Plug-in hybrid electric vehicles (PHEVs) represent a blend of traditional combustion engine technology and modern electric vehicle innovation. These vehicles utilize a rechargeable battery to power an electric motor, alongside a gasoline or other fuel-based internal combustion engine (ICE). A key feature of PHEVs is their ability to be charged from external electricity sources, such as home wall outlets or dedicated charging stations, in addition to the conventional methods of ICE and regenerative braking. Typically, a PHEV will operate primarily on electric power, drawing from its battery until it reaches a near-depleted state. At this point, the vehicle seamlessly transitions to using its internal combustion engine, extending its driving range.
Key Components Explained
To understand how a plug-in hybrid operates, it’s essential to examine its core components:
Auxiliary Battery: Similar to a traditional car battery, the auxiliary battery in a PHEV is a 12-volt system. It plays a crucial role in initiating the vehicle’s systems before the high-voltage traction battery is engaged. It also powers the car’s various accessories, such as lights and onboard computer systems.
Charge Port: This is the gateway for external charging. The charge port allows you to connect your PHEV to an external power source, whether it’s a standard household outlet, a Level 2 charger at home or work, or a public charging station. This connection enables the replenishment of the high-voltage traction battery pack.
DC/DC Converter: The traction battery pack operates at a high voltage. The DC/DC converter is vital for stepping down this high-voltage DC power to a lower voltage. This lower voltage DC power is necessary to charge the auxiliary battery and operate the vehicle’s various low-voltage accessories.
Electric Generator (Regenerative Braking System): An electric generator is used during braking. When you decelerate or brake, the generator captures the kinetic energy from the rotating wheels and converts it back into electrical energy. This energy is then fed back into the traction battery pack, increasing the vehicle’s overall efficiency and range. Some PHEV designs integrate the generator function with the electric motor itself, creating a motor-generator unit.
Electric Traction Motor: This motor is the primary driving force when the PHEV is operating in electric mode. Powered by the traction battery pack, the electric motor propels the vehicle’s wheels. Like the generator, some systems combine motor and generator functions into a single unit.
Exhaust System: As PHEVs have an internal combustion engine, an exhaust system is still necessary. This system safely channels exhaust gases produced by the engine away from the vehicle. It includes a three-way catalytic converter to minimize harmful emissions released into the atmosphere.
Fuel Filler: For models that utilize gasoline, the fuel filler is the standard point for refueling. It’s designed to securely connect with a fuel dispenser nozzle, allowing for the gasoline tank to be replenished just like a conventional gasoline car.
Fuel Tank (Gasoline): This tank stores the gasoline that powers the internal combustion engine. The gasoline serves as a secondary energy source, allowing for extended driving range once the electric battery is depleted.
Internal Combustion Engine (Spark-Ignited): The ICE in a PHEV is typically a spark-ignited gasoline engine. Fuel is injected into the engine’s intake manifold or directly into the combustion chamber. The fuel-air mixture is then ignited by spark plugs, generating power to drive the vehicle or charge the battery, depending on the driving mode and system design.
Onboard Charger: When you plug your PHEV into an AC power source, the onboard charger is responsible for converting this AC electricity into DC electricity. This DC power is what the traction battery pack needs for charging. The onboard charger also manages the charging process, communicating with charging equipment and monitoring critical battery parameters like voltage, current, temperature, and state of charge to ensure safe and efficient charging.
Power Electronics Controller: This unit acts as the brain for managing electrical power within the PHEV system. The power electronics controller regulates the flow of electrical energy from the traction battery to the electric motor. It precisely controls the motor’s speed and torque output, optimizing performance and efficiency.
Thermal Management System (Cooling): Maintaining optimal temperatures for various components is crucial for performance and longevity. The thermal system in a PHEV is responsible for regulating the temperature of the engine, electric motor, power electronics, and battery pack. This system ensures all components operate within their ideal temperature ranges, preventing overheating or damage.
Traction Battery Pack: The high-voltage traction battery pack is the energy storage powerhouse of the PHEV’s electric drive system. It stores the electrical energy that powers the electric traction motor. The capacity of this battery pack determines the electric-only driving range of the PHEV.
Transmission: The transmission system in a PHEV transfers mechanical power from both the engine and/or the electric traction motor to the vehicle’s wheels. It ensures that power is delivered efficiently to drive the vehicle under various conditions, whether using electric power, gasoline power, or a combination of both.
