Electrochemical Cell Impedance Diagnostic via Dual-Frequency Modulation
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Solution Overview
Problem
Existing methods for determining the impedance of electrochemical energy storage cells, such as lithium-ion cells, lack reliability, which can lead to inaccurate temperature management and potential damage due to unreliably determined power output limitations.
Innovation Solution
A diagnostic method involving modulation of electric current at two different excitation frequencies, with central and cell-specific measurements, to determine first and second impedance values, allowing for comparison and output of diagnostic information that improves impedance measurement reliability and identifies potential malfunctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single impedance measurement method is used, then the device complexity is reduced, but the measurement precision and reliability deteriorate
Solution Approach 1:
The impedance measurement is segmented into two distinct measurement paths: (1) a central measurement path using a central load and central current measurement for first impedance value determination, and (2) a cell-specific measurement path using a predefined cell-specific load and voltage measurement for second impedance value determination. This segmentation allows each measurement path to be optimized independently, improving overall measurement reliability while maintaining manageable system complexity through modular architecture.
Solution Approach 2:
The system implements feedback by comparing the first impedance value (from central measurement) with the second impedance value (from cell-specific measurement). This comparison provides diagnostic information that feeds back into the system, enabling verification of measurement accuracy and detection of malfunctions. The feedback mechanism enhances measurement reliability by cross-validating results from two independent measurement approaches.
2Reliability
If impedance measurement is performed continuously, then the reliability of operational management is improved, but the energy consumption increases
Solution Approach 1:
The system performs impedance measurements periodically rather than continuously, using two different excitation frequencies (first and second excitation frequencies) in an alternating or sequential manner. This periodic measurement approach with frequency modulation allows the system to obtain reliable impedance data for operational management while minimizing energy consumption by keeping measurements discrete and controlled rather than continuous.
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 method enhances the accuracy of impedance determination, enabling reliable monitoring and maintenance of electrochemical energy storage cells, thereby improving their performance and service life by providing precise diagnostic information for operational management.
Implementation Method 1
determination of a first impedance value on the basis of the measured electric current and on the basis of the measured electric voltage
Implementation Method 2
modulation of an electric current occurring due to an electrical connection between the energy storage cell and a central load
Data Source
AI summary
A diagnostic method and a diagnostic system for an electrochemical energy storage cell, and a vehicle including the diagnostic system. An electrical current due to an electrical connection between the energy storage cell and a central load is modulated at a first excitation frequency and is measured centrally. An electrical voltage at the energy storage cell is measured and a first impedance value is determined based on the electrical current and the electrical voltage. Also, a previously-known electrical current due to an electrical connection between the energy storage cell and a predefined cell-individual load is modulated at a second excitation frequency. The electrical voltage occurring at the energy storage cell is measured and a second impedance value is determined based on the previously-known electrical current and the electrical voltage. Diagnostic information is determined and output based on a comparison of the first impedance value with the second impedance value.