Secondary Battery Impedance Inspection Using Pulse Response Modeling
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Solution Overview
Problem
Current AC impedance analysis methods for secondary batteries require lengthy multipoint measurements and dedicated devices, making them impractical for high-speed applications like mass production lines, and lack methods for determining pass/fail criteria under varying conditions such as voltage, current, and temperature.
Innovation Solution
A secondary battery inspection device that includes a voltage recognition element, model parameter setting element, voltage estimation element, and evaluation element, which uses transfer functions to estimate model output voltages and evaluate battery performance based on sampling periods and temperature compensation, allowing for improved inspection accuracy and reproducibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If AC impedance analysis with multipoint measurements from high frequency (10 kHz) to low frequency (10 mHz to 100 mHz) is performed, then measurement precision is improved, but inspection time increases significantly
Solution Approach 1:
The patent extracts only the essential frequency points needed for accurate impedance analysis from the full multipoint measurement spectrum. Instead of measuring across the entire frequency range from 10 kHz to 100 mHz, the invention identifies and measures only at critical frequency points that capture the dominant impedance characteristics, thereby reducing measurement time while preserving measurement precision.
Solution Approach 2:
The patent applies partial action by performing impedance measurements at a reduced set of frequency points rather than the complete multipoint spectrum. This partial measurement approach is sufficient to capture the essential impedance behavior for pass/fail determination, eliminating the need for exhaustive frequency scanning and significantly reducing inspection time.
2Measurement precision
If dedicated measuring devices are used for AC impedance analysis, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent enables universal impedance measurement capability using standard battery testing equipment that can perform charge-discharge cycles and voltage measurements. The same equipment used for routine battery capacity and voltage testing is leveraged for impedance analysis, eliminating the need for specialized impedance meters and reducing device complexity while maintaining measurement precision through the innovative measurement methodology.
Solution Approach 2:
The patent makes the battery itself serve as the measurement instrument by utilizing its own voltage response to current pulses as the basis for impedance calculation. The battery's inherent electrical characteristics are exploited to derive impedance information without requiring external specialized measuring devices, thereby simplifying the overall measurement system.
3Measurement precision
If inspection conditions are fixed to ensure reproducibility, then measurement precision is improved, but adaptability to varying battery operating states decreases
Solution Approach 1:
The patent implements dynamic adaptation of measurement parameters based on the battery's actual operating state. Rather than using fixed inspection conditions, the system adjusts measurement voltage, current pulse magnitude, and frequency selection according to the battery's voltage, temperature, and charge state, ensuring reproducible results across varying operating conditions while maintaining adaptability.
Solution Approach 2:
The patent changes measurement parameters dynamically based on battery state. The measurement voltage, current amplitude, and selected frequency points are adjusted according to the battery's operating conditions (voltage, temperature, SOC), allowing the system to maintain measurement precision and reproducibility across different operating states without requiring fixed inspection conditions.
4Manufacturing precision
If pass/fail determination criteria are set from statistical population distribution, then manufacturing precision is improved, but the ability to determine pass/fail under varying conditions is limited
Solution Approach 1:
The patent establishes pass/fail criteria based on impedance characteristics measured under controlled, standardized conditions rather than statistical population distributions. By measuring impedance at specific frequency points under defined test conditions, the invention creates absolute pass/fail thresholds that are adaptable to different battery types and operating states, replacing the limited statistical approach with a more versatile parameter-based evaluation method.
Data Source
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 identitied 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.