What are Hybrid Electric Vehicles (HEVs) and How do they work?

What are Hybrid Electric Vehicles (HEVs) and How do they work?

What is a hybrid vehicle? Any vehicle that combines a minimum of two sources of energy for propulsion is a hybrid vehicle. The two sources can be either gasoline or diesel fuel combined with a battery. In true hybrid vehicles, both of the power systems can propel the vehicle separately. Some vehicles use fuel to charge the battery through a generator. This battery then propels the motor. However, that is not a true hybrid as it uses only one source of energy for the end propulsion. However, if the fuel and batteries – separately or together – are able to propel the vehicle, then it’s a true hybrid vehicle (HV).

If that’s what defines a hybrid, how does one actually work? A hybrid electric vehicle uses a gasoline/diesel engine along with a battery to power an electric motor. Both of these power sources are configured through different settings to attain specific objectives: enhancing driving range, increasing fuel efficiency, or increasing the power of the vehicle.

How do hybrid electric vehicles (HEV) work?

HEVs use fuel as a primary source of power and do not require an external electrical source to recharge their batteries. A true HEV has both an internal combustion engine (ICE) and an electric motor. Both the ICE and electric motor work together to propel the vehicle. This combination helps increase the efficiency of the engine. The power distribution allows vehicles to achieve optimum power under most driving conditions.

Based on power distribution, there are three types of HEV:

  1. Series
  2. Parallel
  3. Series-Parallel.

Series Hybrid: Range Enhancer

In this combination, the internal combustion engine drives an electric generator and not the wheels. The generator not only charges the battery, it also powers the motor that propels the vehicle. This setup is also known as a range-extended electric vehicle (REEV) since the ICE powers the battery and motor but never directly propels the wheels.

Parallel Hybrid

Here, both an ICE and an electric motor propel the wheels. Both work in tandem and deliver optimum power output. The batteries in the vehicle charge when the motor works as a generator. These vehicles cannot drive standalone in pure electric mode.


These vehicles use both the ICE and the moto, both of which can work alone or in tandem. Power distribution helps the vehicle operate within its optimum range as much as possible, giving it high efficiency.

Finally, all of these HEVs include a raft of exciting technological features. The most common are below.

Regenerative Braking

Vehicles possess huge kinetic energy when in motion. To stop the vehicle this energy needs to be reduced, when the driver applies brakes to stop, that kinetic energy needs to go somewhere. In regenerative technology, the electric motor applies resistance to slow down the wheels and stop the vehicle. During this period, the motor operates as a generator and converts the kinetic energy from the wheels into electrical energy. This energy is then stored in the batteries for later use.

Electric Motor Drive/Assist

Internal combustion engine vehicles require additional power in many driving scenarios. While driving at slow speeds, driving uphill, or accelerating, the vehicle needs more power. This additional power comes from burning more fuel. However, in HEVs this additional power comes from the electric motor. This also allows HEVs to use a smaller engine, which in turn increases the efficiency of the vehicle. Sometimes at speeds slow enough that ICEVs require maximum power, the HEV’s electric motor alone propels the vehicle, cutting out the gas-powered engine entirely.

Automatic Start/Shutoff

Some HEVs use a feature that automatically switches off the engine when the vehicle comes to a halt. Doing so saves energy and fuel. The engine restarts by itself when the accelerator is engaged.

Technology for HEVs and EVs is changing fast. Innovation in this field is making amazing strides, making HEVs vehicles of the future.

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