What is a hybrid?
A hybrid car is a car that uses both an internal combustion engine and an electric motor for power, but only uses gasoline as fuel. (Diesel hybrids exist, but are primarily used in locomotives and other very heavy-duty applications.) Hybrids have a small, high-voltage battery to power the electric motor, but , no need to plug it in.
In the absence of an external power source, electricity is recovered for the motor during braking in a process called regenerative braking (regen for short). If you’re an F1 racing fan, you may have heard of the Kinetic Energy Recovery System (KERS). Regenerative systems do not replace conventional brakes, but serve as an important replacement. The electrical energy collected in this process is stored in a battery and immediately reused during the next acceleration. When you leave the stoplight, the saved energy gets your car moving again, possibly delaying restarting the gasoline engine until you reach 25 mph. If you stop it again, the cycle repeats. This makes hybrid cars much more fuel efficient in the city than non-hybrid cars, not to mention on the highway itself.
How does regenerative braking work?
Regen is a natural evolution of electric motor functionality. Applying electricity to an electric motor makes the car move (or helps it move). When the car moves, that same motor becomes a generator, reversing the flow of electrons and using that movement to feed electricity back into the battery. This is why hybrid electric motors are sometimes called motor generators. Importantly, this process slows the car down, so regeneration is triggered when you hit the brakes or go down a hill, and is managed by the computer.
One-pedal driving (a process that triggers regeneration when you lift the throttle) is primarily found in full EVs, not hybrids. This is because EVs have larger electrical systems and much larger batteries. How small are hybrid batteries? They are typically no more than 1 kilowatt hour (kWh) and only 1 to 2 percent of the size of a full electric vehicle battery.
Still, the hybrid regen is powerful enough for most everyday decelerations. The computer constantly monitors how hard you press the brake pedal, so it matches traditional brakes (pads and rotors) during sudden stops and emergency situations. This regeneration-first approach maximizes the collection of electricity for propulsion, resulting in significantly improved fuel efficiency. Regen is the basic element that all hybrid cars have in common, but there are differences when it comes to how the gasoline engine is used.
parallel hybrid
This is the most common type, which uses both a gasoline engine and an electric motor to run. You can also do both at the same time. Electric motors are more effective at low speeds because their high initial torque and efficiency make the most of limited battery energy. After a delayed restart, the gasoline engine joins and eventually takes over as speed builds and settles into cruise conditions, at which point the engine reaches its sweet spot. Some designs sandwich a single motor between the engine and a conventional transmission, while others use an arrangement of two electric motors working together to act as a continuously variable transmission for the engine. Examples of the former include early Honda hybrids and current Hyundai and Kia products such as the Elantra. The latter covers hybrid vehicles from Toyota, Lexus, Maverick, and other Ford companies.
series hybrid
This type is less common, but is growing in popularity. They also use battery energy recovered through regeneration to propel the vehicle at low speeds, and a main drive motor that recovers energy during deceleration. As speed increases and energy becomes low, the engine is switched on, driving a second dedicated generator that converts gasoline power into electricity and continues to power the battery. This means the wheels are electrically driven at all speeds, and the power delivery always feels smooth and seamless. The downside is that it requires an extra step to convert gasoline to electricity, reducing efficiency, but the new approach makes this less important. Honda is the latest champion of this type, found in the latest versions of the Civic, CR-V, and Accord Hybrid.
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Like anything else, hybrid systems do not adhere to such definitions. Toyota’s Hybrid Synergy Drive is primarily a parallel system, but its dual-motor design also allows short-term series generation when the engine’s most efficient operating speed produces more power than the driver needs . Similarly, Honda’s latest Primary Series hybrid system can clutch the engine to directly drive the wheels under certain conditions if the computer determines it is more efficient. Both exceptions are good because they show that engineers are pursuing the most efficient solution, not the easiest to explain.
Hybrid benefits
The main advantage of hybrids is the ability to recover and reuse braking energy that would otherwise be lost as heat or wear in the brakes. What most people are interested in is using this recovered energy to conserve fuel and increase MPG by using the electric motor to delay starting the gasoline engine, but for sports-oriented Hybrids use the recovered energy to increase overall power and speed.
Fuel-saving hybrids are a great option for people looking to save money or reduce their carbon footprint. After all, high MPG and low carbon emissions are two sides of the same coin. If you live in an apartment or only own one car, an EV may not be practical. Hybrids, on the other hand, are purely gasoline-powered vehicles with no strings attached or special refueling requirements.
In more practical terms, hybrids focus on regenerative braking, which means brake pads and rotors last much longer than regular cars. There’s also no separate starter motor as the electric motor takes care of that. The hybrid’s small battery also takes up less space and does not require expensive battery chemistry.
Other types of hybrids
Mild hybrids, sometimes called belt alternator starters or BAS hybrids, have a 48-volt battery and cannot produce meaningful propulsion. However, such systems have an additional regenerative function, which allows the starter and alternator to be combined into one unit, seamlessly starting the engine “in gear,” so to speak, and allowing the start-stop to start automatically. Make your system run smoothly.
A fuel cell hybrid is a series hybrid with an electric motor, regenerative braking, and a small high-voltage battery. But they don’t have gasoline engines. Instead, there are fuel cells, devices that convert hydrogen gas into electricity, with the only byproduct being water. Therefore, fuel cell hybrids always run on electricity and are as quiet as EVs. The company’s hydrogen tanks can be filled in five minutes, just like a regular car, but the stations are very limited in availability, mostly in California’s major population centers.
Plug-in hybrids are regular hybrids with significantly larger batteries designed to cover 20 to 50 miles at full speed on electricity alone. This is where all the issues with EV battery charging center around, but it’s less severe since a plug-in hybrid’s battery is about a quarter the size of an EV. This makes it easy to plug in at home, and those who can manage this end up owning a part-time EV with no leads. That means it’s an EV commuter during the week, but has full gas capability for long trips. It also retains the benefits of a regular hybrid, making it efficient even when running on gasoline. The downsides include a larger battery that costs more to purchase, a larger battery that is more likely to encroach into cargo space, and a potentially smaller gas tank.
Dan Edmunds was born into the automotive world, but not in the way you might imagine. His father, a former racing driver, opened a race car manufacturing shop called Auto Research, where Dan honed his skills as a metal fabricator. He then attended engineering school, then he attended SCCA showroom stock racing, a combination of which landed him suspension development jobs at two different automakers. His writing career began when he was picked up by Edmunds.com (no relation) to establish a testing department.