Quantifying Electric Vehicle Battery's Ohmic Resistance Increase Caused by Degradation from On-board Data

Power battery, as the power source and one of the most significant components in electric vehicles, influences the vehicle's dynamic performance, service life and safety directly. A deeper understanding of the battery characteristics on real-world electric vehicle applications is beneficial for its energy management optimization, service life prolongation and safe operation. This paper presents a novel method which can estimate the ohmic resistance of lithium-ion power battery accurately with only current and voltage information based on a combination of model linearization, least square algorithm and data-pieces idea. Real-world battery operational data of three electric vehicles over around two years are collected in high frequency and analyzed by the proposed method. The battery ohmic resistance increase is quantified by comparing the resistance-temperature fitting curves of adjacent two years. Results show that the investigated power batteries' ohmic resistances are sensitive to ambient temperature and ohmic resistance can serve as a suitable index for evaluating battery degradation.