E-bike, pedelec or bicycle with pedal assistance?
The European directive defines bicycles with pedal assistance as bicycles which are equipped with an auxiliary electric motor and having the following characteristics:
- maximum continuous rated power of 250 W;
- output progressively reduced and finally cut off as the vehicle reaches a speed of 25 km/h;
- output cut off sooner than 25 km/h when the cyclist stops pedalling.
Vehicles that meet these characteristics are considered to be, for all intents and purposes, traditional bicycles. As such, they do not require homologation, insurance, registration/plate or a driving license. Conversely, if a vehicle does not meet these characteristics, it cannot be treated like a bicycle and would, therefore, be considered as motorcycles.
The most appropriate definition of bicycles equipped with an electric motor is therefore bicycle with pedal assistance, however the terms e-bike and pedelec (from pedal electric cycle) are also commonly used.
There are different types of direct-current electric motors, with tension in a range from 12 V to 48 V, installed on one of the two wheels, often on the rear one.
The e-bike motors are divided into two categories:
The brushless motor is the most used in bicycles, although more expensive, as it doesn’t require any type of maintenance.
We talk about a maximum nominal power of 250 W, because these motors are generally capable of delivering peak power, under stress and for a short period of time, which are well above their continuous rated power.
Today most manufacturers of bicycles with pedal assistance use the lithium-ion battery (Li-ion), with variable capacity and amperage variables. These batteries are more reliable and allow a riding autonomy from 40-50 km up, depending on the level of assistance and on the weight of the vehicle and of the rider. Another advantage of lithium batteries is that they have no "memory", so you can recharge them even partially without waiting to discharge them completely and without compromising durability.
Until a few years ago we were using mainly lead batteries from 12 V to 24 V, now outdated as very heavy, less efficient as well as more polluting.
The battery is the most expensive component of an electric bike, so be careful when you buy an electric bike, since the decrease of the price often decreases the autonomy and increases the weight. Given the lower cost of lead batteries compared to lithium-ion batteries, there are still several cheap e-bikes, which often do not deliver the same quality and performance levels.
Also the nickel batteries are not recommended, as they are not yet at the top of the efficiency and above all because they discharge when not used.
The capacity of the batteries for bicycles is measured in Watt-hours (Wh): the greater is the value of Wh, the better is the performance in terms of duration or autonomy. For completeness of information, Wh 1 corresponds to Ampere / hour (Ah) multiplied by the Volt of the battery itself. For example, a battery of 36 V with 10 Ah has a value of 360 Wh.
The autonomy of the pedal-assisted bicycles
We begin with a clarification: the factors that affect the autonomy of the battery of an electric bike are several, so it is somehow difficult to give accurate information.
In addition to the power and the capacity of the battery, also other factors influence the performance: the efficiency of the motor, the level of assistance selected, the length and the slope of the climbs, the rider's weight, the weight of the bicycle and, although to a minimal extent, the wind or the level of inflation of the air chambers.
That said, we can still determine that a good electric bike with lithium battery under normal conditions (average level of pedal assistance, rider's weight less than 90 kg and minimum slope) can assist the ride for about 55 km, which increase in the case of flat route and decrease in the presence of different climbs. We can therefore determine an average autonomy in the range between 45 km and 80 km.
The lifetime of the batteries
Also in this case, it is difficult to determine with certainty the lifetime of batteries, since much depends on their usage and of course on the type. If not specified in the technical datasheets, we shall ask manufacturers, who can provide information on the number of recharges after which the battery will begin to gradually decrease its capacity. As a matter of fact, we have to be aware that all types of battery gradually lose capacity over time.
To optimize the use and duration, it is recommended to take the following precautions:
- Avoid prolonged exposure to extreme temperatures
- Do not leave the battery attached to the charger for a long time after the charge is complete
- Avoid that the lithium batteries are fully discharged
- Do not leave batteries unused for long periods
- Avoid impacts or shocks that could damage the components
The pedalling sensor
It is a key component, which detects the strokes on the pedals and thus switching on or off the motor. The European legislation about e-bikes in fact indicates that the motor provides pedal assistance only when pedalling, otherwise the vehicles would be considered as scooters.
Two are the most diffused types of sensors:
- The most common sensors detect the rotation of the pedals by magnets. The greater is the number of magnets positioned on the disk, the better is the responsiveness of the engine which is activated more quickly.
- More complex sensors detect also the effort impressed by the cyclist on the pedals, allowing to determine the power needed to feed the motor, based on how hard the rider is pedalling.
While the simple sensors pedalling are less reactive in the starting phase, once activated the engine can spin the pedals without making any effort, care of the engine. It is true also that pedalling with greater intensity increases the battery life.