Battery Capacity Loss Calibration Using Dual Coulometry Checks
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Solution Overview
Problem
Existing methods for determining battery capacity loss and aging in lithium-ion batteries face challenges due to non-linearity and complexity of physical and chemical processes, leading to inaccurate measurements, especially with standard test devices that lack the necessary precision for high-precision coulometry (HPC) measurements.
Innovation Solution
A method and device that utilize a series of load cycles with charge and discharge phases to determine average capacity loss by calibrating current measurements using different calculation rules, optimizing the calibration to achieve agreement between first and second discharge capacities, thereby improving measurement accuracy and enabling precise HPC measurements even with standard testers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard test devices are used for battery capacity loss measurement, then device complexity and cost are reduced, but measurement precision deteriorates due to excessive measurement uncertainty
Solution Approach 1:
The measurement system performs self-calibration by automatically determining calibration factors through comparison of charge and discharge capacities across multiple load cycles. The system uses its own measurement data to correct systematic errors without requiring external calibration equipment or manual intervention, thereby achieving high precision with standard test devices.
Solution Approach 2:
The system implements a feedback mechanism where measurement results from charge and discharge phases are continuously compared and used to adjust calibration factors. The calibration factors are iteratively optimized based on the agreement between first and second discharge capacities, creating a closed-loop system that progressively improves measurement accuracy.
2Measurement precision
If high-precision coulometry measurements are performed with standard testers, then measurement cost is reduced, but measurement precision deteriorates due to incorrect calibration
Solution Approach 1:
The invention introduces calibration factors as an intermediary element that mediates between the standard tester's raw measurements and the true capacity values. These calibration factors act as a corrective layer that transforms inaccurate standard measurements into high-precision results, enabling HPC-level accuracy with conventional equipment.
Solution Approach 2:
The system dynamically adjusts calibration parameters (calibration factors) based on measured capacity data from multiple load cycles. By changing these parameters iteratively to optimize the agreement between charge and discharge capacities, the system transforms standard tester output into high-precision measurements without requiring hardware modifications.
3Measurement precision
If calibration is optimized to improve measurement accuracy, then measurement precision is improved, but calculation complexity increases due to optimization procedures
Solution Approach 1:
The system performs preliminary calibration by determining calibration factors during an initial phase using measurement data from multiple load cycles. This preliminary calibration establishes a baseline correction that simplifies subsequent measurements, as the optimization is performed once rather than continuously, reducing overall computational complexity while maintaining high 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
The method enhances measurement accuracy by eliminating inaccuracies from incorrect calibration, allowing for precise determination of capacity loss and aging, making high-precision measurements possible with standard testers that would otherwise be inaccurate, and reducing the burden on batteries during testing.
Implementation Method 1
In HPC measurements, relatively small differences in the amounts of charge added to and removed from the battery are determined by integrating measured currents
Data Source
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AI summary
High-precision coulometry measurements for aging estimation of lithium-ion batteries are improved by determining a battery capacity value from current measurement data using two different calculation methods that, in principle, should yield the same result. The current calibration, which specifies the relationship between the actual current and the measured current, has a different impact on the two calculation methods. This can lead to discrepancies in the results if the current calibration is faulty. An optimization procedure is used to determine a current calibration where the results of the two calculation methods agree as closely as possible, thereby reducing or completely eliminating errors.