New impedance spectroscopy from SMART TESTSOLUTIONS complements fuel cell test bench

Stuttgart, May 2025: SMART TESTSOLUTIONS has developed a new type of impedance spectroscopy (EIS) for the electrochemical measurement of fuel cell stacks as part of the "FullStack TS fuel cell test bench" funding project. The solution enables time-synchronous EIS measurements on hundreds of individual cells within a cell stack.

The FullStack TS research project for heavy-duty applications has now been completed. The new EIS system was successfully integrated into the newly developed test stand for full-stack fuel cells with an output of up to 200 kW by MS2 Engineering und Anlagenbau GmbH, which was put into operation at the Fraunhofer Institute for Solar Energy Systems in Freiburg.

Electrochemical impedance spectroscopy can be used to obtain valuable information about the processes taking place inside a bipolar electrochemical system, in the case of a PEM fuel cell, for example, internal cell resistance or membrane moisture content. The new impedance measuring systems from SMART TESTSOLUTIONS are characterized by a decentralized design with compact, galvanically insulated measuring heads that are mounted directly on the cell stack.  This technology not only ensures high signal fidelity and short cable runs, but also increases safety, as no high voltages need to be routed outside the temperature chamber of the test bench.

Other key features of the multi-channel EIS modules are the time-synchronous measurement on a large number of channels and the comparatively low measurement costs. Current impedance spectroscopy devices are limited to just a few channels, which means that time-synchronous measurements are not possible for fuel cell stacks with several hundred cells.

"Our aim was to make high-resolution, multi-channel EIS measurements economically feasible and technically robust, even under harsh environmental conditions" explains Wolfgang Neu, Managing Director of SMART TESTSOLUTIONS. "The newly developed MCM U02AC modules achieve this through a combination of robust industrial hardware, modular design and powerful software that simplifies operation and data analysis."

In addition to developing the new EIS solution, SMART TESTOLUTIONS has adapted and validated its already available systems for monitoring cell voltages in fuel cells and electrolysers, CVM G5, as part of the research project, so that up to 600 cells can be monitored at 1000 measured values per second per measuring channel, and at an operating temperature of -20 to 105 °C. This means that the systems are also suitable for aviation applications.

Due to its modular design and temperature resistance, the newly developed solution can also be used in other electrochemical systems such as batteries, electrolyzers and redox flow batteries with slight modifications.