Battery Impedance via Power Spectral Density
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Solution Overview
Problem
Existing methods for determining the electrical impedance of electrochemical batteries require additional signals and substantial equipment, making them impractical for use in vehicles due to space and weight constraints.
Innovation Solution
A non-intrusive method that measures voltage and current over time at the battery terminals, transforming these signals into frequency data to calculate the complex electrical impedance without superimposing additional signals, using power spectral densities and segmentation to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional impedance measurement methods using sinusoidal signals and signal processing tools are employed, then measurement precision is improved, but device complexity and equipment requirements increase substantially
Solution Approach 1:
The method uses the battery's own operational voltage and current signals during normal operation to determine impedance, without requiring external test equipment or additional signal injection. The battery management system processes the naturally occurring signals to extract impedance information, making the system self-sufficient and eliminating complex external measurement apparatus.
Solution Approach 2:
The invention extracts impedance information from the existing operational voltage and current signals by removing the load current component and analyzing the relationship between voltage fluctuations and current variations. This extraction approach obtains impedance data without adding external test equipment, resolving the contradiction between measurement precision and device complexity.
2Measurement precision
If additional signal injection equipment is used to determine impedance, then measurement accuracy is improved, but the method becomes impractical for vehicle applications due to space and weight constraints
Solution Approach 1:
The battery management system utilizes the battery's own operational signals during normal vehicle operation to determine impedance characteristics. By processing the naturally occurring voltage and current data without requiring external signal injection equipment, the method eliminates additional weight while maintaining measurement accuracy for battery state estimation.
3Reliability
If galvanostat equipment is used for impedance measurement, then measurement reliability is improved, but ease of operation deteriorates due to difficulty of use in operating vehicles
Solution Approach 1:
The method enables the battery management system to perform impedance measurements using the battery's own operational signals during normal vehicle operation. This self-service approach eliminates the need for external galvanostat equipment and complex test setups, making the measurement process simple and convenient while maintaining reliability through sophisticated signal processing of the operational data.
Solution Approach 2:
The battery management system performs multiple functions simultaneously: it monitors battery operation, processes voltage and current signals, and determines impedance characteristics all within the same system during normal operation. This multi-functionality eliminates the need for separate specialized measurement equipment, improving ease of operation while maintaining measurement reliability.
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 allows for reliable and efficient determination of electrical impedance, applicable to various battery types, reducing equipment needs and providing accurate impedance data for battery management and state evaluation.
Implementation Method 1
transforming said time signals into frequency signals; said frequency signals are segmented into several segments
Implementation Method 2
for each segment, a power spectral density of the current signal Ψ I (f) is determined, and a cross power spectral density of the voltage and current signals Ψ IV (f) on each of said segments
Data Source
Figure 1~2B
Figure 3
AI summary
The method involves acquiring time signals measuring voltage and current at terminals of an electrochemical system, and converting the time signals into frequency signals. The frequency signals are realized into segments, and a power spectral density of the current signal and a cross power spectral density of voltage and current signals are determined on each segment. Electrical impedance of the electrochemical system is determined by calculating a ratio of the power spectral density of the current signal and the cross power spectral density of the voltage and current signals. An independent claim is also included for a system for estimating an internal state of an electrochemical system for electric power storage.