On-line Measurement of Internal Resistance of Lithium Ion Battery for EV and Its Application Research

Abstract

Internal resistance of the battery can really reflect its own characteristics, which including health status of the battery, inconsistency, state of charge, thermal runaway. On-line measurement of internal resistance can real-time monitor the running state of each battery and accurately, can report fault state of the battery and handle fault in time. This paper implements the practical engineering module of on-line measurement of internal resistance of lithium ion battery for EV (Electric Vehicle) using AC analysis. The detection precision and stability of the module are less than 0.3%. Based on experiments, the paper studies the stability and temperature characteristic of internal resistance of lithium battery. It also studies the relationship between the internal resistance and SOC, charging current with experiments. This paper analyzes the relationship between the internal resistance and default of the battery, such as inconsistency of batteries, excessive charging current, changing of work state, overcharging. Keywords: lithium ion battery; On-line measurement of internal resistance; AC analysis; the property of internal resistance; fault diagnosis of battery