How Hybrid Cars Work

Ever since people started to care about fuel economy, car manufacturers implemented technologies to improve the efficiency of engines. Diesel engines were designed precisely for those reasons a century ago. However, today, they are deemed too dirty and pollutive to be a viable alternative to petrol engines. To make cars more fuel-efficient and more environmentally-friendly, car companies decided to get help from electricity – that’s how hybrid vehicles were born.

Today’s hybrid cars use an internal combustion engine (ICE), electric motor, and batteries to improve the economy and reduce emissions. That said, the hybrid car definition includes other technologies as well. Any powertrain that uses a combination of two different energy sources is considered a hybrid.

toyota hybrid driving modes

Nonetheless, most hybrid technologies that didn’t use electricity to aid the engine are out of use today. Those include bi-fuel cars (petrol and ethanol), Petro-air hybrids (compressed air), and Petro-hydraulic hybrid (pressurized liquid). All these technologies are exciting from an engineering standpoint, but aren’t that useful in the real world. That’s why, when we refer to hybrid cars today, we are talking about petrol-electric hybrids. Electric cars, on the other hand, aren’t hybrids – they use only electricity as propulsion. With all that said, are hybrid cars worth it? People around the world seem to agree – and hybrid car sales continue to rise. Toyota and Volvo, just to name a few, even plan to hybridize their whole lineup in the coming years. However, to fully understand the phenomenon that is hybrid cars, we need to see how they work and what are hybrid car’s advantages, and disadvantages.

How Do They Work?

In beginner’s terms, hybrid vehicles use electricity to aid the petrol engine during driving. Thanks to the added power and torque, the engine consumes less fuel, yet still provides ample acceleration. However, this doesn’t answer the main question – where does the electricity come from?

Every hybrid car today uses batteries to store electricity on board. Some older hybrids used Ni-Mh batteries, which are heavier and less energy-dense. Newer hybrids, on the other hand, use Li-ion cells that are lighter and have more abundant energy density. The batteries store electricity from the kinetic energy of the car. For example, when the driver is decelerating, the electric motor acts as a generator and charges the batteries. The engine can also charge the cells, while plug-in hybrids let the driver charge the batteries via an electric outlet.

hybrid gas electric engine

Using its internal charge, the battery delivers back the stored electricity to the electric motor. The motor-generator then connects to the gearbox or the final drive of the car, depending on the model. On most hybrids, the electric motor can move the vehicle by itself, without any help from the gasoline engine. On the so-called mild hybrids, the electric motor only aids the internal combustion engine.

How do Hybrids Behave in the Real World?

On the road, hybrids behave differently depending on the conditions. During average acceleration, they mostly rely on the electric motor to save fuel. If the driver wants more power, the ICE works together with the electromotor. When the vehicle is cruising, the engine charges the battery and keeps the constant speed. This happens because the internal combustion engine works optimally at highway speeds.

However, if the vehicle moves downhill, the ICE might completely shut down. It’s the same when the driver uses the brake pedal – the electromotor starts charging the batteries with the kinetic energy instead. Finally, when the car is stationary, if the batteries aren’t empty, the petrol engine shuts down. Then, the stored electricity powers the auxiliary systems on some cars. If the cells are empty, the ICE powers the auxiliary systems and provides electricity to the battery.

What are the Various Types?

We can classify hybrid cars on the market today in three different types. Let’s see which are they and what makes them different.

  • Mild hybrids use electricity only to aid the internal combustion engine. These cars usually can’t move on electric power alone. An example of the mild-hybrid powertrain is the 48V Bosch system that Volkswagen AD Group uses in its vehicles. These cars use only gasoline, and you can’t charge the batteries externally.
  • Full hybrid cars can drive on electricity alone, using both motors, or only the ICE. Toyota’s famous “Hybrid Synergy Drive” system is the prime example of a full-hybrid system. Compared to mild hybrids, these vehicles have a much better fuel-efficiency. Toyota’s hybrid car battery life is around 2-3 miles. Their cells also can’t be charged from the outside. In other words, the driver only puts gasoline in these cars.
  • Plug-in hybrid vehicles can be charged via an electric outlet. These vehicles usually have an electric-only range of about 35-45 miles with fully-charged batteries, depending on the model. When the cells are empty, the ICE and electromotor work together. In this case, plug-in hybrids behave like full hybrids.

toyota prius plug-in hybrid

Hybrid Cars Pros and Cons

While some questioned hybrid powertrains in the past, today, everybody agrees that they are the way forward. Compared to vehicles powered only by internal combustion engines, hybrid cars are much more benefical. However, there are also some disadvantages to this technology that might deflect potential buyers.

Advantages of Hybrids

  • Outstanding city fuel economy – hybrid cars consume less fuel in urban environments than ICE-powered vehicles. Their city EPA mileage ratings are excellent, even on some more powerful models. Some full-hybrid cars also have better city EPA ratings than highway EPA ratings.
  • Fewer emissions – hybrid cars are greener than conventional vehicles. They produce fewer greenhouse gasses, but also less NOx and exhaust particulate matter.
  • Quicker off the line – hybrid cars have stronger acceleration than ICE-powered vehicles. If you thought about the Prius here, let us remind you of the Acura NSX or the Porsche 918 Spider, both offered in hybrid versions.
  • Hybrids are usually more reliable, despite the sophisticated engineering inside them. The main reason? The internal combustion powerplant is used much less than on classic vehicles.
  • Hybrids require less maintenance. For example, the brakes are used less in hybrid cars because the motor/generator provides most of the deceleration. Oil replacement intervals are also longer on hybrid vehicles.

Disadvantages of Hybrids

  • Higher price than conventional cars – this makes them a less-enticing option for drivers that don’t cover a lot of miles.
  • The EPA highway fuel economy isn’t fantastic. Sure, hybrids might still be more efficient than ICE-powered vehicles, but the difference is much smaller here.
  • The heavy batteries make hybrids less responsive in corners and put more weight on the tires. However, engineers bypass these issues by placing the cells below the seats and keeping the center of gravity low.

Are Hybrid Cars Worth It?

Simple mathematics shows that if you cover 15,000 to 20,000-miles annually, hybrid cars are worth the higher sticker price. Usually, hybrids cost around $3,000 to $4,000 more than their ICE-powered counterparts. Annually, you will save around $400 to $600 on gas alone, but you will also save on maintenance. In 6-7 years, the hybrid car should become cheaper. However, if you don’t drive a lot (10,000-miles annually), gas-powered vehicles are an affordable and cost-effective option.

The price is only part of the story here. Hybrids produce much fewer emissions, which means that they are better for the environment. If you view them only from that standpoint, petrol-electric vehicles are 100% worth it.

Which Hybrid Cars are the Best?

It is tough to single-out hybrid cars today simply because there are too many on the market. That said, journalists and magazines consider Toyota’s hybrids to be the best in the world, along with models from the Lexus division. They offer the best fuel-efficiency in its class, excellent reliability, and the highest warranty. The Japanese manufacturer also has the most comprehensive hybrid portfolio. Toyota offers hybridized versions of the Corolla, Camry, Avalon, RAV4, and Highlander, and some hybrid-only models, such as the Prius. Honda is also at the forefront of hybrid technology with the Insight, while Ford, Hyundai, and Kia also offer hybrid versions of their popular vehicles. Volkswagen, BMW, Mercedes-Benz, and Audi mostly rely on mild-hybrid or plug-in hybrid technologies, but they still aren’t as popular as their ICE-powered machines.

Do you own a hybrid car? Let us know what your thoughts are on the driving experience in the comment section below.

Find a hybrid car repair manual for your vehicle here.

About Ivo G

Hey guys and girls, I’m Ivo, a passionate car enthusiast with a particular weakness for rear-wheel-drive and stick-shift gearbox cars. Meanwhile, I don’t mind getting my hands dirty – I have experience as a Certified Head of Service at a Toyota Dealership, and knowledge that I wish to share with you.

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