Use Batteries Long-Lasting And Safely in Electric Cars

Real-Time Measurement Method Use Batteries Long-Lasting And Safely in Electric Cars

2025-08-04 Source: Fraunhofer IFAM | Translated by AI 4 min Reading Time

A novel measurement method enables optimized battery management in electric cars. Impedance spectroscopy from Fraunhofer IFAM analyzes detailed measurement data on battery condition in real time during operation. This makes it possible to use batteries even for safety-critical applications.

Laboratory setup for computer-assisted real-time impedance measurement on a lithium-ion battery cell for condition analysis.(Image: Fraunhofer IFAM) — Laboratory setup for computer-assisted real-time impedance measurement on a lithium-ion battery cell for condition analysis.
(Image: Fraunhofer IFAM)

Powerful and safe batteries are a key component for the success of electromobility. Accordingly, measuring a battery's capacity and condition is crucial. The most informative method here is impedance spectroscopy. Impedance itself cannot be measured directly; it is calculated from the ratio of current to voltage. It provides information about the state of charge (SOC) and allows conclusions to be drawn about the internal condition, including cathodes, anodes, or electrolytes (SoH, State of Health), as well as the safety condition.

To obtain all the necessary data, complex measurements and analysis methods are required. Furthermore, impedance measurement has so far only been feasible during rest periods. It typically takes up to twenty minutes before the data for battery characterization is available.

The information provides a precise, in-depth, and differentiated picture of the battery's interior.

Determine Measurement Values for the First Time During Ongoing Operation

Researchers at the Fraunhofer Institute for Manufacturing Technology and Advanced Materials—IFAM—have further developed the method under the leadership of Prof. Fabio La Mantia. Dynamic impedance spectroscopy now makes it possible, for the first time, to obtain measurement data on the battery's status during ongoing operation and make them available in real time. The information gathered goes far beyond just details about charge capacity or remaining operating time; it provides a precise, in-depth, and differentiated picture of the battery's internal structure. This also allows for the individual prediction of the battery cell's potential lifespan.

Existing battery charge level displays, which are integrated into vehicle electronics in electric cars, for example, also measure continuously during use but provide less information, respond significantly slower, and are less accurate.

“Dynamic impedance spectroscopy initially opens up new possibilities for optimizing battery management and thus extends the lifespan of batteries. Additionally, it paves the way for the use of batteries in safety-critical applications,” explains project manager Dr. Hermann Pleteit.

High-Resolution Measurement Method And Direct Analysis

In the novel method, a multi-frequency test signal is superimposed onto the discharge or charge current. The different frequencies provide insights into the status of specific components or processes within the battery. The response signal of current and voltage is measured up to one million times per second. All data from the high-resolution measurement process are fed into simultaneous data processing. From this, software calculates the impedance values' progression and deduces the condition of the respective battery cell.

We have developed algorithms that significantly reduce the data volume before analysis without distorting the information.

Dr. Hermann Pleteit., project manager, Fraunhofer IFAM

To ensure that results are available in real time despite the enormous volume of data generated during high-resolution measurements, the Fraunhofer researchers applied an additional trick. "We developed algorithms that significantly reduce the data volumes before analysis without distorting the information," says Pleteit. This way, real-time monitoring of all aspects of the battery's condition through impedance spectroscopy offers significant advantages.

The image shows a layered structure of transition metals (blue) and sulfur (yellow). The space between the layers can be occupied by sodium ions (purple) and organic solvent molecules (red, brown). (Image:Y. Sun et al., Nature Materials 2025)

Quickly Shut Down Overheated Cells

Impedance also allows conclusions to be drawn about the temperature inside the cell. Therefore, battery management systems can, for example, immediately detect during an electric vehicle's operation if a cell heats up significantly in a specific area using impedance data. They can then shut down the cell or reduce its performance. Traditional temperature sensors become unnecessary; they are mounted on the battery's outer casing and detect thermal issues only with a delay, often when it is too late and the cell is already damaged.

Charging stations for electric vehicles also benefit from this. For instance, one could choose between particularly fast charging and slower but more gentle charging. During a quick stop at a rest area, the battery management system ensures fast charging without causing dangerous temperature spikes or overloading the internal components. If the car is parked at the charging station for several hours, the management system charges the battery slowly and gently to extend its lifespan.

Such systems could be used in eco-friendly electric aircraft. This market is just beginning to develop.

Dr. Hermann Pleteit., project manager, Fraunhofer IFAM

Application Also Interesting for Renewable Energy And Aviation

Providers of renewable energy such as wind or photovoltaic systems, which need to balance fluctuations in power production with energy storage, gain stable and consistently controllable battery systems with Fraunhofer technology.

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Date: 08.12.2025

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Real-time condition monitoring even makes it possible to consider future use in safety-critical scenarios. “Such systems could be used in eco-friendly electric aircraft, for example. This market is just beginning to develop. Manufacturers in the shipping industry are also showing interest,” says Pleteit.

Impedance spectroscopy is not only suitable for the currently common lithium-ion batteries, but the method is also applicable to battery types based on solid-state, sodium-ion, or lithium-sulfur technologies, as well as other future technologies.