A lithium-ion cell's internal resistance influences its performance. A cell's power density, dissipation, efficiency, and state of health (SoH) depend on its internal resistance. A cell's internal resistance or impedance is complex and varies with the state of charge, temperature, size, chemical makeup, construction, and age. Researchers often choose electrochemical impedance spectroscopy (EIS) over other methods to measure internal cell impedance as it provides the most complete characterization.
EIS measurements use a potentiostat / galvanostat instrument that applies a small signal AC current or voltage stimulus over a wide range of test frequencies, typically spanning millihertz to kilohertz. It then measures the resultant voltage or current response and uses digital signal processing to determine the complex impedance values at the test frequencies. Researchers can recognize characteristics and relate them to physical phenomena within the battery. And, they can construct a model of its resistance, that researchers readily recognize. With the results, researchers can construct models using series and parallel combinations of passive components.
EV battery cell test solution
Ensuring the performance and overall cost of EV requires characterizing and analyzing EV batteries at the cell level. The Keysight EV battery cell test solution, which includes the Keysight Scienlab Battery Test System, evaluates the performance of battery cells by measuring capacity, efficiency, internal resistance, and cell lifespan. The solution provides 25 to 1,600 A measurement capabilities with up to 64 individually calibrated EIS measurement channels, making the solution fast and accurate. The purpose-built Scienlab Energy Storage Discover software helps to automate common compliance, load, and endurance tests.
