Battery Aging Parameter Determination via Multi-Frequency Impedance
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Solution Overview
Problem
Existing methods for determining the aging state of lithium-ion batteries in electric vehicles are either time-consuming, require the battery to be unavailable for extended periods, or provide limited informative value, making it difficult to accurately assess the battery's capacity and aging state.
Innovation Solution
A method that automatically applies electrical currents with different frequencies to the battery to measure impedance, allowing for the reliable and quick determination of aging parameters, state of charge, and temperature, using a controller to detect vehicle usage and perform measurements when the vehicle is not in operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the battery is completely discharged and then fully charged to measure capacity, then the aging parameter can be determined accurately, but the battery is unavailable during the measurement process
Solution Approach 1:
The patent applies preliminary action by performing impedance measurements at multiple frequencies before the battery is fully discharged or charged. By measuring impedance at different frequencies (including low frequencies below 1 Hz) during normal operation, the system can predict aging parameters without requiring complete discharge-charge cycles, thus maintaining battery availability while obtaining accurate aging data.
Solution Approach 2:
The patent replaces the mechanical/discharge-based capacity measurement method with an electrical impedance spectroscopy method. Instead of physically discharging the battery to measure capacity, the system uses electrical signals at multiple frequencies to measure impedance, from which aging parameters are derived through mathematical models. This substitution eliminates the need for battery unavailability while maintaining measurement accuracy.
2Ease of operation
If electrochemical impedance spectroscopy is used to determine aging state, then the battery remains available during measurement, but the predictive power is limited
Solution Approach 1:
The patent enhances the traditional electrochemical impedance spectroscopy by adding the frequency dimension. Instead of measuring impedance at a single frequency or limited range, the system measures impedance at multiple frequencies spanning from below 1 Hz to higher frequencies. This multi-frequency approach provides additional data dimensions that improve the predictive power of aging state determination while maintaining battery availability during measurement.
Solution Approach 2:
The patent changes the measurement parameter from single-frequency impedance to multi-frequency impedance spectrum. By varying the frequency parameter and measuring impedance at multiple points across a broad frequency range, the system extracts more information about the battery's internal state. This parameter change enables more accurate prediction of aging state, capacity, and state of charge without requiring the battery to be taken offline.
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 rapid and accurate assessment of battery aging, state of charge, and temperature, allowing for improved management and development of battery technology, with the ability to automatically perform measurements without requiring the battery to be unavailable for extended periods.
Implementation Method 1
A method for determining an aging parameter of a battery... automatically applies electrical currents with different frequencies to the battery to measure impedance
Data Source
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AI summary
The invention relates to a method for determining an aging parameter KSOH of a battery (12) comprising the steps (a) acquiring an impedance Z of the battery (12) at various frequencies f, such that a Nyquist curve and a real part curve plotting a real part of the impedance Z against the frequency f are obtained, (b) determining at least one of the following SOH parameters, which can be selected from a predetermined list, (c) forming an SOH line vector PSOH→ from the SOH parameters and all mixed terms of the form pSOH,m·pSOH,n, m= 1, ..., 11, n= 1, ..., m. According to the invention, (d) multiplying the SOH line vector PSOH→ with a stored calibration vector ASOH→ is provided, such that the aging parameter KSOH is obtained.