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  • 01 August, 2022

  • 15 Min Read

Hybrid electric vehicles (HEV): Explained

Hybrid electric vehicles (HEV): Explained

Automakers like Maruti, Toyota, and Honda have launched more hybrid electric vehicles in India.

What is a hybrid electric vehicle?

  • A hybrid electric vehicle uses an Internal Combustion engine ICE (a petrol/diesel) and one or more electric motors to run. It is powered by the electric motor alone, which uses energy stored in batteries by the ICE or both.
  • In addition to the internal combustion engine, they also have an electric motor and a battery.
  • The HEV is more complex as it has electric vehicle (EV) components and a conventional ICE (the cars we use as of now) component.
  • HEV contains a low-voltage auxiliary battery, a traction battery pack to store electricity for the electric motor, an electric generator, an AC/DC converter, a power electronics controller, a thermal system to maintain working temperature, an ICE, a fuel tank, a fuel filler, a transmission, and an exhaust system.

How do HEV powertrains work?

[Powertrains means an assembly of gears and associated parts by which power is transmitted from the engine to the driving axel.]

  • The HEV powers the car in a series, parallel, or series-parallel (power split) method.
  • Parallel HEV may use any of the power sources (either IEC power generators OR electric motor) based on driving conditions and will alternate between the electric motor and IEC to keep the car moving.
  • Series HEV only uses the electric motor to drive the wheels and the ICE is used to recharge batteries.
  • Series-parallel HEV offers a combination of both models and allows to split power, where the power is routed from the ICE alone or from the battery to the electric motors to drive the vehicle.

In all three, the battery is recharged through regenerative braking technology.

How does a regenerative braking System (RBS) work?

  • In RBS, the kinetic system can recover the energy lost during braking and then use this energy to recharge the high-voltage battery of the vehicle.
  • An electric system generates electricity through a motor during sudden braking and a hydraulic system uses pressurized tanks to store the vehicle’s kinetic energy and offers a high energy recovery rate ideal for the vehicle.
  • The efficiency of HEVs and EVs will in large part be determined by their ability to recover as much energy as possible while braking, with a higher degree of energy recovery lowering fuel consumption.
  • The amount of recoverable energy depends upon factors like vehicle speed and stopping pattern.
  • While regenerative braking systems are already available in most electric vehicles (EVs), the technology is also used in electric railways.

A regenerative braking system (RBS) used in automotive applications has several advantages like better braking efficiency in stop-and-go traffic which enhances fuel economy and also helps in reducing carbon emissions. Besides, RBS also helps in energy optimization resulting in minimum energy wastage.

Types Of Hybrid Vehicles:

The HEVs can be categorized into micro, mild and full hybrid vehicles, based on the degree of hybridization.

  • Full HEV will have a larger battery and a more powerful electric motor compared with a mild HEV. As a result, a full HEV can power the vehicle for longer distances using just electric mode.
  • Mild HEV cannot drive using only the electric motor and uses the battery at traffic lights or in stop-and-go traffic to support the ICE.
  • Micro hybrids do not offer electric torque assistance as they lack an electric motor, but they have an idle stop-start system and energy management functions.

Full HEVs offer better fuel economy compared with the other two types of HEVs but they also cost more than them.

  • Plug-in hybrid electric vehicles (PHEVs) that are just like full HEVs, but they can be charged using a wall outlet, as they have an onboard charger and a charging port. PHEVs generally use the electric motor until the battery is almost drained, and then automatically switch to the ICE.

What is the main advantage of using hybrid technology??

  • Fuel efficiency is one of the main advantages of using hybrid technology.
  • Most vehicles with hybrid technology offer fuel efficiency, more power, and minimum carbon emissions.
  • Will cut down emissions of global warming pollutants by a 1/3 to 1/2.
  • It will greatly reduce dependence on fossil fuels.


  • The high vehicle cost- Battery, a vital component of an HEV, increases the cost of the vehicle, making it pricier than vehicles powered only by an ICE. The RBS also adds to the higher cost of an HEV.
  • Import dependency- upon countries like China and Australia for lithium-ion batteries used in EVs.

Government Initiative

FAME India – Hybrid and Electric vehicles scheme

  • Union Government on 1 April 2015 launched the Faster Adoption and Manufacturing of Hybrid and Electric vehicles (FAME)
  • The scheme was launched as part of the National Mission for Electric Mobility to boost eco-friendly vehicle sales in the country.
  • This scheme was launched to achieve the goals of the National Electric Mobility Mission Plan (NEMMP).
  • The Phase I-lasted from 2015 to 2019
  • Phase II of FAME started in 2019 and is expected to be completed by this year.
  • It mainly focuses on four areas such as technology development, demand creation, pilot project, and charging infrastructure.

HEV has the potential to reduce carbon emissions and achieve the Paris climate commitment. Countries need to collaborate for technology transfer and to create global as well as domestic markets for EVs.

Source: The Hindu

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