What are the components making up an EV powertrain?

With the increasing popularity of electric vehicles (EVs), more people are wondering what are the components making up an EV powertrain? Have you?

For over 100 years, internal combustion engines (ICE) have been the powertrain of choice for personal vehicles around the World. However, automobile manufacturers, politicians, and stakeholders are pushing to replace ICE vehicles with electric vehicles (EVs) as the vehicle of choice by automotive consumers in the future.  What are the components making up an EV powertrain?

The components making up the powertrain of ICE vehicles are common knowledge. Because of the novelty associated with ICE vehicles, there is still a lot of mystery in terms of what they entail.

While I have been a fan of cars, specifically ICE cars such as Porsche, Lexus, and BMWs, I have taken a great deal of interest in EVs, specifically, how EV powertrains can be implemented in automobiles designed for ICE powertrains.

What is a powertrain?

The collection of all the parts that propel your car forward is called the powertrain. The engine of your car generates power, which the powertrain then transfers to the wheels on the ground. Engine, transmission, driveshaft, axles, and differential are the main parts of a
powertrain.

What are the components making up and EV powertrain?

An ICE powertrain is made up of hundreds of moving parts. In contrast, an EV powertrain is estimated to consist of up to 60% fewer parts.

What are the main components of an EV powertrain?

The main components of an EV powertrain are the electric motor, battery pack, DC-AC converter, and onboard charger.

Battery pack – The battery pack, which is composed of many lithium-ion cells, stores the
energy required to power the car. Battery packs provide direct current (DC) output.

Electric motor – The electric motors convert electrical energy to mechanical energy,
which is then sent through a transmission to the wheels. Many EVs employ motor-generators that can also carry out regeneration.

DC-AC Converter – The battery pack’s DC energy is converted to AC and sent to the electric motor. A complex motor control system, also known as the powertrain electronic control unit controls the frequency and magnitude of the voltage supplied to the electric motor to manage speed and acceleration in accordance with the driver's instructions communicated by accelerating and braking.

On-board charger – The on-board charger converts AC received through charge ports to
DC and controls the amount of current flowing into the battery pack.

What are the secondary components making up an EV?

There are several secondary components in the form of hardware and software that make up a complete EV powertrain. They include:

Electronic Control Units (ECU) – ECUs facilitate data processing and sharing. They are essentially software programs connected with the powertrain components. Within an EV, several small ECUs each perform a specific task.

The primary ECUs used in EVs are:

Battery Management System (BMS) – The BMS monitors and reports the condition of the batteries and acts when a problem arises. A secondary goal is to monitor the efficient use of the batteries between other systems making up the EV powertrain, including sensors and other ECUs.

DC-DC Converter – A battery pack delivers electricity at a fixed voltage. The various
electrical systems making up an EV require electricity at different voltages. The DC-DC converter helps distribute power to different systems by converting the output power from the battery pack to the correct level for each system. This electricity is delivered through a
wiring harness.

Thermal Management System (TMS) – The TMS is responsible for maintaining the optimum operating temperature range for powertrain components.

Body Control Module (BCM) – The BCM is responsible for controlling and monitoring the
functions of electronic accessories such as power windows, mirrors, security, and vehicle access control.

Now, that we have discussed the primary and secondary systems making up an EV, how does an electric vehicle work? What types of electrical power does an EV utilize?

What is alternating current (AC) power?

AC is an electrical current, or flow of charge, that periodically changes direction, i.e., it alternates. AC power can be generated from renewable sources that use rotating generators, such as wind or hydropower turbines. AC can also be transported over long distances efficiently. This is why all of the world’s electricity grids use AC power, and why you can find AC power in your home and office.

What is direct current (DC) power?

DC always moves in a straight line and can be generated by renewable power technologies such as solar panels. Among other things, DC can be used for energy storage and LED lighting. Batteries store DC power, and though you may have never realized it, every time you charge your laptop, the charger converts the AC power from the grid into DC power for your laptop’s battery.

What is the relationship between AC and DC power?

In summary, the grid provides us with AC electricity, which is then transformed into DC power so that it may be stored in batteries, like the one used to power an EV. Solar power is also generated as DC power.

How do AC and DC charging work in an electric vehicle?

A charge to an EV is received in either the form of AC or DC power. However, an EV battery only stores DC power. The only difference between the two is where the conversion from AC to DC happens.

When you use a DC charging station, the conversion of the grid’s AC power to DC takes place inside the station itself, allowing DC power to flow directly into the battery. Larger converters can be utilized to convert AC power from the grid very quickly because the conversion process takes place inside the charging station and not the EV. As a result, some DC stations can fully charge an EV in 15 minutes while supplying up to 350 kW of electricity.

What are the differences between AC and DC charge curves?

Another key difference between AC and DC charging is the charging curve. With AC charging, the power flowing to an EV represents a flat line (so, not much of a curve at all). This is due to the relatively small onboard charger that can only receive a limited power spread over longer periods.

DC charging, on the other hand, forms a degrading charging curve. This is due to the EVs battery initially accepts a quicker flow of power but gradually takes less as it reaches full capacity.

As an example, imagine a glass as the EV’s battery, a water bottle as a DC charging station, and the water inside that bottle as the power. At first, you can quickly fill the glass with water, but you’ll need to slow down as you get to the top, so the glass doesn’t overflow.

The same logic can be applied to DC fast and ultra-fast charging. This is why EVs require less power once the battery is around 80 percent full, hence the degrading curve you see below.

Home EV chargers convert AC power to DC power, which may take hours to complete a charge cycle. In contrast, high-speed EV chargers receive electricity as DC power.

What is the relationship between AC and DC power in EVs?

In the field of electric transportation, AC and DC are both significant. The grid provides AC electricity, which is changed into DC and then stored in an electric vehicle's battery. The conversion from AC to DC when utilizing an AC charging station takes place inside the EV using an onboard charger, which is frequently constrained. A home EV charger converts AC to DC power.

In contrast, high-speed charging stations convert AC to DC power within the charge station, using a larger converter.

Concluding thoughts about EV powertrains

There is a lot of mystery surrounding EV powertrains amongst the general population. However, they are a relatively new technology to most that are evolving very quickly. In contrast, internal combustion engine (ICE) technology has been around for over 100 years. As a result, more is known about them than EV technology.

As EV technology matures and goes mainstream, especially in an era of high gasoline prices and a hostile political environment, more and more people will come to understand it and realize that, in my opinion, it is more simple than ICE technology.

What do you think? Is EV powertrain technology simpler than ICE powertrain technology?