Get Basics of Electromobility Guide for Volkswagen Touareg SUV Second Generation (2010-2018)

Basics of Electromobility

The topic of “electromobility” basically refers to all vehicles that are driven by means of electrical energy. This

includes both battery-powered vehicles and hybrid vehicles (full hybrid vehicles) or vehicles with a fuel cell.

Classification of electric vehicles

Electric vehicles are categorised primarily according to concept and their names indicate how the electrical energy

is supplied:

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Internal-combustion

engine

Hybrid drive

Electricity generated in the vehicle

Petrol/diesel

Conventional

petrol/diesel

vehicles

Full hybrid (HEV)

Like mild hybrid plus: 

Micro hybrid

Mild hybrid

Like micro hybrid plus: 

The electric components

are only used for the start/

stop function.

The electric motor supports

the combustion engine. 

Purely electric driving is

possible.

The electric motor supports

the combustion engine. 

It is not possible to drive

exclusively with electricity. 

Regenerative braking

The Touareg 2011 is the first

production vehicle with electrical

hybrid drive from Volkswagen.

It is among the full hybrids.

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Terminology

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Emission-free vehicles that do not release exhaust gases into the environment during operation are also called

“zero-emission vehicles” (ZEV).

Battery-powered vehicles that are moved exclusively by an electric drive are also called “battery electric vehicles”

(BEV). The energy required to run the vehicle is supplied by a high-voltage battery that is charged with the mains.

The “Electric Vehicle Index” (EVI) measures the development of electromobility. It uses nine different criteria to

evaluate both the market for electric cars and the production in different industrial nations. The current order of

investigated countries is: USA, France, Germany, Italy, Japan, China, Korea, Spain, United Kingdom, Denmark,

Portugal and Ireland.

Hybrid drive

Electric driving

Charging with electricity from the mains

Electric vehicles with fuel

cell (FCBEV) 

Moved only by an electric

drive. 

The energy for operation is

produced by a fuel cell. 

It is fuelled with hydrogen.

Hybrid with 

range extender (RXBEV)

Like BEV plus: 

Electric vehicles with 

battery (BEV)

Moved only by an electric

Plug-in hybrid (PHEV)

Like HEV plus: 

drive. 

Plug-in hybrids have high-

voltage batteries that can

also be charged externally

via the electrical mains.

The range is extended by a

combustion engine that

generates electrical

energy for the electric

motor.

The energy required to run

the vehicle is supplied by a

high-voltage battery that is

charged with the mains.

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Overview of the abbreviations used:

BEV - Battery Electric Vehicle

HEV - Hybrid Electric Vehicle; full hybrid vehicle

FCBEV - Fuel Cell Battery Electric Vehicle; battery-powered vehicle with fuel cell

PHEV - Plug-in Hybrid Electric Vehicle; vehicle with full hybrid drive and external charging facility

RXBEV - Range Extender Battery Electric Vehicle; battery-powered vehicle with additional generator drive 

to increase range (range extender)

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Basics of Electromobility

The main components of an electric vehicle

The whole drive system in electric vehicles includes:

-

High-voltage battery with control unit for battery regulation and necessary charger

Electric motor/generator with electronic control (power electronics) and cooling system

Gearbox incl. differential

Brake system

High-voltage air conditioning for vehicle interior

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Electric motor/generator

Gearbox with differential

Power electronics

1

2

3

High-voltage lines

4

High-voltage battery

5

Electronics box with control unit for battery regulation

Cooling system

6

7

Brake system

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High-voltage air conditioner compressor

High-voltage heating

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10

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12

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Battery charger

Charging contact for external charging

External charging source

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The electric motor/generator

The term electric motor/generator is used instead of alternator, electric motor and starter. In principle, any electric

motor can also be used as an alternator. When the electric motor/generator is driven mechanically, it supplies

electrical energy as an alternator. When the electric motor/generator is supplied with an electrical current, it works

as a drive. Electric motors/generators used for propulsion are water-cooled. Air cooling would also be possible,

however.

In full hybrid vehicles (HEV), the electric motor/generator also functions as the starter for the combustion engine.

Three-phase motors are often used as the electric

motor/generator. A three-phase motor is powered by

a three-phase alternating current. It works with three

coils that are arranged in a circle around the rotor to

form the stator and are each electrically connected to

one of the three phases. Several pairs of permanent

magnets are located on the rotor in this synchronous

motor. Since the three coils are supplied sequentially

with a current, toher they generate a rotating

electrical field that causes the rotor to rotate when the

electric motor/generator is used to drive the vehicle.

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When used as an alternator, the movement of the

rotor induces a three-phase alternating voltage in the

coils that is transformed into a direct voltage for the

high-voltage battery in the power electronics.

Normally so-called “synchronous motors” are used in

vehicles. In this context, the term “synchronous” means

“running in synchronism” and refers to the ratio of the

rotation speed of the energised field in the stator coils

to the rotation speed of the rotor with its permanent

magnets.

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Electric motor/generator (1), rotor (2), stator (3), power

electronics (4) and high-voltage battery (5)

The advantage of synchronous motors compared with

asynchronous motors is the more precise control of

the motor in automobile applications.

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Basics of Electromobility

Strengths of the electric motor/generator

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The electric motor/generator is very environmentally compatible thanks to the lack of noise and harmful emissions.

The electric motor/generator responds quickly, has good acceleration figures and a high level of efficiency. 

In contrast to combustion engines, electric motors supply their nominal power steplessly over a broad rev range.

The maximum torque is available even at low revs (i.e. when pulling away) and only falls away once the motor

reaches very high speeds. As a result, neither a manually operated gearbox, an automatic gearbox nor a clutch

are required in principle.

The direction of rotation of an electric drive motor is freely selectable. It can therefore turn clockwise to move the

vehicle forwards and anti-clockwise to reverse it.

Electric motors start automatically. A separate starter motor is not required. Electric motors have a simpler design

and have considerably fewer moving parts than internal-combustion engines. Only the rotor with its permanent

magnets rotates inside the electric motor/generator. There are no vibrating masses as in internal-combustion

engines. Oil changes are not necessary as lubricating oil is not required. Consequently electrically powered

vehicles are low-maintenance in terms of their drive unit.

The high-voltage battery

The battery is the heart of electric vehicles. The high-

voltage battery is charged, for example, externally via

High-voltage battery

a mains socket. It supplies its direct voltage to the

power electronics. 

The power electronics convert the direct voltage into

an alternating voltage and supply the electric motor/

generator with three electrical phases via the three

wires (U, V and W). The electric vehicle starts moving.

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The high-voltage battery at the rear of a high-voltage

vehicle

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Explanation of terms

The term accumulator is sometimes used for rechargeable batteries. Originally batteries and accumulators were

two different types of storage media for electrical energy. Today, the term rechargeable battery is generally used.

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Battery

Rechargeable battery/accumulator

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Rechargeable battery

Battery

Charging source

In its original meaning a battery refers to a storage

medium for electrical energy that cannot be

recharged. The battery is made up of so-called

primary cells. 

A rechargeable battery is made up of secondary cells.

The most familiar rechargeable battery is the lead-acid

battery that is commonly used as a car battery.

Electrical energy is also stored in a secondary cell. As

with non-rechargeable batteries, the available quantity

of energy is determined by the number of secondary

cells that are connected to each other. The chemical

reaction that occurs here is easy to reverse, however,

in contrast to the primary cell. This means you can

recharge the discharged battery with energy again

with the aid of a charger.

The total voltage depends on the number of and

voltage of the individual cells.

A primary cell releases the chemical energy it has

stored as electrical energy in a chemical reaction. 

The original charge state cannot be restored by

means of electrical recharging.

Did you know?

The cycle stability of laptop batteries and mobile telephone batteries is around 500 cycles. This means that these

batteries can be charged from flat to full up to 500 times due to their technical configuration. After that, these 

batteries only have approximately 50% of their original capacity. The capacity is given as the “State of Capacity”

(SOC). The SOH (State of health) indicates the “health” of the battery.

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Basics of Electromobility

In the following section, the term high-voltage battery (HV battery) is used for the rechargeable battery that

supplies electricity to the electric motor/generator.

The typical electrical data for a high-voltage battery, like the nominal voltage, the efficiency and the energy

density, depend on the type of chemical substances that are used for the internal configuration of the energy

storage medium.

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Energy density

This figure indicates the performance of a battery related to its weight. The higher the energy density, the more

energy can be stored and then released again to perform a task. The unit of energy density is watt hours per

kilogram [Wh/kg] and is calculated from the electrical work [Wh] and the weight [kg] of the battery. The range of

an electric vehicle can be determined from the energy density.

Example of high-voltage battery weighing 85kg and supplying 288volts and a current of 6.5amperes: 

The electrical power (P) is equal to the electrical voltage (U) times the electrical current (I); P = U x I. 

U = 288volt and I = 6.5amperes 

P = 288V x 6.5A = 1872VA; 1VA corresponds with approx. 1W (unit watt) 

P = 1872W or 1.872kW (unit kilowatt) 

The electrical work is equal to the electrical power multiplied by the time. 

This high-voltage battery can therefore perform electrical work of 1872Wh (watt hours) over an hour (1h). 

Calculation of energy density: 1872W x 1h : 85kg = 22.02 Wh/kg

Life

The life of a battery is described by the cycle stability. The cycle stability of a high-voltage battery is set at a total of

3,000 cycles over a period of 10 years, i.e. 300 cycles/year. On the basis of this property, so-called “automotive

batteries”, i.e. batteries for use in a high-voltage vehicle, cannot be compared with the “consumer batteries” used

in laptops or mobile telephones.

Efficiency

The efficiency of a rechargeable battery is given as a percentage. In simple terms, the efficiency indicates how

much of the energy that is invested into charging can be made useful again when the battery is discharged. 

A battery can never have 100% efficiency since a small part of the charging energy is released in the form of heat

(charge loss).

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Functional principle

The function of a battery is based on the fact that

metals have different levels of electrode potential. In

this context, precious means that two metals like zinc

and copper differ in their chemical ability to release

electrons. The elements can be arranged in a so-

called electro-chemical series on the basis of this

chemical property. Zinc releases electrons easily. This

means it is easy to oxidise. Copper does not give up

electrons for a chemical reaction so easily. This means

it is more difficult to oxidise.

Excerpt from electro-chemical series of metals: 

Al - Aluminium

Zn - Zinc

Fe - Iron

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Cu - Copper

Au - Gold

If you hang a zinc rod and a copper rod in a suitable

electrolytic solution in separate containers, both

metals will release ions into the electrolytes at

different rates and will leave electrons in the metal

rod. In one container there are many positive zinc

ions in the solution and many electrons in the zinc rod.

In the other container, there are only a few positive

copper ions in the solution and a few electrons in the

copper rod. If both containers are now connected to

each other by an ion bridge, a charge exchange will

occur due to the different ion concentrations. Due to

the high excess of electrons in the zinc rod, it will act

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Schematic diagram of a battery

as an anode while the copper rod forms the cathode. A voltage can be measured between the two due to the

different electron concentrations. If you connect both electrodes with a conductor, the electrons will flow from the

anode to the cathode. This set-up is generally called a galvanic cell and is the simplest form of a battery. If energy

is released from the battery, the anode is the minus pole. In rechargeable batteries, the same electrode can

alternately work as the anode or cathode depending on whether the battery is being charged or discharged.

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Basics of Electromobility

Types of rechargeable battery

The different types of rechargeable batteries are distinguished by the materials used for the electrodes and

electrolytes. The most common rechargeable batteries are lead-acid, nickel-cadmium, nickel-metal hydride and

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lithium-ion batteries. They will be described briefly in the following section and their main features will be

presented.

Lead-acid battery

The traditional 12V vehicle electrical system battery. Plates made from lead and lead/lead oxide are used as

electrodes. Sulphuric acid is the electrolyte.

Lead-acid batteries require maintenance. This means that distilled water needs to be topped up to ensure the

required electrolyte liquid level. Lead-acid batteries are not very suited to powering purely electrically driven

vehicles because they are very heavy in relation to their volume and would thus take up a large space in the

vehicle. This would reduce the load capacity of such a vehicle.

A lead-acid battery can in some cases lose a large part of its capacity after just six years. 

If damaged, electrolyte (acid) can leak.

Nickel-cadmium battery

Cadmium (Cd) and a nickel compound are used for the electrodes in these batteries. Potassium hydroxide is used as

the electrolyte. Therefore this type is also called an alkaline battery. They have a higher energy density than lead-

acid batteries and are less prone to damage and electrolyte leaks. Nickel-cadmium batteries are subject to a

memory effect. This type of battery can cope with deep-discharging or overcharging only to a certain extent. 

It becomes less efficient as a result. Cadmium and cadmium compounds are poisonous.

Nickel-metal hydride battery

These batteries use a nickel compound and a compound of another metal for the electrodes. Potassium hydroxide is

also used as the electrolyte. They have a higher energy density than Ni-Cd batteries and are relatively resistant to

damage.

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Even if a memory effect does not occur to the extent of the Ni-Cd batteries, these batteries do also lose efficiency

over the course of their life. This loss in efficiency is reversible to a certain extent. One advantage of the nickel-

metal hydride batteries: they do not contain any poisonous heavy metals like lead or cadmium. The electrolyte is

stored in the battery in solid form. Only a few droplets will escape even if the housing is broken.

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Lithium-ion battery

This is one of the newer battery generations that uses lithium compounds for its internal set-up. Various lithium-

metal oxides and graphite are used as electrodes. Different solvents for lithium salts form the electrolyte. Lithium-

ion batteries contain only a small amount of water and do not have a memory effect. Compared with the nickel-

cadmium batteries, they have more than twice as much energy density. This means that this battery type requires

less space in an electric vehicle leaving more room for the occupants and the luggage compartment.

Lithium (Li) is a chemical element. The word lithium originates from the Greek word “lithos” meaning stone because

it was discovered in stone in 1817. Like sodium, lithium belongs to the alkali metals due to its chemical behaviour

and is considered to be a light metal due to its low density. After hydrogen and helium, it is the third lightest

chemical element.

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0.534g/cm (in comparison: H O = 1g/cm )

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Density

In form of lithium-carbonate (Li CO ); 

Usage in batteries

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approx. 3 kg of pure lithium are required to build a battery delivering 20kWh.

Quick charging due to low ion radius. 

No memory effect

Advantages

If lithium-Ion batteries are exposed to high temperatures, decomposition processes can result in the

battery. This can lead to fire or the emission of dangerous gases. Therefore you should always

observe the manufacturer's warning information when working with these batteries.

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Basics of Electromobility

Fuel cell

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Hydrogen tanks

Electric drives

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High-voltage battery

Fuel cell

The fuel cell is a development for alternative drives. Using the principle of energy conversion, the process that

takes place in the fuel cell to produce electrical energy from chemical energy is similar to a combustion engine. The

energy conversion from “fuel” to output is much more direct with the fuel cell. For this reason, the efficiency of a

fuel cell is greater than a combustion engine. You can thus look at a fuel cell as a motor.

In a combustion engine, the chemical energy that is contained in the fuel molecules is converted into kinetic energy

by combustion. This can then be used to drive a gearbox or supply an alternator. In a combustion engine, a large

amount of energy is converted into heat due to friction. In the fuel cell, chemical energy is converted into electrical

energy. In contrast to a combustion engine, no additional alternator is required to generate electrical energy. The

fuel used is industrially manufactured hydrogen that is converted into water in the fuel cell with the oxygen from

the air. Hydrogen does have less energy than the hydrocarbons contained in fuel, but it is easier to combust and

there are only small losses in the energy conversion. Furthermore there is no combustion residue or harmful

exhaust gases as with combustion engines.

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Structure of a fuel cell

A hydrogen/oxygen fuel cell is a special form of

galvanic cell. The main components are two

electrodes (1) e.g. nano tubes made from carbon with

a platinum coating that serves as a catalyst (2) and a

special membrane (3). Various compounds can be

used as the electrolyte. The special membrane is gas

tight, non-conductive for electrons and permeable for

protons (hydrogen nuclei without electrons). The

oxygen (O₂) comes from the ambient air and does not

need to be filled specially.

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2

1

Schematic diagram of a fuel cell

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A

C

How it works

Hydrogen (H₂) and oxygen (O₂) are sent separately

to the two electrodes: the hydrogen to the anode (A)

and the oxygen to the cathode (C). The hydrogen

releases two electrons with the help of the catalyst

and splits into two positively charged hydrogen nuclei

(protons). These can penetrate the membrane and

pass through it because there are fewer protons in the

electrolyte on the other side of the membrane

(cathode side) than on the anode side (diffusion). The

oxygen absorbs electrons catalytically at its electrode

and then immediately reacts with the free hydrogen

protons to form water (H₂O).

Electricity is generated by burning hydrogen.

If you connect the anode and cathode to each other electrically, a current will flow due to this reaction (4). 

Electrical energy is produced directly in the fuel cell from the conversion of hydrogen into water.

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Basics of Electromobility

Further high-voltage components

Inverter

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The inverter is also known as transducer or DC/AC converter. It has the job of converting the 3-phase alternating

voltage of the alternator into a direct voltage for charging the battery. The three phases of the alternating voltage

are first commutated and then smoothed in order to obtain an almost constant direct voltage. In the reverse case,

the direct voltage from the battery is converted into a 3-phase alternating voltage when the electric motor is

driven.

DC/DC converter

A DC/DC converter is basically a transformer. It is used to transform the high direct voltage from the high-voltage

battery into a corresponding low charge voltage for charging the 12V onboard supply battery. DC/AC converters

and DC/DC converters are often combined with other electronic components of the high-voltage system in a power

electronics module.

Charging source/charging contact

A charger that is incorporated in the high-voltage system in the vehicle is also called an AC/DC converter. It

converts the alternating current supplied from the mains via the charging contact into a direct current since only

direct currents can be stored in batteries.

Charging with direct voltage (DC charging) is also possible. The supply of a direct voltage via a public electricity

system is complex, however.

High-voltage system

The high-voltage system is separate from the 12V vehicle electrical system with one exception. The DC/DC

converter is the only component that is connected to both electrical systems. All high-voltage lines are coloured

orange and are highly resistant to damage. They are further reinforced by an additional woven sleeve that is also

orange in colour. Electrical connectors for the high-voltage system are reverse polarity protected and colour

coded. The electrical consumers outside the high-voltage system (e.g. lights, steering, vacuum pump for brake

servo and cigarette lighter) are powered by the conventional 12V vehicle electrical system.

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Other high-voltage units

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In addition to the pure drive components, further units and components can be supplied with high voltage in high-

voltage vehicles. Examples are the air conditioning system and/or the heating and ventilation system. 

In high-voltage vehicles that are run without combustion engine, all units that are driven mechanically by the

combustion engine, for example, with a belt drive, need to be operated electrically. This does not necessarily have

to be done with the high voltage. Instead, the units can also be configured as 12V components that are supplied

via the 12V onboard supply (e.g. power steering pump, brake servo, ...). Units will be configured as high-voltage

components only if a high output is required, like with the air conditioner compressor. All high-voltage units are

marked with a warning sticker.

Gearbox

Pure electric vehicles (BEV) do not require the traditional gearbox with several speeds. The polarity of the electric

motor is simply reversed when you want to reverse the vehicle. This means that the direction of rotation of the

electric motor changes. This is done with a gear selector lever, which simply has the positions “Neutral”, “Forwards”

and “Reverse”. The speed can be regulated steplessly with the accelerator pedal. Full hybrid vehicles (HEV) and

plug-in hybrid vehicles (PHEV) still have a conventional gearbox. As a rule, these are not manual gearboxes, but

automatic or dual clutch gearboxes.

Brake system

In simple terms, an electric vehicle has two independent brake systems. One system is the traditional mechanical/

hydraulic brake system. The second brake system is formed by the electric drive motor as a “motor brake”. The

advantage of this “motor brake” compared with the combustion engine is that the energy released by the electric

motor/generator during braking and deceleration is recovered and fed into the high-voltage battery. This so-

called regenerative braking contributes to the high efficiency of the electric vehicles in particular in city traffic. 

At the same time, the wear of the vehicle brakes is reduced by the regenerative braking system.

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Basics of Electromobility

Drive train configurations

An electric vehicle is driven by at least one electric drive motor. It can be configured as a four-wheel drive vehicle

or with one drive axle. Further hybrid variants are also possible. These are described in SSP450 “The Touareg

Hybrid”.

The two main concepts are presented in the following section.

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drive with in-wheel motors

drive with just one electric drive motor in the central drive train

Drive with in-wheel motors

The following table provides an overview of the different drive train configurations with in-wheel motors.

Front-axle drive

Rear-axle drive

Four-wheel drive

2 in-wheel motors

4 in-wheel motors

Design

Features

The wheels are connected directly to the in-wheel

motors. Today, the in-wheel concept is used for

electric scooters, electric bicycles and electrical driven

wheel chairs.

-

No drive shafts are required

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-

No differential gearbox required

Disadvantages

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The unsprung masses in the wheel are greater

compared with the wheels on a conventional

vehicle.

Advantages

-

High mass of driven components (inertia and

torque of whole vehicle affected)

Independent vehicle concept required

Control is complex. Both electric motors need to

run synchronously.

-

Four-wheel drive technically possible.

The output axles of the in-wheel motors are

directly on the wheel.

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High efficiency of drive because there are hardly

any mechanical losses.

-

The combination with a hydraulic friction brake is

still necessary at present.

Possibility of regenerative braking.

There is limited space on the wheel.

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Drive with electric motor in central drive train

The following table provides an overview of the different drive train configurations for vehicles with one central

electric motor.

Front-axle drive

Rear-axle drive

Four-wheel drive

1x central electric motor and 1x central electric motor and 1x central electric motor and

two drive shafts

2 x central electric motors

and four drive shafts

two drive shafts

five drive shafts plus transfer

box

Design

Features

The electric motor/generator drives a gearbox, the

drive shafts and thus the wheels. In a pure electrically

powered vehicle, a reduction gearbox is sufficient.

Four-wheel drive can be achieved with a propshaft

from the front axle drive. Another possibility is to use

a second electric motor.

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Two drive shafts on each driven axle

A differential on each driven axle

Propshaft required

Advantages

Disadvantages

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Single-axle drive simple to design

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Output shaft of central electric motor/generator is

Four-wheel drive technically possible

Combination as hybrid drive (HEV / PHEV /

RXHEV) very much possible

not on the drive axles.

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Differential required

Reduction gear required

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Integration in existing vehicle concept is possible

Volkswagen is currently only using drives with a central electric motor/generator as the only drive or

in combination with combustion engines as hybrid drives. In-wheel motors are currently not used.

Future use in vehicles is conceivable, however.

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Basics of Electromobility for Your Volkswagen Touareg SUV Second Generation (2010-2018)

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