Electric Scooter Controller Guide: Principles, Technology & Common Issues
The Role and Importance of Scooter Controllers
In an electric scooter, three core components determine its performance: the battery (energy storage), the motor (drive force generation), and the controller (coordination and management). If the battery is like a fuel tank and the motor is like an engine, then the controller is the brain of the entire vehicle.
The controller receives signals from the throttle, brakes, and other inputs, making real-time decisions about voltage and current output to drive the motor. It not only affects acceleration from standstill, hill-climbing ability, and braking response, but also largely determines the overall energy efficiency and riding experience of the scooter.
Understanding how controllers work not only helps you choose the right scooter, but also enables users to determine whether common performance issues are controller-related. This article will provide a basic introduction to electric scooter controllers.
Basic Working Principles of Controllers
Variable Speed Control under Constant Voltage Power Supply
Most electric scooters use lithium batteries that output stable direct current (DC), typically at voltages like 36V, 48V, or 60V – this voltage remains constant. The controller’s core responsibility is to “flexibly adjust output under constant voltage conditions”, allowing the motor to produce different speeds and thrust according to riding demands.
Think of the battery as a water reservoir – the controller is like a faucet at the outlet. It can’t change the water pressure in the reservoir, but it can control how long the water flows.
The Controller’s Core Method: PWM (Pulse Width Modulation)
The controller achieves the “magic” of voltage regulation through a technique called PWM (Pulse Width Modulation).
Inside the controller are many fast-switching power semiconductors (like MOSFETs) that switch between “on” and “off” states at extremely high frequencies (thousands or even tens of thousands of times per second).
- When the switch is on, the motor receives full voltage
- When it’s off, the motor receives 0V
The proportion of “on time” is called the duty cycle.
For example:
- 100% duty cycle = always powered, motor runs at maximum speed
- 50% duty cycle = powered half the time, motor feels like it’s receiving half voltage
- 0% duty cycle = no power, motor stops
In real controllers, PWM cycles are very short – for instance, 20 kHz (cycle = 1/20,000 seconds = 0.00005 seconds). This means every 0.00005 seconds, the controller executes an “on or off” decision. Due to this high-speed switching, the motor doesn’t perceive each individual on/off cycle, but instead experiences a continuous, stable “average voltage”.
By adjusting the average voltage, the controller effectively regulates the current needed to drive the motor, thereby controlling the torque the motor produces, and ultimately achieving speed control.
Control Logic Architecture in Controllers
Most electric scooter controllers use a speed loop and current loop control strategy to achieve precise control and motor protection.
Speed Loop
The throttle actually provides a “target speed”. The controller uses a “speed loop” to compare the current motor speed with the target value and determines how much current to output to reach the target speed.
Current Loop
According to the formula (τ = Kt × I), current determines thrust. The motor’s torque τ (which is the driving force) is directly proportional to the current (I) flowing through it.
The controller continuously monitors motor current and adjusts the PWM duty cycle according to the target current value to achieve the ideal current level. This feedback loop is called the “current loop”.
The current loop responds quickly and precisely, adjusting output within milliseconds, protecting the motor from overcurrent damage while ensuring smooth and powerful riding.
The control logic works as follows: “Speed loop → determines target current” and “Current loop → actually adjusts PWM”. Through this two-layer closed-loop structure, precise control is achieved through coordination.
Advanced Technologies in Modern Scooter Controllers
FOC (Field Oriented Control)
High-end controllers often use FOC (Field Oriented Control), a more advanced control method than traditional “square wave control”.
FOC precisely calculates current phase to keep current always aligned with the motor’s magnetic field, improving efficiency and response speed. Its advantages include:
- Quieter operation: Motor noise is significantly reduced
- Smoother performance: Gentle acceleration without jerking
- More energy-efficient: Higher current utilization, reduced losses
Regenerative Braking (Energy Recovery)
Some scooters support regenerative braking, where the motor generates electricity during deceleration or downhill riding, “recovering” kinetic energy and storing it back in the battery. This not only extends range but also reduces brake pad wear. However, actual energy recovery is currently limited.
The controller plays a dual role of “speed control + charging management” in this process.
Controller and BMS (Battery Management System) Cooperation
Controllers work closely with the Battery Management System (BMS), playing a crucial role in overall vehicle energy consumption and safety:
- Real-time monitoring of battery voltage and current
- Prevention of overcharging, over-discharging, or current anomalies
- Power distribution and temperature protection
High-performance controllers can even connect to smartphones via Bluetooth, displaying real-time controller status and fault information.
Common Issues and Misconceptions
1. Is Higher Controller Power Always Better?
Not necessarily. Higher power means higher current and stronger thrust, but it also means greater load on the battery and motor, reducing range. If the battery can’t keep up, it may cause power cuts or component damage.
2. Will the Electric Scooter Controller Still Be Compatible After Replacing the Motor or Battery?
It depends. Controllers have limited operating voltage and current ranges – exceeding these ranges means incompatibility. After replacing a motor, you also need to confirm that the controller supports the motor type (such as brushless BLDC/brushed).
3. Why Does Hill Climbing Sometimes Result in “Sudden Power Loss” or “Insufficient Power”?
This could be the controller entering overcurrent protection mode, unstable battery output, or delayed PWM control logic response. High-quality controllers generally have comprehensive fault tolerance and protection mechanisms.