Battery State Estimation via Impedance Loop Analysis
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Solution Overview
Problem
Conventional methods for determining battery properties using electrical impedance measurements require specific adaptations for different battery types and are limited to estimating remaining capacity and service life only for batteries with pre-determined relationships, making them unsuitable for general application across various electrochemical batteries.
Innovation Solution
A computer-implemented method that provides a series of electrical impedance measurements, translates and scales them, and applies a weighting function to form loops in the complex plane, allowing for the estimation of battery state based on the size of these loops, which can be used to calculate the battery's state of health, charge, or capacity without requiring specific adaptations for each battery type.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods use electrical impedance measurements with pre-determined relationships, then remaining capacity and service life can be estimated, but the method requires specific adaptations for each battery type and is limited to batteries with pre-determined relationships
Solution Approach 1:
The patent applies universality by developing a loop-based analysis method that works across different battery types without requiring specific pre-determined relationships for each type. The method uses standardized processing of impedance measurements through loop formation in the complex plane, making it applicable to various electrochemical batteries including lithium-ion, lead-acid, and nickel-based batteries. This eliminates the need for battery-type-specific adaptations while maintaining estimation accuracy.
Solution Approach 2:
The patent transforms the impedance measurement approach by changing from direct impedance value analysis to loop-based analysis in the complex plane. By representing impedance data as loops formed by consecutive measurements and analyzing loop sizes rather than absolute impedance values, the method achieves type-agnostic battery state estimation. This parameter transformation enables the same analysis framework to work across different battery chemistries and configurations.
2Measurement precision
If specific adaptations are made for different battery types, then measurement precision for that battery type improves, but device complexity increases
Solution Approach 1:
The patent extracts the essential diagnostic information from impedance measurements by focusing on loop formation patterns rather than battery-specific parameters. By taking out the common features present in all electrochemical batteries (the loop-based impedance response) and using only those for analysis, the method achieves universal applicability without requiring battery-type-specific calibration data, lookup tables, or pre-determined relationships, thereby reducing system complexity.
3Adaptability or versatility
If loop-based analysis is used to emphasize curve progression features, then adaptability across battery types improves, but measurement precision may be affected by loop size variations
Solution Approach 1:
The patent inverts the conventional approach by not trying to normalize loop sizes across different batteries, but rather using the loop size variations themselves as diagnostic information. Instead of making all loops comparable through normalization (which would lose battery-specific characteristics), the method analyzes the absolute loop sizes and their changes over time, turning what could be seen as a source of variability into a useful diagnostic signal that reflects actual battery state changes.
Data Source
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AI summary
A computer-implemented method and a battery state estimating system for estimating a battery state of an electrochemical battery, including: weighting (S22) the electrical impedance measurements (10) of a provided series of electrical impedance measurements according to a weighting function that is dependent on the index (s) of the series or on the measurement frequency (fs), resulting in at least a series (21) of consecutive elements of the series of measurements (10), when point-to-point connected in the complex plane of the electrical impedance in a sequence according to the index (s) of the series of measurements (10), forming at least one loop (22) in the complex plane; calculating (S24) a measure of the size of the at least one loop (22) in the complex plane; determining (S26) an estimation of a battery state of the electrochemical battery (44) based on the calculated measure of the size of the at least one loop (22) in the complex plane; and outputting (S28) the estimation of the battery state.