Electric Bycycle Conversion

  • Hi everyone! I stopped into the makerspace today to drop off a little donation and a few of the members showed some serious interest in my bicycle I built a couple years back. So I thought I would put together some basic information about my bike, and if anyone has questions I’d love to answer them! I’ve learned a ton while building this and would do things differently if I were to do this again.

    The Bike
    The base bike is a devinci jack XP that bought it a few years back because it’s aluminum and has disk brakes. The tires are 29" rather than the typical 26", makes it fairly smooth on road, but this is entirely unnecessary for most purposes, and the gearing changes with the larger tires. The smaller your wheels, the more torque you’ll get, so many low power e-bikes use 20" wheels. A standard 26" bicycle would be just fine for conversion though. I can’t recommend disk brakes enough for an e-bike conversion, traditional brakes aren’t designed for much over 30 km/h and won’t stop you fast enough to be able to be safe in traffic. That said though, legally all e-bikes are restricted to 32 km/h

    The Motor
    I bought a BBS02 750w mid-drive electric motor, it has an integrated controller and free-wheel gear so that when the system is off you can pedal with no resistance. I considered a few types, namely geared or direct drive front/rear hub motors, but ended up choosing a mid-drive to keep my weight balance centralized, since it ads around 10 to 15 lbs to the bike.
    The motor I bought was on sale on ebay but plenty of ebike parts shops sell these things. Given the chance again, I would probably buy a motor from a guy that makes them out of Toronto, http://middriveebike.com/, because of price and design. Much as I like the fully integrated system, the BBS uses some plastic gears that I’ve heard wear out over time. Also 750 watts works out to nearly exactly 1 hp, fun fact!

    Other options are available for off-road oriented builds, ones that put the motor into the triangle of the frame, rather than hanging it off the front where it might be hit too.

    The battery
    A 48v 20 amp hour LiFePO4 battery, custom built by BMS battery which takes me around 30 km with no pedaling at max power, I can push it to nearly 100km if I use about half power, or if I’m climbing the hill from north shore to TRU, I can make it there and home with a bit to spare which is around 20 km for me. Mine is a rack battery, definitely not my first choice but for the capacity I wanted, finding a downtube, or triangular frame battery was not an option at the time. 36v batteries are far easier to find!

    Common Questions

    • How fast does it go? I can hit just over 50 unassisted on flat ground, I carry about 30 km/h while going up the hill to TRU
    • How much did it cost? just under $1000 (not including the price of the bike) which has more than paid for itself in parking, insurance and gas savings.
    • Why mid drive? Because I wanted to maintain my gearing, something I’ve come to learn is less important for a road bike, but useful off-road.
    • Where did you learn this? Much of my information comes from Reddit and the Endless sphere forums.

    So when you put it all together, here’s my bike!
    Pointers for your own project
    if anyone wants to build their own bike first I’d love to talk to them! Firstly, I do not recommend BMS battery (Or any overseas battery manufacturer) instead get one nearby, even from the US if you must. The reason for this is because the import costs are rather expensive and it nearly doubled the cost of my battery. The fees worked our to over 30%, and taxes were added ontop. As a bonus point, TNT shipping is the only international company that will transport batteries, they must be send by ground/sea meaning you’ll be waiting a month or two for something to arrive.

    Mid-drive motors are great but more complicated to install than a hub motor. Front hub motors are wonderfully simple to install, and low power motors don’t even need a torque arm (something that protects your fork from shearing off, which will happen if you’re using much more than 300 watts). But they’ll effect the weight of the front end, depending on the size of motor you get of course, and the front wheel drive idea doesn’t benefit a lot of people, and they’re terrible for climbing hills. A rear hub is between the two for complexity, some kits more or less just drop into place making them super simple and the drive dynamics of the bike don’t change.

    Most of these homebrew kits don’t facilitate regenerative braking, to get that you’d need to look into a kit from BionX, where they sell the motor and battery together. The problem with these is they cost around $2000 and they have a maximum power of 300 watts.

    So what did I miss? Any questions?

  • Linux

    Awesome write-up!
    I’ve been thinking about this off and on for a number of years but never felt the range was sufficient. The range you are getting makes it sound realistic.
    What did this conversion cost you?

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