Electric cars are becoming increasingly popular due to heightened emissions concerns and rising gas prices. Understanding the fundamentals of an electric vehicle is crucial for any EV owner or prospective EV driver.
The main components of an EV are the battery pack, power inverter, and electric motor. EVs can also regenerate energy during slowing and braking, which can help further reduce their reliance on the gasoline engine.
Battery Pack
The battery pack is the heart of an electric car. It stores the energy to drive your vehicle and run accessories like radios and air conditioners. It must be powerful enough to get you where you need to go with minimal recharging and efficient sufficient to reduce the time you spend at charging stations. Additionally, the parts of an electric car include components such as the electric motor, battery pack, power electronics, charging port, and regenerative braking system, all working together to power the vehicle while producing zero tailpipe emissions.
EV battery tech has evolved dramatically. Delivery vans were available only by closed-end lease in the 1990s. Modern EV batteries are much more reliable and offer a greater range than ever.
To make the countless individual batteries that are used in an EV work as efficiently as possible, they are grouped into modules and packs. Cells are a single battery, modules are clusters of cells, and packs are groups of modules.
Most EVs use lithium-ion battery cells, but alternative chemistries are also used. For example, they are often found in hybrid vehicles and offer a comparatively longer life cycle.
All the individual batteries that are used in an EV are connected using busbars, wires, or other distribution conductors. TIMs (thermal interface materials) such as pastes, adhesives, or gap fillers are inserted between battery components to join them mechanically and improve thermal properties. Safety features include a manual service disconnect (MSD), which breaks electrical continuity to the pack for servicing purposes.
Power Control Unit
The power control unit, or the ECU or motor controller, is essential to your EV. This small device significantly determines how much an electric car can accelerate and how long it will last on a single charge. It controls numerous functions, including power conversion and distribution, battery management systems, and regenerative braking control.
During initial startup, the PCU converts 200V DC from the traction battery to 540V three-phase AC that can be used to start the engine. It then manages the power flow to all other circuits in the vehicle, ensuring that all electrical systems receive the necessary current without draining the battery.
When driving, the PCU turns the electrical energy from the traction battery into mechanical energy that can be delivered to the wheels via a single-speed reduction gearbox. The PCU can also convert back-emf generated by the motor during regenerative braking into power to charge the traction battery.
With the growth of EVs in recent years, the number and sophistication of ECUs distributed around road-going vehicles continue to rise. The need to meet functional safety standards such as ISO 26262 has been a significant driver, along with the desire to future-proof architectures by enabling ‘by-wire’ control and actuation. This means all subordinate control units can be consolidated into a single physical area of the vehicle, with serial comms coordinated by a domain controller such as the VCU.
Electric Motor
Many EVs run purely on electricity, known as pure Electric Vehicles (EVs). Other EVs use the motor to supplement their internal combustion engine’s power. This combination is known as a Hybrid Electric Vehicle (HEV).
In the case of a pure EV, the motor converts electrical energy from the battery into mechanical energy that drives the car’s wheels. This is a much more efficient process than the one used in conventional gasoline engines, which typically only convert 12%-30% of the energy stored in gasoline to power the wheels.
A stationary component known as the stator and a spinning component known as the rotor make up every electric motor. The stator contains a series of coils that, when excited with electric current, create a magnetic field that interacts with the magnets in the rotor to generate torque. This rotational force is transferred to the transmission and, through a differential, to the car’s wheels to move it forward.
A few different types of electric motors are in use today, including DC, AC induction, and permanent magnet synchronous (PMSM). DC motors are commonly found in devices like toothbrushes and washing machines. They have a relatively simple design and require little maintenance. They operate using the left-hand rule, where current flowing through a coil creates a magnetic force that pulls the rotor shaft to rotate.
Transmission
The transmission is one of the most critical components of an electric car. It determines how much power is sent to the wheels, which affects acceleration and top speed. It also helps to maintain optimal battery efficiency. This is why it’s essential to understand how an EV’s transmission system works.
In conventional cars, the transmission matches a motor’s power output to the driving wheels through internal gears. This is needed because a gas engine’s range of rotations per minute sometimes corresponds to how fast the wheels need to spin to reach maximum performance.
On the other hand, electric motors can generate high amounts of torque throughout their entire range of speeds. This means that a single gear is sufficient for most EVs. However, some manufacturers have developed dual-speed transmissions for higher-performance models. For example, it uses a front electric motor to drive the wheels and a rear engine to provide added traction and power.
While multiple-speed EV transmissions aren’t standard, they offer additional functionality and can further improve performance. For example, using different gear ratios, an EV can achieve peak torque at lower RPMs than a conventional car, making accelerating and reaching top speed easier. In addition, these systems are simpler and more efficient than traditional transmissions, which makes them an essential part of the high-tech future of the automotive industry.