The number of magnets or the total weight of magnets required for an electric vehicle depends largely on the type of motor, the size and design of the motor, and the power output required. The total weight of magnets required for a permanent magnet synchronous motor is very large, much larger than the total weight of magnets for other components, such as sensors. Specifically, for a permanent magnet synchronous motor, the number of magnets is a key factor in determining efficiency and performance.
In general, the motors in electric vehicles are usually between 50 kW and 250 kW, and some high-performance models even exceed this range.
For a typical electric vehicle motor, a rough estimate is that about 1-2 kg of magnets is required for every 10 kW of power output, although this can vary greatly depending on the design.
Based on this estimate, an electric vehicle equipped with a mid-range power permanent magnet synchronous motor may require about 20-30 kg of NdFeB magnets for the motor, depending on the power of the permanent magnet synchronous motor.
High-performance or larger motors, such as Tesla’s dual-motor system or similar, require more magnets, weighing up to 50 kg or more.
In addition to the motor, several other components in an electric vehicle (EV) also use magnets, primarily for sensors and actuators. Here’s a breakdown of other key parts that require magnets or magnetic materials:
Magnetic Sensors
Hall Effect Sensors: These sensors are used in motors to detect the position of the rotor and provide feedback to the motor controller. They typically use small quantities of rare-earth magnets like neodymium to create a magnetic field.
Wheel Speed Sensors: These sensors use magnets and are crucial for ABS (anti-lock braking systems) and traction control. Each wheel may have its own sensor, so the total number of magnets required depends on the number of wheels and systems.
Current Sensors: Some electric vehicles use magnetic-based current sensors for measuring the motor current and optimizing performance. These are often based on the Rogowski coil or fluxgate sensors.
Electric Power Steering (EPS)
Steering Motors: In many modern vehicles, especially electric and hybrid models, steering is assisted by an electric motor rather than a hydraulic system. The motor often uses permanent magnets to provide the necessary torque to assist the driver.
Position Sensors: These sensors are typically used to monitor the position of the steering wheel and ensure proper feedback. They may also use magnets, especially in electric power steering systems.
Actuators (Various Vehicle Systems)
Door Lock Actuators: These may use small motors with magnets for locking and unlocking doors. Some EVs use electric actuators to control latches, windows, or hatches.
Electric Seats & Mirrors: Adjustable seats and mirrors often use small electric motors with permanent magnets.
Climate Control: In some systems, small motors or actuators with magnets are used to control vents, flaps, or other components in the HVAC (Heating, Ventilation, and Air Conditioning) system.
Battery Management System (BMS)
While the BMS itself doesn’t typically use large quantities of magnets, it may rely on magnetic sensors to monitor things like battery temperature, current flow, and other operational metrics in some designs. Additionally, magnets could be used in certain safety or protection features in the BMS.
Regenerative Braking System (RBS)
While regenerative braking primarily relies on the motor (and therefore magnets in the motor), there may also be magnetic sensors or actuators in the braking system to adjust braking force based on speed, battery charge, and other factors.
Magnetic Bearings (Optional in Some EVs)
Magnetic Levitation (MagLev) Bearings: In high-performance or experimental vehicles, magnetic levitation bearings may be used in motors or other rotating machinery. These use powerful magnets to reduce friction and improve efficiency.
Total Magnet Usage in an EV:
Permanent Magnets in Motor: The largest use of magnets, typically around 20–50 kg, depending on the motor size.
Sensors and Actuators: The total magnet weight for sensors and actuators could add another 2–10 kg of magnets, depending on the complexity and number of components. This includes the motor position sensors, wheel speed sensors, EPS, and other small actuators.
Therefore, a rough estimate is that an electric vehicle may require 25–70 kg of magnets in total, depending on the design and features of the car. The majority of the magnet weight comes from the motor, but additional magnets are required for auxiliary systems like sensors, actuators, and power steering.
