Computationally Efficient Protective Methodology for Lithium-Ion Battery Cells Based on Safe Sets

Battery management systems (BMSs) play a crucial role in the reliability of lithium-ion batteries in electric vehicles. A BMS aims to maximize the efficiency and lifespan of the battery cells in the managed battery pack while ensuring the electric vehicle safety. This paper proposes a novel methodology of the BMS based on safe sets. A safe set of the Li-Ion battery cell is the set of admissible states and corresponding admissible currents on a fixed prediction horizon. Thus, the methodology based on safe sets allows one or more current changes, i.e., constant or multidimensional current profiles on the prediction horizon that maintain the posed cell constraints. Furthermore, the paper offers a computational procedure for the safe set approximation for which the nonlinear dual-polarization equivalent circuit model (ECM) of the cell is used. Due to the non-convexity of the safe set of the battery cell, the safe set is constructed as a union of single polytopes for different ranges of state of charge. The proposed methodology is carried out throughout a case study by comparing safe sets with one-, two-, and five-dimensional current profiles.