Power Battery Li-Plating Detection Using SOC-Impedance Fitting
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Solution Overview
Problem
Existing methods for lithium plating detection in Li-ion batteries require thorough charging and discharging in a laboratory environment, are complicated, and lack applicability for real-world conditions, making it difficult to detect lithium plating non-destructively.
Innovation Solution
A method utilizing impedance data measured in a non-driving state of a vehicle to calculate a Li-plating score by fitting AC impedance values as a function of State of Charge (SOC), using a goodness of fit to determine the degree of lithium plating, applicable during charging, discharging, or when the vehicle is parked.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing Li-plating detection methods are used, then detection accuracy can be achieved, but the detection process is complicated and requires thorough charging and discharging in laboratory environment
Solution Approach 1:
The patent extracts only the necessary impedance data points from the charging/discharging process, specifically measuring AC impedance at the beginning and end of constant current charging/discharging phases. This selective extraction of critical data points eliminates the need for thorough laboratory charging/discharging cycles while maintaining detection accuracy, directly resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
Instead of requiring complete charging and discharging cycles for detection, the patent applies partial action by measuring impedance at specific stages (beginning and end of constant current phases) during normal vehicle operation. This partial measurement approach achieves sufficient detection accuracy without the excessive complexity of full laboratory testing protocols
2Reliability
If existing Li-plating detection methods are used, then detection can be performed, but they lack applicability for real-world conditions and require laboratory environment
Solution Approach 1:
The patent makes the detection system universal by integrating it into the vehicle's existing BMS and utilizing AC impedance measurements that can be obtained during normal charging/discharging operations. The method works across different environments (laboratory and real-world), different charging/discharging rates, and different temperature conditions, eliminating the need for specialized laboratory equipment and procedures
Solution Approach 2:
The detection method utilizes the vehicle's own charging/discharging operations to generate the necessary impedance data. During normal vehicle use, the BMS already performs AC impedance measurements for other purposes, and the patent leverages these existing measurements for Li-plating detection, making the system self-sufficient and highly adaptable to real-world conditions without requiring separate laboratory testing
3Measurement precision
If AC impedance values are measured at multiple SOCs during non-driving state, then Li-plating detection accuracy is improved, but measurement time and complexity increase
Solution Approach 1:
The patent performs preliminary action by measuring AC impedance at the beginning of constant current charging/discharging phases, which provides baseline data for Li-plating detection. By capturing impedance data at these predetermined points before significant changes occur, the method achieves accurate detection without requiring continuous or frequent measurements, thus reducing measurement time while maintaining precision
Solution Approach 2:
The patent segments the charging/discharging process into distinct phases (constant current and constant voltage) and measures AC impedance only at the beginning and end of constant current phases. This segmentation approach identifies and measures only the critical data points needed for detection, eliminating redundant measurements and significantly reducing measurement time while preserving detection accuracy
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
Enables simple and accurate lithium plating detection without affecting vehicle use, utilizing non-driving states for data collection, improving calculation efficiency and applicability.
Implementation Method 1
calculating, at each of the plurality of SOCs, an AC impedance value at a corresponding frequency according to a response by the cell to the plurality of AC pulses
Data Source
AI summary
A computer-implemented method for Li-plating detection of a cell of a power battery. The method includes: obtaining a plurality of AC impedance values for the cell measured at a plurality of States of Charge (SOCs), in which the plurality of AC impedance values are measured in a non-driving state of a vehicle; fitting the AC impedance values as a function of SOC based on the plurality of AC impedance values; and calculating a goodness of fit for the function, and calculating a Li-plating score for the cell based on the goodness of fit, in which the Li-plating score is used to indicate a degree to which Li-plating occurs in the cell.