Connection Loss Detection Algorithm of Parallel-connected Cells Based on Change of Battery SOC

The battery pack consists of parallel-connected cells to satisfy the power and mileage per charge of the eco-friendly vehicles. The vehicle specifications determine the number of battery cells connected in parallel by the type of battery. In driving conditions, such as sharp bumps and rough roads, the welding used for the interconnection between the cells may become loose, potentially causing the cells to detach from the battery module. The detachment leads to a reduction in the capacity of the battery pack and increases cell-to-cell variation among the parallel-connected battery cells. The detection algorithm for identifying disconnections among parallel-connected cells in a module is essential for ensuring the safe operation of the battery pack. This paper introduces a novel method for detecting contact loss among parallel-connected cells by utilizing the state of charge (SOC) change rate of the cells. The algorithm utilizes the estimated internal resistance and the variation in the slope of the estimated SOC change to detect connection losses within a battery module. The proposed method is verified with the simulation using Matlab/Simulink. The performance of the proposed algorithm is validated in various cases with some scenarios.