The number of models with hybrid drive is constantly increasing, but not all cars under this name operate in the same way. Some differ only slightly from traditional vehicles, while others are very close to electric cars. Let’s take a look at how different hybrid systems can be.
Internal combustion engines, whether diesel or gasoline, are most efficient (that is, consume the least fuel and emit low exhaust gases relative to achieved performance) in a very narrow range—simply put, when the accelerator pedal is pressed hard and the engine RPM is low. It would be beneficial to operate in this mode as often as possible, but in driving, we rarely have the opportunity to drive under such conditions.
Here, the electric motor comes to the rescue, which can be optimally used for movement, driving at lower speeds, or during braking, when it can serve as a generator to recover energy that would otherwise be lost. These are precisely the situations where internal combustion engines have the lowest efficiency. Therefore, hybrid vehicles that utilize both types of drive—electric and internal combustion engine—have entered the market. This way, it is possible to combine the advantages of both drives and reduce their drawbacks.
Hybrids in Different Forms
However, under the general term “hybrid,” there are many different systems, which often have little in common. A few years ago, it was popular to create so-called micro-hybrid systems, which practically amounted to using start-stop systems.
Mild Hybrid (MHEV)
Currently, the basic level of “hybridity” is the mild solution, sometimes referred to as mild hybrid technology. In this case, we are dealing with a system that is essentially an advanced start-stop system supplemented by the ability to recover some energy typically lost during braking. However, this system only supports the internal combustion engine without the ability to drive the vehicle independently when the main internal combustion engine is turned off.
True Hybrid Options (HEV and PHEV)
Here we transition to “true” hybrids. They utilize components that allow driving in internal combustion engine mode, electric drive, or in combined mode, with the ability to charge batteries while driving, braking, or stopping (though this depends on specific solutions).
The next step in development is plug-in hybrids, which allow for battery charging from a socket, increasing the driving range using only the electric motor. All of this contributes to reducing carbon dioxide emissions within the vehicle lineup.
REX – Are They Hybrids Too?
There are also vehicles with a so-called range extender, where the internal combustion engine serves as a generator of electrical energy for the vehicle, allowing for battery charging while driving. This significantly increases the car’s range—at first glance, similar to plug-in hybrids. However, the range extender is not a direct source of vehicle propulsion—the car cannot move without the participation of the electric motor—which somewhat does not fit the definition of a hybrid vehicle. A similar situation, but from the opposite aspect, applies to mild hybrids. You can read more about various solutions below.
Types of Hybrid Drives
Mild Hybrid (MHEV)
About ten years ago, even cars with start-stop systems were referred to as hybrids. Today, “mild” systems (mild, soft hybrid drives/MHEV) are considered the basic level of hybridization, where the classic starter and alternator are replaced by a single device, and sometimes a small auxiliary battery is added.
These systems allow for energy recovery during braking, which is then used to power systems and batteries, reducing the load on the engine. However, it is generally not possible to drive in fully electric mode.
Examples of Models:
- Audi Q8
Hybrid elements are integrated into models like the Audi Q8, but they are also found in other models from this German brand. Audi uses a more advanced 48-volt system for energy recovery, instead of the standard 12-volt system, with the generator and starter combined into one device. - Mazda 3 Skyactiv X
A classic example of a mild hybrid system is the Mazda 3 Skyactiv X. Mazda simply explains how the system works without excessive advertising of its advantages. There is no separate electric drive, and energy recovery is used for starting, powering electrical systems, and reducing the load on the engine. The expected fuel savings (in optimistic estimates) range from 5 to 10%. - Smart Fortwo mhd
Due to the negative perception of the classic start-stop system, Smart referred to this system as micro hybrid drive (mhd) for their 2009 model. At that time, this system was known as a micro-hybrid, and although it is difficult to consider it a true hybrid today, the name was widely used back then.
Hybrids (HEV)
Hybrid Electric Vehicles (HEV), often referred to as “full hybrids,” represent a step towards greater electrification of vehicles. This system uses at least two motors: an internal combustion engine and an electric motor. This combines their advantages and reduces disadvantages: vehicles have a large range and good performance while minimizing losses during idle states, slow driving, and in transitional modes (for example, after sudden acceleration).
The hybrid system allows for driving in fully electric mode (though usually limited to a few kilometers and low speeds, such as parking). These vehicles also retain the advantages of mild hybrid systems. Toyota was a pioneer in this segment, and today most manufacturers offer such vehicles.
Examples of Models:
- Fiat 600 Hybrid
An interesting example. The vehicle lies at the border between mild and more advanced hybrid systems. Although it has a belt-driven start-stop system, it also features an electric motor integrated into the dual-clutch transmission, as well as an additional battery, theoretically allowing for 100% electric driving. However, only for a distance of up to 1 km and at speeds up to 30 km/h. In practice, this system primarily supports the conventional internal combustion engine, reducing its load, even though it is constructed similarly to full hybrids. - Dacia Jogger Hybrid
Even the popular Dacia has a hybrid version, utilizing a system developed by Renault. The internal combustion engine produces 94 HP, while the 49 HP electric motor is integrated into the transmission and allows for driving in EV mode. There is also a 20 HP generator-starter. - Citroen DS5 Hybrid4
An interesting case. The internal combustion engine (2.0 HDi) powers the front wheels, while the electric motor is placed on the rear axle, with no mechanical connection to the front (a similar solution is used in hybrid Toyotas and Lexuses with 4×4 drive). Thus, the vehicle has all-wheel drive, and both motors can operate independently or together. - Toyota Prius
A classic in the hybrid world. It has been on the market since 1997 and is now in its fifth generation (also available as a plug-in; the popular third generation is pictured). It uses a unique method of connecting the internal combustion engine and two electric motors (one for propulsion, the other as a generator/starter) using a planetary gear.
Plug-in Hybrids (PHEV)
Plug-in hybrid vehicles (known by the acronym PHEV) are equipped with more powerful electric motors and larger batteries, enabling them to travel several kilometers, and sometimes even several dozen kilometers, in “zero-emission” mode. Batteries can be charged while driving, but this is not the most economical option, as they are primarily designed for charging from electrical outlets (this is when the vehicle’s energy balance is the most optimal).
To fully utilize the advantages of plug-in hybrids, it is best to have easy access to charging points. After the battery is drained, vehicles operate as ordinary hybrids, but due to the greater mass, they become less economical.
Examples of Models:
- BMW M760e
Hybrids, including plug-in models, have been developed to reduce fuel consumption and exhaust emissions. However, in the case of luxury sedans like the BMW M760e, it is hard to talk about savings since the prices of these models start at around 150,000 euros. Under the hood is a 3.0-liter engine. - Ford Kuga Plug-In Hybrid
The Kuga is listed here as an example of a plug-in hybrid, but it is also available in two other versions: MHEV and HEV. The most advanced version has a power of 225 HP and an electric range of up to 88 km (realistically closer to 60 km). - Kia XCeed PHEV
Variants of the Ceed model rank among the cheapest PHEV hybrid models on the market. Under the hood is a 1.6 GDI engine with a total system power of 141 HP. The manufacturer states that the electric range is 57 km.
Cars with Range Extenders (REX)
Cars with range extenders are often referred to as REX, which comes from the English term “Range EXtender.” At first glance, their system may resemble plug-in hybrids, but the concept is completely opposite. These cars use an internal combustion engine and a developed electric module that is most often charged from the electrical grid. The main source of propulsion is the zero-emission motor, while the internal combustion engine acts as a generator, enabling driving once the batteries are drained. This is a specific solution that was forgotten for some time but is now reappearing in interesting forms.
Examples of Models:
- Mazda MX-30 e-Skyactiv R-EV
The MX-30, which was previously fully electric, has received a new version with a built-in generator that uses a Wankel engine. With the engine running at 4000 RPM, it can recharge the battery, which enables driving without restrictions (assuming that the electric motor delivers sufficient power). The battery capacity is relatively small (17.8 kWh) compared to other electric cars. The result is an electric range of 85 km. - BMW i3 REX
A well-known model that quickly gained recognition in Europe is the BMW i3 REX, which uses a two-cylinder engine to charge the battery. With a range of 150 km on battery power alone, this model is now slowly disappearing from the market. - Opel Ampera-e
The Ampera-e electric car had a built-in generator that allowed it to drive hundreds of kilometers on a single charge. A significant advantage of this vehicle was the high electric range that was primarily made possible by the capacity of the battery. - Audi RS Q e-tron
- In a recent edition, Carlos Sainz won the Dakar in the Audi RS Q e-tron, which also uses a range extender. Two electric motors, taken from Formula E, provide a total of about 390 HP, while a third motor, a 2-liter four-cylinder TFSI, serves as a generator. This setup charges the 52 kWh batteries but does not assist in driving. Despite the additional weight of 2,100 kg, Audi had the advantage of greater efficiency, allowing for driving with lower fuel consumption.
Conclusion
The hybrid car market has changed significantly. The first models, like the Toyota Prius, were almost experimental. However, the experiment proved successful, and the technology has become reliable and easily adaptable to various models. Now, almost every manufacturer offers some solutions that can be considered hybrid drives. The majority of new hybrids are plug-in models, which are the most expensive and complicated to produce compared to fully electric vehicles. The use of efficient electric modules positively impacts the results of official fuel consumption tests while also allowing for the use of smaller internal combustion engines.