VS - Electrical Systems From Stop-Start to Hybridization

Vehicle braking contributors Vehicle braking contributors

Cruising

Deceleration Deceleration

Acceleration Acceleration

Cruising

Stable regime Stable regime

Engine-On Coasting Engine-On Coasting

Recovery Recovery

Vehicle speed Vehicle speed

Oil pump Water pump Compressor Camshaft Oil pump Water pump Compressor Camshaft

Braking Braking

Engine and drive train frictions Engine and drive train frictions

Aerodynamics Aerodynamics

Pumps and valve train Pumps and valve train

Alternator Alternator

Rolling

Rolling

Engine torque consumers - Engine braking Engine torque consumers - Engine braking

Regen torque Braking torque Regen torque Braking torque

Driving phases Driving phases

In a braking phase, some free conversion from vehicle kinetic energy to board-net electrical energy can be performed by increasing the electrical demand on the alternator. Increasing the electrical demand on the alternator must be understood as harvesting some spare electrical energy for further uses, considering that an appropriate battery pack is able to store this amount of energy. No fuel being required to generate this energy (no torque demand at engine level), the global drivetrain efficiency is thus improved, this is the aim of energy recovery during braking also known as regenerative braking. Increasing the electrical demand generates in essence more counter torque on the alternator and engine belt-drive, expanding the natural engine-

braking level thus the vehicle global braking level. The desire to recover energy through regenerative braking can result in different braking torque being applied to the wheels on front and rear axles requiring a smart balancing between recovery demands and conventional braking to ensure vehicle controllability. While it is often referred to as regenerative braking, some energy conversion can be applied to some engine-on coasting phases even if the brakes are not necessarily applied. Regenerative braking level highly depends on machines and battery technologies. While 2017 is a turning point for affordable Mild- Hybrid expansion using dedicated lithium-ion battery packs, some past generations used to recover energy in more modest conditions.

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