How Does a Hybrid Car Work? 3 Power Modes Explained!

Petrol and diesel cars use an internal combustion engine to burn fuel and generate power. EVs use electric power stored in batteries. But what about hybrids? How does a hybrid car work? How does it combine fuel and electric power to enhance its efficiency?

If you’re looking for clear answers to all these questions, this guide is for you. In this guide, we’ll explain how a hybrid car works in different modes. By the end, you’ll know exactly how hybrid cars help reduce emissions and save money.

So, let’s dive right in!

What is a Hybrid Car?

A hybrid car combines an internal combustion engine with an electric motor. The electric motor draws power from a battery whereas the engine runs by burning traditional fuel. Together, they power the drivetrain of a petrol hybrid car.

Sounds simple enough? Well, it’s not that simple.

Hybrid systems are extremely complex because they integrate multiple components working in harmony. Unlike traditional cars, hybrids can switch between or blend both systems. This flexibility saves fuel and cuts emissions.

In most cases, you don’t need to plug them in, they charge while you drive. However, some hybrid types offer limited electric-only driving.

At low speeds or in traffic, the electric motor usually takes over. When more power is needed, the petrol engine kicks in. As a result, you get better mileage and smoother performance. That’s why hybrids are popular for city driving and short commutes.

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7 Key Components of a Hybrid Car

Before, we delve into the working of a hybrid car, it’s important to know what are its key components. Knowing these components will help you understand how does a petrol hybrid car work. So, let’s break them down one by one.

i. Battery (Auxiliary)

The auxiliary battery is a small but important part of a hybrid car. It powers the car’s electronics before the main battery starts up. The lights, radios, and dashboard systems of your car rely on it.

In hybrids, this low-voltage battery works alongside the bigger traction battery. You don’t notice it much, but it’s always working in the background.

It helps keep everything running smoothly when the car is off or starting up. Without it, many basic systems wouldn’t function. It also helps support key safety and control features.

ii. DC/DC Converter

This is a clever device that manages energy flow in a hybrid car. It takes high-voltage power from the main battery and converts it into lower-voltage power. That lower voltage is what your lights, stereo, and other accessories need.

It also recharges the auxiliary battery while you drive. Without this converter, the electric systems wouldn’t get the right power. It acts like a power manager, making sure everything gets what it needs.

iii. Electric Generator

The electric generator is one of the most important components of a hybrid car. When you brake, it uses that motion and turns it into electric power, just like any other generator. This energy goes back to charge the main battery. It’s a big reason why hybrids save fuel. This process is called regenerative braking.

Instead of wasting energy as heat, you reuse it. You get a little boost in battery power every time you slow down. This makes city driving even more efficient. The generator works with the motor to balance power and recovery.

vi. Electric Traction Motor

Next up, we have the electric traction motor. This motor is what moves the car using electric power. Usually, it works when you’re driving slowly or pulling away from a stop.

However, in some hybrid cars, it can even power the car alone for short distances. This motor also plays a key role during regenerative braking.

It’s efficient and reduces engine strain, especially in traffic. You get better performance and lower emissions without changing how you drive.

v. Power Electronics Controller

Think of this as the brain of the hybrid car. It manages where power goes and when to use it. The controller decides how much electric power must be sent to the motor. It also controls how much power goes back into the battery. This ensures smooth switching between petrol and electric drive.

However, you don’t notice the transitions; they feel natural because of this controller. It helps balance performance, efficiency, and battery health. Without it, a petrol hybrid system wouldn’t work properly.

vii. Thermal Management System

The thermal management system keeps everything at the right temperature. It cools down the engine, electric motor, and, batteries. This system prevents overheating and helps your hybrid last longer.

Heat can damage parts or lower efficiency if not managed. That’s why hybrid cars have specialised cooling systems. Some use fans, while others use liquid coolant. Either way, they play an important role so that you enjoy worry-free driving.

vii. Transmission

The transmission systems in hybrid cars are not the same as transmission systems in conventional cars. They are often more advanced and complex. This is why it is worth mentioning separately.

It not only transfers power to the wheels but also combines the power from the engine and electric motor. They adjust power flow depending on how you’re driving.

How Do Hybrid Cars Work? (3 Powerflow Modes Explained)

Hybrid cars work by shifting between different power modes. Each mode helps you drive more efficiently based on the situation. There are three main types of Powerflow modes used by hybrid cars.

Let’s discuss each in detail:

i. Electric-Only Mode

In this mode, the electric motor alone drives the car. It’s most often used at low speeds or when driving gently. For example, in traffic or parking, you’ll likely be in electric mode. No fuel is used, which saves money and cuts emissions. You’ll notice how quiet the car becomes.

This mode is perfect for city driving or short local trips. As long as the battery has a charge, you stay in electric mode. Once more power is needed, the engine kicks in.

ii. Engine-Only Mode

Here, the car runs purely on the petrol engine. This usually happens while driving on motorway or when climbing steep hills. In these cases, the electric motor might not provide enough power alone. The engine steps in to supply additional power.

This mode offers strong, steady performance for longer drives. It also helps recharge the battery while running. When conditions change, like slowing down, the hybrid system may switch back to electric-only mode or the hybrid mode which we’re going to discuss next.

iii. Combined/Hybrid Mode

Combined mode is the most complex and involves both the engine and electric motor working together to power the vehicle. This mode activates during acceleration, while towing heavy load, or when extra power is required, such as overtaking or climbing hills.

The electric motor supplements the engine’s output, providing a power boost while optimising fuel efficiency. The hybrid control system continuously adjusts power distribution between the engine and motor based on speed, load, and battery state of charge.

It’s a key reason hybrids feel lively but stay efficient. Again, the car switches modes on its own based on your driving.

4 Major Types of Hybrid Systems

Different hybrid cars use different types of hybrid systems. There’s s slight difference in how each system works and each system comes with its own set of advantages. 

Let’s break them down.

i. Parallel Hybrid

In a parallel hybrid, both the engine and electric motor can drive the wheels. They can work together or take turns, depending on the situation. This is the most common type of hybrid system. It balances power and efficiency well. The car decides the best mix based on your speed and demand.

Parallel hybrid Models: Toyota Prius and Hyundai Ioniq use this setup. It’s great for everyday driving, offering smooth transitions and fuel savings. You don’t need to plug it in—regenerative braking recharges the battery. That makes it easy and convenient to use

ii. Series Hybrid

In a series hybrid, only the electric motor drives the wheels. The engine is there just to generate electricity. It charges the battery, which then powers the motor. This setup means the engine power never reaches the wheels directly. You get smooth, quiet driving because its running on electric power only. 

This system works great in stop-and-go driving. They are a popular choice for London taxis, where reduced CO2 emissions result in exemptions from the ULEZ charge.

Series hybrid Models: The BMW i3 and Chevrolet with a range extender used a series system. It’s good for urban use and short trips. However, it may struggle at high speeds since it relies entirely on the battery for motion. Still, it offers a very electric-like driving feel.

iii. Mild Hybrid

A mild hybrid uses a smaller electric motor to assist the engine. However, the motor can’t power the car on its own. It helps during start-up, acceleration, and stop-start traffic. This boosts fuel economy and reduces emissions slightly. You’ll notice smoother restarts and better low-speed performance.

Mild hybrid Models: Suzuki Swift Hybrid  and Audi A6 TFSI are mild hybrids. You don’t need to charge them or change how you drive. They’re an affordable way to improve efficiency without going fully hybrid. It’s ideal for those who want some benefits of hybrid tech with fewer changes.

iv. Plug-In Hybrid Electric Vehicle (PHEV)

A plug-in hybrid, also called a PHEV, has a much larger battery that you can charge. It allows you to drive longer distances on electric power alone. Once the battery runs low, the petrol engine takes over. This gives you the best of both worlds, electric driving and petrol backup.

PHEV Models: Mitsubishi Outlander PHEV and Toyota RAV4 PHEV are popular models. You can often get 20–40 miles of electric-only range, perfect for daily commutes. It’s great for people who want to go electric but still need petrol for longer trips. Just remember to plug it in regularly for best results.

Advantages and Disadvantages of Hybrid Cars

Advantages of Hybrid Cars in the UK:

• Qualify for reduced vehicle road tax in the UK.
• Some hybrid vehicles may qualify for ULEZ charge exemptions and London congestion charge discounts.
• Some hybrid vehicles may qualify for LEZ charge exemptions in certain cities.
• Enjoy quieter, smoother rides in busy urban areas.
• Save money on fuel, especially in city traffic and stop-start conditions.
• Most hybrids don’t need home charging. The battery charges while driving.

Disadvantages of Hybrid Cars in the UK:

• Higher purchase price compared to traditional petrol cars.
• Usually have higher maintenance costs due to complex transmission and hybrid control system.
• Battery replacement can be costly after some years of use.
• Less boot space due to battery placement.
• Not the best choice if you mostly drive long distances without stops.

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Frequently Asked Questions (FAQs)

1. Do hybrid cars need to be plugged in?

Most hybrid cars don’t need to be plugged in. They recharge their batteries through regenerative braking and by using the petrol engine as a generator. This means you can drive them like a regular petrol car.

However, plug-in hybrid electric vehicles (PHEVs) do require charging. PHEVs have larger batteries and can run longer on electric power alone.

You can plug them into a home charger or public charging points. So, whether you need to plug in depends on the type of hybrid you have.

2. How long do hybrid car batteries last?

Hybrid car batteries usually last between 8 to 15 years. Many manufacturers offer warranties covering 8 years or 100,000 miles. However, the battery life depends on driving habits and climate conditions. In the UK, moderate weather helps batteries last longer.

Proper maintenance and gentle driving also extend battery life. Replacing a hybrid battery can be expensive, but it is rarely needed early. Overall, hybrid batteries are designed to last the car’s lifetime in most cases.

3. Are hybrid cars ULEZ compliant?

Hybrid cars can be ULEZ compliant, but it depends on their emissions standards. Most petrol hybrids registered after 2006 meet the required Euro 4 standard. However, diesel hybrids must meet the stricter Euro 6 standard to be ULEZ compliant. If your hybrid meets these standards, you won’t pay the daily ULEZ charge in London.

Remember, not all hybrids are exempt, so it’s important to verify before driving in ULEZ zones. You can check your car’s ULEZ status online using your registration number. This helps you avoid unexpected fees while enjoying cleaner, greener travel.

4. What is the difference between a plug-in hybrid electric vehicle (PHEV) and an electric vehicle?

A PHEV combines a petrol engine and an electric motor. It has a larger battery than a regular hybrid and can be plugged in. You can drive on electric power alone for limited distances, usually 20–40 miles. When the battery runs out, the petrol engine kicks in for longer trips.

However, an electric vehicle (EV) runs only on electricity with no petrol engine. EVs need charging from external power sources all the time. While PHEVs offer more flexibility, EVs produce zero emissions on the road.

5. Do hybrid cars pay congestion charges?

Yes, hybrid cars have to pay the Congestion Charge in London. Only battery electric (BEV) and hydrogen fuel cell vehicles qualify for the exemption, and the exemption is due to be discontinued completely from December 25th 2025. 

Final Thoughts: Should You Buy a Hybrid Car in the UK?

Hybrid cars represent a smart middle ground between traditional petrol/diesel vehicles and fully electric cars. By combining an internal combustion engine (ICE) with an electric motor, they deliver better fuel efficiency, lower emissions, and smoother performance.

However, whether or not you should buy a hybrid car depends on your individual needs. If you mostly drive in stop-and-go traffic a hybrid might be a good choice. But if you travel frequently on motorway, EVs might be a better option.

If you’re ready to save on fuel, reduce emissions, and enjoy a smoother ride, consider switching to a hybrid. At Exchange My Car, we make upgrading your car easy. Get multiple instant offers for your current car and move into a fuel-efficient hybrid with hassle-free car collection and fast payment.

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