Battery Module SoH Grading Using Weighted EIS Parameters
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Solution Overview
Problem
Current methods for grading the state of health (SoH) of batteries, especially for electric vehicle applications, are inefficient and inaccurate, requiring several hours to perform and being susceptible to extraneous factors like temperature and state-of-charge, which limits their suitability for high-throughput applications like second-life battery grading.
Innovation Solution
A system utilizing Electrochemical Impedance Spectroscopy (EIS) combined with open-circuit voltage and temperature measurements, fitted to an equivalent circuit model, to generate weighted equivalent circuit parameters for precise SoH determination, enabling direct measurement of residual capacity with reduced noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional charge-discharge cycle methods are used to determine battery capacity, then measurement accuracy is improved, but testing time increases to several hours
Solution Approach 1:
The patent replaces the mechanical charge-discharge cycling process with an electrochemical impedance spectroscopy (EIS) measurement system. The EIS measuring unit applies small AC perturbations across a frequency range and measures the battery's impedance response, substituting the time-consuming charge-discharge cycles with a rapid electrical measurement that takes only minutes while providing accurate capacity estimation through equivalent circuit modeling.
Solution Approach 2:
The patent changes the measurement parameters from direct capacity measurement through charge-discharge cycles to impedance-based indirect measurement. By measuring impedance at multiple frequencies and fitting to equivalent circuit models, the system extracts capacity information without performing full charge-discharge cycles, thereby reducing testing time while maintaining accuracy through mathematical modeling of the battery's electrochemical characteristics.
2Productivity
If EIS measurements are used to determine SoH rapidly, then processing time is reduced to minutes, but measurement accuracy deteriorates due to extraneous factors like temperature and state-of-charge
Solution Approach 1:
The patent implements feedback mechanisms where the measured impedance data is continuously fitted to equivalent circuit models, and the model parameters are refined iteratively. The system uses the fitted equivalent circuit parameters as feedback to correct for temperature and state-of-charge effects, adjusting the capacity estimation based on the relationship between impedance characteristics and known degradation patterns, thereby maintaining accuracy despite environmental variations.
Solution Approach 2:
The patent introduces equivalent circuit models as intermediary elements between the raw EIS measurements and the final capacity determination. The equivalent circuit parameters serve as mediators that translate the complex impedance data into meaningful capacity estimates, filtering out the effects of temperature and state-of-charge variations through the modeling process and providing a more accurate representation of the battery's true state of health.
3Measurement precision
If detailed battery grading is performed for second-life applications, then valuation accuracy is improved, but processing time increases limiting throughput
Solution Approach 1:
The patent replaces the traditional detailed charge-discharge testing protocol with rapid EIS measurement and equivalent circuit modeling. This substitution enables detailed battery grading for second-life applications by extracting multiple parameters (capacity, resistance, time constants) from the impedance spectrum, providing comprehensive valuation information in minutes rather than hours, thereby maintaining accuracy while dramatically increasing throughput for commercial grading operations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for rapid and accurate SoH assessment of battery modules in minutes, reducing processing time by up to 98% while maintaining high accuracy, making it suitable for high-volume commercial operations and scalable for various battery chemistries.
Implementation Method 1
an Electrochemical Impedance Spectroscopy (EIS) measuring unit to generate EIS spectra of one or more battery modules
Implementation Method 2
means for measuring an open circuit voltage of the battery modules
Implementation Method 3
means for measuring a temperature of the battery modules
Data Source
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AI summary
Systems and methods of monitoring and testing a battery module, including generating Electrochemical Impedance Spectra (EIS) of one or more battery modules, fitting the EIS spectra to an equivalent circuit model to establish equivalent circuit fit parameters, measuring an open circuit voltage of the one or more battery modules, measuring a temperature of the one or more battery modules, combining the EIS equivalent circuit fit parameters with measured open circuit and temperature values to determine weighting parameters of the equivalent circuit fit parameters, applying the weighting parameters to the equivalent circuit fit parameters to generate weighted equivalent circuit fit parameters, and generating a state-of-health (SoH) measurement of the one or more battery modules based on the weighted equivalent circuit fit parameters.