Issues in Practical Impedance Measurement of Li-ion Batteries

Li-ion batteries have become extensively applied in various consumer products and power-distribution systems. The increased use of the batteries have raised environmental issues as most of the used batteries are landfilled instead of recycled upon reaching end of life. The reusability of a battery can be evaluated by applying the battery state-of-charge (SOC) and state-of-health (SOH). While it is difficult to directly measure these quantities, the battery internal impedance can be measured to obtain the SOC and SOH. Recent studies have shown real-time methods based on broadband perturbations such as pseudorandom binary sequence (PRBS) to rapidly and accurately obtain the impedance. However, the presented methods are often sensitive to external noise which can lead to false battery characterization. This work presents some of the main sources of measurement errors and proposes techniques to minimize their effect. Experimental measurements based on a commercial Li-ion battery is presented and used to demonstrate the effectiveness of the proposed techniques.