Online magnetic field monitoring in lithium-ion batteries for electric vehicles

Lithium-ion batteries (LIBs) are considered as the main power source in electric vehicles (EVs), plug-in hybrid electric vehicles (PHEVs) and many other residential or commercial applications. To provide reliable performance, a number of solutions for the offline and online state of charge (SoC) estimation and state of health (SoH) have been suggested in the literature. As the existing solutions are still facing reliability and robustness problems, a smarter condition monitoring system (CMS) is requiered. The main drawback of the existing CMS solutions is the lack of accurate estimation approach for the long-term aging of LIB cells. Particularly, in a real-time system, aging is strongly tailored to the accurate online estimation of SoC and SoH. In this paper, an online monitoring system is proposed using the magnetic field measurement from the battery electrolyte. Generation 3 Nissan Leaf cell is used to demonstrate the feasibility of SoC estimation using the direct measurement of charging activity (current density) within a cell. To validate the final results of the magnetic field imaging, a model of the studied battery has been simulated in COMSOL Multi-physics software.