Characteristics of Battery SOC According to Drive Output and Battery Capacity of Parallel Hybrid Electric Vehicle

Abstract

To mitigate global warming caused by vehicles, emission regulations have been implemented for all automobiles. Hybrid electric vehicles (HEVs) are being designed to meet consumer demand for eco-friendly vehicles that offer increased power and improved fuel efficiency. HEVs are powered by an internal combustion engine (ICE) in combination with one or more electric motors that use electrical energy stored in a secondary battery, which is typically a lithium-based battery. With the use of such a hybrid drivetrain system, the fuel efficiency can be improved over that of conventional ICE vehicles. In this study, we conducted a vehicle-driving experiment to evaluate a transmission-mounted electric device (TMED) type parallel HEV using a chassis dynamometer and on-board diagnostics (OBD) signal-measuring equipment. In addition, we performed a numerical analysis using the CRUISE vehicle simulation code with experimental data. In our analysis, the engine output, which affects the torque of the drive motor, and the capacity (energy density) of the lithium-ion polymer battery were set as variables that affect the fuel-economy performance. As a result of this numerical analysis, a hybrid power-drivetrain model based on CRUISE was developed, and the current balance was evaluated according to the change in the battery capacity. We found that the battery state of charge (SOC) dropped because of a decrease in battery capacity. Thus, we predicted that the lithium-ion battery capacity would be reduced.

Comparative numerical evaluation of ECE-EUDC cycle performances of a hypothetical car equipped with three types of propulsion systems: conventional, series hybrid and parallel hybrid

“…To mitigate the effects of global warming, the hybrid electric vehicle uses a thermal engine in combination with at least one electric motor (some are acting as electric generators), therefore fuel efficiency is improved compared to conventional vehicles [2]. Thus, through the efficient management of the hybrid propulsion system, the consumer demand is satisfied by the increased power, the decreased fuel consumption and the ecological factor of the vehicle.…”

Energy Management Control and Optimization for Hybrid Electric Vehicles

“…Last but not least, other works that presented results that came to answer some thoughtprovoking questions related to hybrid electric vehicles and their energy management systems. On the one hand, the effects of the driving torque and capacity (energy density) of the lithium-ion battery on the fuel economy of a parallel hybrid vehicle were studied in [11]. The following conclusions regarding the state of charge characteristics and current balance of the lithium-ion battery were drawn: when the battery capacity is reduced by 20%, by using a variety of strategies (e.g., downsizing, engine operation strategy, state of charge increase) to compensate for the state of charge drop, it will be possible to operate hybrid electric vehicles at lower battery capacities; for efficient battery use, state of charge must be charged to near 50%.…”