1. Powertrain Configuration:
- Parallel Hybrid: In a parallel hybrid system, the ICE and electric motor are mechanically coupled to the drivetrain. When the vehicle operates in hybrid mode, they can both provide power to the wheels simultaneously or work independently depending on the power demand.
- Series Hybrid: In a series hybrid system, the ICE is not directly connected to the wheels. Instead, it acts as a generator to produce electricity, which powers the electric motor that drives the wheels. The ICE in a series hybrid system may never mechanically drive the wheels.
2. Energy Flow:
- Parallel Hybrid: In a parallel hybrid system, power from the ICE and electric motor can flow directly to the wheels or be combined before reaching the wheels. The electric motor can assist the ICE, especially during acceleration, and also recover energy through regenerative braking.
- Series Hybrid: In a series hybrid system, all power sent to the wheels comes from the electric motor. The ICE's only purpose is to generate electricity through the generator, which charges the battery and supplies power to the electric motor.
3. Efficiency:
- Parallel Hybrid: Parallel hybrid systems generally achieve higher fuel efficiency compared to conventional gasoline-powered vehicles, but not as high as series hybrid systems because of more mechanical losses.
- Series Hybrid: Series hybrid systems are typically more efficient in city driving conditions and start-and-stop scenarios because capturing regenerative braking energy and providing low-speed propulsion is the electric motor's sole responsibility. Series hybrids generally use gasoline more efficiently when compared to parallel hybrids.
4. Complexity and Cost:
- Parallel Hybrid: Parallel hybrid systems are mechanically less complex because the ICE and electric motor can directly power the wheels, but they can be more expensive than series hybrid systems due to additional transmission components.
- Series Hybrid: Series hybrid systems are structurally simpler since the power generation and propulsion are separate, but they involve a more intricate electrical system that can increase overall vehicle cost.
It's important to note that hybrid technology continuously evolves and there may be variations and exceptions to these basic differences, and some vehicles may implement variations or combinations of both parallel and series configurations.
