Working of Electric Vehicle

Electric Vehicles

All electric vehicles are called battery vehicles because they run on a huge battery and an electric motor instead of a combustion engine. A large traction battery is used to power the electric motor that is plugged into charging stations which are also called as Electric Vehicle Supply System (EVSE). As it runs on electricity, there’s no combustion, no emission hence there’s no need for a tailpipe. As there are no typical liquid components such as fuel, there’s no pump, fuel line or fuel tank, etc. This makes it light, easier to use, and repair.

The key components of an Electric Vehicle are:

  • Battery
  • Charge Port
  • DC/DC converter
  • Electric Traction Motor
  • Onboard Charger
  • Power Electronics Controller
  • Thermal System
  • Traction Battery Pack
  • Transmission

Auxiliary Battery

In an Electric Vehicle, there are two battery systems. One is the primary battery (traction battery) while the other one is an auxiliary battery. The Vehicle Accessories are powered by providing electricity through the auxiliary battery. It helps to power the Computer System, Headlights, Audio System and some quintessential sensors, etc. It works in tandem with the main battery and simultaneously reduces its load. It also provides safety assistance, since it is a 12V battery; in an instance of an accident, it reduces the risk of damaging complex electronics with the flood of high voltage potential in the main battery by cutting off the supply.

Charge Port

The charge port allows the electric vehicle to draw electricity from an external power to supply charge to the traction battery pack. The charging port has a very basic function of transferring power, but it has a lot of complexity. It also depends on the company's vision, whether they want an open-source system or a closed system. Currently, there are three most prominent charging ports Type-1, Type-2, and Tesla port. Type-1 and Type-2 standards have the same functionality that supports four modes of charging- 2 AC and 2 DC but the sole difference narrows down to the design. Type-1 is CHAdeMO standard while type-2 is SAE J1772. Both systems that have the functionality of charging an electric vehicle up to 80% in approximately 20 minutes are completely incompatible.

DC/DC Converter

This device helps in converting the higher power stored in the traction battery to lower voltage DC power to run the vehicle accessories and to recharge the auxiliary battery. The high power DC/DC converter is necessary for an EV Power supply system. The characteristics of the vehicle such as top speed, acceleration time 0-100 km/h, weight, maximum torque, and power profile such as peak power or continuous power define the power of a converter. Generally, for the consumer vehicle, the power of the converter starts from 20KW and it can be up to 100KW depending on the specifications.

Electric Traction Motor

Electric traction motor drives the vehicle wheels by using power from the traction battery pack. In the conversion of Electrical energy to mechanical energy, this traction motor is used in such a way that the vehicle is propelled to overcome aerodynamic drag, rolling resistance, and kinetic resistance. Its working is as similar as the normal motor but with a ton of complexities. Traction motors require frequent start/stop, high rate of acceleration/deceleration, high torque on low speed- hill-climbing, low torque high speed- cruising, and a much wide range of speed options whereas industrial motors are generally optimized at certain speeds at rated conditions. Therefore, traction motors are so unique; they deserve to be in their class.

Onboard Charger

The primary function of an onboard charger is to take the power as AC coming from the charging port and convert it to DC power which further can be used in charging the traction battery. It also communicates with the charging equipment and monitors battery health. It examines charging temperature, voltage, current flow, and state of charging while charging the traction battery, etc. Since the onboard charger will be permanently mounted in the vehicle, its weight has to be minimized. Efficiency is equally important and there are other benefits of efficiency such as less power loss, less space for the thermal cooling system, reduced weight and increased km, etc. The onboard charging system allows the Electric Vehicle to get a charge from an AC grid system. It gives flexibility to the consumer and therefore plays an important role in the Electric Vehicle.

Power Electronics Controller

It manages the flow of electrical current delivered by the traction battery. Therefore, it controls the speed of the traction motor and the torque it produces. Like the motor cortex of the human brain controls the voluntary action of the human body simultaneously this electronic system controls the movement of an electric vehicle. The traction motors and the torque generated is not uniform since driving a live vehicle is very dynamic. This system helps in controlling the electric vehicle so that the overall control will be maintained. These controllers are also linked with the sensors and in the SOS condition, they also take actions that save human lives in the course of an accident.

Thermal System

This is a cooling system that is attached to the engine, traction motor, power electronics, and sensors to maintain an operable temperature throughout the system. It plays a major role in cooling the system through thermoelectric cooling. In this system, two metal plates are attached simultaneously with a gap filled with a PN junction circuit combination. Once the operation begins, and the temperature of one plate begins to rise, a potential difference is applied so that electrically heat can be transferred to the adjoining plate which is a heat sink. This heat sink is maintained at a temperature lower than room temperature with the help of a cooler. It is the major reason that provides an ability to perform tasks without breaking them down. Since in this system, there are no mechanical devices attached. Therefore, the chances of this system breaking down are substantially reduced.

Traction Battery Pack

The traction battery pack in an electric vehicle is designed in such a way that, it can amperage current over an elongated time. The material used for this battery is specifically designed so that it can accumulate more charges with less weight. The most prominent traction battery packs are Lithium-ion and Lithium Polymer batteries. Another set of batteries that can also be utilized are a Lead Acid Battery. These batteries add up to 60% costing of an electric vehicle. The main difference between Lithium-Ion and Lithium Polymer batteries is in their application. Both the batteries have some set of cycle counts up to which it can work. In a lithium-Ion battery, the ability to store a charge degrades over some time but in Lithium Polymer, the charge retention will be maintained fully till the last cycle count.

Transmission

The electric vehicle does not require a multi-speed transmission system like a combustion system need because the traction motors are capable of providing consistent torque at any given rpm. However, the standard combustion system will need a gear shift transmission at different speeds to sustain the torque. In an electric vehicle, multiple driving modes will guide the system to adjust as per the mode. This system is more efficient and requires minimal effort.