Battery Pack Full-Charge Capacity Estimation via Dynamic Voltage Curves
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for determining the full-charge capacity of battery packs are inaccurate due to the limitations of real-time state of charge (SOC) estimation and the presence of flat areas in OCV-SOC curves, which restrict opportunities for SOC correction, especially in battery packs with individual cell differences.
Innovation Solution
A method that involves obtaining first and second state of charge values, calculating net cumulative charge capacity, and using voltage-capacity curves to estimate full-charge capacities of cells, allowing for more accurate SOC corrections and updates without requiring batteries to stand twice, even in flat areas, by leveraging dynamic voltage curves and ampere hour integral methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If real-time SOC estimation is used to determine full-charge capacity, then the measurement process is simplified and can be performed in real-time, but the accuracy of SOC estimation is insufficient leading to inaccurate full-charge capacity determination
Solution Approach 1:
The patent merges real-time dynamic voltage curve data with static OCV-SOC curve data to determine SOC. By combining the advantages of both methods (real-time responsiveness and accuracy), the system achieves accurate full-charge capacity determination without requiring the battery to stand twice, thus resolving the contradiction between real-time performance and measurement accuracy.
Solution Approach 2:
The patent introduces a voltage-capacity curve as an intermediary tool that bridges the gap between dynamic voltage measurements and static OCV-SOC relationships. This intermediary enables accurate SOC estimation during charging without requiring the battery to be in a static state, thus improving both real-time capability and accuracy.
2Measurement precision
If the battery is left to stand to obtain accurate SOC using OCV-SOC curve, then SOC accuracy is improved, but the time required for correction increases and opportunities for correction are reduced
Solution Approach 1:
The patent performs preliminary calibration during the charging process by obtaining dynamic voltage-capacity curve data. This preliminary action allows the system to prepare accurate full-charge capacity information without waiting for the battery to stand, thus reducing correction time while maintaining accuracy.
Solution Approach 2:
The patent transitions from a static SOC correction method (requiring the battery to stand) to a dynamic method that uses real-time voltage-capacity curve data during charging. This dynamic approach enables continuous correction opportunities without time loss, resolving the contradiction between accuracy and time.
3Productivity
If SOC correction is performed in flat areas of OCV-SOC curve, then more correction opportunities are available, but the correction accuracy becomes impossible due to the flat voltage characteristics
Solution Approach 1:
The patent changes the parameter used for SOC determination from static OCV (which has flat areas) to dynamic voltage-capacity curve characteristics. By using the slope and shape of the voltage-capacity curve during charging, the system can accurately determine SOC even in regions that would be flat in static OCV-SOC curves, thus enabling corrections at any charging point with high precision.
4Measurement precision
If individual cell differences in battery packs are considered, then accurate full-charge capacity determination for all cells is achieved, but the complexity of the determination process increases
Solution Approach 1:
The patent segments the battery pack into individual cells and applies the voltage-capacity curve method to each cell separately. By processing each cell independently using the same unified methodology, the system achieves accurate individual cell capacity determination without requiring complex inter-cell modeling, thus managing complexity while improving precision.
Data Source
AI summary
A method for determining a full-charge capacity of a battery pack includes: obtaining first state of charge values of cells at a first state of charge correction moment; calculating a net cumulative charge capacity from the first state of charge correction moment to a full-charge moment; obtaining a voltage-capacity curve of a fully charged cell from start of a charge termination phase to the full-charge moment; obtaining a second voltage of a not fully charged cell at the full-charge moment; obtaining a capacity difference between the not fully charged cell at the full-charge moment and the not fully charged cell at the first full-charge voltage; calculating a state of charge difference; calculating a second state of charge value of the not fully charged cell at the full-charge moment; obtaining state of charge variations; calculating full-charge capacities; and obtaining a full-charge capacity based on the calculated full-charge capacities.