As in a combustion engine all its parts must work at the same time so that everything works without problems, in an electric vehicle there are a number of technologies that must complement each other. Although once the power reaches the wheels both powertrains work the same, to make that happen the mechanical elements are completely different. When looking to buy an electric car, it is essential know the names of mechanical components and the language with which they are described her CARACTERISTICS.
Each of the eight technologies that make an electric car work. All of them are essential since they are the basis of what will later appear on the dealer’s specifications and benefits sheet.
For now, most of the electric cars on the market have lithium-ion batteries. There are several different settings depending on the shape of each cell: cylindrical, bag-type, prismatic. And there are also different chemistries particularly when it comes to cathode materials. In this case, most are rich in nickel, known as NCM by the initials of its components: nickel, cobalt and manganese. While waiting for a superior technology, such as that of solid electrolyte batteries, lithium ferrophosphate (LFP) has recently proliferated in cheaper electric cars. These are cheaper batteries, without cobalt in their composition, but offering lower energy density.
Individual cells are combined to create battery modules and groups of modules are packed together to form a complete battery. In total, there could be hundreds or thousands of individual cells in each of them, depending on the voltage that each one contributes.
Typical total voltage is in the range of 300 to 400 volts. Lithium-ion batteries require careful control of the temperature and voltage of each cell and must be continually balanced to avoid degrading performance and shortened life. The size of a packet is given by the amount of energy, measured in kilowatt-hours (kWh), which can contain. Currently, the capacities of typical battery packs range from 50 to 150 kWh. The higher this figure, in general, the more autonomy it will offer, although the rest of the components of the electric vehicle also influence the efficiency with which this energy is used.
To manage your temperature, there are manufacturers that include a cooling system that uses the air that circulates around it (forced or not perforated) and there are others that implement a more complex liquid cooling system.
The battery packs are extremely heavy depending on its size. They can easily reach weights of 400 and 500 kilograms. The most common is that they are placed under the vehicle floor, to reduce the height of the vehicle’s center of gravity, which makes electric cars perform well on the road.
Battery management system (BMS)
A battery pack requires extensive control of the temperature and voltage of each cell. The BMS (Battery Management System o Battery management system). It is a fundamental system for the security of electric cars. His work is not only essential, but also very complex, since he must follow the evolution of various parameters in each and every one of the cells that the battery contains.
During the load, the BMS ensures that the cells have the same voltage level (generally within 0.01 volts). Without the BMS, the cells could be overloaded to a level where there could be a danger of fire or explosion. During the downloadWithout it, some of the cells could reduce their performance, forcing the rest of the cells in the module to drain too quickly.
Direct current converter (DC to DC)
The high-voltage battery does the heavy lifting in an electric vehicle, which is powering it for propulsion. However, most of the electrical system of an electric vehicle works with a 12-volt lead-acid battery, similar to the battery with which a combustion vehicle starts.
This 12-volt system operates the lights, horn, HVAC fans, and most computer systems that control the electric drive. A dc to dc converter it takes some of the power from the traction battery and converts it to 12 volts to keep it charged and run all those systems. In some electric vehicles, the traction battery also powers the climate control system, taking advantage of the available power to quickly make the cabin more comfortable.
The controller of an electric vehicle is a microprocessor that receives the driver’s orders, which are generated by the accelerator or brake pedal, and converts them into signals that are transmitted (generally along a CAN / BUS communication line) to the power electronics located on the inverter to provide power to the motor.
In many ways, the controller acts as a electronic brain, accepting the driver’s requests and determining how the engine responds. Therefore, its programming is essential because it depends on it that the vehicle responds to each driving situation.
The Inverter and power electronics
Currently in many cases motors are used brushless electric or brushless motors which are actually synchronous, permanent magnet alternating current motors that mimic the operation of these direct current motors of the first electric vehicles. Before the development of power electronics, these brushed DC motors were used, which received the energy from the battery once adequate for the controller and which were widely used for applications that required speed changes.
The alternating current that feeds them is produced by the investor, which is responsible for taking the direct current from the battery and converting it into alternating current and providing it to the motor. The frequency of alternating current determines the speed at which the motor rotates. The inverter has a position sensor on the motor that allows it to synchronize its current pulses to keep the motor spinning and producing the torque necessary to move the vehicle. The converter takes the commands from the controller and converts them to signals for the motor.
This device uses high level power electronics, capable of providing the voltage and amperage required by the motor at all times. The more robust the inverter, the more efficient and reliable your electric vehicle will be.
The permanent magnet synchronous motors they are currently the most used by the industry. It is a very efficient motor that operates at a higher speed than the brushed DC motor used in the original electric vehicles.
A typical engine of this type is formed by stator and a rotor. This contains four to eight permanent magnets and it rotates in the center section of the motor. The outer stator is surrounded by a series of electrical coils that make up the commutator. The inverter provides energy to the coils in such a way that they become electromagnets that oppose the magnetism of the permanent magnets, producing the movement that when correctly synchronized makes the motor rotate. The permanent magnets that are often used are made from chemical elements of rare earth like niobium or neodymium.
Since electric motors produce their maximum torque from 0 rpm, normally no gearbox requiredInstead, either a direct drive or a gear reduction system is used.
The configuration of engines is very varied. Some electric vehicles use single engine, which feeds the front or rear wheels. Others use a couple of motors, one at the front and one at the rear to create all-wheel drive and provide torque vectoring so that each wheel turns at a different speed as required by the road layout. Occasionally, three engines, two driving the rear wheels and one driving both front wheels. It is also possible to implement motors on wheels, up to a total of four which increases its efficiency and the torque that is transmitted.
The engine cooling It is achieved by using air that is collected from outside or by means of a liquid cooling system. The more power the engine produces, measured in kW, the more performance it will provide, provided the cooling system is able to keep the engine temperature under control.
To increase the efficiency of electric vehicles, it is possible to recover energy from braking and deceleration, which would normally be lost in the form of heat. When a vehicle slows down, the motor can work as a generator, producing electricity while slowing the vehicle. This energy is redirects to battery, helping to recharge it slightly.
The regenerative braking power It can be adjusted thanks to the controller that is capable of achieving a significant reduction in speed without using the normal hydraulic brakes of the vehicle, even stopping it. This electric braking is so aggressive that it allows driving with just one pedal, which does not require the use of the brake. In urban traffic, with constant speed changes and many braking phases, it is possible to add more than 20% to the vehicle’s autonomy.
On-board charger and recharging
Most electric vehicles have an on-board charger that connects to the mains to recover battery power at home, at work, or at non-direct current public stations.
Onboard chargers are limited by the amount of current they can provide. They can accept recharges of 2 kW of power, which offers a domestic installation or 3.6 kW or 7.3 kW, if a special wallbox is used for recharging. In these cases, they are single-phase alternating current installations. In the case of having three-phase alternating current (normally in public installations), it is possible to achieve 11 kW, 22 kW and even 44 kW of charging power. The usual thing in electric vehicles is that they do not exceed 11 kW of maximum power.
When charging is done in direct current The on-board charger is bypassed, the charging post being the one that supplies the cable and the connector and all the control electronics, since the charge is carried out directly to the battery. In these cases, charging power can be achieved ranging from 50 kW to 350 kW.