Hybrid vehicles are making their mark on the automotive industry, growing in popularity alongside electric vehicles (EVs). So what is a mild hybrid vehicle? Is it poised to become the next big thing on the market, or is the term just marketing jargon? Let’s take a closer look at mild hybrids and how they stack up against full hybrids.
What Does Mild Hybrid Mean?
Honda was the first manufacturer to release a mainstream mild hybrid electric vehicle (MHEV) in the US. Their MHEV Honda Insight hit the market in 2000, and since then more mild hybrids have followed suit. The MHEV class serves as a sort of inexpensive electric vehicle alternative, a variant of the hybrid vehicle, but how “electric” is it really?
Mild hybrid systems rely on a battery-powered, low-output electric motor to start, brake, and slow the vehicle. The motor can’t power the car alone, instead relying on a gasoline-fueled internal combustion engine (ICE) to run a majority of the vehicle’s systems and propel the vehicle forward. However, MHEV systems do come with a more powerful electrical system in general.
Like full hybrids, a mild hybrid activates the electric motor in a different fashion to recover some of the kinetic energy it creates when braking, and stores this energy in the high-voltage battery. Both full hybrids and mild hybrids also have a 12-volt battery that receives its 14.5-volt charge through a DC to DC converter connected to the large high-voltage battery system. Both systems recycle this power to charge the high-voltage battery during braking events.
The MHEV system also saves fuel by shutting down the ICE whenever the vehicle’s cruising, stopped, or braking.
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Pro Tip: Early Honda Insight (Gen 1 and 2) platforms have a 12-volt starter and can be driven even if the high-voltage system is offline. Later Prius models don’t have this 12-volt starter but use the high-voltage motor to start the engine.
Mild Hybrid vs. Full Hybrid
When comparing mild hybrid systems to full hybrid systems, take the degree of hybridization into account. The typical assumptions regarding a hybrid vehicle, including greatly increased fuel efficiency and a powerful electric motor, aren’t as applicable to a mild hybrid as they are to a full hybrid.
Both mild and full hybrids use electric motors alongside gasoline engines. There are two electric motors in the transaxle on this type of hybrid, which, on front wheel drive platforms uses a special type of continuous variable transmission that has both motors and the ICE all connected to the three components of a single planetary gearset in the transaxle.
In some full hybrids, like plug-in hybrids, these electric motors can temporarily power the entire vehicle alone, but only for a very short distance.
Mild hybrids, on the other hand, while also in the gasoline-electric vehicle class, have weaker electric motors that can’t propel the vehicle without help. MHEV systems act as power boosters to internal combustion engines. They improve fuel efficiency by working with the ignition and braking systems. So while mild hybrids aren’t as fuel-efficient as full hybrids, they can still improve fuel efficiency by 10 to 15 percent.
Mild Hybrid Benefits and Drawbacks
Mild hybrids have benefits and drawbacks, especially when compared to full hybrids and traditional ICEs.
Benefits
One of the main benefits of a mild hybrid vehicle is that they’re much more affordable than full hybrids. Their simpler internal design is much less costly for manufacturers to produce, which translates to a smaller price tag at the dealership. They also provide better fuel economy and produce fewer CO2 emissions than ICEs. Transitioning to a mild hybrid vehicle is easier since you don’t need to modify your driving habits at all.
Drawbacks
Mild hybrid cars are definitely closer to traditional ICE vehicles than to electric vehicles. They produce more pollutants and have lower fuel economy than full hybrids. They also have very short electric-only range, with most models having no electric-only range at all. Additionally, mild hybrids don’t qualify for federal tax credit, unlike fully electric and plug-in hybrid vehicles.
Ultimately, mild hybrid vehicles have their charms and their caveats. If you’re simply after a more fuel-efficient vehicle that drives almost no differently compared to an ICE vehicle, then check out a mild hybrid. Whether its benefits are enough to earn it a place in your garage is up to you.
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