A Novel Impedance-based Method for Structural Monitoring of Automotive Lithium-Ion Battery Packs

Abstract

The high-voltage battery represents the key component of electrified automotive drive-trains. State-of-the-art lithium-ion cells (LIC) are commonly used due to their high specific energy. The cells are stacked and reinforced by a rigid frame. In addition to mechanical loads during operation, this substructure must also withstand inherent stresses caused by the swelling of the cells. A mechanical failure of the frame results at best in a vehicle breakdown but may also cause a short-circuit and catastrophic thermal propagation in one or more cells. Here we propose a novel method to monitor cell modules in-operando based on the measurement of the cell impedance. There are various sensitivities of the impedance, such as regarding temperature or State-of-Charge, but, as will be shown, it is also influenced by external mechanical loads. Two experimental setups are conducted. First, a simple test is presented during which the phenomenon was initially observed. Secondly, another experiment is carried out to resolve the presumed sensitivity across relevant compression forces. The measurements confirm the initially observed phenomenon. Finally a brief perspective for an effective and industrializable monitoring system is given.