Battery Internal Resistance Measurement Using Equivalent Circuit Fitting
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Solution Overview
Problem
Existing methods for measuring internal resistance of batteries are hindered by varying line lengths in mass production, leading to inconsistent inductance and capacitance, making precise resistance measurement difficult.
Innovation Solution
A method and apparatus using an equivalent circuit model with resistance and inductance elements to fit an initial internal resistance value, calculating the internal resistance within a frequency range of 100 Hz to 10 KHz, and employing a processor to derive the accurate internal resistance value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional resistance measurement is used with varying line lengths, then measurement process is simple, but measurement precision deteriorates due to inconsistent inductance
Solution Approach 1:
The patent applies parameter changes by transforming the measurement approach from direct resistance measurement to impedance measurement across multiple frequencies. By measuring impedance at different frequencies (e.g., 100 Hz, 1 kHz, 10 kHz) and using equivalent circuit model parameters (resistance R, inductance L, capacitance C) to fit the data, the method achieves accurate internal resistance extraction despite varying line inductance. The key equation R = Z(ω) - jωL demonstrates how changing the measurement parameter from single-point resistance to frequency-dependent impedance enables precision measurement.
2Measurement precision
If equivalent circuit model fitting is used to achieve accurate measurement, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the complex measurement task into distinct frequency points (e.g., 100 Hz, 1 kHz, 10 kHz) and processing each separately. The equivalent circuit model is fitted at each frequency point independently, extracting local impedance characteristics. This segmented approach transforms a difficult continuous measurement problem into manageable discrete steps, where each frequency point contributes specific information about the battery's internal resistance, inductance, and capacitance.
Solution Approach 2:
The patent uses the equivalent circuit model as an intermediary between the raw impedance measurements and the final internal resistance value. Instead of directly measuring resistance, the method introduces an equivalent circuit model (comprising R, L, C elements) that mediates the relationship between measured impedance and actual internal resistance. This intermediary model allows extraction of accurate resistance values by accounting for the effects of line inductance and other parasitic elements through mathematical fitting.
3Measurement precision
If multiple frequency points are measured, then internal resistance accuracy improves, but measurement time increases
Solution Approach 1:
The patent applies partial action by selecting specific discrete frequency points (e.g., 100 Hz, 1 kHz, 10 kHz) rather than measuring across the entire frequency spectrum continuously. This partial measurement approach captures the essential characteristics of the battery's impedance behavior at key frequencies, providing sufficient accuracy for internal resistance determination without the time cost of exhaustive frequency scanning. The method uses just enough measurement points to achieve the required precision.
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
Accurate measurement of internal resistance values, improving the identification of batteries with high short-circuit defects, suitable for mass production and quality management.
Implementation Method 1
obtaining an initial internal resistance of the battery electrically connected to the battery-internal-resistance-measuring apparatus
Implementation Method 2
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
Data Source
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.