Battery Internal Resistance Measurement with Equivalent Circuit Fitting
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Solution Overview
Problem
Existing methods for measuring the internal resistance of batteries are hindered by varying line lengths in production lines, which affect inductance and capacitance, making precise measurement difficult.
Innovation Solution
A method and apparatus using an equivalent circuit model to fit resistance and inductance elements, allowing for accurate internal resistance measurement through a frequency range of 100 Hz to 10 kHz, employing a battery-internal-resistance-measuring apparatus with a processor and memory to derive the internal resistance value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional resistance measurement methods are used in mass production, then measurement speed is sufficient for production lines, but measurement precision deteriorates due to varying line lengths and inductance
Solution Approach 1:
The patent applies parameter changes by measuring impedance across multiple frequency points (e.g., 100 Hz to 10 kHz) rather than a single frequency. This frequency-domain approach transforms the measurement parameters to capture both resistive and inductive components, enabling accurate separation of battery internal resistance from line inductance through mathematical analysis of the frequency-dependent impedance characteristics.
Solution Approach 2:
The patent segments the total impedance into distinct components by fitting an equivalent circuit model. The measurement system separates the impedance contribution from the battery (internal resistance and capacitance) from the contribution from the measurement lines (inductance and resistance), allowing precise extraction of battery parameters despite varying line characteristics.
2Measurement precision
If line length is kept constant to reduce inductance variation, then measurement precision improves, but adaptability to different production line configurations deteriorates
Solution Approach 1:
The patent implements universality by developing a measurement method that functions accurately across diverse production line configurations. The equivalent circuit modeling approach universally accounts for different line lengths and inductance values by treating them as variable parameters in the model, allowing the same measurement system to adapt to any line configuration without requiring physical modifications or calibration adjustments.
3Measurement precision
If simple resistance measurement is used, then device complexity is low, but measurement precision deteriorates due to inductance interference
Solution Approach 1:
The patent introduces an equivalent circuit model as an intermediary framework that mediates between the raw impedance measurements and the battery parameters. This model serves as a mathematical mediator that systematically relates the measured impedance at different frequencies to the underlying battery characteristics, enabling accurate parameter extraction without requiring direct physical separation of resistance and inductance components.
Data Source
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AI summary
Provided is a method of measuring an internal resistance of a battery by using a battery-internal-resistance-measuring apparatus, the method including obtaining an initial internal resistance of the battery electrically connected to the battery-internal-resistance-measuring apparatus, fitting an equivalent circuit model including resistance elements, which correspond to an internal resistance component of the battery and a resistance component of the battery-internal-resistance-measuring apparatus, and an inductance element, which correspond to an inductance component of the battery-internal-resistance-measuring apparatus, based on the initial internal resistance, and deriving an internal resistance value of the battery based on a fitting result of the equivalent circuit model.