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Now that we know the different kinds of electric vehicles and all the different ways they can be powered! let's take a deeper look at what a Battery electric vehicle is made up of.

Battery Electric Vehicles (BEVs), compared to classic internal combustion engine (ICE) vehicles, are fairly simple and easy to operate. The simplest powertrain architecture consists of a high voltage battery, an electric motor with a power electronics controller and a single-speed gearbox. BEVs are also called pure electric vehicles, in order to distinguish them from Hybrid Electric Vehicles (HEVs), which have a hybrid powertrain (internal combustion engine plus electric motor).

We will be focussing on Battery Electric vehicles for now and their components! more specifically only the powertrain part of an EV.

A vehicle's powertrain – the “in simpler terms, the go parts of your vehicle” – consists of the Motor, transmission, and drivetrain (the components that get the engine's power to the wheels and down to the ground)

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There are many types of Battery electric vehicles! or BEVs in short, here's a list.

• Neighbourhood electric vehicles: small vehicles, very low range (less than 25 km)
• City electric vehicles: small vehicles, low range (less than 50 km)
• Performance battery-electric vehicles: these are the equivalent of the classic passenger vehicles, with the range between 100 and 600 km

Most of the BEV architecture have the powertrain on the front axle and the high voltage battery in the floor, between the front and rear axle. This configuration gives plenty of volume for the passenger area and boot/trunk.

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The high voltage battery, being the heaviest electric component of the vehicle, is positioned very low, in the body floor. This gives another advantage, a very low centre of gravity, which improves the overall stability of the vehicle.

Here is an example of a Jaguar I-pace Electric car, completely stripped! you can see the inner battery placements and motor placements.

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A. The Batteries (The storage component)

Schematic build-up of an automotive battery system (Courtesy of Samsung SDI)

let's take a look at the main component of an EV, i.e the Battery or the storage component.

We use the word "storage component" here because electric vehicles can either be powered by batteries or via hydrogen fuel cells! and both of these store energy in the vehicle!

The energy storage component in a pure battery electric vehicle is the high voltage (HV) battery. The nominal voltage is, in most of the cases, between 360 and 450 V. A BEV has also a low voltage battery, the usual 12 V battery, which is used as a power supply for the auxiliary equipment (lightning, multimedia, etc.).

The battery is the key component of the EVs because:

• The range of the vehicle depends almost entirely on the HV battery,
• It is the heaviest electrical component,
• It is the most expensive electrical component.

There are different types of high voltage batteries, the chemistry being the main distinguishing factor. The most common HV batteries for BEV are the lithium-ion batteries. These have also different “flavours”:

• Metal-oxides (e.g. Lithium Manganese Oxide, LiMn2O2)
• Phosphates (e.g. Lithium Iron Phosphate, LiFePO4)

Usually in automotive applications! phosphate lithium-ion batteries are more suitable because they are safer in terms of chemical and thermal hazards.

The Battery management system

Battery Management Systems are the brains behind battery packs. They manage the output, charging and discharging and provide notifications on the status of the battery pack. They also provide critical safeguards to protect the batteries from damage.

A battery pack usually consists of several individual cells that work together in combination. Ideally, all the cells in a battery pack should be kept at the same state of charge. If the cells go out of balance, individual cells can get stressed and lead to premature charge termination and a reduction in the overall life of the battery.

The cell balancers of the battery management system, extend the life of the battery by preventing this imbalance of charge in individual cells from occurring.

The second most important function performed by a battery management system is energy management.

The key to energy management is "Coulomb counting." For example, if you have 5 people in a room and 2 people leave you're left with three if three more people enter you now have 6 people in the room. If the room has a capacity of 10 people, with 6 people inside its 60% full. A battery management system tracks this capacity. This state of charge is communicated to the user electronically through a digital bus

Battery management systems for smaller electric vehicles also include an embedded charger consisting of a control device, an inductor (which is an energy storage device), and a discharger. The control device manages the charging algorithm.

For lithium-ion cells, The ideal charging algorithm is constant current and constant voltage.

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B. The Drivetrain

Image (3): Renault Zoe powertrain Credit: Renault

Looking at Image 3, we see the complete powertrain of an electric vehicle!

1. Power electronic controller. - Explained in detail in Image 4
2. Stator. (Part of a motor) - Explained in detail in Image 5
3. Rotor. (Part of a motor) - Explained in detail in Image 5
4. Single-speed gearbox and differential.

1. Power electronic controller.

Image (4): Renault Zoe power electronics Credit: Renault

Looking at Image 4, we see an example Power electronic controller of an electric vehicle! Here are the parts highlighted

1. Rectifier
2. DC-DC converter
3. Input filter
4. Inverter

The power electronics control module has several subsystems,

Each subsystem is responsible for a control function. When the vehicle is charged from a home electrical grid (e.g. 220 V)

1. The rectifier converts the alternating current (AC) into direct current (DC), which is fed into the high voltage battery.

2. The DC-DC converter is responsible with the lowering of the high voltage (e.g. 400 V) to the low voltage network (12 V).

3. The inverter controls the electric machine speed and torque by converting the direct current from the battery into alternating 3-phase current for the electric machine.

4. When the vehicle is in energy recuperation phase (braking) the inverter is doing the opposite conversion, from 3-phase AC to DC.

5. The input filter reduces the electric noise or interference generated during regenerative braking. when energy is fed back into the batteries via the motors.

Understanding motors

The torque is provided by an electric machine. In passenger vehicle applications there are mainly two types of electric motors already in use,

• Permanent magnet machines.
• Inductance machines.

It’s more appropriate to call them electric machines instead of motors because they can also generate electrical energy during vehicle braking. This mechanism is called energy recuperation/regeneration.

You will learn more about motors in the coming chapters, but for now, the basic function of electric machines is to produce torque and generate energy.

When the vehicle accelerates, the electric machine takes electrical energy from the HV battery and produces torque. This is the motor phase. When the vehicle is braking, the kinetic energy of the vehicle is used by the electric machine to produce electrical energy. This is the generator phase.

Let's learn more about Electric Motors in the next chapter. click next target to continue