Hybrids have been around for well over a decade, and today, they’re more familiar to more drivers than ever. Numerous recent advances in technology and engineering have made today’s hybrids more powerful, more efficient and more compromise-free than ever, though hybrid cars still work, by and large, in the same way they always have: by combing propulsion from both a gasoline and electric drive system to achieve maximum fuel efficiency.
Want to know more about how hybrid cars work? Check out our Illustrated Guide to Hybrids. After you do, you’ll know things about batteries, understand what a power inverter is, and be more interesting at parties.
What is a Hybrid?
A hybrid is car propelled by a combination of gasoline and electric power. Using a conventional gasoline engine to drive the wheels, as well as a motor–generator, the hybrid car creates its own supply of electricity, which is stored in an on-board hybrid battery. When needed, power stored in the hybrid battery is used to drive the electric motor–generator, applying torque to the wheels and reducing the load on the gas engine.
So, in certain situations, electricity, not gasoline, is used to boost acceleration and performance. Many hybrid cars can even drive solely on stored electricity in some conditions. The result of combining an electric motor and a gasoline engine is a reduction in fuel use, a reduction in emissions, and, in many cases, improved performance.
Most hybrid cars use a conventional gasoline engine to create most of the power required for propulsion, as well as to drive the motor-generator which recharges the hybrid battery. Often, the gas engine in a hybrid car runs the high-efficiency Atkinson Cycle, which manipulates valve timing for optimal efficiency. Other minor tweaks are common, though ultimately, the gas engine in a hybrid car works in much the same way as the gas engine in any other car.
The Motor Generator
The motor–generator typically sits between the engine and wheels, often attached to, or integrated within, the vehicle’s transmission. The motor–generator serves two functions, referenced by its name.
As a motor, the motor–generator receives power from the hybrid battery and assists the gas engine in driving the wheels, or, drives the wheels all by itself, with the gas engine off.
As a generator, the motor–generator creates electricity, which is sent back into the hybrid battery. In generator mode, the motor–generator is driven either by the spinning action of the gasoline engine, or by the action of the rotating wheels of the car, in a process called regenerative braking. During regenerative braking, the rotation of the vehicle’s coasting wheels drives the generator, not the gasoline engine. In effect, regenerative braking creates electricity for storage in the hybrid battery every time the car slows down or brakes.
The Hybrid Battery
Hybrid batteries come in many shapes, sizes and chemistries. Lately, automakers are focused on making smaller and more powerful hybrid batteries, which are lighter, and take up less space within the cabin. Many hybrid models have their battery mounted behind the rear seats, or under the floor of the trunk. The hybrid battery has a cooling system to keep it at the optimal temperature for recharging and durability, and often consists of many smaller, internal cells, connected to one another. As the hybrid car drives along, the battery is constantly made to charge and discharge, while being maintained at a constant temperature, for maximum efficiency. Pictured is the battery pack in the new, 2017 Chevrolet Malibu hybrid. Notably, a new rectangular shape of the individual battery cells allows more cells (and therefore, more power) to be stored in the unit, compared to the cylinder-shaped cells in older hybrid batteries.
The Power Control Unit
The hybrid power control unit (the silver box next to the engine above) consists of inverters and converters, used to convert electricity from low voltage to high voltage (and vice versa), as well as from AC to DC, as power is generated, switched and distributed between various vehicle components. The power control unit is the central hub of the hybrid system, and works to ensure that all parts of the system have the proper amount, and type, of electricity to do their jobs. As the process of inverting and converting electricity generates plenty of heat, most power control units are liquid-cooled.
The Hybrid Success Story
The Toyota Prius is the world’s most popular and successful hybrid car model. Today, several generations in, the 2016 Prius is one of the most advanced hybrid cars on the road, and one that showcases the very latest in hybrid car technology and engineering. Prius has a four-cylinder gas engine, a hybrid battery, and an advanced Continuously Variable Transmission (CVT) which combines output from the gas and electric drive systems. Like many hybrid cars, the Prius is even capable of fully electric operation in certain situations, where the vehicle can be propelled solely by the electric motor, using no fuel.
A plug-in hybrid works the same way as a standard hybrid, with one key difference. Using a specialized, higher-capacity battery, drivers can plug this type of hybrid into an electrical outlet to further charge the battery before they drive. Where a standard hybrid doesn’t generate enough surplus power to drive solely on electricity for extended periods, plug-in hybrids allow drivers to top-up the battery by plugging the car in. The result is a considerable increase in the range the vehicle can drive on electricity alone, often several dozen kilometres, as opposed to three or four. Once the surplus power is depleted, the plug-in hybrid continues to function like a normal hybrid until it’s recharged.
A simple, effective and low-cost ‘Light Hybrid’ alternative was introduced in recent years by GM with their eAssist system. A motor–generator is connected to the front wheels and the engine. Regenerative braking is possible, and stored power is used to recharge a battery pack, just like a normal hybrid. The difference? The eAssist system simply uses that stored power to boost the gas engine, rather than to fully propel the vehicle in some situations. The result is a smaller, lighter and less complex system than a full hybrid, as well as improved fuel economy and performance over a gasoline-only car. For instance, in the 2017 GMC Sierra, GM’s eAssist system gives drivers 44 lb-ft more torque, improved mileage, reduced emissions, and no compromise.
This is the Porsche 918 Spyder, and it’s bonkers. One of the world’s fastest cars, the 918 Spyder is also a plug-in hybrid. Using powerful electric motors and a gasoline V8 engine in sync, output approaches 900 horsepower, though the 918 Spyder can be driven solely on electricity, and with zero emissions, for nearly 20 kilometres on a single charge. Using the latest in hybrid technology, Porsche has created a lightning-fast supercar that uses its hybrid system as both a tremendous performance advantage, and a tremendous fuel saving tool. Other exotic carmakers like McLaren and Ferrari are using hybrid technology to boost performance and fuel efficiency, too.
Advanced aerodynamics go hand in hand with hybrid powertrains to improve fuel efficiency and reduce emissions. With a high-efficiency powertrain and high-efficiency aerodynamics working together, drivers get even better mileage, and a quieter drive too. Some examples of advanced aerodynamics include active grille shutters, which regulate the airflow around and through the front of the vehicle in real time, to constantly fine-tune aerodynamic performance. Hybrid cars often use uniquely shaped wheels too, with a design that’s more aerodynamic. Revised hybrid-specific bumpers and underbody close-out panels are other implements typically used to help hybrid cars slip effortlessly through the air.
Hybrid cars achieve top levels of efficiency by minimizing the operation of the gas engine, which can cause issues in wintertime, as that gas engine is the primary means of heating the vehicle cabin. Run the gas engine too much when it’s cold outside, and fuel mileage suffers. Don’t run it enough, and vehicle occupants will be cold.
Nowadays, manufacturers have come up with numerous solutions to this issue. Grille shutters mentioned earlier, help. So does the Exhaust Gas Heat Recovery system. By capturing heat from the engine’s exhaust stream while it’s running and transferring it to the engine coolant, the engine can provide more warmth to the cabin, with less time spent running. This reduces fuel consumption by reducing the need to run the gas engine as often for heat. Some hybrid models even use occupant detection sensors, to focus cabin heating only on occupied seats for further fuel savings.