What is a Hybrid Electric Vehicle?

What is a Hybrid Electric Vehicle (HEV)?

A hybrid electric vehicle (HEV) is a vehicle that uses both an internal combustion engine (ICE) and an electric motor. The two systems work together to optimise fuel efficiency, reduce emissions and improve overall performance. In an HEV, the ICE powers the vehicle and recharges the battery, while the electric motor assists during acceleration or low-speed driving when fuel consumption is typically higher.

There are two main types of hybrids:

1. Mild hybrids – electric motors assist the engine but do not power the vehicle independently. Mild hybrids often help improve fuel efficiency and enhance acceleration, but they cannot be powered by electricity alone.

2. Full Hybrid – These vehicles can run on electricity alone at low speeds or for short trips, but the engine takes over at higher speeds or when more power is needed. Full hybrids typically have higher fuel efficiency and lower emissions than mild hybrids.

How Does a Hybrid Electric Vehicle Differ from Other Vehicles?

Let’s analyse the main differences between hybrid, pure electric and conventional internal combustion engine (ICE) vehicles:

Hybrid Electric Vehicle (HEV) vs Pure Electric Vehicle (EV)

• Power source: Hybrid cars use a combination of a petrol engine and a generator, while electric vehicles are powered entirely by batteries and have no petrol engine.
• Range and emissions: Hybrids reduce emissions compared to conventional petrol cars, but electric vehicles have zero tailpipe emissions. However, electric cars depend on charging infrastructure and have a limited range per charge, whereas hybrids can seamlessly switch to petrol, offering more extended range and flexibility.
• Charging requirements: one of the most significant differences is how they are charged. Electric cars can only be recharged using an external power supply, whereas most hybrids charge their batteries through regenerative braking and the petrol engine.

Hybrid Electric Vehicle (HEV) vs Internal Combustion Engine (ICE) Vehicle

• Fuel Efficiency: Hybrid vehicles are more fuel efficient than internal combustion engines because they can rely on electricity for specific driving scenarios. This reduces the total amount of petrol used.
• Environmental impact: Hybrids will emit less carbon dioxide than internal combustion engine vehicles, making them a more environmentally friendly option than fuel cars, especially in urban areas, where they can switch to electric-only mode in low-speed areas, where hybrid electric vehicles emit little to no carbon dioxide.
• Performance: The electric motor in a hybrid car provides extra torque during acceleration, resulting in a smoother and faster start-up compared to a conventional combustion engine car.

How Do Hybrid Electric Vehicles Charge?

Strictly speaking, hybrid electric vehicles can also be divided into self-charging hybrid electric cars and plug-in hybrid electric vehicles, which are fundamentally different in charging.

1. Self-charging hybrid electric vehicles (HEVs)

A self-charging hybrid electric vehicle usually does not require external charging equipment to charge the battery. It is charged in two ways:

• Regenerative braking: When the vehicle is braked, kinetic energy generated during the vehicle’s movement is converted into electrical energy and stored in the battery using a regenerative braking system. This process is particularly effective in city driving or with frequent starts and stops.
• Engine charging: When the internal combustion engine is running, the engine also charges the battery. This ensures the battery has sufficient charge to support it when electric assistance is required, such as providing additional power during acceleration or at low speeds.

2. Plug-in hybrid electric vehicles (PHEVs)