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What is A Mild Hybrid Car?

By Phil Gardner | November 17, 2021


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Find out what a mild hybrid car is, how they differ from regular hybrids and plug-in hybrids and whether you should buy one...

 What is A Mild Hybrid Car?

Hybrid cars come in varying shapes and sizes, but also in varying degrees of Hybrid-ness. Some are more Hybrid than others. A Mild Hybrid is a car that uses both a petrol engine and an electric motor in unison, however, the electric motor only performs a supplementary role to the engine.

Each manufacturer has a different approach to their ‘mild hybrid’ cars, but generally speaking, the electric motor performs a similar role in all of them. The main aim is to reduce the fuel consumption and CO2 emissions of the vehicle by using a small electric generator to take on the roles of the starter motor and help with accelerating. 

Most mild hybrids use a small 48-volt electrical system, which steps into power components that would typically operate using the power of the engine, allowing the whole car to run more efficiently.

Mild hybrids are only able to provide a small amount of electrical power to the car, and they are not able to run off electricity alone, unlike Plug-In Hybrid cars and self-contained hybrid cars.

It is thought that a mild hybrid car is about 15% more efficient than its like-for-like petrol or diesel-powered alternative.

 How Do You Charge a Mild Hybrid Car? 

Mild Hybrid cars cannot be plugged into a wall and do not need to be proactively charged by the owner. The onboard battery is much smaller than in regular hybrid vehicles and therefore requires much less power to charge.

You charge a mild hybrid by simply driving the vehicle. Kinetic energy is harnessed under braking and turned into power which, in turn, regenerates the onboard battery. You can therefore seamlessly switch to a mild hybrid car from a regular petrol or diesel car without noticing any difference whatsoever, other than at the fuel station where you’ll be saving money.

 How Many Types of Hybrid Cars are There?

There are 3 main types of Hybrid vehicles, and they can be explained as follows:

  • Mild Hybrid: A small electric motor is used to alleviate some of the taxing roles of the engine, such as stop/ start functionality and heavy acceleration. Mild Hybrids charge themselves and are often some of the cheapest hybrids to buy on the market however they are not able to run on electricity alone and therefore always require fuel.
  • Parallel or Self-contained Hybrid: These are hybrid cars that do not need to be charged via a charging point and instead they top their batteries up via regenerative braking and from their combustion engine. These hybrids have larger onboard batteries than Mild Hybrids and are typically able to cover up to 15 miles or so on electricity only. 
  • Plug-In Hybrid: These are the Hybrids that can be plugged in using the countries network of public charging points or via a domestic charger. Plug-In Hybrids are by far the most efficient hybrid vehicles available and some models are now able to offer in excess of 50 miles of electric-only driving on a single charge. 

Mild Hybrid models are certainly the most accessible hybrids on the market, and they’re the only hybrids available with a manual gearbox. The trade-off is that they are only slightly more efficient than non-hybrid vehicles and they don’t see the benefits of savings in road tax as they are unable to cover any distance on electric power only.

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