Types And Operation Of Electric Vehicles

types of electric vehicles

Worldwide are several types of electric vehicles we have heard about. This article is a classification and a summary working description of electric vehicles so that they become easy to identify.

Types of Electric Vehicles

The classification based on the drive-train and fuel type used. This mode of classification divides the vehicles in:
Internal Combustion Engine (ICE)
Alternative Fuel Engine
Electric Vehicles(EV)
The conventional ICE vehicles include gasoline and Diesel vehicles. The alternative fuel vehicles are the vehicles using other fuels than gas or Diesel like autogas, natural gas, biodiesel, biofuel, or hydrogen. The ICE vehicles in both forms use mechanical drive-train.

The battery-electric(all-electric) vehicles use energy source for propulsion. All-electric vehicles use electric drive train.
For propulsion electric vehicles can be hybridized. Generally, are Hybrid Electric Vehicles(HEV), Plug-in Hybrid Electric Vehicles(PHEV), Battery Electric Vehicles(BEV), Fuel Cell Electric Vehicles(FCEV), and probably in the future solar electric vehicles.

The hybrid electric vehicle has a source of energy gasoline or Diesel and for the propulsion can use either an electric motor or an internal combustion engine.

The plug-in hybrid is similar to the hybrid electric vehicle only that it can use the charging port to charging its battery.
In contrast, the pure electric vehicle has not an engine motor and is powered only by electricity without fossil fuel.

Finally, in the case of fuel cell and solar electric vehicles, the source of energy is from hydrogen using fuel cell panels. Here the propulsion is done using an electric motor.

Gasoline-Diesel Vehicle(ICE)

A gasoline car usually uses a spare plug engine, and the compression engine systems are using in Diesel vehicles. The Internal

Combustion Engine(ICE) is a heat engine in which the combustion of a fuel occurs with an oxidant. The engine through a complex mechanical transmission transforms the chemical energy into useful power to the wheels.

 

Hybrid Electric Vehicle(HVE)

Similar to a gasoline vehicle, hybrid electric vehicles are powered by an ICE as well. However, in addition, an electric motor helps to drive the vehicle by using the energy stored in the batteries. The battery is recharging by taking the energy from the engine by using the electric motor that an electric generator. To operate the motor that a generator of energy, is used as a clever power electronic drive motor. The benefit of this extra power is a motor smaller and a fuel economy. This is a parallel hybrid design where both the engine and electric motor can power the wheels at the same time.


A series-hybrid vehicle works differently. The internal combustion engine is powering a generator. This generator provides electrical power for the traction motors and to charge the battery. This method was used for locomotives for years. The traction motor is the only power grid unit with a connection directly to the wheels. The ICE motor at this system is operating at its most efficient point to generate the necessary current for driving the traction motor or charging the battery.




The third type of hybrid is the series-parallel. It operates either in series or parallel mode by using a parallel-split. It has, also, a generator to charge the battery like a series hybrid. Also, it has an engine and motor working together to power the wheels as seen in the parallel hybrid. If these types of electric vehicles hybrid are more flexible in terms of driving modes, are more expensive and more complex. Toyota Prius is a model of series-parallel hybrid.

HEV series-parallel vehicles

Plug-in Hybrid Electric Vehicle(PHEV)

Plug-in hybrid electric vehicles are similar to hybrid electric, they have an engine and electric motor for propulsion. The difference is that PHEVs are longer and can be charged by on-board charger. This is besides the fact that the battery can be charged using the ICE when it is driving. This permits the PHEV to drive more time. This means PHEV can drive electric in the city and switch to fossil fuel on the highway, removing the range-anxiety (see another article). Example Chevrolet Volt- Plug-in Hybrid series-parallel architecture.

PHEV electic vehicles

Battery Electric Vehicle(BEV)

HEV and PHEV continue to use fossil fuel combustions and of course, have tailpipe emissions. This is their main disadvantage. All-electric vehicle(Battery Vehicle) has only an electric motor and no internal combustion engine- see: electric car components
The vehicle uses a high-voltage traction battery pack to power the motor and, also, the battery is charging from a power outlet when it not work.

battery electric vehicles

Fuel Cell Vehicle(FCEV)

Fuel cell removes the large battery from a battery electric vehicle with a fuel cell stack to generate electricity from hydrogen. It is still necessary for a small battery to power the electric motor using the motor drive.

fuel cell electric vehicles

A fuel cell vehicle has the advantage of short refueling time and extended drive range compared with electric vehicles. Example: Hyundai Tucson, Toyota Mirai.

Basic Of Electric Car Charging

To start electric mobility it is essential to a fast, reliable, and safe system of charging for the electric car. Electric mobility will never become reliable and comfortable until there are charging facilities in predictable ranges. The investment in charging infrastructure is a long-term business. Similar was the construction of the gasoline stations a century ago. Fast charging has a big role in the electric car industry. We have heard about AC and DC charging, below are some information.

Alternative Current Charging(AC)

The flow of energy on the electricity grid is of alternating current. All household appliances use this type of energy. Just to operate an electric car the battery needs direct current. So the current must be converted. To convert the current is necessary three main pieces.

electric energy power flow

The first part is the AC/DC converter. It converts the power from AC to DC. The second is the charging cable with a connector that is used to transfer the power from the external power source to the electric car through the vehicle inlet.
The third part is a charge controller responsible for the connection, protection, and control of the charging process. They control the charging current and ensure the optimal temperature between cells of the battery.

AC ELECTRIC CAR CHARGING
An example of a converter is the on-board charger. The size and weight of the onboard charger are dependent on the maximum charging power. Typically, the onboard charger has maximum power in the range of 1.9-22Kw. If the range power increase the onboard charger dimensions will also increase. However, the onboard charger dimensions are limited due to vehicle size.

Direct Current Charging(DC)

The solution to increasing the charging power is to move the AC/DC charger converter outside the vehicle. This is an off-board charging solution, it is named DC charging.
With no size and weight restrictions, the DC charger has a maximum charging power 50-350Kw. The DC power aliments directly the car.

AC/DC electric car charging
Of course in the care have both AD and DC charging which could use depending on the situation. Most vehicles have separate vehicle inlet for AC and DC charging.

Types of Connectors

The connectors are divided according to the AC and DC charging by the connector type and charging power levels.
For AC charging- Type 1 connector is using in the USA and Japan, while Type 2 and 3 are using in Europe.

AC connectors
For DC charging- the CHAdeMO Type 4 connector is using by Japanese manufacturers globally, while the American and European car manufacturers are using a combined AC/DC connector  CCS-COMBO. Tesla uses the same connector meant for AC charging for DC charging as well. China has its own DC connectors.

DC connectors

 

Charging Modes

AC and DC charging power can be divided into three levels. Level 1 goes up to 10Kw power, Level 2 has a charging power up to 50Kw. Both AC and DC can provide Level 2 power. Over 50Kw, only DC charging is capable to provide charging power as high as 350Kw.
This level (Level 3) name it fast charging.
We can measure the range per hour of charging. Supposing that a car drives 5Km using 1 Kwh of energy.
Level1/AC and DC/0-10Kw power/ range of 50-250 per hour of charging
Level2/AC and DC/10-50Kw power/ range of 50-250 per hour of charging
Level3/Only DC/50-350Kw power/ range of 250-1750 per hour of charging

electric car charging type

Mode1- This is the slow AC charging, there is no connection between the vehicle and the charging point.
Mode2- A slow AC charging from a regular electricity socket. In plus the charging cable has an In Cable Control and Protection Device (IC-CPD).
Mode3- This mode provides both slow and semi-fast charging through a charging station. The charging station is responsible for the control, communication, and protection of the charging process.
Mode4- This mode uses a specific socket for electric vehicles. Has a cable with a plug to use for DC charging. In the case of DC charging, the AC/DC connecter is located in the charging station.

Electric Car Work Principles and Parameters

Here I am looking at the principles of the work of an electric car based on the electric power flow.

Because in another article I have written about the main parts of electric vehicles.  Also, are some key parameters that have to remember here to understand electric cars.

How Does Electric Car Work

We will look at the bellow figure and will analyze it step by step.

electric car work
The power comes from the AC grid to charge the battery. The flow continues through the AC/DC on-board charger (see electric car components) and DC/DC converter. When the car is in driving mode, the power from the battery goes from the battery DC/DC converter to the high voltage DC bus. Then DC/AC inverter of the motor drive sends the power to the motor.

The motor then converts the electrical energy to the mechanical energy that is sent to the wheels via the transmissions. On the route intervenes a DC/DC uni-directional converter that down on the voltage from the high voltage DC bus to charge the auxiliary battery that aliments the vehicle accessories.

Electric Car Parameters

Battery Capacity

The nominal battery capacity Enom measured in Wh or Kwh , is the total electric energy that can be stored in the battery. Is the maximum filling capacity with the energy of a battery. The battery has a capacity between 10-100 Kwh. The higher the capacity, the more energy the battery can store on the unit of time.
Popular, the name of battery capacity is the energy of the battery.

State of charge

The battery state of charge(SoC) is the ratio between the amount of energy currently from the battery, Ebatt, and the battery capacity(total energy), Enom
Bsoc=Ebatt/Enomx100

Range

Rmax(Km) is the maximum distance that an electric car can drive when the battery is full. Usually, an electric car work is testing by a standard driving cycle to estimate the range. The range’s unit of measure is miles, kilometers, or other units.

Available range

R(Km) is the maximum distance witch a car is unning with the current state of charge of the battery.

Energy Consumption Per Kilometer

D(Kwh/Km). When is testing a vehicle by a standardized driven cycle the electric vehicle efficiency is the consumption of energy from the batteries per unit of distance drive.  It could be also the energy from the grid to charge the battery.
The unit of measure is Kwh/Km or Kilowatt-hour per mile.

MPGE and Motor Power

MPGE(mile per gallon equivalent) is the distance in miles walking per unit of energy use by vehicles. The rating is based on EPA formula.

Motor Power is the power from the motor to the wheels for propulsion. The power is sensitive or negative depending on the car is driving or under regenerative braking.

Motor power is measured in W(Watt), Kilowatt(Kw), or horsepower.
The motor power is calculated as the product of motor torque, Tm, and motor rotation wm
P=Tmxwm
Tm -measured in Newton-meter(Nm)
wm- motor rotation is measured in radius per second (rad/s)

Ideally, an electric car must have a high range, low energy consumption per kilometer, and high MPGe.
R=Ebatt/D=Bsoc/100xEnom/D

The battery is the most important part of the electric car. The cost of an electric vehicle is according to it. Understanding the battery performance is very important.

The performance parameters that are specifically for the battery:

Nominal Voltage- Vnom(unit of measure is volt V)- It is the voltage rate of the battery when it is full of current. When a battery is discharging or is loading, the voltage reduces gradually to a lower value.

Nominal Current – Inom ( measured in amper A)- It is the rated current of the battery for charging or discharging.




Ampere-Hour- Qnom(measured in Ah)- An ampere-hour is a unit of electric charge that corresponds to the charge transferred by a steady current of one ampere flowing for one hour or 3600 coulombs. The total amount of energy from the battery is calculating by the product of battery ampere-hours and battery nominal voltage. The effective ampere-hour of a battery is determining by the charging/discharging current as is describing by Peukert’s law.
Enom=QnomxVnom

Charge/Discharge Efficiency- ( in%) This parameter refers to the fluctuation rate of the battery current. When charging or discharging the battery, the energy is not constant.

Charge/Discharge Rate- (unit of measure C-rate)- This parameter describes the magnitude of current drawn from or input into the battery, in terms of the nominal ampere-hour of the battery.

Battery-Electric Car Components And Function

This article provides details about the main components of an electric car and its functions. Information is about the battery-electric car that is powered by the traction battery pack.  We will look at the main parts which are: the battery, the electric motor, and the power electric converter.

In the figure are the key parts of an electric car. First, we have a charging port with the connector and cable. Then it is a high voltage traction battery and the low voltage auxiliary battery. Are an electric motor and a transmission system that propel the car. Plus, several power electronic converters used for battery charging, for
driving the motors and for regenerative braking.

electric car components
The schematic second figure shows how the different components are connected in an electric car.

electric car components and functions

Electric Cars Components

Charging Port

The first component we look is the charging port with the connector and cable. Together these connect to an external power supply to charge the traction battery pack.

On-Board-Charger

If the car gets current from the conventional electric grid you need an on-board charger, that is a power electronic converter. A power converter is a semiconductor device acting like speed switches. This device modifies the input voltage and current. The ob-board charger converts the incoming alternating current or AC power supplied via the charge port to direct current or DC power for charging the traction battery.

High- Voltage Traction Battery

A pack of batteries is the basic piece of the electric car. Generally, the traction battery pack is located at the bottom of the car. The main role is to store energy for the propulsion of the car. The battery monitors and regulates the battery charging characteristics such as voltage, current, and charge rate.

Measure unit for the range of battery or the content of battery is kilowatt-hours. The range of batteries for electric cars is 10-100kwh.
For electric cars are applying different types of battery technologies.

First is the lead-acid. The solution to use lead-acid batteries for an electric vehicle is limited. These batteries have low acid density, sensitivity to temperature and, a short life cycle.

Next is the Nickel- Metal-Hydride (NiMH) batteries. The batteries work for traction and for high energy content. Lithium-based batteries are the most popular. Lithium batteries  Lithium-ion-liquid electrolyte and, Lithium-ion-polymer electrolyte batteries. Lithium-ion batteries have high energy density.

Battery Power Converter

The power flows from the battery to the motor and to the vehicle accessories like light and audio system is generating. To generate the power flow between these devices it is necessary to use a power electric converter.

In an electric car, a DC to DC converter – the battery power converter- increase the battery power voltage of the traction battery pack to a higher voltage needed to drive motor drive.
A secondary DC to DC converter is used to down the voltage of the traction battery pack to charge the lower voltage auxiliary battery.

Motor Drive

The component that contains the speed, torque, and rotational direction of the motor.
Depending on the motor, the motor drive can be DC to AC inventor or a DC/DC converter that controls the power flow between the battery and the motor. The motor drive is capable to move the power to the motor for propulsion but to remove out the motor for regenerative braking.



Electric Motor

The electric motor is one of the vital components of an electric car. The electric motor converts electrical energy to mechanical energy for driving the wheels by the transmission. Electric cars use a single gear transmission with differential compared to variable gear from internal combustion engine vehicles.

The electric cars are automatic gear cars because the electric motor delivers close full torque at all speeds. Further, the same electric motor works either for propulsion or for regenerative braking. Commonly used motor types: Brushed DC motor, Induction motor, Permanent magnet motor, Switched reluctance motor.

Auxiliary battery and Power electronics converter

The auxiliary battery provides electricity to start the car. This fact happens before the traction battery to be coupled. The Auxiliary battery aliments vehicle accessories. The power electronic converter controls different power converters directly. It uses the driver accelerator and brake pedals to control the power flow and select the operating mode between driving and regenerative braking. It controls the on-board charger and the battery charging together with the battery management system