I decided to convert my city cruiser bicycle into a comfy e-bike. After researching the various ways to do this, I settled on a mid-drive kit. The typical way to make an e-bike is to mount the motor in the hub of one wheel. This is the easiest (cheapest) conversion because it disrupts the rest of the bike the least, and will fit most bikes. But if the wheel gets a flat, the motor and wiring become a hassle. The other way is to mount the motor in the crankshaft between the pedals. This crank, or mid-drive, position gives the bike more effective power per motor wattage, and is especially favored by bikers wanting to climb hills. Having the motor weight in the center also retains better balance, particularly as the motor gets bigger and more powerful. But it is more work to install.

Decent new mid-drive e-bikes go for at least $3,000 and above. I bought a new Luna Cycle Bafang BBS02 mid-drive kit, including a monster 48v battery for $800. The motor is 750 watts, which is the legal street limit in the US. It’s crazy powerful, will zoom you up any hill, even off road, and I have yet to exhaust the battery in a single ride.

My praise for the Luna kit is that everything is included: brakes that cut the power off when applied, throttle, display, speed sensors, cables, cranks, motor and battery with mount and charger. Once I got everything installed correctly, it worked immediately without a hitch. The major downside is that the kit arrives without shred of documentation, not even a list of parts, and that not much for this kit will be found on their website. Scattered on their site, and other forums they point to, are hints here and there for older models. Some elementary diagrams or measurements of the kit would have helped a lot. I wound up emailing my questions which Luna did answer, but I spent a lot of time figuring fundamental things out myself. In addition, advance bike modification skills like removing crankshafts, re-cabling, taking chains apart, are needed, so I wound up watching a lot of youtube for this. This kit is truly for DIYers.

Here is what I wished they had told me before I started:

1. Before you order the kit, you may need to disassemble the crankshaft and measure to be sure the Bafang motor fits. This is difficult because those Bafang measurements are hard to find and there are other parts of your bike that can interfere with this odd-shaped motor and crank.
2. The new brakes, display, throttle, on-off button need handlebar real estate, so you’ll need straight handlebars, not drop downs.
3. The mid-drive only uses your back set of gears, so you’ll remove the front derailleur.
4. If you are lucky, your battery will fit inside the triangle bike frame; if not, you need to find a place for it and hope the wires are long enough. Good luck in finding out those dimensions.

By email support, by reading as many forums as I could, by re-doing steps, and by mucho youtube, I succeed in converting my dad bike into an awesome electric bike that can climb fast and furious. Compared to a off-the-shelf ebike, the kit is a good bargain in spite of its dismal instructions.

-- KK 05/15/18