EXPLAINER | What exactly is a mild hybrid vehicle?

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  • Fuel prices keep increasing so many South Africans are looking for alternative vehicle solutions to lighten the load.
  • Vehicles have also become somewhat complicated and powertrains more sophisticated.
  • Volvo Car South Africa offers a varying range of products to best demonstrate what a hybrid vehicle is.

Vehicle systems have become somewhat complicated in recent times. There's no longer just petrol- or diesel-driven cars; now there are electric vehicles, hydrogen vehicles, plug-in hybrids and mild hybrids.  

Volvo Car South Africa is one automaker whose powertrain line-up features varying degrees of electrification to cater to a wide spectrum of needs, hence we'll use it as an example to explain its range from mild-hybrid derivatives to plug-in hybrid vehicles (PHEVs) and fully electric models. While the latter two are fairly self-explanatory, the definition of a mild hybrid is perhaps not quite so well understood.

READ | Looking for a car that ticks plenty of boxes? Haval's self-charging H6 HEV has it all

So, what exactly is a mild hybrid and what are its key benefits?

Volvo XC60 B5
Volvo XC60 B5

Well, like a plug-in hybrid, a mild-hybrid powertrain – as employed by various B-badged models in the XC40, XC60, XC90, S90 and V90 Cross Country line-ups – features both an internal combustion engine and an electric motor.

However, since the electric components play only a supporting role to the petrol engine, mild-hybrid vehicles aren't designed to run on battery power alone (one of the defining features of plug-in hybrids). Instead, the compact 48-volt lithium-ion battery pack and integrated starter generator – the latter replacing the traditional starter motor and alternator – work to assist the combustion engine when it is under load, boosting off-the-mark response while also adding a degree of smoothness and linearity to acceleration. 

2021 Honda Fit Hybrid EHEV
2021 Honda Fit Hybrid EHEV

In addition, the integrated starter generator fires up the petrol engine faster than a conventional starter motor is able to, resulting in noticeably smoother, almost seamless transitions when the vehicle's stop-start feature is active. This makes for a far less disruptive experience in slow-moving traffic. 

A further benefit, of course, is a reduction in tailpipe emissions, which means less of an impact on the environment. Volvo's B-badged mild-hybrid models achieve this without the need to plug in to a traditional source of electricity, since a clever brake-by-wire set-up interacts with the on-board energy recovery system to harvest what would otherwise be lost kinetic energy under deceleration. This energy is then used to charge up the compact battery, ready to support the petrol engine when required.

Haval HEV GT
Haval HEV GT

Finally, since this is the most conservatively electrified option in the broader hybrid family, the typical mild hybrid offers an almost unchanged driving experience when compared with conventional combustion-engined vehicles (and, again, likewise requires no access to a charging point). It thus demands virtually no recalibration from drivers new to the technology, all while delivering smoother, more powerful acceleration.

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