Secondary Battery Inspection via Impulse Current Impedance Modeling
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Solution Overview
Problem
Current AC impedance analysis methods for secondary batteries require multipoint measurements across a wide frequency range, making the inspection process time-consuming and impractical for mass production lines. Additionally, the need for dedicated measuring devices and constant inspection conditions limits the method's applicability and reproducibility.
Innovation Solution
A secondary battery inspection device and method that uses a processor and memory to model the secondary battery's internal resistance through an equivalent circuit model. The device applies an impulse current and measures voltage and temperature, allowing for the estimation of battery health through evaluation indices derived from the Nyquist plots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If AC impedance analysis with multipoint measurements across wide frequency range is performed, then measurement precision is improved, but inspection time increases
Solution Approach 1:
The patent extracts only the essential frequency points needed for accurate battery inspection from the full frequency spectrum. Instead of performing multipoint measurements across the entire frequency range, the invention identifies and measures only at specific critical frequencies (including DC and selected AC frequencies), thereby maintaining measurement precision while dramatically reducing inspection time
Solution Approach 2:
The patent applies partial action by performing impedance measurements at a limited set of frequencies rather than across the complete frequency range. The equivalent circuit model is constructed using measurements at specific frequency points (DC, low frequency, and high frequency points), which is sufficient to accurately represent battery characteristics without requiring exhaustive frequency sweeps
2Measurement precision
If dedicated measuring device is used for AC impedance analysis, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent enables universal application of the inspection method by using a charge/discharge device that can perform both charging/discharging operations and impedance measurements. The same device that applies current pulses for battery conditioning can also measure voltage responses for impedance analysis, eliminating the need for separate dedicated impedance measurement equipment and reducing overall system complexity
Solution Approach 2:
The inspection system uses the battery's own charge/discharge operation to generate the measurement signals. The current pulses applied during normal charging/discharging serve dual purposes: both as operational current and as the excitation signal for impedance measurement. The voltage response during these operations is used to calculate impedance characteristics, allowing the system to self-diagnose without external specialized equipment
3Reliability
If inspection is performed under constant conditions, then reproducibility is improved, but adaptability to different operating states decreases
Solution Approach 1:
The patent implements dynamic adaptation by automatically adjusting measurement frequencies and equivalent circuit model parameters based on the battery's current operating state (SOC, temperature, current). The system selects appropriate frequency points and model configurations according to real-time battery conditions, enabling consistent and reproducible measurements across varying operational scenarios rather than requiring fixed constant conditions
Data Source
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AI summary
Provided is a secondary battery inspection device capable of improving inspection accuracy while simplifying the inspection of a secondary battery. Value of a model parameter of a secondary battery model is identified based on a sampling period T. In the secondary battery model, impedance of internal resistance of a secondary battery 200 is expressed by an IIR transfer function and an FIR transfer function. When impulse current I(t) is input to a specified model as the secondary battery model the value of the model parameter of which is identified, a model output voltage as a voltage change form output from the specified model is estimated. The performance of the secondary battery 200 according to the sampling period T is evaluated based on the measurement result of the voltage of the secondary battery 200 when the impulse current I(t) flows into the secondary battery 200, and the specified model output voltage.