IC for online EIS in automotive batteries and hybrid architecture for high-current perturbation in low-impedance cells

This paper describes a new custom IC optimised for online Electrochemical Impedance Spectroscopy (EIS) characterisation of battery packs at the cell-level, with 200 mA peak perturbation current. In addition, a new hybrid power architecture is demonstrated that has been designed to be embedded in the battery management system of a new electric pick-up truck. The hybrid architecture consists of 1) a linear current regulator, 2) a small ultracapacitor, and 3) an isolated Cuk converter that is part of the balancing system, which also supplies the 12V auxiliary loads. The architecture leverages the signal processing capabilities of the IC and extends the perturbation range to 40 A peak while limiting the thermal losses. Experimental EIS measurements are performed for four parallel-connected 44 Ah Lithium Nickel-Manganese-Cobalt-oxide pouch cells, each with 1 mQ nominal internal resistance, at 40 A peak excitation current.