The motor controller is one of the most important components of an electric bicycle or e-bike. It is an electronic device that manages the operation of an electric motor. It also connects to all the other main parts of an electric bike, including the battery, brakes, sensors, throttle, and motor.
The motor controller acts as the brain of the e-bike, controlling the functions of the e-bike's electrical components. This is why it is essential to select the ideal motor controller for the application. In this article, we will discuss the key specifications of an e-bike motor controller and how to select the right one.
The e-bike motor controller
An e-bike motor controller — also called an electric e-bike controller and electric speed controller — is responsible for managing the bike's critical functions. It acts as a central hub, which connects the battery, engine, accelerator, display, pedal assist system, sensors and other electrical components.
The motor controller determines the speed of the e-bike by receiving signals from the accelerator or pedal assist system and controlling the power supplied to the motor. It can also ensure safety by limiting the e-bike's maximum speed and turning off the motor when the brakes are pressed.
This is not everything! The motor controller also manages additional features such as regenerative braking, communication interfaces, display management and others. The controller is placed in a sealed protective case and can be mounted as is or attached to the bicycle frame, depending on the design of the electric bicycle.
The role of the engine controller
The motor controller is responsible for managing several critical functions of an e-bike. It takes input from an electrical component of the bike and, based on that input, determines what to return to another component. In this way, he controls the general functioning of the e-bike.
The functions that an e-bike's motor controller manages are the following:
Power regulation: The motor controller considers rider input and the chosen level of assistance when determining how much electrical power to give the electric motor. This ensures the engine receives the ideal amount of power for various riding scenarios and degrees of assistance.
Overvoltage and Low Voltage Protection: The engine controller monitors battery voltage continuously, protecting the engine against low and overvoltage. It immediately shuts down the engine if the voltage reaches full load or drops below a set threshold.
Speed control: The motor controller controls the speed of the e-bike by interpreting signals from pedal assist sensors, accelerator or other speed sensors. It maintains a consistent bike speed based on the rider's input and the rider's chosen level of assistance.
Steering control: The motor controller manages the direction of the electric motor, allowing the e-bike to move forward or backward.
Battery management: The motor controller monitors the battery's charge level, protecting against situations that could shorten its lifespan, such as deep discharge or overcharge. The controller optimizes energy efficiency by managing the flow of energy to and from the battery.
Overcurrent Protection: The controller reduces current flow to the motor if it consumes more power. The controller protects the field effect transistor (FET) and motor windings.
Sensor Integration: The motor controller connects to various sensors on the e-bike such as pedal, speed, torque sensors, etc. To provide a smooth and responsive riding experience, it evaluates sensor data and modifies engine performance in real time.
User interface: The motor controller manages an e-bike's user interface — where riders can adjust settings and store data (such as speed, battery life, and distance traveled).
Communication interfaces: The engine controller manages communication interfaces such as USB or Bluetooth for firmware updates, customization, and integration with external devices or applications.
Thermal management: The engine controller monitors the engine temperature to prevent overheating. It implements thermal protection measures, such as reducing power output if the temperature becomes too high.
Fault detection and protection : The motor controller recognizes and reacts to malfunctions or defects in the system, implementing safety measures to protect the motor, controller or other parts of the e-bike from failure or damage.
Regenerative braking: When braking, the electric motor works as a generator to transform kinetic energy into electrical energy, which is subsequently redirected to the battery.
Types of Electric Bike Motor Controller
There are several types of e-bike controllers, depending on the bike and its motor and other features (such as regenerative braking).
Here are some of the motor controllers available for e-bikes:
Pedal Assist Controllers (PAS): These controllers assist with pedal sensors based on the rider's pedaling input. Cyclists can select from several levels depending on the type of support they would like when cycling.
Throttle-based controllers: These controllers allow riders to directly regulate the power and speed of an electric bike's motor by manually squeezing a throttle that resembles a motorcycle. This provides a more direct control method, allowing users to adjust the bike's speed without pedaling.
Combo PAS and Throttle Controllers: Some e-bike systems come with throttle and pedal assist controls, giving riders the option of how they would like to operate the e-bike.
Torque sensor controllers: These controllers calculate the force delivered to the pedals and provide assistance based on the rider's effort. By modifying assistance levels in response to the rider's pedaling efforts, torque-sensing controllers provide a more responsive and natural pedaling experience.
Mid-Drive Controllers: These controllers are mounted in the middle of an electric bike's bottom bracket and distribute power effectively. They can handle various terrains while maintaining balance.
Hub Motor Controllers: These controllers are for e-bikes with hub motors built into the wheel (front or rear). They regulate the bike's torque, speed, and power delivery to the hub motor.
The following motor controllers can be used based on the e-bike motor.
Brushed DC Motor Controllers: These controllers have a connection and permanent magnets. They require a set of switches to change the current going to the motor and are easy to operate. Most e-mobility options use brushed motor controllers, such as pedelecs, e-bikes, scooters, electric bikes and other lightweight EVs.
Brushless DC Motor Controllers: BLDC motors are most commonly used in e-bikes. These motors are permanent magnet brushless designs. They are typically reliable, efficient, and easy to operate and maintain. There are phases controlled by a set of switches in the set of six. At least two transistors (switch/MOSFET) per phase are included with brushless controllers. Some BLDC controllers also come with hall sensors, which provide feedback on the rotor position to control the switching sequence. A BLDC motor relies on the precise timing of current pulses in the motor windings to generate continuous rotation. Hall sensors help determine when to alternate the current in the motor windings.
Other types of motor controllers available for electric bikes are as follows.
High Torque Controllers: These controllers produce greater torque and are ideal for applications that require more power, including electric cargo or off-road bikes.
Smart Controllers: Bluetooth and Wi-Fi connectivity are examples of built-in connectivity options that come with smart controllers. They allow users to connect to a smartphone app for monitoring, customization and more functions.
Firmware-Programmable Controllers: Sophisticated controllers allow users to customize performance factors such as acceleration, top speed, and other aspects by updating the firmware.
Regenerative braking controllers: These controllers transform kinetic energy into electrical energy during braking, improving energy savings and extending battery life.
Motor Controller Specifications
These are the important technical specifications of an e-bike motor controller.
- Rated Voltage: This indicates the voltage range that the controller can handle. It must match the voltage of the e-bike battery.
- Current rating: This indicates the maximum current the controller can handle. It is crucial to determine the power and compatibility with the electric bike motor.
- Wattage: This is determined by multiplying the voltage and current ratings. Represents the maximum power that the controller can provide to the motor.
- Motor type: This indicates the type of motor the controller is designed for (i.e. for a BLDC or brushed DC motor).
- Operating Modes: This indicates the available operating modes, such as pedal assist, throttle only, or a combination of both.
- Control method: This is the control strategy that the controller uses, such as pulse width modulation (PWM), field-oriented control (FOC), or other control algorithms.
- Efficiency: This specifies the efficiency of the controller (that is, how well it converts electrical energy from the battery into mechanical energy in the motor).
- Temperature Range: The operating temperature range within which the controller can function correctly.
- Size and weight : The physical dimensions and weight of the controller are essential for its integration into the e-bike frame.
- Certifications: These indicate whether the controller complies with industry standards or certifications, ensuring its safety and performance.
- Protection features: Protection mechanisms such as overheat protection, overcurrent protection, and short circuit protection are important to ensure the safety and durability of the controller.
- Regenerative braking: This indicates whether the controller supports regenerative braking, allowing the motor to act as a generator during braking to recharge the battery.
- Communication interfaces : This specifies any communication interfaces, such as Bluetooth or USB, that allow firmware updates, customization, or connectivity with external devices.
- User interface: Indicates the interface through which the pilot can interact with the controller, be it a display, buttons or a smartphone application.
- Pedal assist sensor compatibility: Should indicate compatibility with different pedal sensors, such as cadence or torque sensors.
- Throttle Type: Indicates the type of throttle the controller supports, including twist grip, thumb throttle, or other variations.
How to choose an e-bike motor controller
The first thing to consider when choosing a motor controller for an electric bike is the rated voltage and current. The voltage rating must match the motor voltage. The controller power rating is the voltage rating multiplied by the current rating. The rated power should be slightly higher than the engine power.
If the controller is programmable, the voltage of the controller must match both the motor and the battery. Power may be limited in programmable controllers.
The current rating of the controller is its maximum phase current, which must be less than the battery output current. Then you will need to see the maximum current rating of the motor controller. Generally, 15-MOSFET controllers are rated at 40A, 9-MOSFET controllers are rated at 25A, and 6-MOSFET controllers are rated at 18A.
The motor will heat up more and more if the controller supplies more current than it can handle. The varnish coating on the wires loses its quality as the engine overheats. This causes a short circuit, which causes the motor to heat up quickly and damage the windings.
Then check whether the controller's conduction type is square or sinusoidal. Sine waves have less noise, increasing efficiency when traveling uphill or carrying heavy objects on the bike. These controllers provide more consistent and seamless management of overall operations. However, sine waves are more expensive and require more power. They are also limited to using corresponding engines for operation.
Square wave controllers are more affordable and can work with different motors. They are efficient in acceleration and braking, but generate more noise and have somewhat vigorous or unbalanced control. They are also not as efficient or smooth on hills or with a lot of added weight on the e-bike.
The Hall sensor also makes a significant difference when used with BLDC motor controllers. These controllers offer a dual mode on e-bikes. The engine's Hall sensor detects rotation, and the controller produces a voltage in response to the sensor inputs. With more torque when accelerating and less power consumption, this motor controller is typically more reliable.
In addition to electrical specifications, the size and weight of the motor controller are important considerations and must match the design of the e-bike. Additionally, when choosing a motor controller, features such as regenerative braking, overheat protection, overcurrent protection, and short circuit protection should also be considered.
Other controller considerations relate to an e-bike's user interface options, communication interfaces, throttle type, and compatibility with pedal sensors. The type of motor supported by the controller, current-voltage rating, size and weight of the controller, and additional features are generally proportional to the cost. Therefore, a motor controller within the desired budget with ideal features should be selected.
Conclusion
The motor controller of an electric bicycle is its most important component. Motor controllers are available in various types and configurations and must match the e-bike's design, motor, battery, voltage-current rating, riding type, and operating modes.
