Hioki ALDAS-E EIS Measurement System for In-Situ Electrolyzer and Fuel Cell Stack Analysis
As water electrolysis and fuel cell technologies continue to scale from laboratory development into real-world energy infrastructure, measurement requirements are changing rapidly. Engineers no longer need only cell-level bench data. They increasingly need accurate, high-speed, in-situ electrochemical impedance spectroscopy (EIS) on kilowatt- to megawatt-class stacks during actual operation. The Hioki ALDAS-E EIS Measurement System is designed for exactly this purpose. Hioki positions ALDAS-E as an EIS measurement system optimized for large-scale electrolyzers and fuel cells, enabling impedance analysis of large stacks during active demonstration and commercial operation rather than only under simplified offline test conditions.
One of the ALDAS-E’s biggest advantages is its ability to perform EIS measurement on kW to MW class stacks in actual operation. Hioki explains that for large electrolysis cells, where high current flows from the rectifier to the stack in multi-wire configurations, multiple current sensors can be combined to measure currents up to 10 kA. This allows the system to detect small AC signals in the presence of noisy DC current while the cell remains in service. For engineers trying to optimize operating points, understand degradation, or analyze stack behavior under realistic load conditions, that is a major step beyond conventional electrochemical measurement workflows.
The system is also designed to provide simultaneous observation of stack performance and multiple individual cell states. Hioki states that ALDAS-E supports 1 to 48 input channels, allowing users to track total stack impedance and individual cell impedance at the same time. This multi-channel capability helps users move from simple overall performance trends to more detailed diagnostics of cell-to-cell variation, which can be critical when evaluating stack uniformity, identifying weak cells, or monitoring degradation mechanisms across larger systems.
Another major strength is measurement speed. Hioki notes that low-frequency impedance measurement is essential for observing the diffusion resistance region, but it is typically time-consuming. The product page states that a typical electrochemical instrument may take about 30 minutes to scan from 10 kHz to 0.01 Hz, while the ALDAS-E can complete the same measurement in about 7.6 minutes across 8 channels simultaneously under the stated fast-mode conditions. For users managing large electrolyzer or fuel cell development programs, this faster multi-channel throughput can significantly improve test efficiency and reduce bottlenecks in evaluation workflows.
The ALDAS-E is also engineered for stable performance in the low-frequency range. Hioki explains that its current sensor method avoids the temperature drift issues often seen with shunt-based methods. The company says this approach provides stable, high-precision current measurement with minimal variation even below 1 Hz, which is especially important in EIS applications where low-frequency accuracy can strongly affect interpretation of internal electrochemical processes.
From an integration standpoint, the ALDAS-E is designed to fit into existing systems with minimal disruption. Hioki states that it connects in parallel to existing electrolysis cell and fuel cell systems and does not require a dedicated power supply or load. The use of external current sensors also helps simplify installation without requiring major system modifications. For operators and development teams working with existing demonstration platforms or commercial systems, this is a practical advantage because it reduces setup complexity while preserving normal operating configuration.
In terms of core specification, the ALDAS-E supports measurement targets including electrolysis cells, fuel cells, and cell stacks. It measures impedance (R, X, θ, Z), voltage, and current, and offers both Logging Mode and EIS Mode. Hioki lists a measurement voltage range of 1.5 V to 1000 V, measurement current range of 400 mA to 2000 A with the CT6877A, a maximum of 10 kA depending on sensor combination, and a measurement frequency range of 10 mHz to 100 kHz. The system also supports display modes including Nyquist plot, Bode plot, and logging plot, which helps users move from raw measurement to interpretation more efficiently.
Hioki also supports flexible system sizing. The ALDAS-E is available in multiple rack cabinet configurations, including 13U, 19U, and 24U arrangements, with different channel-module combinations and corresponding power requirements. The product page lists approximate weights of 85 kg, 125 kg, and 150 kg depending on configuration, along with 100 V to 240 V AC power input and wired LAN communication to a Windows 11 PC. This makes the platform suitable for more permanent integration into advanced energy test environments where scalability and structured installation are important.
Another strength of the ALDAS-E is current sensor compatibility. Hioki lists support for a broad range of AC/DC current probes and sensors, including models from 20 A up to 2000 A, with frequency bandwidths extending as high as 10 MHz depending on sensor type. This gives engineers flexibility to adapt the system to different electrolyzer or fuel cell operating ranges and measurement environments. The product page also notes that the CT9557 sensor unit is required when using two or more current sensors.
For engineers and organizations developing next-generation hydrogen systems, fuel cell stacks, and high-power electrolysis platforms, the Hioki ALDAS-E offers a specialized solution for moving EIS measurement out of the lab and into real operating environments. Its combination of high-speed impedance measurement, multi-channel stack observation, low-frequency stability, and easy integration with existing systems makes it a strong platform for advanced electrochemical diagnostics and performance analysis.
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