Battery Test Bench



Johannes Claßen

Chief Engineer - M.Sc.


+49 241 80 48156



The Center for Mobile Propulsion's battery laboratory allows investigating individual cells and entire modules for vehicles in the form of direct current (DC) tests and electrochemical impedance spectroscopy (EIS).

As they can be performed independently of module or pack design or the powertrain, cell-level tests are particularly interesting. With appropriate DC cell test systems, not only capacitance and pulse tests are carried out, but also permanent measurements to investigate cyclic lifetime. With regard to currents, the measurement technology is suitable for testing cells with very high capacitance, which are currently gaining importance in the automotive industry, and also has a very high current accuracy for recording quasi-idle voltage curves for small cells.

EIS is a powerful and widely used non-invasive test method for characterizing lithium-ion batteries used in both research and development. As a non-destructive technique, EIS can be used as a diagnostic or prognostic tool at various points during the life of a battery: for characterization, quality assurance, estimation of state of charge, aging and safety. Thanks to precisely defined excitations, EIS enables the appropriate characterization of various physicochemical processes, most of which remain uncovered in other time domain investigations such as pulse tests or driving profiles. In addition, there is a high degree of reproducibility, which can only be affected by nonlinear phenomena taking place in the battery itself. With respect to cell aging, EIS is used to study the degradation and degradation mechanisms of commercial lithium-ion batteries during cyclic and calendar aging and to understand the effects of various cycling or storage conditions, including temperature, rate of cell charge and discharge (C-rate), overcharge or deep discharge, depth of discharge and other conditions, and manufacturing factors. At the Chair of Thermodynamics of Mobile Energy Conversion Systems, several current PhDs are performing EIS measurements on cyclically aged cells, continuously determining the changes in the impedance spectrum, and implementing the aging behavior in battery cell models. This is pursued for models of very high accuracy as well as reduced models suitable for battery management systems (BMS) for battery state determination and thermal management.

All battery testing is performed in climatic chambers under variable thermal conditions in a safe environment by using the latest ‘Pyro Bubbles’ extinguishing technology. In this test environment, it is possible to test batteries in various electrical stress situations and to identify entire maps of model parameters under defined boundary conditions from the recorded data.