My motivation for building this bike was to make biking more fun. With the same pedal effort, I can bike twice as far and twice as fast, which makes the bike more likely to be used for running errands. In 'pedal assist mode', the motor will multiply your pedaling effort, the power in PAS mode is limited to 50%, but this still makes you feel like a super athlete! There is also a thumb operated throttle that will let you control the motor up to 125% (960 Watts), so it rides just like a motorcycle. On flat ground, at full throttle this bike will run 31.8 MPH without pedaling. The range with my 44V 5Ah pack is about 15 miles, this is while using the highest pedal assist mode, and occasional full throttle runs up hill.
The reason I went with a Mid-Drive motor (as opposed to a hub motor) was to take advantage of my bike's gearing. The motor can be much smaller since low gears can be selected for hills, or high gears for high speed. The motor has enough torque to easily do a wheelie up my driveway without pedaling. The motor kit I bought makes for a very clean install because the controller, gear reduction, and many of the sensors are built into the motor housing, this reduces the number of wires significantly. The result is a pretty stealthy look. Here is a review comparing other Mid-Drive motors, ElectricBike.com Review
Added a Tesla sticker!
Pins to hold down the lid
|This is the bike I converted. I bought it on Craigslist because it had an 8 speed internal hub which allows you to shift while stopped, and also shift while you pedal. It also has a very clean look, no front or rear derailleurs, and no tensioner. The motor is barely visible behind the crank and main gear.|
| The water bottle is just a water bottle, the batteries are inside the rack mourned bag. That bar on the stem is for Penny's bike seat. She likes to press the throttle when we ride! Having a black bike helps hide all of the cables.|
|The motor is a Bafang BBS02 750 Watt, it's a Permanent magnet DC brushless motor, the controller is built into the motor housing, and the gear box uses helical gears so it is almost completely silent. The motor is rated 20 amps at 48 voltes peak. This is the review that was the deciding factor for me going with this motor, ElectricBike.com Review of Bafang BBS02|
|View of the bottom of the motor. It can be installed on almost any bike. There are only 3 cables coming out, one for the battery, one for the wheel speed sensor, and one cable goes to the handlebar mounted devices. The motor will eventually rotate its' way up till it is against the frame, make sure to run your cables so they won't get pinched. My shifting started getting slow to respond, that is how I realized the cables were getting pinched. |
|I'm using 3 RC car batteries (4S Lipo) wired in series to get 44VDC, 5Ah. This gives me about 15 minutes of full current, at full throttle (typically just a few seconds of full throttle gets you up to 25mph, then the bike uses less current). Real world experience, I get about 15 miles using the highest pedal assist mode which gives me a cruising speed of 20 mph. Battery cost was $25/each from HobbyKing.com, be sure to buy from the USA warehouse to save shipping costs|
|Close up showing how the batteries are hooked in series, no additional connectors required, it just happened to work out that way!|
Update - I finally received my low voltage monitors. They will beep if any cell drops below 3.3 volts, preventing permanent damage.
|Batteries hooked up in parallel for charging, I can hook up to 6 in parallel and charge at once. The charger I'm using keeps track of how much energy (mAh) has been put into the battery, so I get a feel for how much capacity I have used up. |
HobbyKing Parallel charging board
Update - New 300 Watt charger and 24v power supply! I can now charge at 19 amps instead of only 3. This brings the charge time down to 45 min, instead of 5 hours. This charger is actually slightly smaller in physical size compared to my 50 watt charger. |
Update - Happy to report I can pull a full 20A and can charge a full 15,000mAh in 50 minutes.
|Pedal Assist Mode (PAS) (+) and (-) buttons on the left allow the motor to amplify how hard you pedal. The thumb throttle on the right will let you run the motor at full power without pedaling. The display is back lit at night which is nice.|
The brake levers that come with the Bafang kit include a brake switch that instantly shuts off the motor.
|Speed sensor, nice that it has an LED on it to show that it is working (or not working in my case)|
|All the parts that came in the kit. It is a Bafang BBS02. The whole kit was $489 shipped. Compared to other kits, it's expensive, but it does come with everything you need except the battery.|