Water electrolysers split water into hydrogen and oxygen using electric current. They are a crucial component of a hydrogen economy. Cell voltage monitoring systems are used to monitor electrolysers and contribute to safe operation.

What do operators of electrolysers need CVM systems for?

Cell voltage monitoring is used to increase the efficiency and avoid unplanned failures of an electrolyzer. It complements various other analysis techniques necessary to operate electrolyzers in a stable, reliable and predictable manner: from the quality of the chemicals and raw materials used to the continuous monitoring of energy demand.

By measuring the voltage values in the individual electrolyser cells with the help of Cell Voltage Monitoring, changes in the performance of the electrolyzer can be detected at an early stage.  The condition and performance of the individual cells are continuously monitored, which increases operational reliability and enables predictive maintenance.

  • Voltage monitoring

    The CVM system monitors the voltages of the cells of the electrolysis stack. Single or multiple cell sensing is possible.

  • Increase in process reliability

    Unusual changes in the voltages of one ore more cells of the electrolyzer stack are registered immediately. Prompt action can be taken.

  • Early fault detection

    Defects such as damaged cell membranes or the unplanned premature aging of cells are detected at an early stage.

  • Predictive maintenance

    Early problem detection enables predictive maintenance and reduces unplanned downtime and costs.

Cell voltage ­monitoring for water electrolyzers

In electrolysers, our CVM systems contribute to system safety by monitoring the voltage in the cells. The exact design of the systems is always carried out in close consultation with our customers. For example, an explosion-proof design with the measurement technology housed in an ATEX-certified enclosure is available on request, as is the case here with our CVM Ex product.

Functionality of electrolysis

Electrolysis represents the reverse reaction of a fuel cell. Like a fuel cell, an electrolyzer consists of several cells arranged in a row, each equipped with two electrodes, an anode and a cathode. The electrolyte is a solution that allows current to flow between the electrodes. In an electrolyzer for water electrolysis, the electrolyte usually consists of water and a small amount of acid or base to increase conductivity.

Another essential component of an electrolyzer is a power source. Electricity from renewable energy sources such as wind or sun is used for the production of green hydrogen, which enables a sustainable reduction of climate-damaging emissions.

When the electric current flows through the electrolysis cell, oxidation takes place at the anode, releasing oxygen (O2). At the cathode, hydrogen (H2) is produced by reduction. A separator separates the two electrodes to prevent the gases produced from mixing.

Graphics about eletctrolyse

What types of electrolyzers are there?

Das Verfahren der Elektrolyse ist nicht neu. Elektrolyseure gibt es in verschiedenen Ausführungen für verschiedene Zwecke. Viele Produkte unseres Alltags sind ohne sie gar nicht denktbar.

Alkaline electrolyzers

Alkaline electrolysis has been tried and tested for many decades. These electrolyzers use an alkaline solution (usually potassium hydroxide) as the electrolyte. They operate at higher temperatures and pressures and have high efficiency. Alkaline electrolyzers are characterized by high long-term stability and are often used for industrial applications.

Proton ­exchange ­membrane electro­lysers (PEM)

PEM electrolyzers use a polymer membrane as electrolyte. Anode and cathode are separated by this gas-tight membrane, only positive hydrogen ions can pass through the membrane. PEM electrolyzers have a faster reaction rate, which makes them very suitable for power-to-X applications. They can be regulated between 10 and 100 percent nominal power during operation.

Solid Oxide Electrolysis (SOE)

Solid oxide electrolysers operate at very high temperatures (600-1000°C) and use solid oxides such as ceramic materials as electrolytes. They achieve very high efficiencies of up to 80 percent. However, high-temperature electrolysis is currently still in the development stage towards industrial use. The main challenges are the required long-term stability and thermal cycle stability.

High-Temperature Electrolyzers

These electrolyzers operate at very high temperatures (above 800°C) and use solid oxides as electrolytes, such as zirconia. They have the advantage of being able to generate heat as a by-product, which can be useful for process integration in industrial plants. High-temperature electrolysers do not split liquid water but water vapor into its components hydrogen and oxygen.

Partner for your Cell Voltage Monitoring (CVM)

At SMART TESTSOLUTIONS, we recognized the importance of high-performance energy storage systems and generators early on. More than 20 years ago, we launched our first system for monitoring cell voltages on fuel cells and electrolysers. In the meantime, our CVM systems are used by well-known customers in many countries around the world. You too can benefit from our expertise in the reliable monitoring of electrolyzers. Please contact us, we will be happy to advise you.

An application case from practice

Hystar monitors PEM electrolyzer with CVM system from Smart Testsolutions

For the Norwegian company Hystar, SMART TESTSOLUTIONS is implementing a CVM system for monitoring a containerized PEM electrolyzer. In addition to the actual measurement technology for recording the individual cell voltages in the electrolyzer, the system also includes a solution for cell contacting as well as wiring and housing.

Our CVM components
for electrolysers

CVM Modules

CVM G5S measuring module


CVM Modules

CVM G6S measuring modules


CVM Modules

Cell Voltage Simulation IntelliSim


CVM Accessories

Cell Voltage Pickup


CVM Accessories

Mounting frame


CVM Accessories

Software adaptions


CVM Accessories

Customised Harnesses


CVM Accessories



Your contact

Do you have questions about Cell Voltage Monitoring for electrolysers or are you planning to use it? Then please contact me. Just send me an email and I will get back to you.

Wajih Wertateni

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