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How do hybrid cars work?

What does a hybrid car do?

A hybrid car works by utilising both a petrol-powered internal-combustion engine (ICE) and an electric motor that is powered by a battery. There are also diesel hybrid cars, but these are far less common - petrol hybrids are like birds, diesel ones are a bit more like dodos. 

If the thought “How does an electric car work?” has ever crossed your mind, the answer is quite simple: they are vehicles that have a rechargeable battery pack that powers an electric motor, completely doing away with the need for fossil fuels and their harmful emissions. 

What is a hybrid car and how hybrid cars work is a tiny bit more complicated.

Hybrid car technology is usually divided into three main types: a mild hybrid (also known as power-assist hybrids and battery-assisted hybrid vehicles or BAHVs), a hybrid electric vehicle (HEV) and a Plug-in Hybrid Electric Vehicle (PHEV)

Each have different-sized battery packs, different ways those battery packs are charged and different ways in which the ICE and electric motor work in conjunction with each other to power the car. 


Hybrid engines consist of a traditional ICE and an electric motor powered by a hybrid car battery, although in a BAHV the former is the main source of power, while the latter is usually used only when the car is coasting, braking, or stopped.

While some hybrids have an electric-only mode, BAHVs do not - the electric motor is only used to mildly assist the car’s combustion engine and is never relied on fully as the car’s main source of power. 

BAHVs may also use regenerative braking, a process where kinetic energy that’s created from the car slowing down can either be stored away for later in the battery, or can be used to power the electric motor directly. 

The electric motor in a BAHV is usually mounted between the internal-combustion engine and transmission, taking the place of the torque converter.

A BAHV will reduce your fuel consumption and emissions, but not by a whole lot - you’ll want a HEV or PHEV if you want to make any kind of meaningful difference to the amount of petrol you use and the emissions your car creates.


A full hybrid places a bit more emphasis on the use of the battery-powered electric motor, meaning both it and the battery itself will be a bit larger compared to what you’ll find inside a BAHV. 

HEVs make use of regenerative-braking technology to recharge the car’s battery and power the electric motor, forgoing the need to ever have to plug-in the battery to charge it (more on that later). 

There are varieties of HEVs, however, that use the ICE to turn an electrical generator, which can either recharge the vehicle’s battery or directly power the electric motor.

In an effort to further reduce emissions, many HEVs (like many cars in general) also employ a stop-start function where the ICE is shut down whenever the car is idle (if you’ve ever heard a car’s engine cut out and then quickly restart again while you’re waiting at traffic lights, that’s what’s going on). 

HEVs typically use the ICE as the primary source of power while the battery-powered electric motor acts as a kind of “power boost” to assist during different driving conditions, like when the vehicle requires rapid acceleration. 

HEVs are becoming increasingly popular due to their ability to reduce emissions and save on fuel costs when compared to traditional ICE vehicles. 


These types of hybrids do exactly what you think they do: they plug in to an external electric power source to charge up their battery packs, rather than relying on other forms of energy-generating technology, like regenerative braking. 

The battery pack and electric motor is typically a much more substantial part of a PHEV, meaning they’re bigger, heavier and take longer to charge compared to the smaller batteries you’d find in a HEV or BAHV. 

The benefit, though, is that the battery offers the PHEV a sizeable range of electric-only running (and thus zero-emission motoring). 

This also reduces the “range anxiety” experienced by EV drivers worried their battery will run out of charge while they’re in transit, as the petrol engine is always there on standby to kick in and take over should the battery become depleted. 

PHEVs aren’t completely green, due to the fact they still employ the use of an ICE from time to time, and the electricity they use can often be generated using harmful fossil fuels. 

Renewable, zero-emission electricity generated by means such as wind power, solar energy or hydroelectricity can also be utilised, however, to further reduce the impact of a PHEV. 

The future of hybrids

Hybrid vehicles are expected to continue growing in popularity in the coming years, with hybrid sales projected to keep rising until they peak in 2027 with a global market value of $792 billion.

There’s also a decent chance that hybrids using lithium-ion batteries will eventually be superseded by full-electric cars that use a hydrogen fuel cell, but that technology is still some years away from hitting the consumer market in a meaningful way.

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