CONTENTS

  • Introduction

  • Classification of EV

  • Parts of EV

  • Types of motor & Working

  • Battery

  • Types of Energy Storage

  • Battery Management System (BMS)

  • Regenerative Braking

  • Converters & Inverters

  • Transmission

  • Controllers

  • E - Differential

  • Charging

  • Battery Technology

Introduction

Welcome to the world of electric vehicles

A vehicle that employs one or more electric motors for propulsion is referred to as an electric vehicle (EV). It may be driven independently by a battery, a collector system, or electricity from extravehicular sources (sometimes charged by solar panels, or by converting fuel to electricity using fuel cells or a generator). Road and rail vehicles, surface and underwater watercraft, electric aeroplanes, and electric spacecraft are all examples of EVs.

Electric vehicles (EVs) originally appeared in the late 19th century when electricity was one of the favoured forms of motor vehicle power, offering a degree of comfort and simplicity of use that gasoline automobiles of the day were unable to match. For almost 100 years, internal combustion engines predominated as the primary means of propulsion for automobiles and trucks, while electric power remained prevalent in other vehicle types, such as trains and smaller vehicles of all kinds. A fresh interest in an electric transportation infrastructure emerged in the latter half of the 20th and the beginning of the 21st centuries as a result of the negative environmental effects of the petroleum-based transportation infrastructure and the concern of peak oil. Due to technology advancements, a greater emphasis on renewable energy, and the possibility to lessen the impact of transportation on climate change, air pollution, and other environmental concerns, EVs have had a comeback in the 21st century.

Electric cars are included among the top 100 modern options to combating climate change by Project Drawdown. Electric vehicles (EVs) vary from conventional cars in that the electricity they use may be produced using a variety of fuels, including nuclear power, renewable energy sources like solar and wind power, or any combination of those. Electric vehicle emissions and their carbon impact vary depending on the technology and fuel utilised to generate the power. Depending on the vehicle, a battery, flywheel, or supercapacitors may be used to store the power. Internal combustion engine vehicles often only get their energy from one or two sources, which are typically non-renewable fossil fuels. Regenerative braking, which recovers kinetic energy generally lost during friction braking as heat as power is returned to the on-board battery, is a fundamental benefit of electric cars.

Electric Vehicles

Hello Champion,

Welcome to the course & virtual internship on electric vehicles. This programme designed for anyone who is interested in learning about EV technologies.  So let's start learning...

Once again "Welcome aboard" 

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Classification Of EV

There are four different kinds of electric cars on the market:

Battery Electric Vehicles (BEVs)

BEVs are also referred to as all-electric cars (AEV). Electric drivetrains driven solely by batteries are used in BEV-based electric vehicles. The enormous battery pack that houses the electricity needed to power the car may be charged by hooking it into the power grid. One or more electric motors are then powered by the fully charged battery pack to drive the electric vehicle.

Main Components of BEV:

Drive train, Battery, Control Module, and Electric Motor

Working Principles of BEV:

The DC Battery's energy is transformed into AC to power the electric motor. A signal is transmitted to the controller as soon as the accelerator is depressed. By altering the frequency of the AC electricity delivered to the motor by the inverter, the controller modifies the speed of the vehicle. The motor then joins and, via a gear, causes the wheels to turn. The motor transforms into an alternator and generates electricity when the brakes are applied or the electric vehicle is slowing down, sending it back to the battery.

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Hybrid Electric Vehicle (HEV)

HEVs are also referred to as parallel or series hybrids. HEVs have an electric motor in addition to an engine. Fuel powers the engine, while batteries provide electricity for the motor. Both the engine and the electric motor turn the transmission at the same time. Wheels are then propelled by this. 

 

Main Components of HEV:

Electric Motor, An Engine, Power Supply with a controller and an Inverter, Fuel container, Control Unit

Working Principles of HEV:

Similar to a typical car, the gasoline tank provides the engine with energy. The electric motor powers the batteries. The transmission can be turned simultaneously by the engine and the electric motor.

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Plug-in Hybrid Electric Vehicle (PHEV):

The term "series hybrid" also applies to PHEVs. Both an engine and a motor are present. You have a choice of two types of fuels: conventional fuel (like gasoline) and alternative fuel (such as biodiesel). A battery pack that can be recharged can also power it. The battery can receive external charging.

PHEVs have at least two operating modes: All-electric Mode, in which the automobile runs entirely on its motor and battery Hybrid Mode, which uses both electricity and gasoline or diesel

Main Components of PHEV:

Fuel Tank, Control Module, Battery Charger, Electric Motor, Engine, Inverter, and Battery (if onboard model)

Working Principles of PHEV:

PHEVs operate in an all-electric mode at start-up and continue to do so until their battery pack is empty. When the battery runs out, the engine kicks in and the car becomes a regular, non-plug-in hybrid. An external electric power source, an engine, or regenerative braking can all be used to charge PHEVs. The electric motor functions as a generator when the brakes are engaged, utilising the energy to charge the battery. The electric motor increases the power by combining with the engine, allowing for the use of smaller engines without sacrificing performance and raising the vehicle's fuel efficiency.

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Fuel Cell Electric Vehicle (FCEV)

Another name for FCEVs is zero-emission vehicles. To create the electricity needed to power the car, they use "fuel cell technology." The fuel's chemical energy is instantly transformed into electric energy.

Main Components of FCEV:

Fuel-cell stack, hydrogen storage tank, an electric motor, and a battery with a converter and a controller

Working Principles of FCEV:

The electricity needed to power this vehicle is produced on the FCEV itself.

Parts of EV

Lets explore different parts of an electric vehicle

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Battery Pack

In contrast to an internal combustion engine, which has a gasoline tank full of petrol, an electric vehicle's energy source is its battery pack. The car's drive, heating, cooling, lights, and other equipment are all powered by the battery pack. Since battery packs normally use direct current (DC) electricity, alternating current (AC), which is used when charging at home (Level 2), is converted to DC.

Electric/Traction Motor

A traction motor is an electric motor used for propulsion of a vehicle, such as locomotives, electric or hydrogen vehicles, elevators or electric multiple unit.

Power Inverter

A power inverter is needed to convert the DC power from the battery for use with AC motors. The power inverter can also operate in reverse, transforming regenerative braking's AC power into the battery's DC power.

Onboard Battery Charger

The majority of EVs come with an integrated battery charger. Instead of DC fast charging, these devices are utilised for regular AC charging (level 1 or 2). To prevent any electric harm, they serve the purpose of limiting the overall amount of power entering the battery.

Battery Management System

To safeguard the battery and increase its lifespan, a battery management system (BMS) regulates the current flow in and out of the battery. Every EV has a BMS created especially for the vehicle. Given that any alterations would also need to be made appropriately within the BMS, this could restrict future EV upgrades that might be made.

Charging Port

This port functions just like the access port on a regular car, only it allows access to the charge port rather than supplying fuel. Both serve as the energy source's entrance ports into the car.

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The standard for the kind of EV charging connector or plug varies depending on the region and the vehicle. There is an ongoing debate about universal plug technology. The Combined Charging System (CCS) is supported by a significant number of international manufacturers in North America and Europe, while Japan and its automakers utilise CHAdeMO, and China, which has the largest market for electric vehicles, employs GB/T.

 

There are also several power levels accessible in each location, depending on the type of plug.

 

European EV Plug Standards

 

There are some similarities between EV charging connector types in Europe and North America, but also some discrepancies. The voltage in a typical home is 230 volts, which is almost double the voltage in North America. Because of this, Europe does not use "level 1" billing. Second, all manufacturers in Europe, with the exception of Tesla, utilise the IEC 62196 Type 2 connection, often known as mennekes, as the industry standard rather than the J1772 connector.

 

Tesla, however, just swapped the Type 2 connector for the Model 3 from their proprietary connector. Although the Tesla connector is still used in Model S and Model X vehicles sold in Europe, it is believed that they will also ultimately transition to the Type 2 connector in that region.

 

The DC fast charging standard used in Europe is also the same as that used in North America, with Nissan and Mitsubishi the exceptions. Although it has the same name as the J1772 connection used in North America for the CCS system, the Type 2 connector and the two dc rapid charge pins are combined differently in Europe. The Tesla Model 3 currently operates in Europe using the CCS charging standard, and Tesla has equipped its Supercharger locations with CCS connectors as well.

 

North American EV Plug Standards

 

The SAE J1772 connection, often known as the J-plug, is used by all electric car manufacturers in North America (apart from Tesla) for Level 1 (120 volt) and Level 2 (240 volt) charging. Every car sold by Tesla comes with a Tesla charger adaptor cable that enables it to use J1772-compatible charging stations. All electric vehicles sold in North America are therefore compatible with any charging station equipped with the J1772 connection.

 

It is crucial to understand this since every level 1 or level 2 charging station other than Tesla's offered in North America uses the J1772 connection. For instance, the standard J1772 connection is used by all of our JuiceBox devices. However, using the adaptor connection that Tesla gives with the car, Tesla automobiles may charge on any JuiceBox charging station. EVs from other manufactures cannot use Tesla's own charging stations without purchasing an adapter since they utilise a unique Tesla connection.

The J1772 connection is used by every level 1 and level 2 charging station available today, with the exception of those built by Tesla. This may sound a bit complicated, but one way to look at it is that any electric car you purchase today may use a charging station that has one.

 

DC Fast Charge EV Plug Standards in North America

 

For DC fast charging, which is high-speed EV charging that is exclusively available in public places, most typically along major freeways where long-distance travel is usual, things are a little more difficult. Since residential buildings typically lack the necessary energy, DC fast chargers are not accessible for charging at home. Additionally, using DC fast charging stations more than once or twice a week is not advised because the rapid pace of recharging might shorten the battery life of an electric car if done too frequently.

 

An electric car may be fully charged using a DC fast charger in as little as 20 minutes using 480 volts, which makes it possible to go great distances without worrying about running out of power. Unfortunately, DC Fast Chargers utilise three distinct types of connections rather than only two, as they do for level 1 and level 2 charging (J1772 and Tesla).

 

The CCS (Combined Charging System) connection adds two more pins below the J1772 charging port. The J1772 connection and the high-speed charging pins are "combined" in this device, giving it its name. The Society of Automotive Engineers established and adopted CCS, which is the acknowledged standard in North America (SAE). General Motors (all divisions), Ford, Chrysler, Dodge, Jeep, BMW, Mercedes, Volkswagen, Audi, Porsche, Honda, Kia, Fiat, Hyundai, Volvo, smart, MINI, Jaguar Land Rover, Bentley, Rolls Royce, and other automakers have all committed to using the CCS standard in North America.

 

CHAdeMO: Tepco, a Japanese utility, created CHAdeMo. It is the accepted norm in Japan, where CHAdeMO connectors are used by almost all DC fast chargers. In contrast, only Nissan and Mitsubishi are presently selling electric vehicles in North America that employ the CHAdeMO connection. The only electric vehicles that utilise the CHAdeMO EV charging connection type are the Nissan LEAF and the Mitsubishi Outlander PHEV. Kia stopped selling CHAdeMO in 2018 and now provides CCS. Contrary to the CCS system, CHAdeMO connections need a separate ChadeMO inlet on the automobile since they do not share a portion of the connector with the J1772 inlet. To support two different charging plugs, a wider charge port area is required.

 

Tesla: Tesla utilises the same connection for DC rapid charging, level 1 and level 2. There is no need for a special connector for DC rapid charging, as required by other standards, because the Tesla connector is proprietary and accepts any voltage. Tesla's DC quick chargers, or Superchargers, are only compatible with Tesla automobiles. These stations are only available to Tesla customers and are installed and maintained by Tesla. A non-tesla EV could not be charged at a Tesla Supercharger station, not even with an adaptor cable. This is so that the car may be verified as a Tesla before being allowed access to the electricity through an authentication procedure.

Cooling/ Heating System

If included, the cooling and heating system functions as a thermal management system with the aim of extending the battery pack's lifespan. It is necessary to lessen temperature distributions that are unequal. When the battery is fast charging or on a hot day, it functions by cooling the battery. Additionally, it gets the battery warm on chilly days and/or gets it ready for quick charging. The thermal management system functions by integrating forced air cooling, thermoelectric cooling, and liquid cooling. To maximise battery life and operating circumstances, this system collaborates with the battery management system.

Controller (C)

The controller's primary job is to regulate the electrical energy that will be distributed to electric motors from batteries and inverters. While the automobile pedal serves as the primary input for the controller itself (which is set by the driver). The speed of the car will be determined by this pedal setting, which will also affect the frequency or voltage variation that will enter the motor. In a nutshell, this device regulates the flow of electrical energy supplied by the traction battery, regulating the torque and speed of the electric traction motor. This element will determine how an electric vehicle operates.

Transmission (F)

The transmission uses the electric traction motor's mechanical energy to drive the wheels.

DC/DC Converter (G)

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This is one of the components used in electric cars that transforms higher-voltage DC power from the traction battery pack into the lower-voltage DC power required to operate the vehicle's accessories and recharge the auxiliary battery.

Types of Motors and Working

DC Motor

The following three categories of DC motors:

  • Standard-style "brushed" motor. This motor can produce a lot of initial torque and has simple speed control, but it will probably need more maintenance.

  • DC brushes-less motors (BLDC). These are an improved version of traditional DC motors because they do not contain "brushes." They require far less maintenance, are more effective, and still provide a high starting torque.

  • Synchronous Permanent Magnet Motor (PMSM). The PMSM permanent magnet motor works similarly to a BLDC but uses magnets to provide a steady magnetic field. Due to their high power rating, you can find these motors in high-performance EVs. 

AC Motor

There are two categories of AC motors:

  • Asynchronous. The electric-powered stator (coil of wire contained inside the engine casing), sometimes referred to as an induction motor, creates a rotating magnetic field. For prolonged driving at greater speeds, this motor is recommended.

  • Synchronous. The revolving magnet really functions as the motor rotor. The ideal use of these motors is for city driving, which involves frequent starting and stopping.

Since they can operate in reverse and transform mechanical energy into electrical energy, both varieties of AC motors can benefit from "regenerative braking."
Since AC motors are more common and more cost-effective (in terms of power-to-weight ratio), even though they have less torque, most EVs employ them.
Internal combustion engines are substantially less efficient than electric motors, which typically have an efficiency of over 95%. EV motors are also more compact, lighter, and less expensive.

Traction Motor

An electric motor used to propel a vehicle, such as a locomotive, an electric or hydrogen vehicle, an elevator, or an electric multiple unit, is known as a traction motor.
Traction motors are used in electrically powered rail vehicles (electric multiple units), other electric vehicles (such as electric milk floats, elevators, roller coasters, conveyors, and trolleybuses), vehicles with electrical transmission systems (diesel-electric locomotives, electric hybrid vehicles, and battery-operated vehicles), and electrically powered rail vehicles.

The first kind of traction motors are direct-current motors with series field windings. With considerable torque at low speeds for vehicle acceleration and falling torque as speed increases, they offer a speed-torque characteristic beneficial for propulsion. The field winding may be set up with many taps to change the speed characteristic, allowing for somewhat smooth operator control of acceleration. Using pairs of motors on a vehicle under series-parallel control offers an additional level of control; for sluggish operation or high loads, two motors can be driven in series off of a direct-current source. These motors may be run in parallel to increase the voltage available to each and enable faster speeds when higher speed is necessary. Different voltages may be used across a rail system, with greater voltages used on long stretches between stations and lower voltages used close to stations when only slower operation is required.

The AC series motor, commonly referred to as the universal motor, is a variation of the DC system. It is essentially the same technology but runs on alternating current. The motor behaves similarly to when it is powered by direct current since both the armature and field current reverse simultaneously. In order to achieve better operating conditions, AC railways are frequently supplied with current at a lower frequency than the commercial supply used for general lighting and power. To convert commercial power from 50 or 60 Hz to the 25 Hz or 1616 2⁄3  Hz frequency used for AC traction motors, special traction current power stations or rotary converters are used. The AC system enables speed control with switchgear on the truck and efficient power distribution along a rail line.

Due to their constant speed characteristic, AC induction motors and synchronous motors are simple and inexpensive maintenance, but difficult to employ for traction motors. An AC induction motor can only operate at a limited speed range, which is dictated by the design of the motor and the frequency of the AC power source. A locomotive may now use a variable frequency drive, which enables a broad range of speeds, AC power transfer, and tough induction motors without wearing elements like brushes and commutators. This is made possible by the development of power semiconductors.

 

Mechanical Characteristics:

A traction motor must be robust and capable to withstand continuous vibrations since service conditions are extremely severe.

 

The weight of the traction motor should be minimum in order to increase the payload capacity of the vehicle. This is achieved by using high- speed motors, the upper limit being fixed by excessive centrifugal stresses

 

The traction motor is located underneath a motorcoach (except in a few electric locomotives). The space underneath a motor coach is limited by the size of the driving wheels and the track gauge. The traction motor, therefore, must be small in overall dimensions especially in its overall diameter.

 

The traction motor must be totally enclosed, particularly when mounted beneath the locomotive or motor coach, to provide protection against ingress of dirt, dust, water mud, thus, for the magnetic circuit of traction motor cast iron, which cannot withstand continuous vibrations, is not suitable. Use of cast steel or fabricated steel, which gives more mechanical strength, is made in place of cast iron. Those parts of the motor, which are not highly stressed; must be made of pressed or fabricated steel plates and light alloys

Electrical Characteristics: 

 

High Starting Torque:

A traction motor must be capable of developing high starting torque, especially when the train is to be accelerated at a reasonably high rate such as in case of urban or suburban services.

 

Simple Speed Control:

The traction motor should be amenable to simple speed control methods as an electric train has to be started and stopped very often.

 

Self-Relieving Property:

The speed-torque characteristics of the motor should be such that the speed may fall with the increase in load. The motors having such speed- torque characteristics are self- protective against excessive overloading as power output of a motor is proportional to the product of torque and speed.

 

Possibility of Dynamic or Regenerative Braking:

The traction motor should be amenable to easy and simple methods of rheostatic and/or regenerative braking.

 

Capability of Withstanding Voltage Fluctuations:

Traction motor should be capable of withstanding rapid fluctuations in supply voltage without undue effect on its performance since in traction work rapid voltage fluctuation owing to heavy current inrush at start, is a common feature.

 

Capability of Withstanding Temporary Interruption of Supply:

Traction motor should be capable of withstanding temporary interruptions of supply without undue rush of current, since it occurs at the instant of crossing over the cross-overs and section insulators.

Overload Capacity:

Traction motor should be capable of taking excessive load as it is subjected to very arduous duty.

 

Parallel Running:

In traction work, usually more than one motor (two or four motors per motor car) are required. Traction motors, therefore, should be of such speed torque and current-torque characteristics that when they are operated in parallel and mechanically coupled, they share the load almost equally. 

No motor meets all the requirements mentioned above. Most suitable motors for dc systems are the series and compound motors whereas for ac systems the single phase series motors and 3-phase induction motors are employed.

 

Rating and Ventilation of Traction Motor:

The motors are designed for intermittent loading as well as continuous loading. The motors employed in traction work are subject to intermittent loading particularly in case of tramway and suburban services, therefore, traction motors are given one-hour rating as well as continuous rating. The ratings have been fully defined in Indian Standard Specifications (1SS). The continuous rating of an ordinary self-ventilated motor is approximately one-third to one-fourth of its one hour rating while the continuous rating of a forced ventilated motor is about four-fifth of its one hour rating.

The motors employed in traction work are usually totally enclosed so that protection against the ingress of dust, dirt, mud and water may be provided, Since the weight and overall dimensions of the motor are to be kept to the minimum, efficient cooling is, therefore, essential. For cooling purpose either self-ventilation (by using a fan mounted on the motor shaft which blows air through suitable ducts in the motor) or forced ventilation (by employing an external fan) is used. In either case care must be taken in designing the ducts to prevent their becoming choked with dirt and axial rather than radial ducts are always used.

Forced ventilation is invariably employed in case of locomotives, as it is operative even when the vehicle is stationary but for motor coaches and road vehicles, self-ventilation is usually employed as it does not cause noise due to fans employed for this purpose.

AC Motor

There are two categories of AC motors:

  • Asynchronous. The electric-powered stator (coil of wire contained inside the engine casing), sometimes referred to as an induction motor, creates a rotating magnetic field. For prolonged driving at greater speeds, this motor is recommended.

  • Synchronous. The revolving magnet really functions as the motor rotor. The ideal use of these motors is for city driving, which involves frequent starting and stopping.

Since they can operate in reverse and transform mechanical energy into electrical energy, both varieties of AC motors can benefit from "regenerative braking."
Since AC motors are more common and more cost-effective (in terms of power-to-weight ratio), even though they have less torque, most EVs employ them.
Internal combustion engines are substantially less efficient than electric motors, which typically have an efficiency of over 95%. EV motors are also more compact, lighter, and less expensive.

Battery

A battery is an essential component of any electric vehicle (EV). The battery needs to be built to meet the demands of the motor or motors and charging mechanism that a vehicle uses. For plug-in hybrid electric vehicles (PHEVS), hybrid electric vehicles (HEVS), and all electric cars, they are crucial (EVs).
Physical limitations like effective packaging within the body of the vehicle to maximise capacity are included in this. The placement of the battery within a vehicle must be taken into account by designers as the battery is the primary source of weight in an EV and can affect power efficiency and handling characteristics (which is typically why you will frequently see batteries placed under the floor pan of the vehicle).

Types of Energy Storage

Systems

In HEVS, PHEVS, and EVs, the following energy storage systems are employed. Battery Types: Lithium-ion Due to their high energy per unit mass compared to other electrical energy storage methods, lithium-ion batteries are currently employed in the majority of portable consumer electronics, including cell phones and laptops. Additionally, they are very energy-efficient and have a high power to weight ratio. reduced self-discharge and strong performance at high temperatures Although it is possible to recycle the majority of lithium-ion battery parts, the expense of material recovery continues to be an issue for the sector. The majority of PHEVS and EVs on the market today use lithium-ion batteries, albeit the chemistry is frequently different from that of batteries used in consumer electronics. To lower the price and increase their useful life, research and development are continuing.

Nickel-Metal Hydride Batteries

Commonly found in computer and medical devices, nickel-metal hydride batteries have adequate specific energy and specific power capabilities. Lead-acid batteries have a substantially shorter lifespan than nickel-metal hydride batteries, which are also more secure and abuse resistant. In HEVS, these batteries have been frequently used. The primary issues with nickel-metal hydride batteries are their high price, significant heat generation at high temperatures, high discharge, and the requirement to manage hydrogen loss.

Lead-Acid Batteries

High power lead-acid batteries are possible to create, and they are also affordable, secure, and trustworthy. However, their employment is limited by their low specific energy, poor cold-temperature performance, and short calendar and life cycle. Although sophisticated high-power lead-acid batteries are being developed, they are only used as accessory loads in currently on the market electric-drive vehicles.

Ultracapacitors

In a polarised liquid sandwiched between an electrode and an electrolyte, ultracapacitors store energy. The liquid's surface area grows along with its ability to store energy. Vehicles with ultracapacitors may accelerate more quickly, climb hills more easily, and recover brake energy. Because they assist electrochemical batteries in balancing load power, they may also be helpful as secondary energy storage systems in electric-drive cars.

Battery Management System (BMS)

Any electronic system that controls a rechargeable battery (cell or battery pack), such as by safeguarding it from operating outside of its safe operating range, monitoring its state, calculating secondary data, reporting that data, controlling its environment, authenticating it, and/or balancing it, is referred to as a battery management system (BMS).

 

The BMS will also regulate the battery's recharging by directing the energy that has been collected (through regenerative braking) back into the battery pack (typically composed of a number of battery modules, each composed of a number of cells).

The cooling medium for battery thermal management systems can be air, liquid, or some other type of phase transition, and they can be passive or active. The ease of air cooling is a benefit. Such systems can be active, utilising fans for airflow, or passive, depending merely on the convection of the surrounding air. Commercially, the battery systems of the Honda Insight and Toyota Prius both utilise active air cooling. The main drawback of air cooling is its lack of effectiveness. The cooling technique requires far more electricity to function than active liquid cooling does. The additional cooling mechanism parts also increase the BMS's weight, which decreases the effectiveness of batteries used in transportation.

Since liquid coolants often have higher thermal conductivities than air, liquid cooling offers a larger natural cooling potential than air cooling. Either the coolant flows through the BMS without coming into contact with the batteries, or the batteries can be submerged in the coolant directly. Due to the lengthened length of the cooling channels, indirect cooling has the potential to produce significant temperature gradients across the BMS. This can be decreased by pushing the coolant through the system more quickly, although doing so compromises thermal uniformity.

A lithium-ion battery system must have a BMS (Battery Management System). This gadget controls each battery cell in real-time, connects with outside devices, manages the computation of the state of charge, measures temperature and voltage, etc. The final battery pack's quality and lifespan are determined by the BMS selection.

 

Due to their high charge density and light weight, lithium-ion batteries have emerged as the preferred battery by electric vehicle makers. These batteries are quite unstable despite having a lot of power for their size. These batteries must never be overcharged or discharged under any circumstances, necessitating the monitoring of their voltage and current. This process becomes a little more difficult because an EV battery pack is made up of numerous cells, each of which needs to be individually monitored for safety and effective operation. This process calls for a system that has been specifically designed for this purpose, known as the Battery Management System.

 

When constructing a BMS, many considerations must be taken into account. The precise end application for which the BMS will be utilised determines all other considerations. BMS are utilised in addition to electric vehicles (EVs) in any application that uses a lithium battery pack, including solar panel arrays, wind turbines, power walls, etc. No matter the application, a BMS design should take into account all or some of the following elements.

Control of Discharging: The fundamental job of a BMS is to keep the lithium cells within the safe working range. An ordinary Lithium 18650 cell, for instance, will have an under-voltage rating of about 3V. The BMS is in responsible of ensuring that none of the cells in the pack are discharged below 3V.

Charging Control: The BMS should also keep an eye on the charging process in addition to the discharging. When batteries are charged improperly, they frequently suffer damage or have a shorter lifespan. A two-stage charger is used for lithium batteries. Constant Current (cC) refers to the first stage of charging the battery, when the charger delivers a steady current. The second stage, known as the Constant Voltage (CV) stage, is employed when the battery is almost full. During this stage, a constant voltage is given to the battery at a very low current. In order to avoid overcharging or fast charging the batteries, the BMS should make sure that the voltage and current during charging do not exceed set limitations. The battery's datasheet contains the maximum permitted charging voltage and charging current.

State-of-Charge (SOC):

State of charge (SoC) is the level of charge of an electric battery relative to its capacity. The units of SoC are percentage points (0% = empty; 100% = full). An alternative form of the same measure is the depth of discharge (DoD), the inverse of SoC (100% = empty; 0% = full). SoC is normally used when discussing the current state of a battery in use, while DoD is most often seen when discussing the lifetime of the battery after repeated use.

 

Cell Balancing:

A BMS's ability to maintain cell balancing is another crucial capability. For instance, the voltage of all four cells in a pack of four connected in series should be constant. The entire pack will be affected if one cell has a lower or higher voltage than the others, for example, if one cell is at 3.5V while the other three are at 4V. These three cells will reach 4.2V during charging, whereas the fourth cell will have only achieved 3.7V. The first cell to discharge to 3V before the other three will also be this one. In this approach, the efficiency is compromised since this one cell prevents the other cells in the pack from being used to their full capacity.

Cell balancing is a solution that the BMS must apply to address this issue. Although there are many different cell balancing methods, the active and passive methods are the most frequently employed. The objective of passive balancing is to push the cells with excess voltage to discharge through a load, such as a resistor, until their voltage equals that of the other cells. The stronger cells will be used to charge the weaker cells during active balancing to equalise their potentials. Cell balancing will be covered in more detail in a subsequent post.

 

Thermal Control:

The operating temperature has a significant impact on the longevity and performance of a lithium battery pack. In comparison to a regular room temperature, hot climates tend to cause the battery to deplete more quickly. The temperature would rise even more if excessive current usage were added on top of this. This requires a battery pack with a thermal system that uses primarily oil. In frigid areas, this thermal system should not only be able to lower the temperature but also, if necessary, raise it. The BMS is in charge of monitoring each cell's temperature and adjusting the thermal system as necessary to maintain the battery pack's overall temperature.

 

Powered from the Battery itself:

The battery itself serves as the EV's only power source. Therefore, a BMS should be built so that it may be powered by the same battery that it is meant to manage and safeguard. Though it might seem straightforward, this makes the BMS's design more challenging. Not as ideal Power: Even while the car is running, charging, or in optimal mode, a BMS should be active and running. Due to this, the BMS circuit must be operated continually; as a result, it is essential that the BMS consume relatively little power in order to prevent excessive battery drain. The BMS and associated circuits tend to automatically drain the battery when an EV is left uncharged for weeks or months before eventually requiring it.

 

Galvanic isolation:

The BMS serves as a conduit between the EV's battery pack and electronic control unit (ECU). To display all of the data gathered by the BMS on the instrument cluster or dashboard, the ECU must receive the data. As a result, the standard protocol such as CAN communication or LIN bus should be used to maintain constant connection between the BMS and the ECU. It should be possible for the BMS design to offer galvanic isolation between the battery pack and the ECU.

 

Data logging:

The BMS needs a sizable memory bank since it must store a lot of data. Only when the battery's charging history is known can values like the Sate-of-health (SOH) be computed. As a result, the BMS must monitor the battery pack's charge cycles and charge time starting on the installation date and interrupt this information as needed. This also helps with after-sales support or problem analysis.

 

Accuracy:

The voltage across a cell rises or falls gradually when it is charged or discharged. Unfortunately, a lithium battery's discharge curve (Voltage vs. time) includes flat portions, which makes the voltage change quite small. To determine the SOC value or use it for cell balance, this change must be precisely measured. A well-designed BMS should have a minimum accuracy of 1 to 2 mV and a maximum accuracy of t0.2 mV. Typically, the technique makes use of a 16-bit ADC.

 

Processing Speed:

To determine the value of SOC, SOH, etc., the BMS of an EV must perform extensive number-crunching. There are numerous algorithms for doing this, some of which even employ machine learning. The BMS is hence a processing-hungry device. In addition to this, it must measure the cell voltage across hundreds of cells and quickly detect any slight changes.

Regenerative Braking

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Vehicles in motion have a lot of kinetic energy, and when brakes are used to slow one down, all of that energy must be dissipated. When internal combustion engine cars first appeared, brakes were completely friction-based and used the kinetic energy of the car to generate waste heat in order to slow it down. Simply put, the environment lost all of that energy.
Fortunately, as a species, we have devised a superior method. Regenerative braking converts a large portion of the kinetic energy lost during deceleration back into stored energy in the battery of an electric car by using the motor of the vehicle as a generator. Then, instead of drawing more energy from its own stores, the car uses a large portion of the energy that was previously stored during regenerative braking when it accelerates.

Recognizing that regenerative braking does not magically extend an electric vehicle's range is vital. Electric vehicles become less inefficient, but not necessarily more efficient. The best approach to operate any car would essentially be to accelerate to a constant speed and then never use the brake pedal. Your best range would be achieved by simply never slowing down in the first place, as braking will take energy away and force you to expend more energy to accelerate again.
But it is clear that is not realistic. Regenerative braking is a good alternative because we need to brake frequently. Simply said, it reduces the wastefulness of the braking process while retaining its inefficiency.

 

How well does regenerative braking work?

 

In order to assess regenerative braking, efficiency and effectiveness must be considered separately. Despite having a similar sound, the two are very dissimilar. Efficiency is a term used to describe how successfully regenerative braking recovers energy lost during braking. Does it convert all of the kinetic energy back into stored energy, or does it just squander a lot of it as heat? Effectiveness, on the other hand, describes the actual magnitude of the influence that regenerative braking has. Will you notice much of a difference, or will your range be increased measurably?

 

Efficiency:

No machine can operate at maximum efficiency (without breaking the laws of physics). since any energy transfer will ultimately result in some loss in the form of heat, light, noise, etc. Regenerative braking efficiency varies across different cars, motors, batteries, and controllers, but it typically ranges between 60 and 70 percent. According to Tesla, the energy being captured often loses between 10 and 20 percent to regen and another 10 to 20 percent when the energy is converted back into acceleration. The majority of electric vehicles, such as cars, trucks, electric bikes, electric scooters, etc., follow a fairly common design. Remember that this 70% figure does not imply that regenerative braking will result in a 70% gain in range. Your range will not increase from 100 miles to 170 miles as a result of this. This merely means that 70% of the kinetic energy lost during braking can later be converted into acceleration. Because of this, reporting the system's efficiency alone does not really imply anything.Even if someone is incredibly productive when they work, if they just put in an hour a day, they are probably not getting much done. The efficiency of regenerative braking is what ought to pique our curiosity more.

 

Effectiveness:

Things start to get extremely intriguing at this point. The extent to which regenerative braking can extend your range serves as a gauge of its efficiency. Does it increase your theoretical range by 5%? fifty percent more? still more? As you may have already surmised, regenerative braking's efficiency varies greatly depending on a variety of elements, such as road cond Regenerative braking works far more efficiently in stop-and-go city traffic than it does in highway commuting. This should make sense because frequent braking will allow you to recover far more energy than long stretches of driving without using the brakes. Terrain also has a significant impact here, since uphill driving offers little opportunity for braking, whereas downhill driving will recover energy considerably more quickly due to the prolonged braking intervals. Regenerative braking can be used almost continually to control speed while continuously charging the battery on lengthy downhills.

For the simple reason that bigger cars have significantly more momentum and kinetic energy, vehicle size may be the biggest determinant in the effectiveness of regenerative braking. A four-wheel electric car has far more kinetic energy when moving than an electric bicycle or scooter, just as a large flywheel is more efficient than a tiny flywheel.
Finding comparable data can often be challenging. During strong braking, Tesla vehicles display regenerative braking power, such as 60 kw, but that does not address the more intriguing point. Not the strength of our brakes every time we slam on the brake pedal, but how much energy we are recapturing over the course of a trip.

 

Fortunately, several Tesla drivers have used various data tracking apps to feed back information regarding their energy contribution. Up to 32 percent of the total energy used by Model S drivers has reportedly been recovered while going uphill and then returning downhill. This would essentially extend a car's range from 100 miles to 132 miles, for instance. Others have reported recapturing between 15-20 percent of their total kWh usage on average during routine excursions, while one Model S P85D owner claimed about 28 percent energy recapture (forum in Danish).

 

For smaller EVs such as personal electric vehicles, the numbers aren't quite as optimistic. We can see an average regeneration rate of 4-5 percent on a variety of electric bicycles with regenerative braking options, with a maximum regeneration rate of around 8 percent in mountainous terrain. The results for other electric personal vehicles, such as electric skateboards and scooters, are comparable and typically in the low single digits. Remember that this is not the system's actual efficiency (as in how much braking energy is lost in the energy transfer).
It is the efficiency (as in how much further your range increases due to the use of regenerative braking). This is largely caused by the lighter weight of personal electric vehicles, as was already mentioned. They just have less kinetic energy to convert back into the battery because they carry less motion.

 

Does it matter how well regenerative braking works?

 

Regenerative braking can occasionally be employed more as a marketing tactic than a feature in the e-bike industry. Since larger gearless motor electric bicycles are typically the only ones that can do regenerative braking, these manufacturers will highlight the efficiency of their products. Manufacturers of geared motorcycles and other vehicles without regenerative braking will discard it as ineffectual and simply not worthwhile at the same time.

Even while regenerative braking is less effective in smaller, more personal electric vehicles than it is in electric cars, it still has a number of advantages.
The increased braking force is one of the main advantages of regenerative braking for smaller personal EVs. The rear wheel always uses a conventional disc brake. As a result, the scooter's cost, weight, and complexity are decreased because it has two separate brakes that are activated by a single brake lever. Regenerative braking also makes it possible for electric skateboards to get brakes, which was previously only possible with the varied braking of your shoe sole on the pavement. Regen-based electric braking is a much-welcomed safety feature on popular electric skateboards like the Boosted Board, which can go at speeds of far over 20 mph.

Regenerative braking also prolongs the life of conventional brake components like wires and brake pads. Since electric bicycles and scooters ride farther and faster than their non-electric cousins and would ordinarily wear out brake pads considerably more quickly, they can be a pain to maintain and replace. Due to its freewheeling geared motors, one of my e-bikes lacks regen, and it seems like I am always tweaking and changing the brakes. However, I find that on e-bikes with regenerative braking, I can frequently rely almost totally on it, which means my brake pads are rarely used.

Regenerative braking will, in the end, never be as successful in smaller vehicles as it is in larger ones due to simple physics. The absence of regen in e-bikes and other PEVS is not a deal-breaker as a result. However, regenerative braking has advantages beyond straightforward energy recovery.

Converters and Inverters

Two essential components operate together in hybrids and other electric vehicles (EVs) to manage power and recharge the circuits. The inverter and converter's cooperative operation is shown in the following diagram.

 

Inverter:

An inverter is, generally speaking, a piece of electrical equipment that changes electricity from a DC (Direct Current) source into an AC (Alternating Current) that can be used to power a machine or appliance. In a solar power system, for instance, the inverter converts the power held in batteries that have been charged by solar panels into regular AC power, which powers plug-in outlets and other typical 120-volt appliances. In a hybrid or electric vehicle, an inverter performs a similar job, and its operational theory is quite straightforward.. For example, the primary winding of a transformer inside the inverter housing receives DC power from a hybrid battery. The primary winding of the transformer receives electrical charge, which abruptly reverses and flows back out through an electronic switch (typically a group of semiconductor transistors). The secondary winding circuit of the transformer receives AC current as a result of the in/outflow of electricity. In the end, this induced alternating current electricity powers an AC load, such as the electric traction motor of an electric vehicle (EV). Similar to an inverter, a rectifier accomplishes the exact opposite by converting AC power to DC electricity.

 

Converter:

This electrical gadget, which is more appropriately known as a voltage converter, actually modifies the voltage (either AC or DC) of an electrical power source. Step-up converters (which raise voltage) and step-down converters are the two types of voltage converters (which decreases voltage). A converter's most common purpose is to take a relatively low voltage source and step it up to a high voltage for heavy-duty work in a load that consumes a lot of power, but they can also be used in reverse to lower voltage for sources that only have light loads.

 

Inverter/Converter Tandem Units: As the name suggests, an inverter/converter is a single unit that contains both an inverter and a converter. Both EVs and hybrids employ these components to control their electric propulsion systems. The inverter/converter gives current to the battery pack for recharging during regenerative braking as well as power to the motor/generator for vehicle propulsion. It also has a built-in charge controller. In order to reduce their physical size, hybrids and electric vehicles (EVs) both employ relatively low-voltage DC batteries (around 210 volts), but they also typically include extremely effective high-voltage AC motors or generators (about 650 volts). The interaction of these dissimilar voltage and current types is choreographed by the inverter/converter device.

These devices create a tremendous quantity of heat due to the employment of transformers and semiconductors (and the resulting resistance encountered). For the components to remain functional, adequate cooling and ventilation are essential. Because of this, inverter/converter installations in hybrid vehicles have separate, independent cooling systems that include pumps, radiators, and other cooling components.

Transmission

Transmission System for EV: Ching-Feng Wang's patent application contains information about the transmission system. 

The motor, inverter, and battery that make up an electric vehicle's transmission system are crucial components of the entire operating system: •When the stator receives a three-phase input, a rotating magnetic field is produced, which induces a current in the rotor and causes it to begin revolving. The frequency of the AC supply determines the induction motor's speed, which means that the drive speed can be altered by altering the frequency of the power supply.
While an engine can operate at any speed without a speed-varying transmission, electric cars can operate at any speed.

A gearbox transmits the power produced in the electric car motor to a driving wheel. Due to the motor's versatility and efficiency across a range of situations, the EV only uses a single-speed transmission. The motor's output speed is slowed down in two stages using speed reduction and torque multiplication. Another crucial aspect of an electric car is the differential configuration, which allows the open differential to manage torque rather than the slip differential.

Selective braking and interrupting the power supply are two ways to disable the differential's traction control. Regenerative braking is a feature of electric vehicles because they may be driven with just the first pedal and save a significant amount of kinetic energy in the form of electricity as the accelerator is depressed.. During regenerative braking, the motor acts as a generator so wheels drive the motor. After conversion, the produced electric energy can be kept in the battery. Drive wheel and vehicle will slow down as a result of the opposing electromagnetic field's action on the rotor, allowing the vehicle to be stopped and controlled by a single pedal.
Instead of a clutch pack, the electric car uses a planetary gear set and torque converter. As previously established, an electric induction motor is efficient from 0 RPM all the way up to about 6,000 RPM (a speed that a car may never need to operate at!), therefore EVs only have one driving gear (a step-down transmission).which is required for acceleration, at RPM. Multiple gears on an EV would be advantageous but still not essential in a world without friction because the motor's maximum efficiency could be fully utilised. But for the time being, adding gears would just make a straightforward, dependable system more complex.

The existence of a clutch in an electric car is actually illogical. Adding a clutch to an electric car is illogical because an electric motor cannot stall, which is why a clutch is required in a conventional internal combustion engine in the first place.

Controllers

The electronic system that controls the electric vehicle's speed and acceleration between the batteries and the motor functions similarly to a carburetor in a car that runs on gasoline. The controller regulates the energy flow from the battery and converts the direct current from the battery into alternating current (for AC motors only).

In contrast to a carburetor, a controller may also make a motor into a generator and reverse the motor's direction of rotation (so that the kinetic energy of motion can be used to recharge the battery when the brake is applied).Early electric vehicles used DC motors, and the vehicle's acceleration and speed were managed by a straightforward variable-resistor type controller. This kind of controller constantly drew the entire amount of current and power from the battery. High resistance was utilised to lower the current to the motor when it was operating at low speeds when full power was not required. With this kind of setup, a considerable portion of the battery's energy was lost in the resistor due to energy loss. Only at high speeds was the entire available power utilised.

Modern controllers use pulse width modulation, an electrical technique, to change acceleration and speed. The current flow to the motor is quickly interrupted (turned on and off) using switching devices like silicon-controlled rectifiers. Short intervals (when the electricity is shut off) allow for high power (high speed and/or acceleration). Longer intervals result in low power (low speed and/or acceleration). The majority of car controllers also incorporate a regenerative braking system. When a vehicle slows down, regenerative braking is employed to use the motor as a generator to recharge the batteries. During regenerative braking, the motor/controller converts some of the kinetic energy typically absorbed by the brakes and converted to heat into electricity, which is then utilised to recharge the batteries. Regenerative braking decreases brake wear and lowers maintenance costs while also extending the range of an electric car by 5 to 10%.

E- Differential

Along with improved traction control, the electronic differential represents a technological development for electric vehicles. The electronic differential enables various wheel speeds and supplies each driving wheel with the necessary torque. In multi-drive systems, it is utilised in place of the mechanical differential. The inner wheels describe a smaller turning radius than the outer wheels, therefore while cornering, they rotate at different speeds. The electronic differential controls the power to each wheel so that all wheels receive the necessary torque by utilising the steering wheel command signal, throttle position signals, and motor speed signals. The PID control for each wheel motor serves as the foundation for the proposed control framework. Following that, the PID Control system is assessed in a Matlab/Simulink environment.

The advantages of the electronic differential include replacing the mechanical differential and mechanical transmission with more effective, lightweight, and tiny electric motors that are connected directly to the wheels utilising a single gear reduction or an in-wheel motor. EV differential:

The majority of electric vehicles only have one electric motor. As with an engine-driven vehicle, the drive from this motor must be transmitted to the wheels via a differential in the drive axle.
Tesla produces a four-wheel drive dual-motor Model S with one motor driving the front wheels and the other driving the back wheels. Due to this, two differentials—one for each axle—are required. It is possible to have two or four distinct motors, each driving a wheel separately. Since there is no mechanical connection between the wheels in this design, a differential is not necessary.

Charging

We must first assess the needs of the vehicles we are attempting to accommodate and the batteries they employ. Energy storage needs range from 0.5 kWh to 50 kWh, and current carrying capacity ranges from 20 A to 200 A, necessitating chargers designed specifically for the applications.

Whether via a standard socket outlet or, more recently, from a purpose-built DC charging station, chargers deliver a DC charging voltage from an AC source. The techniques for managing the charge and safeguarding the battery against over-voltage, over-current, and over-heating are of utmost importance. These charging features are built within and specific to the battery.

Electric bike chargers are often discrete, inexpensive devices. They are typically not placed on the bike to reduce weight, and charging occurs at home. Only the relatively low power bike batteries can be charged with their power handling capacity, making them completely unsuitable for use in passenger cars.

In most cases, passenger car chargers are positioned inside the vehicle. This is due to the possibility of using the vehicle far outside of the confines of the range provided by a single battery charge. They are required to bring the charger on board the vehicle due to this. A typical household electrical socket-outlet can be used for charging at home, but the amount of power available is quite low, and charging takes a long time—up to ten hours or more, depending on the size of the battery. This is not necessarily a problem because charging often takes place at night, but it might be if the car is not at its home base. Most automobiles are equipped with a greater power charging option that may be used in commercial settings or with a higher power residential installation, and such low power charging is typically employed in emergencies. This greater power facility is often implemented using a three-phase electricity supply.

Commercial electric vehicles offer more possibilities, but they also require larger batteries and higher power charging stations to meet reasonable charging times. Many of them adhere to predetermined delivery routes that are only a short distance from the base, and they all return to the base at night. Off-board charging is feasible in these circumstances, reducing the vehicle's weight and interior volume. These programmes can be modified to include battery swapping capabilities. Each vehicle may have two batteries, one of which is charged and the other of which is in operation. This has the potential to increase a vehicle's practical range when employed in long-distance shuttle applications. Each time it travels, the car drains the battery, picking up a fully charged one at the destination and leaving the depleted one to be recharged in preparation for the next trip. However, each vehicle under this shuttle option requires three batteries.

The majority of modern EV applications employ lithium-ion batteries, which are replacing the nickel metal hydride batteries that were used in early HEVS because they can store more energy and produce more power. Due to this, only Lithium-ion batteries are supported by the majority of EV chargers.

 

Charging Stations:

 

The energy is merely sent to the car by charging stations, typically in the form of a high voltage AC or DC source. They typically lack the capabilities of a charger, which must convert electrical energy into a form suitable for direct application to batteries. As can be seen from the broad spectrum of possible users mentioned above, the EV community need a variety of power supply alternatives. Three general power levels have been established, however a very wide range of possibilities are possible within these levels to take into account the various existing power grid standards of the national energy generating utilities.

 

Single Phase is considered Level 1

 

grounded receptacles are used with alternating current (AC) in household applications.
When using Single or Three Phase Alternating Current (AC) Sources from 208-240V at up to 80 Amps, Level 2 can provide up to 20 kW of power.
Direct Current DC charging, sometimes known as "fast charging" is level 3. Level 3 chargers produce extremely high Currents of up to Amp voltages up to 600 Volts, producing a maximum power of 240kw, in order to achieve very quick charging periods.

 

The Charger:

 

Every charging system uses the grid's AC electricity to convert it to DC power at the proper voltage for charging the battery. Except for bicycles, Level 1 and Level 2 chargers are totally integrated into the vehicle in EV applications. However, with Level 3 charging systems, the vehicle's onboard charger and the charging station perform different duties.

 

Level 1 and Level 2 Chargers:

 

The charger acts as the power conditioning device, which contains the AC to DC conversion, the power management unit, which transmits a changeable DC voltage to the battery, and other filtering functions, in low power, level and level applications. The battery and the battery management system are closely related (BMS). It monitors the crucial battery operating parameters of voltage, current, and temperature, regulates the charging rate to deliver the required constant current constant voltage (CC/CV) charging profile, and activates the protection circuits if the battery's operating limits are exceeded, isolating the battery as required. e and might just include a circuit interrupting device and a ground fault detection device (ClD). Level 1 charging can be utilised with a single-phase AC power outlet for private, domestic installations and is not subject to invoicing or verification. Unless charging is installed at home or provided as a free service in the workplace or shopping centre, the charger will likely need additional intelligence to communicate with the charging station to verify that the use is permitted to draw power from that particular source and to enable it to bill the customer for the energy transferred. As with many Level 2 installations, the charger is made to function with public charging stations.

 

The grid can supply either single phase or three phase AC electricity to level 2 charging stations. The Level 1 and Level 2 self-contained systems allow the charger the ability to connect to many AC power sources.

 

The operation of Level 3 chargers is identical to that of Level 1 and 2, however due to the extremely high power levels used, the AC/DC conversion, power conditioning, and control circuits grow significantly in size and cost, necessitating the use of expensive, heavy-duty components. Instead of the charger, the charging station makes more sense for performing these tasks so that multiple people can share the equipment. This enables significant cost and weight savings in the vehicle's onboard charger, and more effective designs for the charging station may be feasible with a larger budget. Since power control is not implemented within the battery in this situation, the BMS must interact with the charging station to regulate the voltage and current given to the battery.s no influence over how the vehicle's batteries are charged. That is what the battery management system and charger on the car itself are for. This control is provided by the charger through the CAN Bus, which relays its requests to the charging station. The charger and BMS are also in charge of controlling safety features for separating the battery and safeguarding the passengers of the vehicle.

The charging station will cost more even though moving some of the traditional charger functions within it allows for cost reductions in the vehicle. Currently, level 3 charging stations range in price from 15 lakh to 35 lakh INR (about $20,000 to $50,000). Additionally, there are expenses associated with providing grid connection. They can not easily be linked to the grid anywhere because each station requires a lot of power—up to 240 kWatts. The utility that produces the power must offer a separate supply line that can deliver the extremely high Currents required.

 

Today marks ten years since a jetpack lowered NASA's Curiosity rover on Mars, beginning the SUV-sized explorer's search for proof that Mars once had the conditions necessary to host microscopic life. What is Curiosity's trick for  staying active at the ripe old age of ten? Of course, a team of hundreds of committed engineers working both locally at JPL and remotely from home.

Battery technology 

The State of Charge (SOC)

 

The SOC is defined as the available capacity stated as a percentage of some reference, often its present capacity (i.e., at the most recent charge discharge cycle), however this ambiguity can cause misunderstanding and mistakes. It is not often an absolute measurement of the energy remaining in the battery in Coulombs, kWh, or Ah, which would be less perplexing. Instead of the cell's actual capacity, the rated capacity of a new cell should be the preferable SOC reference. This happens as a result of the cell's capability steadily declining with age. In this circumstance, even if the cell were completely charged, the SOC would only be 80% of the claimed capacity. For instance, when the cell nears the end of its life, its real capacity would be approaching just 80% of its rated capacity. Further reductions in effective capacity are caused by temperature and discharge rate effects. If the user relies on the SOC prediction as he would in a genuine gas gauge application in an automobile, this discrepancy in reference points is crucial.

Unfortunately, rather than the rated capacity, the SOC measurement reference is frequently defined as the cell's current capacity. In this scenario, a fully charged cell that is getting close to the end of its useful life could have a S0C of 100% but only have an effective capacity of 80% of its rated capacity, necessitating the application of adjustment factors to the estimated capacity in order to compare it to its rated new capacity. In order to avoid the difficulty of calculating and accounting for the age-related capacity modifications, which are simply ignored, using the present capacity as opposed to the rated capacity is typically a design shortcut or compromise.

 

It would be the same as gradually diminishing the gasoline tank's capacity over the course of a vehicle's lifespan without the driver being informed if the SOC estimate was based on the battery's current capacity rather than its rated capacity when it was new. Ageing and environmental conditions must be taken into consideration if a precise estimation of the charge left in the battery is needed.

It suffices to know a cell's S0C in relation to the other cells in the battery chain for cell balancing applications. The ageing and environmental changes, which apply to all cells equally, may be disregarded for this purpose since all the cells will have been subject to the same effects during their existence.

 

SOH (State of Health): 

 

The State of Health is a "measurement" that illustrates a battery's overall health and capacity to produce the required performance as compared to a brand-new battery. It considers variables like self-discharge, internal resistance, and charge acceptance. It assesses the battery's capacity over the long run and provides a "indication," rather than an exact measurement, of how much of the battery's possible "lifetime energy throughput has been used up so far and how much is still available. It can be compared to the "odometer" display feature on a car, which shows how many miles have been driven since the car was new. A battery's performance or "health" tends to steadily decline over the course of its lifespan owing to irreversible physical and chemical changes brought on by usage and ageing, until finally the battery is no longer functional or dead.

In contrast to the SOC, which can be measured by checking the battery's actual charge, the SOH is not precisely defined. It is a subjective measurement since different individuals generate it from several quantifiable battery performance measures and interpret it in accordance with their own set of guidelines. Rather than being a measurement, it is an estimation. This allows comparisons between estimates created with various test tools and methodologies trustworthy, which is OK as long as the estimate is founded on a consistent set of principles.

Due to the fact that they only provide fresh batteries, battery manufacturers do not define the SOH. Only when batteries have begun to age, whether on the shelf or after being put into operation, does the SOH apply to them. Therefore, test equipment makers or users must specify the sOH definitions.

 

DoD (Depth of Discharge):

 

The depth of discharge (DoD) of a battery is the proportion of the battery's total capacity that has been drained. For instance, the DoD is around 96 percent if you have a Tesla Powerwall that can store 13.5 kilowatt-hours (kWh) of power and you discharge 13 kWh. A battery's lifespan will decrease the more it is charged and drained. A battery should normally not be completely discharged because doing so significantly reduces the battery's usable life. Many battery manufacturers offer a maximum DoD that is ideal for the battery's performance.

 

You should not use more than 8 kWh of a 10 kWh battery without recharging, for instance, if the battery's manufacturer advises a maximum DoD of 80 percent. You can see why DoD is crucial to take into account: a higher DoD enables you to utilise more of the battery's stored energy. These days, the DoD of many contemporary lithium ion batteries is advertised as being 100%.

The number of charge/discharge cycles that your battery will go through throughout its usable life, or "cyclic life," depends on how much of its capacity you typically utilise. The batteries will last longer if you constantly discharge them at a lesser percentage than they would if you often drain them to their maximum DoD. A battery could have 15,000 cycles at a 10% DoD but only 3,000 cycles at an 80% DoD, for instance.

 

Battery recycling 

 

Only a tiny percentage of electric-drive cars have reached the end of their useful lifespan since they are still a relatively new technology in many regions. Due to the lack of post-consumer batteries from electric vehicles, the infrastructure for recycling batteries is quite small. The market for recycled batteries might grow as electric-drive vehicles become more prevalent. When a battery reaches the end of its useful life as well as during manufacture, widespread battery recycling would prevent dangerous elements from entering the waste stream. The development of battery recycling techniques that minimise the effects of utilising lithium-ion and other types of batteries in automobiles is now under work. However, not every recycling procedure is the same:

 

Smelting: Salts or basic elements are recovered by smelting procedures. These procedures are now in use on a wide scale and are compatible with a variety of batteries, including nickel-metal hydride and lithium-ion. High temperatures are used to smelt organic materials, such as the electrolyte and carbon anodes, which are then burnt as fuel or reductant. The precious metals are retrieved and transported for refining so that the finished product is appropriate for any use. The slag, which is currently utilised as an ingredient in concrete, contains the additional elements, including lithium.

 

On the other extreme, certain recycling procedures directly recover materials that are suitable for batteries. Diverse physical and chemical procedures are used to separate the components, and all active substances and metals can be recovered. Direct recovery is a low-temperature procedure that uses less energy.

 

Middle processes: This third kind of process is halfway between the first and second extremes. In contrast to direct recovery, these procedures may take different types of batteries, but they also recover materials further along the production line than smelting does.

 

Recovery of high-value materials is frequently hampered by the need to separate the various battery components. Therefore, in order for electric-drive cars to be successful from a sustainability perspective, battery design that takes into account disassembly and recycling is crucial. Standardising battery types, components, and cell architecture would help make recycling simpler and more affordable.

Classification Of EV

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There are four different kinds of electric cars on the market:

 

Battery Electric Vehicles (BEVs)

BEVs are also referred to as all-electric cars (AEV). Electric drivetrains driven solely by batteries are used in BEV-based electric vehicles. The enormous battery pack that houses the electricity needed to power the car may be charged by hooking it into the power grid. One or more electric motors are then powered by the fully charged battery pack to drive the electric vehicle.

Main Components of BEV:

Drive train, battery, control module, and electric motor

Working Principles of BEV:

The DC Battery's energy is transformed into AC to power the electric motor. A signal is transmitted to the controller as soon as the accelerator is depressed. By altering the frequency of the AC electricity delivered to the motor by the inverter, the controller modifies the speed of the vehicle. The motor then joins and, via a gear, causes the wheels to turn. The motor transforms into an alternator and generates electricity when the brakes are applied or the electric vehicle is slowing down, sending it back to the battery.