Comparing Full Hybrid and Mild Hybrid

Hybrid Cars

In Vietnam, Toyota was the first automaker to introduce the hybrid version of the Corolla Cross in August 2020. Following that, it sequentially introduced the Camry hybrid and Corolla Altis hybrid, with all three green models sharing the common feature of a Full hybrid configuration. Approximately two years after Toyota sold its first hybrid, Suzuki Vietnam also equipped its first hybrid configuration in the B-segment MPV category with the Ertiga hybrid. This is a Mild hybrid configuration, meaning a light hybrid. Both the Corolla Cross and Ertiga were the first models in their respective segments to have a hybrid version. So, what is the difference between these two hybrid technologies? Let's find out with AOZOOM civilized headlight upgrades in the article below.

Understanding Full Hybrid and Mild Hybrid Cars

A hybrid car (also known as a hybrid electric vehicle or HEV) is a type of automobile that uses two power sources simultaneously: an internal combustion engine and an electric motor, meaning the car runs on both gasoline and electricity. The first hybrid car was launched in 1899, built by Pieper, Liège of Belgium, and the electrical transmission company Vendovelli and Priestly of France. After a long process of research and development, the concept of hybrid electric vehicles truly became appealing in the 1990s.

Japanese automakers played a significant role in commercializing this vehicle line. In 1997, Toyota launched the Toyota Prius hybrid sedan. Around the same time, Honda also introduced the Honda Civic and Honda Civic hybrid. These are considered the first cars marking the official commercialization of hybrid vehicles in the modern era.

Hybrid Car Structure

The structure of a hybrid car is similar to that of a conventional internal combustion engine car. The engine connects to the transmission system to drive the wheels. However, a hybrid car has an additional electric motor that shares the driving task or assists the internal combustion engine.

For this mechanism to coordinate smoothly and operate seamlessly, some other supporting parts are needed, such as the battery and power converter. The battery (or high-voltage battery) is a device that stores and supplies energy to the electric motor. The power converter helps convert the power source of the engine into multiple parts for different purposes, such as driving the car and charging the battery.

Types of Hybrid Engines

Hybrid cars are classified into 3 types based on their basic transmission structure:

Series

The electric motor directly transmits power to the wheel drive system. The internal combustion engine only undertakes the task of supplying energy to the electric motor and charging the battery.

• Advantages: The gasoline engine mainly operates only when driving long distances, thus helping to save fuel and reduce environmental pollution.
• Disadvantages: With this type of system, the battery capacity and size are large because the electric motor undertakes the main power transmission role. The gasoline engine can easily become overloaded because it must constantly supply energy to the electric motor and battery.

Parallel

Both the electric motor and the internal combustion engine jointly undertake the power transmission role. When the electric motor works, when the internal combustion engine works, or when both work together is decided by the central control unit depending on the operating conditions.

• Advantages: The car achieves higher power due to having two power sources. The battery capacity and size are not too large.
• Disadvantages: The system has a complex structure and high production costs."

Full Hybrid Cars

Hybrid

A hybrid system combines both series and parallel systems. This system maximizes the strengths and overcomes the weaknesses of the two individual systems. It is currently the preferred system for manufacturing hybrid vehicles today.

Types of Hybrid Cars

There are several main types of hybrid cars that differ primarily in how power is coordinated and when power is coordinated between the electric motor and the internal combustion engine.

Full Hybrid

A full hybrid vehicle (also known as a parallel hybrid) is a type of hybrid car where the electric motor and the internal combustion engine can operate independently or in combination, depending on the driving conditions. The electric motor battery can self-charge using energy supplied by the internal combustion engine. This type of full hybrid vehicle can run entirely on electricity, entirely on gasoline/diesel, or a combination of both.

The electric motor often operates independently at low to medium speeds. However, it can only travel short distances due to the battery's limited range. On the other hand, the battery has the advantage of recharging quickly using the internal combustion engine. In this type of vehicle, the internal combustion engine is responsible for both powering the wheels and generating energy to charge the battery for the electric motor.

In full hybrid vehicles, when the car is just started and idling, the electric motor will work alone. When the car starts moving, depending on the driving style, the control unit will decide when to engage the internal combustion engine, when to engage the electric motor, or when to engage both simultaneously.

If driving at low speeds with gentle acceleration, the electric motor usually operates independently. If the accelerator pedal is pressed deeply, the control unit will activate the internal combustion engine for rapid acceleration as desired by the driver. If the speed has stabilized, for example, maintaining a steady speed in the medium range of 50-60 km/h, the internal combustion engine will automatically turn off, and only the electric motor will operate. In general, with full hybrid cars, the electric motor works almost throughout the vehicle's operation. The gasoline engine will engage in situations where the car needs significant pulling power, such as during acceleration or high-speed driving. Toyota's hybrid models such as the Toyota Prius, Toyota Corolla Hybrid, Toyota Camry Hybrid, Toyota Corolla Cross Hybrid, Toyota RAV4 Hybrid, etc., all belong to this full hybrid category.

Characteristics of Full Hybrid Mode

• Pure electric driving mode;
• Pure gasoline driving mode;
• Both gasoline and electric driving mode;
• Energy regeneration mode during deceleration.

Mild hybrid

A Mild Hybrid Electric Vehicle – MHEV (mild hybrid) is a type of hybrid car with both an electric motor and an internal combustion engine, but the electric motor cannot operate independently. In this type of vehicle, the electric motor only plays a supporting role for the internal combustion engine and cannot operate independently like a full hybrid.

Mild hybrid Car

A mild hybrid is a type of hybrid vehicle that has both an electric motor and a combustion engine, but the electric motor cannot operate independently. The primary function of the electric motor is to allow the internal combustion engine to turn off when the vehicle is coasting downhill, braking sharply, temporarily stopped, etc., and then quickly restart it. Additionally, the electric motor also generates power to increase the traction for the internal combustion engine. The battery of the electric motor is recharged through the process of regenerative braking.

Mild hybrid vehicles also use an electric motor combined with an internal combustion engine, but neither can operate separately. Instead, the small electric motor only plays a supporting role for the internal combustion engine. Basically, this is the cheapest hybrid technology due to its simpler engine structure, and its energy-saving and power-boosting effects are not significant.

Comparing Full Hybrid and Mild Hybrid

Cost

Compared to a full hybrid system, a mild hybrid system is generally less expensive due to its simpler structure and lower production costs. However, because the electric motor only plays a secondary role, the efficiency in optimizing power and the fuel-saving capability of a mild hybrid vehicle will not be as good as that of a full hybrid vehicle. But in reality, mild hybrids still help save 10–15% of fuel. This improvement is quite significant when the car is running at low speeds (a time of high fuel consumption and emissions).

Operation

The difference between the two technologies is more clearly demonstrated during operation. For example, the Corolla Cross HEV, when the start button is pressed, does not emit a sound (engine cranking noise) like conventional cars. Instead, the Suzuki Ertiga emits a "Beep," and the driver's central display indicates that the vehicle is ready to move. Because it starts with an electric motor, the cabin of a full hybrid vehicle has no noise, and since the power is supplied by the battery pack, the internal combustion engine is not yet operating. The car consumes no gasoline and emits no CO2 into the environment; the driving experience immediately after starting is similar to that of a pure electric vehicle.

With a mild hybrid configuration, the car still starts with the normal engine cranking noise, indicating that the internal combustion engine is ready to operate. At this point, a mild hybrid vehicle is not much different from conventional gasoline-powered models; the internal combustion engine starts operating and emits CO2 into the surrounding environment.

Operating electric vehicles

With the Corolla Cross 1.8HEV, when engaging drive, the car still utilizes the electric motor to assist this process, as many studies indicate this consumes a significant amount of fuel. Depending on the driver's accelerator pedal input and the remaining battery level, the vehicle will automatically select the appropriate power source. Pressing the accelerator firmly signals to the car that the driver wants to accelerate quickly, so the internal combustion engine starts immediately, while also charging the battery pack. The driver can monitor this entire flexible process through the operational status display screen.

Conclusion

Hopefully, this article has provided you with more information about Full Hybrid and Mild Hybrid vehicles, enabling you to make an optimal choice.

Thank you for reading!

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