CHAPTER FIFTEEN A Roadmap to Understand Battery Performance in Electric and Hybrid Vehicle Operation Bor Yann Liaw 1 and Matthieu Dubarry Hawai'i Natural Energy Institute, SOEST, University of Hawai'i at Manoa Honolulu, HI 96822, USA Contents 1. Introduction 2. Field Test Data Collection and Analysis 2.1 Vehicle usage pattern analysis 2.2 Representative usage schedule 3. Laboratory Battery Tests 3.1 Assessing battery performance 3.2 Understanding battery degradation mechanisms 3.2.1 SOC determination by relaxed cell voltage 375 378 378 380 382 384 385 387