Three motor types
The right engine system can significantly enhance the driving experience. But not all motors are the same. Standard pedelec drives on the market differ significantly in terms of performance and character. Which drive system is the right one is determined not least by personal preference.
E-bike motor: hub motor
Hub motors sit directly on the axle of the front or rear wheel. They transmit their power to the wheel almost silently and without loss, can be very powerful and react sensitively. However, no gear hub, such as the popular Shimano Nexus or the continuously variable Enviolo, can be fitted to pedelecs with rear hub motors. Because the chain and sprockets are not integrated into the electric drivetrain, their wear is significantly less than with mid-drive motors. Powerful rear hub motors are therefore ideal for touring bikes.
E-bike motor: mid-motor
They are ideal all-round drives: most pedelecs are equipped with mid-mounted motors. Mid-mounted motors sit between the cranks and transmit their power via the bottom bracket to the chainring and from there via the chain to the rear wheel. The chainring, chain and sprocket therefore wear out more quickly than with hub motors. Due to the position of the motor in the frame node, the centre of gravity of the bike is low and central, which is advantageous for handling. Unfortunately, only one chainring can be fitted to most models. Centre motors can be combined with hub and derailleur gears.
E-bike motor: Low Assist drive
Low-assist drives are the first choice for lightweight urban pedelecs, commuters and designer bikes. The power-reduced drives are usually located on the rear wheel hub, but they are also available as centre motors. Due to their size and low weight, they are suitable for bikes where the motorisation should not be visible. Compared to more powerful drives, they consume less energy, so they can also manage with smaller batteries. The systems offer designers a great deal of freedom in the construction of filigree frames. The lightweight wheels compensate for some of the lower motor power.
Full performance
Variety of e-bike motors
Commercially available motor models differ significantly in terms of power and torque. The harmony between pedelec and rider therefore not only determines the riding characteristics of the bike, but also the characteristics of the drive. An e-bike motor that provides a powerful push even with little pedalling force and a low cadence is suitable for an energy-saving and relaxed riding style with many stops. If, on the other hand, the drive increases in power in proportion to the pedalling force, it is more suitable for sporty cyclists.
Energy consumption also depends to a large extent on the power characteristics: Drives whose power increases slowly but steadily with the pedalling force generally run more economically than those that maximise even low pedal pressure. So if you invest more leg power yourself, one battery charge will get you further. Incidentally, most pedelec drives provide significantly more power than their rated output of 250 watts suggests. Continuous outputs of more than 500 watts are the rule rather than the exception.
Two graphics of an e-bike motor test
The graph above shows the power curve of a pedelec drive as a function of the pedalling power at different cadences (pedalling frequencies). Good to see: The motor only reaches its maximum power at higher cadences (light blue, green).
The graph below shows the torque and power curve depending on the cadence. The high torque of more than 80 Nm at a low cadence helps when starting off and accelerating.
E-bike batteries
The capacity of lithium-ion batteries for pedelecs has almost doubled in ten years. However, large batteries are significantly heavier and more expensive than those with a lower capacity. The following therefore also applies to energy sources: the intended use is decisive.
Until a few years ago, batteries with a maximum energy content of 500 watt hours (Wh) were standard. Things started to change in 2020. Within a year, the battery capacity of some market-relevant motor system manufacturers climbed first to 625 Wh and then to 725 to 750 Wh. Because the available motor power can hardly be increased within the legal framework and thus its energy consumption, the possible range of pedelecs increased significantly; 90 kilometres are easily possible.
However, the high capacity is reflected in the weight. A standard 500 Wh battery weighs just under three kilos, a 725 Wh model more than four. The 250 Wh battery of a low-assist system, on the other hand, only weighs around 1.5 kilos. This means that a light city bike only needs to be plugged in after around 30 to 40 kilometres of power-assisted riding. For heavy touring pedelecs, however, the significantly higher achievable range clearly favours a large, high-capacity battery. For design reasons, most manufacturers favour Intube batteries. They are now standard from the mid-range upwards. However, Ontube batteries, which are mounted outside the frame tubes, are much easier to remove - as protection against theft or to charge them at home. The small "invisible" power sources of low-assist drive systems often cannot be removed from the down tube without tools.
Glossary
- Pedelec stands for Pedal Electric Bicycle and refers to a bicycle whose motor is activated solely by pedalling. Pedelecs are legally recognised as bicycles. The rated power of the electric drive may not exceed 250 watts and the motor may provide assistance up to a maximum of 25 km/h.
- E-bike is a collective term for electrically powered bikes. This includes pedelecs, S-pedelecs (max. 500 watts, 45 km/h) and electrically powered bikes without pedals and without limits on power and speed. It also includes electrically powered mopeds and motorbikes.
- Battery capacity/watt hour (Wh): The energy content or battery capacity of pedelec batteries is specified in Wh. The value describes the energy that a system with an output of one watt absorbs or releases/consumes in one hour. On average, a pedelec drive consumes around six to nine watt hours per kilometre.
- Motor power/torque: Although the rated motor power of pedelecs is limited to 250 watts, their maximum power can rise to over 500 watts. The torque, on the other hand, describes the force with which the motor drives the rear wheel. The higher the torque, the more powerfully and dynamically the motor accelerates.
- Low-assist drive: The term low-assist motors has become established for small, power-reduced drives with a maximum output of up to around 350 watts. These lightweight and inconspicuous drives are suitable for delicate and stylish designer bikes as well as for lightweight city bikes. The systems include small batteries, usually up to around 250 Wh.
