600-A Test System for Aging Analysis of Automotive Li-Ion Cells With High Resolution and Wide Bandwidth

The ongoing research in the field of automotive lithium-ion (Li-Ion) cells for battery-operated electrical vehicles requires specialized test equipment for long-term aging analysis of a large number of cells. A single testing device has to support both aging with realistic driving profiles and advanced characterization methods, such as electrochemical impedance spectroscopy, which offer further insight into aging processes and help to improve the lifetime of batteries. In this paper, we discuss the deficiencies of the existing approaches for battery testing and present a new single-cell test system with a current capability of up to 600 A fulfilling these requirements. The circuit topology which is necessary for high measurement accuracy and wide excitation bandwidth is described in detail. A composite power stage with a rise time down to 3 μs in combination with 18-bit measurement resolution is utilized to achieve this objective. The performance and the accuracy of the test system are demonstrated by the measurements of automotive Li-Ion cells. Realistic driving cycles are performed with minimal deviations between desired and measured values. The wide bandwidth and the low noise of the tester enable high-quality impedance spectroscopy as well as arbitrary current pulses with high time resolution. More than 100 single-cell test systems have been built and are used for long-term aging studies of automotive Li-Ion cells.