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How Do Hybrid Drive Systems Work?

If you read the automotive headlines, it can be easy to think that the electric-car revolution is about to take a major leap forward. After all, mainstream automakers are promising to electrify many of their current models by 2020, and that includes top sellers like the Ford F-150. And premium brands, such as Jaguar and Land Rover, are claiming they’ll do the same thing, within the same time frame, to their entire lineups.

Yet for potential customers, it’s important to remember that most of these electrified entries won’t be full-on electric cars: They’ll blend traits from both electric vehicles and gasoline-powered cars. In other words, they’ll be hybrids.

Even though these vehicles still require gas, their hybrid technology can have a magical effect on fuel efficiency. A 2018 Toyota Camry, for example, earns impressive EPA ratings of 29/41 mpg city/highway with its standard powertrain. But adding a hybrid powertrain can raise those grades to 51/53 mpg city/highway. That’s a whopping 75 percent jump in fuel efficiency for city driving and a nearly 30 percent increase in fuel efficiency on the highway.

Of course, hybrid systems aren’t really magic. And they’re not that complicated, either.

(Toyota Motor Sales, U.S.A., Inc.)

What are the Components of a Hybrid Powertrain?

The basic hybrid propulsion system relies on three building blocks. First, doing most of the heavy lifting is a traditional internal combustion engine. In many hybrid vehicles, though, it’s been modified to run on what’s known as the Atkinson cycle. Without getting into too many details, a typical internal combustion engine gets its power from a four-step process. Air and fuel are sucked into the cylinder, the piston compresses the mixture, the spark plug ignites it (forcing the cylinder back down) and then the cylinder rises again to push out the exhaust gases.

The Atkinson cycle, which is named after 19th century engineer James Atkinson, adjusts the timing of the engine’s valves to make sure the cylinders don’t get entirely filled with the fuel-air mixture. Obviously, this means less fuel is used. This also causes these engines to produce less power, but the electrical part of the hybrid powertrain compensates for this shortcoming.

The hybrid system’s onboard battery packs and electric motors provide notable advantages when it comes to efficiency. The battery packs supply electricity to the electric motors, and the motors help to significantly reduce the workload and fuel consumption of the internal combustion engine. Some hybrids can even store enough electricity for a significant all-electric driving range.

The new generation of hybrid sports cars, like the Acura NSX, don’t rely so much on electricity to replace gasoline power; they use it to provide supplemental muscle. When a hybrid system is used in this way, gas and electric sources can unite to give a vehicle’s total system output a major boost.

(American Honda Motor Co., Inc)

How Many Electric Motors Do Hybrids Have?

The NSX also brings us to another distinguishing feature among hybrids: the number of electric motors they have. For example, Acura’s new supercar has three: a motor driving each front wheel, and a single motor driving both rear wheels. On the other end of the spectrum, the 2018 Buick LaCrosse has just one motor. This kind of flexibility is a notable benefit for hybrid automakers, allowing them to fine-tune performance to better meet customers’ needs, including the need for electrically assisted all-wheel drive.

(General Motors)

Are There Different Types of Hybrid Vehicles?

Broadly speaking, there are two types of hybrids: standard hybrids and plug-in hybrids. The key difference between the two has to do with where the vehicles get their electricity and how much they can store in their battery packs. We’re not talking about the ultimate upstream source of that electricity, which is an issue for another day. We’re focused on more immediate sources, starting with regenerative braking.

This technology is standard for both kinds of vehicles and works by recapturing some of the energy lost during braking. Rather than being converted into heat, the energy is transformed into electricity and stored in the vehicle’s battery pack.

Plug-in hybrids complement regenerative braking with the ability to recharge by being be plugged into an outlet or charging station, in a manner that mirrors the recharging process that takes place with an all-electric vehicle. In fact, some plug-in hybrids, including the Chevrolet Volt, are sometimes called extended-range electric vehicles since they’re more like electric cars with onboard gas-powered generators.

Plug-in hybrids also have higher-capacity battery packs than standard hybrid vehicles. Looking only at the vehicles already mentioned, the battery pack for the hybrid system in the LaCrosse is rated at 0.45 kWh. The Volt plug-in hybrid (which has an all-electric range of 53 miles) provides capacity of 18.4 kWh capacity.

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