Multifault Diagnosis of Li-Ion Battery Pack Based on Hybrid System

Multifault diagnosis of a battery pack is a difficult issue, especially when different faults are with similar characteristics. This article presents a multifault diagnosis approach based on a hybrid system for diagnosing cell parametric faults, sensor faults, and relay faults in a Li-ion battery pack. The battery pack is defined as a hybrid system with hierarchical and decentralized diagnostic structure in order to reduce model complexity and improve diagnosability. The multifault detection and isolation is achieved by integrating an equivalent circuit model (ECM) into hybrid automata and tracing continuous/discrete dynamics from cell level to module level. By using a parameter identification-based method, cell parametric faults are distinguished and diagnosed from sensor faults in cell level. Sensor faults and relay faults are diagnosed through the hybrid system mode estimation and discrete event system diagnosis method in module level. The results of similar fault isolation test and random multifault injection experiments on a real Li-ion battery pack show that the different faults are detected and isolated in reasonable time with high accuracy.