How Do Hybrid Cars Work? Lincoln Tech Explains The Hybrid Powertrain

It seems that hybrid cars are everywhere now, and their popularity is such that as of the 2024 model year, 32 car brands are offering a combined 938 models that operate using some configuration of hybrid power. The hybrid car was born from the idea of combining the best traits of gasoline and electrical power sources into a single fuel-efficient and reliable vehicle. The goal has been to minimize emissions from the use of fossil fuels while maximizing the benefits of electrical power generation into one package.

Why is the Hybrid Car Gaining In Popularity?

The modern world is a busy place, and billions of people travel on a daily basis to commute to work, run errands, travel for leisure, or connect with friends and family. To get from point A to point B, the world population is using over 1.4 billion vehicles.

With that many vehicles running, manufacturers and drivers alike are looking for the most cost- and fuel-efficient way to travel that is also easy on the environment. This is where the concept of the hybrid car comes into focus.

What Is a Hybrid Car Exactly?

All hybrid cars have something in common: they derive their motive power from some combination of gasoline internal combustion engine (ICE) and an electric motor. And while the arrangement and types of components might differ slightly, all hybrids have 4 key Components:

1. Internal combustion engine - in most hybrids it is a gasoline engine, though some larger hybrids might have a diesel unit.
2. Power control unit - Also known as the Hybrid Control Unit (HCU), this module is a computer that deciphers input from the driver (accelerator and brake pedals) and signals from a speed sensor, and uses these variables to manage overall power application, battery charging, torque and motor combinations.
3. Transmission - Depending on the hybrid powertrain design, a hybrid car might utilize a modified conventional transmission (CVT, DCT or automatic or manual transmission), or an EVT which is also known as a power split device¹.
4. Electric motor (and battery) - Both vary in size depending upon vehicle design, intended use, and powertrain configuration.

How these components are arranged and how they are used is what makes some hybrids different from others. We can detail these differences with a discussion on series and parallel hybrid drivetrains.

Hybrid Drivetrains & Regenerative Braking

As stated before, all hybrid cars use an internal combustion engine, electric motor and battery, and a power control unit. How they are configured to generate power and/or motive force is described best by the comparison between series vs parallel hybrid configurations.

Series, Parallel, and Series/Parallel Hybrid Configurations

In the simplest of the hybrid configurations, known as the Series Hybrid Drivetrain, the electric motor is the only motor that is used to apply power to the drive wheels. The electric motor receives its power from one of two sources: the battery, or from the gasoline engine that is turning a generator that supplies current to the electric motor directly. At no time in the Series configuration is the gasoline engine used to directly power the drive wheels.

The term "series hybrid" comes from the fact that the power generation flows along a linear pathway to produce power: the gasoline engine either charges the battery or provides electrical current, and the current is used to power the final drive, which is the electric motor². It is a one-way process (ICE engine to Electrical Motor).

In a Parallel Hybrid configuration, the gasoline engine and electric motor work together to provide the power that turns the drive wheels. There are some benefits to this configuration as combined power supplied by both units allows the car to have a smaller battery pack³. This can reduce both battery cost and vehicle weight. Like in the series hybrid, the gasoline engine can also help charge the battery depending on the power demand during vehicle operation.

Some manufacturers use both configurations to great effect in the series/parallel configuration⁴. While the combined system is more complex than either series or parallel alone, together they also produce the ability for the car to operate on either electric or gasoline systems exclusively if the demands of the road and driving conditions allow it. While this is the ultimate in power source flexibility, its sophistication and added componentry adds cost to the vehicle's purchase price.

Regenerative Braking

Hybrid cars, and EVs for that matter, use the inertia from deceleration during braking to produce electrical power to help recharge the battery. When the driver takes their foot off the accelerator, electrical current stops being fed to the electric motor. Then the spinning of the wheels (and the electric motor attached to it) become a generator during braking, and the reversal of electric current feeds power from motor-turned-generator back to the battery, charging it instead of drawing power from it.

Additional Types of Hybrid Cars

We have covered hybrids of the series, parallel and series/parallel types, which are able to recharge their batteries using gasoline engine generators and regenerative braking. There are also some models that can have their batteries recharged by plugging into a standardized EV charger, or by plugging into an electric socket that is available at home or at work.

This type of hybrid car is called the Plug-In Hybrid Electric Vehicles (PHEVs), and like the previously described hybrids they have both an electric motor with battery and an internal combustion engine. When the power level in the battery runs down, the car can be recharged at home, at a charging station, by running the combustible engine and also through regenerative braking.

Mild Hybrid cars have the same three components: a gasoline engine, electric motor and battery, and a power controller. The battery recharges by regenerative braking, and the car is designed to run on its combined power sources but does cannot run on electrical power exclusively.

The Market For Hybrid Cars Is Growing

Hybrid cars are an electro-mechanical marvel of modern transportation, and their numbers will continue to grow as the public understands how these vehicles work. For those who do purchase hybrids, they will eventually need to take them in for service or repair, and when that happens they might ask themselves "Who Fixes Hybrid Vehicles?". We'll cover that in our next article in this series about the technicians who fix hybrid cars.

References:

¹ " Hybrid transmissions" from https://www.infineuminsight.com/en-gb/articles/hybrid-transmissions/ Published on January 11, 2017. Retrieved on November 25, 2024.

² Section: "Series Drivetrains" in https://www.ucsusa.org/resources/all-about-drivetrains#:~:text=Series%20Drivetrains Published on February 25, 2015, Last updated on March 14, 2018. Retrieved on November 13, 2024.

³ Section: "Parallel Drivetrains" from https://www.ucsusa.org/resources/all-about-drivetrains#:~:text=Parallel%20hybrid%20drivetrains Published on February 25, 2015, Last updated on March 14, 2018. Retrieved on November 13, 2024.

⁴ Section: "Series/Parallel Drivetrains" from https://www.ucsusa.org/resources/all-about-drivetrains#:~:text=Series/Parallel%20drivetrains%20merge. Published on February 25, 2015, Last updated on March 14, 2018. Retrieved on November 13, 2024.

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