motor, and they replaced the 18t rear sprocket with a 21t so I could get the 2:1 ratio Shimano recommends for the Nexus IGH with the new 42t front chainring.
The width of the motor meant I had to replace the Breezer chainguard to fit an Hebie chainglider of the right size to work with the front chainring and the Shimano Nexus 8 IGH. It works well to keep my pants and the chain clean. I upgraded the bicycle touchpoints with Ergon grips, VP flat pedals, and a Brooks B66 sprung saddle.
Power, speed, and weight
Two questions remained: Could the bicycle gears handle the motor's torque and were the brakes capable of stopping a heavy bike?
To ensure the motor cuts out when shifting gears, I had Papillon Cycles fit a gear sensor in line with a new gear cable. This solution is more basic than Bosch's shift detection system, but it works to momentarily cut the power and ease up on the drivetrain. I also had Papillon Cycles replace the front rim brake with a Sturmey Archer 90mm drum brake that stops reliably in all weather.
Adding e-bike-specific components
In addition to the motor and battery, I added a throttle, display, wheel speed sensor, and torque arm on the chainstay to prevent the motor from rotating in the bottom bracket.
I installed e-brake sensors that stop the motor, and managed cables with spiral wrap, neoprene, and zip ties. An Anderson tap was installed in line with the battery wiring harness to power e-bike lights off the battery.
The BBS01 has 6v/3w light connectors but tapping the main battery power wire permits brighter lights. I upgraded from a 1.5w/100-lumen to a 5.5w/400-lumen headlight with a broader beam pattern that allows me to better see dog walkers and joggers at night.
Deciding on an e-bike kit
The simplest and least expensive e-bike kit to install is the Hill Topper Sprinter ($550), which replaces your front wheel, so you don't have to mess with the pedal bike's gearing. The drawback is that the conversion kit offers only a throttle and no pedal assist.
If you want pedal assist, the slightly more expensive hub kits from Ebikeling come with a clip-on cadence PAS sensor. My BBS01 uses both an internal cadence PAS sensor and a wheel speed/spoke magnet sensor. The BBS01 and a 13ah battery currently cost about $750 online.
I chose to fit a Bafang BBS01 mid-drive motor because it offered twice the torque (80nm) of an equivalent 36v hub motor to bike up hills. I weigh 240lb, the bike weighs 35lb plus another 20lb for the motor, battery, and drum brake. Sometimes I tow a trailer with a passenger. The result: The Bafang motor is capable of winching up to 365lb of weight on my rig uphill.
Other Bafang mid-drive models like the BBS02 and BBSHD have a wider stator to provide more torque, with upgraded controller mosfets that can handle the increased current without overheating and would be a better choice for a cargo bike. The BBS01 does what I need it to do.
Some other technical details
Would I do it again? Yes, although I would be interested in trying either a 48v BBS02 motor or the TSDZ2 motor that uses a torque PAS sensor.
How is the bike performing? I highly recommend installing the gear sensor. I tried operator training to cut the power when shifting, but there is no substitute if you want to protect the drivetrain.
Was it cost-effective to build your own e-bike? Installing a Bafang mid-drive requires bottom bracket removal tools and an understanding of bicycle drivetrains. I recommend working with a local bike shop on the conversion as I did.
In return for their help, I became a regular customer, spending an average $200 each year over the past five years, paying for their expertise and shop tools to install/remove the kit and service/upgrade the mechanical bicycle components.
I bought the Bafang mid-drive kit from California E-bike (currently they supply the more powerful BBS02 and BBSHD), as well as the torque arm, gear sensor, and e-brake sensors. I also purchased a Bafang installation tool to tighten the motor lock ring. The Anderson connectors, crimping tool, Anderson tap, and e-bike lights were purchased from Grin Tech.
Other resources I consulted included Reddit's e-bikes wiki list of suppliers, example builds on Electricbike.com, technical info on Endless Sphere, and YouTube videos from E-bike School and Grin Tech. I also reviewed e-bike conversion kits on ElectricBikeReview.com.
Paul is a librarian, cyclist, and Dad, who emigrated to the US from the UK in 2005. He started riding a bicycle for transportation at age 10, delivering newspapers. Currently he rides a Breezer Downtown pedal bicycle converted to an e-bike with a BBS01 kit motor. Paul lives in Arlington, VA.
Favorite e-bike: Tern HSD
CONTRIBUTOR E-BIKE LOVERS