Cell-Level Implementation of Current-Sensorless On-Board Impedance Measurements in Multi-Cell Lithium-Ion Battery Stacks

Battery impedance is an important parameter for estimation of the battery state parameters, such as, state-of-charge (SOC), state-of-health (SOH) and the temperature. However, complexity of the measurement implementation most often prevents wider utilization of the impedance measurement in on-board applications. This paper proposes a cell-level implementation of current-sensorless on-board impedance measurements in multi-cell battery stacks. In the proposed method, the current required for the impedance calculations is estimated based on the voltage measurements and the equivalent circuit resistance compensated by the circuit inductance. Comprehensive introduction on the appropriate battery stack prototype with on-board impedance measurements is presented. The performances of the methods and prototype are validated by experiments on several different different sets of nickel-manganese-cobalt-oxide (NMC) Lithium-ion cells.