Electric mobility is unarguably one of the latest innovations in recent years and it won't be wrong to attribute its rise to the rapid advancements made in scientific technology over the course of the past few decades. Batteries & electric motors form the building blocks of this revolution without which we wouldn’t be enjoying the zero-emissions mobility solutions that we are enjoying today. Electric cars and ebikes might seem completely different modes of transportations, but they both share two similar components, i.e., battery & a motor. This article discusses various types of ebike motors, their working principle, and how each of them differs from one another.
How do Ebike Motors work?
Ebike motors are basically an evolved version of DC motors that are also referred to as brushless electric motors, these motors, as the name implies, provide mechanical energy (rotational motion) without the use of brushes which is also the reason why they are 85-90% efficient compared to the efficiency rating of brushed motors that stands at 75-80%. Motor-powered bikes are always eerily silent which, again, can be attributed to the ebike's brushless hub motor.
Source: Renesas
The working mechanism of an ebike motor is as follows:
· The stators and the permanent magnets are the two most fundamental components of any brushless motor, the stators, are in fact a circular pole upon which wires are winded in a circular pattern.
· Depending upon the type of brushless motor, the permanent magnets are either placed in between the stators or outside the stators, either way, they are also circular.
· The stators upon receiving power from an ebike’s battery become electromagnets and start attracting & repelling the permanent magnets which cause their spinning motion.
· The stators, in turn, are connected to a shaft, which again, depending upon the type of motor, either spins itself or is connected to the motor’s hub, both of these mechanisms ultimately propel the wheel of an ebike.
Mid-Drives:
Source: Bosch
Mid-drive ebike motors, as the name may have already suggested, are ebike motors that are placed right in the center of an ebike. Their prime purpose is to supplement your pedal input in order to take the strain off your legs & feet. Their unique positioning ensures perfect weight balancing of an ebike and at the same time, the center of gravity is also optimized.
Several brands are manufacturing mid-drive ebike motors, but Bosch & Yamaha ebike motors are perhaps the most well-known in the industry. Yamaha’s motors are available in five models, each with different specifications while Bosch’s mid-drive motors also boast several advantages. Nearly all such motors are packed with a safety mechanism that cuts the power to the motor whilst you’re changing gears to avoid chain breakage. Apart from the several advantages, the main disadvantages of such motors are they take reasonable space and are also quite visible, moreover, their output efficiency also gets diminished by the time it reaches the wheel.
Direct-Drive Hub Motors:
Direct-hub motors are the most common type of ebike motors, and they are placed directly into the hub of the rear wheel. Such a motor's shaft essentially becomes the rear axle and instead of delivering power through the chain, it instantly & directly propels the wheel, thus eliminating the need to carve out a designated area for the motor in the middle of an ebike.
The greatest advantage of such motor powered-bikes is they can recoup some of the lost energy using a process called regenerative braking, which is completely identical to the process used in the hybrid & electric cars. As soon as the brake pedal is pressed or the throttle is depressed, the direct-drive hub motor becomes a generator and starts recharging the battery. However, it is important to note that on route rides, the gains are minimal, it is only in areas with steep slopes where you will be able to get the maximum advantage of this feature. In addition to being efficient, provide several other features at a great price point, making them great value for money products for almost every age group.
Geared Hub Motors:
Geared hub motors are essentially a complex version of direct hub motors since they are fitted with a series of gears that tone down the high revolutionary motion generated by the powerful motor and then transfer it to the wheel hub. Such motors are noticeably smaller than direct-hub motors, but it is the gears that make them look wider than their competitors.
The direct-hub motors & geared hub motors combined are considered to be the best ebike motors in the industry, but unlike direct hub motors, the geared hub motors don’t support regenerative braking. This may be counted as their major con, but the lack of regenerative braking allows them to behave more like a traditional bicycle which, to some, is a great advantage.
Mid-Drive Motors vs Hub Motors:
The mid-drive ebike motor provides a more balanced & stable ride which especially comes in handy when climbing rough or rocky terrains as the geared drivetrain of mid-drive motors is ideal for low-speed climbing. Since the wheel of such an ebike is motorless, therefore, changing tires becomes an easier task.
Some disadvantages are typical to ebikes that rely on mid-drive motors, the most significant of which is increased wear & tear of the chain and the sprocket which ultimately results in higher maintenance cost. Moreover, such ebikes are also considerably pricier than their competitors because of special design modifications needed to make room for the motor in the middle.
On other hand, hub motors are more efficient in delivering their power as they’re directly connected to the wheel, also ebikes with such motors are relatively affordable and hub motors also don’t cause as much strain on the chain as a mid-drive motor.
Having mentioned the pros of hub motors, it is worthy to note that ebikes that run on such motors aren’t exactly good at climbing hills, mostly such motors require increased power input which necessitates the use of beefier motors that, in turn, raises the total weight of an ebike which also isn’t centered at an ideal position like a mid-drive motor. Last but not least con is a rather complex way of replacing the rear tire as one has to navigate through the motor and some of the wirings which might prove to be tricky for some folks.
Direct-drive Hub Motors vs Geared Hub Motors:
Though, both the direct-drive and geared hub motors share a common working mechanism, there are some differences that can impact your buying decision. Direct-drive hub motors are capable of achieving higher top speeds because they aren't geared down for torque like the geared hub motors. On the other hand, geared motors are capable of performing well where high torque is needed but their inability to regenerate energy using regenerative braking is a major con for many. This property causes increased strain on the braking system, whereas direct-drive hub motors simply don’t require as much brake maintenance as geared motors simply because they support regenerative braking.
Power Rating Explained:
Power rating is the most commonly used measure to rate an ebike’s motor output, however, the power rating mentioned by any manufacturer is just an arbitrary way of providing an estimate on the maximum performance of an ebike. It just isn't clear how long an ebike will be able to sustain its maximum power output, which is why the battery's voltage & amperage from the motor are a better way of judging an ebike's peak performance. Another great way is to look for an ebike’s peak torque figure, as it is a relatively more accurate & less arbitrary way of getting to know the peak performance of an ebike.