A novel dual time-scale voltage sensor fault detection and isolation method for series-connected lithium-ion battery pack

•A novel dual time-scale voltage sensor fault diagnosis for battery pack is proposed.•All in-pack cells are artificially divided into two different classes.•Two different time-scales are used to diagnose the fault of two classes of cells.•The proposed method is robust enough against unpredictable operating conditions.•The method is still effective when there exist certain faulty current.