It sounds kind of weird, but we are still in the infancy of eBikes and electric vehicles. Yes, some electric bike technology has been around for about 10 years or so, but in the grand scheme of things, we are just barely scratching the surface of potential and innovation with these bikes. Thanks to the Chinese and miniaturization, hub motors have become the prevalent propulsion method on eBikes, and that is purely an economic choice.
As a manufacturer of eBikes, Soul has tested a number of products to evaluate and build what we feel are the best and most dependable electric bikes. As you might guess, dependability is our primary focus, and closely following is performance. With that, we choose to use mid drive systems over hub motors. So lets get into this debate a bit further.
Hub Motors – Big on Budget
Hub motors are great and all, and on a budget, they certainly fill a need. One of the big problems in the industry, and many shops complain of this is that there are many hub motors that we don’t even know who made them, let alone where do we get parts? It gets a bit scary when a virtually new bike fails, the hub motor wont trigger, and there isn’t much that can be done other than replace the motor. But since you don’t know the origins, you have to buy a complete kit, not just the motor. This happens daily in the hub motor world. Now, we can spec out a name brand motor, at a higher cost, and alleviate much of the issues, but we have other aspects of the hub motor to deal with.
Generally, a hub motor will have an internal drive ratio of around 5 or 6 to 1. That is the only mechanical advantage the system provides. For many, this is perfect for their riding needs. Another comparison aspect on hub motors is many of our competitors use a derailleur based drive train. They normally do not put high quality parts on, so you get a basic chain and gear set, an ok shifter, and a low end rear derailleur. The maintenance of the drive train is increased, and is also vulnerable to damage.
We prefer mid drive systems over hub motors. Yes, they are more expensive, but for that added money, the system offers many benefits.
In a hub motor system, you have an external motor controller, the wiring is quite messy, and the setup doesnt reach our benchmark of a simple easy to use bike and is clean and virtually maintenance free. There are a couple of bikes on the market that have tried to solve issues with hub motors, but, it is still a key stumbling block of integrating the system into the bike cleanly.
With a mid drive system like we use from Bafang (the worlds largest eBike motor manufacturer) the components are integrated significantly better. The controller is actually part of the motor for instance. A single harness cable runs from the motor up to the handlebars to help with controls. Other than that, you have the obvious power cables, and one sensor wire for wheel speed. This is a far cleaner approach.
Mid Drives – The Mechanical Advantage
The main reason we prefer mid drive is the mechanical advantage it provides. Remember from before, a hub motor is usually working at a 5 to 1 drive ratio. On a mid drive, we work through the drive train, so we can create pretty any drive ratio we desire. Add in using an internally geared hub. and the simplicity of riding up a hill, or on the flats is as easy as changing gears with the grip shifter. This torque multiplication through the drive train, just like in a car, is what sets the mid drive apart. This ability to vary the gear ratio, gives a significant advantage to mid drive motors.
We have used the Bafang BBSHD system primarily in our builds. It provides 1000w nominal power, and can handle surges beyond 1500 watts for a few moments. We are also employing the Bafang BBS02 into our Sonic Sport builds. The key difference is in case sizes. With electric motors, a bigger case usually equals more torque. The BBS02 is about an inch smaller than the HD motor. The HD will also handle more amperage.
When we built the original Sonic Sport, we were aiming at price point, but were surprised on our first ride of the bike. The Sport is a single speed, 500w system using a 48v 10.5 amp battery. It is the lightest weight eBike we make. Amazingly, it accelerates very hard, and has excellent range. We have reached over 40 miles on rides, and our customers back those figures up. This bike is quite surprising!
Our Sonic and Sonic SS models spec out the wider 170mm rear end frames and employ the Sturmey Archer RK SX3 hub. While we dont recommend shifting under load with the hub, we get excellent results with it on our bikes. Under take off in 1st gear, the bike launches very well, and shows the torque of the BBSHD 1000w motor. On full power, first gear can get you up to nearly 20 mph, and the other gears even faster. While not as efficient in power consumption, the bike can perform both on speed, hill climbing and in lower settings distance.