The developments made in the SPARTACUS projects led not only to a deeper understanding
about sensor based battery monitoring data and SoX,
but also to SERVICES and PRODUCTS provided by the SPARTACUS team for further application.

Electromobility Technology

Dielectric elastomer sensors adapted for monitoring compression load of clamped battery cells. Copyright Fraunhofer ISC
Johannes Ziegler, Detlev Uhl, Holger Böse
Proceedings Volume 12482, Electroactive Polymer Actuators and Devices (EAPAD) XXV; 124820J (2023)]

Electromobility Technology

Dilation over Capacity and differential Dilation dx/dV over Voltage for 4 sensors. The data shows that the thickness changes during a C/10 cycle can be measured. Significant thickness changes were measured at the expected phase transitions of the active material. Copyright Simon Feiler et. al., Fraunhofer ISC, Battery 2030 Annual Conference,May 9-10th 2023, Uppsala (Sweden) 

Battery cell separating layer with integrated dilation sensors

As part of the SPARTACUS project, dielectric elastomer sensors from Fraunhofer ISC were adapted to the specific requirements for detecting volume changes in battery cells. The elastomer sensors perform several essential functions in one material:

  1. Detection of cell expansion: As capacitive deformation sensors, they measure very accurately the dynamic volume changes of the cells during charging and discharging. In addition, they also detect the irreversible and permanent volume change due to cell aging.
  2. Mechanical decoupling: As elastomers with readily adjustable compression modulus, they separate the cells in a battery module from one another and, as a continous damping layer, ensure a more uniform pressure distribution to the individual cells. Pressure peaks that accelerate cell aging can thus be avoided. They also provide thermal shielding, which can be further optimized depending on the application.

Interested in the SPARTACUS sensors? Please contact us!

Specifications deformation sensor

Type of data Value/range Note
Measurement of cell volume changes in z-direction 10 … 300 µm adaptable range, depending on expected cell expansion (dynamic/static)
Sensor sensitivity: dilation 0,16 pF/µm  
Absolute sensor sensitivity: dilation 3 µm depending on preload
Sensor sensitivity: compression load 0.78 pF/kPa  
Absolute sensor sensitivity: compression load 2 kPa depending on preload
Size of sensor element 2 cm x 2 cm size of one sensor element
Mechanical pre-load 25 kPa beneficial for enhanced cell lifetime
Compression modulus 300 kPa optimized stiffness for homogeneous pressure dispersion (adaptable)
Size of sensor array Depending on battery cell adaptable to battery cell dimensions
Sensor thickness ~ 2 mm low installation space
Weight low weight polymer density ~ 1 g/cm³
Sensor array locally resoluted multiple sensors possible on battery cell surface
Lateral resolution 2 cm x 2 cm minimum: 0.5 cm x 0.5 cm
Sensor electronics microcontroller-based low energy consumption



Picture 1 shows the basic construction using the example of a pair of transducers. Preliminary tests have shown that an excitation with raised cosine pulse with five oscillations (RC5) provides short and easy to interpret measurement signals. Copyright Fraunhofer ISC

Measurements with PZT disc transducers (@ 2 MHz)

Measurements with PZT disc transducers (@ 2 MHz) on sensor sheets directly on a KOKAM battery cell showed the dependency on SoC and charging rate. During charging the electrodes become denser and stiffer which yields to a shorter transmission time of the US wave. The drift of ToF – amplitudes is caused by battery heating (measured separately and dependent on charging rate). Copyright Fraunhofer ISC

Detection of mechanical cell properties by ultrasound

Ultrasound is used for structural monitoring and thickness measurement of components. For continuous monitoring of the state of charge and the chemical (ageing) processes inside a battery, the interaction of the ultrasonic waves with differently dense and hard individual layers (lithium de-/intercalation in electrodes) can be used.
The principle requirements for the ultrasonic transducer on the measuring foils within a battery pack are:

  • Small size (max. 20 mm in diameter, small thickness (max. 1-2 mm))
  • Simple and inexpensive components and construction
  • Compatible with processes for mounting additional sensors
  • Wide frequency range (100 kHz – 10 MHz)

Specifications ultra sonic sensors (piezo)

Type of data Value/range Note
Measurement of cell thickness changes in z-direction 30 … 2000 µm  
Sensor sensitivity to battery thickness 10 µm  
Sensor sensitivity to Young´s modulus 100 MPa  
Size of sensor element diameter 10 – 50 mm  
Sensor thickness 1 – 2 mm depending on resonance frequency
Sensor array Locally resoluted Multiple sensors possible on battery cell surface
Lateral resolution 2 cm x 2 cm Minimum: 0.5 cm x 0.5 cm
Sensor electronics Microcontroller-based low energy consumption

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    Project Coordinator

    Gerhard Domann
    Fraunhofer ISC


    Dissemination Manager

    Marie-Luise Righi
    Fraunhofer ISC