A High-Speed Measurement Technique for the Ohmic Resistance of Lithium-Ion Batteries

Lithium-ion batteries are gaining more attention in the rapidly growing industry of electrical vehicles (EVs). Moreover, a lot of efforts are put by the industry to reuse retired EVs batteries in energy storage systems (ESS). To achieve optimal performance of the repurposed xEVs batteries in ESS, they should be similar in characteristic such as capacity, State of Health (SOH) and Remaining Useful Life (RUL). This makes the battery grading techniques to play a crucial role in it. Ohmic resistance measurement is a convenient way to evaluate the battery aging. However, conventional Electrochemical Impedance Spectroscopy (EIS) methods to measure ohmic resistance require complex curve fitting procedures while some others conventional methods are not much accurate. This research proposes a high-speed technique to measure ohmic resistance directly without using these curve fitting procedures. A Combined Phased Multi-Sine (CPMS) excitation is used to perturb the battery in specific frequency band. The require perturbation time is just 1 sec and ohmic resistance is measured using two impedance values. This makes the proposed technique several times faster than conventional EIS methods. The accuracy is verified by performing experiments on three types of Li-ion batteries. The obtain results shows less than 0.15% difference with reference conventional EIS method. This technique is suitable for grading mass xEVs batteries by evaluating their aging.