A Novel Temperature–Hysteresis Model for Power Battery of Electric Vehicles with an Adaptive Joint Estimator on State of Charge and Power

Xu Lei,Guiping Wang,Xi Zhao,Weiyu Liu

doi:10.3390/en12193621

Abstract

The battery state of charge (SOC) and state of power (SOP) are two essential parameters in the battery management system. For power lithium-ion batteries, temperature variation and the hysteresis effect are two of the main negative contributions to the accuracy of model-based SOC and SOP estimation. Thereby, a reliable circuit model is established herein to accurately estimate the working state of batteries. Considering the effect that temperature and hysteresis have on the electrical system, a unique fully-coupled temperature–hysteresis model is proposed to describe the interrelationship among capacity, hysteresis voltage, and temperature comprehensively. The key parameters of the proposed model are identified by experiments operated on lithium-ion batteries under varying ambient temperatures. Then we build a multi-state joint estimator to calculate the SOC and SOP on the basis of the temperature–hysteresis model. The effectiveness of the advanced model is verified by experiments at different temperatures. Moreover, the proposed joint estimator is verified by the improved dynamic stress test. The experimental results indicate that the proposed estimator making use of the temperature–hysteresis model can estimate SOC and SOP accurately and robustly. Our results also prove invaluable in terms of the construction of a flexible battery management system for applications in the actual industrial field.

Highlights

With the rapid development of the automobile industry, the energy crisis and environmental pollution have accelerated the research and application of electric vehicles (EV) [1]
Based on the model-based state of charge (SOC) and state of power (SOP) estimators mentioned above, we propose a joint estimator for these two states
Since the ITS5300 battery test system requires more one cell to collect field data, two cells were connected in series as a battery pack during the experiment, than one cell to collect field data, two cells were connected in series as a battery pack during the and three battery packs were used for the experimental data collection

Summary

Introduction

With the rapid development of the automobile industry, the energy crisis and environmental pollution have accelerated the research and application of electric vehicles (EV) [1]. Power battery is the heart of EV, and its safety and reliability should be ensured [2]. An accurate estimation of the state of charge (SOC) achieves the remaining power of the battery accurately. The SOC is the key factor for the battery management system (BMS) and the basis for the EVs’ power allocation strategies [3,4,5]. The state of power (SOP) is an index reflecting the instantaneous power performance of the battery. Compared with the SOC and the State of Health (SOH), the SOP can more directly reflect the exchange of energy between the battery system and the external system [9]

Objectives

Findings

Discussion

Conclusion