An electric bike refers to a means of transportation that is equipped with a motor, controller, battery, handlebar grips, and other control components and display instruments. It is a supplementary mode of transportation for daily commuting, built upon a regular bicycle by utilizing a rechargeable battery as an auxiliary power source. With the emergence of environmental consciousness, electric bikes are becoming increasingly popular.
The components of an electric bike include a charger, battery, controller, handlebar grips, throttle, pedal assist sensor, motor, lights, and instruments.
Charger:
A charger is a device used to replenish the battery's energy. It generally operates in two modes: two-stage charging and three-stage charging. In the two-stage charging mode, the battery is first charged at a constant voltage, and the charging current gradually decreases as the battery voltage rises. Once the battery reaches a certain level of charge, its voltage increases to the charger's set value, and the charging mode switches to trickle charging. In the three-stage charging mode, the charging starts with constant current to quickly replenish energy to the battery. After the battery voltage rises, it switches to constant voltage charging, where the battery energy is replenished slowly while the voltage continues to rise. When the battery reaches the charger's termination voltage, it switches to trickle charging to maintain the battery and supply self-discharge current to the battery.
Battery:
The battery is the on-board energy source that provides power to the electric vehicle. Lead-acid batteries are commonly used in electric bikes. In addition, nickel-metal hydride and lithium-ion batteries have also begun to be used in some lightweight folding electric bikes.
Usage tip: The controller's main control board has a high working current and generates significant heat. Therefore, it is important not to park the electric bike in direct sunlight or expose it to rain for an extended period to avoid controller malfunctions.
Controller:
The controller is a component that controls the motor speed. It is the core of the electric vehicle's electrical system and has functions such as under-voltage, current limiting, or over-current protection. Intelligent controllers may also offer various riding modes and self-diagnostic functions for the vehicle's electrical components. The controller is the central component responsible for energy management and processing various control signals in an electric bike.
Handlebar grips and throttle:
Handlebar grips and throttle are input devices for the controller. The throttle signal is the driving signal for the electric motor's rotation. The brake lever signal is an electronic signal generated within the brake lever circuit when the electric bike is braked. When the controller receives this signal, it cuts off the power supply to the motor, thereby achieving the braking and power-cutting function.
Pedal assist sensor:
The pedal assist sensor is a device that detects the pedaling force and speed signal when the electric bike is in pedal-assist mode. The controller adjusts the electric drive power to achieve automatic power matching between human power and electric power, driving the electric bike rotation together. The most advanced pedal assist sensor is the central axis dual-side torque sensor, which can measure the pedaling force on both the left and right sides. It uses a non-contact electromagnetic signal acquisition method, thus improving the accuracy and reliability of signal acquisition.
Motor:
The motor is the most crucial component of an electric bike, as it largely determines the vehicle's performance and grade. Most electric bikes use high-efficiency rare-earth permanent magnet motors. There are three main types: high-speed brushed gear-reduction motor, low-speed brushed motor, and low-speed brushless motor. The motor converts the battery's electrical energy into mechanical energy to drive the electric bike's wheels to rotate. There are various types of motors used in electric bikes, with different mechanical structures, speed ranges, and power supply forms. Common ones include brushed geared hub motors, brushed gearless hub motors, brushless gearless hub motors, brushless geared hub motors, high-speed disk motors, and side-mounted motors.
Lights and instruments:
Lights and instruments provide lighting and display the status of the electric bike. The instrument generally displays battery voltage, vehicle speed, riding mode, and light status. Intelligent instruments can also display the fault conditions of various electrical components in the vehicle.
Common Structure:
Most electric bikes use hub motors that directly drive the front or rear wheels. These hub motors, paired with wheels of different diameters depending on the desired output speed, propel the entire vehicle and can achieve speeds of up to 20 km/h. Although these electric bikes may vary in terms of appearance and battery placement, they share common principles of propulsion and control. This type of electric bike is the mainstream in the electric vehicle market.
electric bikes with Special Structures:
A small number of electric bikes use non-hub motors. These electric bikes may utilize side-mounted or cylindrical motors, mid-drive motors, or friction tire motors. Electric vehicles using these types of motors generally have reduced vehicle weight compared to hub motor-driven ones, but their motor efficiency is lower. Under the same battery energy capacity, electric bikes equipped with these motors typically have 5%-10% shorter range compared to hub motor-driven vehicles.
Rapid Development Phase of electric bikes:
Starting in 2005, this phase marked the period of rapid development for electric bikes. Intense competition among companies stimulated technological advancements and the diffusion of new technologies, resulting in a significant improvement in the industry's overall technical level. Battery lifespan and capacity increased by 35%, motors transitioned from single brushed gear motors to efficient brushless motors as the mainstream, with a lifespan improvement of 5 times and an efficiency increase of nearly 30%. Climbing and load-bearing capacities increased by approximately 3.5 times. Along with the performance improvements, manufacturing costs also significantly decreased, and the price-to-power ratio dropped to 21% of its original value. The technical level of controller systems and charging systems also improved substantially.
From 2020 to 2023, the global annual growth rate of electric bikes is estimated to be around 16.9%. The global sales of two-wheeled electric vehicles (including electric bikes) are expected to reach 74 million units in 2022 and projected to reach 81.8 million units in 2023.
