Abstract
In battery electric vehicles the battery system has to satisfy demanding requirements. On the one hand, high power capabilility has to be provided for varying states of charge and temperature. On the other hand, the battery system should achieve a maximum service life, optimal energy efficiency and a high overall driving range. This paper compares a conventional single-cell battery system with two hybrid battery system topologies that aim at improving the mentioned aspects of the conventional system. The hybrid battery systems each comprise two battery parts connected via a dc-to-dc converter, one part including lithium-ion battery cells optimized for high energy density and the other part equipped with high power density type lithium-ion cells. An optimal control problem is formulated and solved with Dynamic Programming. The mentioned topologies are then compared in terms of energy efficiency, power capability and current distribution. A real life driving cycle power demand is used for this comparison. It can be shown that the hybrid battery system reduces the occurrence of high current rates on the high energy battery part and shows better energy efficiency when operated with aged high energy battery cells. Furthermore the hybrid battery system’s potential to obtain a high power capability in low state of charge regions is shown.
Highlights
IntroductionCapacity fade and the scalability of power and energy requirements are challenges in battery system design and operation
An increasing internal resistance, capacity fade and the scalability of power and energy requirements are challenges in battery system design and operation
To get an insight into the electric vehicle’s performance at different stages of the high energy battery lifetime, an investigation for the proposed topologies is done with a high energy battery at begin of life (BoL) and end of life (EoL)
Summary
Capacity fade and the scalability of power and energy requirements are challenges in battery system design and operation. The battery system is the main cost factor within the vehicle’s powertrain [13, 23] To cope with these problems one can find a hybrid battery system topology in literature, combining a high energy and a high power storage part. The hybrid system makes recuperation possible for Fuel Cell Electric Vehicles [28], and provides advantages in terms of power capability [28] and scalability [24]. For Hybrid Fuel Cell and Hybrid Electric Vehicles, optimization problems that can be solved off-line via dynamic programming, are formulated and solved in [1, 17, 19]. An optimal control problem minimizing battery power losses for two hybrid battery system topologies is formulated and solved. The behavior and performance of these topologies is compared to a single-cell battery system for a specified vehicle and driving cycle scenario
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
