Error detection for PHEV, BEV and stationary battery systems

• Survey on possible battery cell errors resulting from fatigue and mechanical degradation.
• Simple method for cell individual capacity estimation is presented, applicable for mutlicell battery systems.
• Cell fault detection method based on evaluation of instantaneous impedance and capacity information is introduced.
• Validation of presented methods under typical battery load conditions.

Battery cells being electrically disconnected resulting from degradation, mechanical stress, or corrosion can lead to hazardous situations during operation of electric vehicles or storage systems in stationary applications. The mentioned errors can be acceptable in some cases when cells or cell strings are connected in parallel, but the failure is to be detected in order to guarantee the reliable and safe operation of the battery system. A method enabling the estimation whether individual battery cells are faulty (cell error or electrically disconnected) by evaluating the mean impedance and capacity information of cell groups is introduced and validated.