Secondary Battery Degradation Assessment via Voltage Transition Analysis
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Solution Overview
Problem
Existing methods for assessing the degree of degradation in secondary battery modules within an assembled battery are inaccurate when variations in degradation are small, and disassembling batteries for individual assessment is complex.
Innovation Solution
A degradation degree assessment device that evaluates battery characteristics, such as voltage transitions, in a predetermined voltage section to accurately assess the degree of degradation with a simple configuration, allowing for the assembly of batteries with reduced variations in degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If secondary battery modules are taken out from an assembled battery to separately assess the individual degrees of degradation, then the measurement precision of degradation is improved, but the device complexity increases
Solution Approach 1:
The patent applies universality by enabling the assembled battery to serve dual functions: it can operate as a complete power source and simultaneously function as a degradation assessment system. The control unit utilizes existing battery modules within the assembled battery to perform impedance measurements on target modules, eliminating the need for separate assessment equipment. This multi-functional approach allows degradation assessment to be conducted without disassembling the battery or requiring external specialized devices.
Solution Approach 2:
The patent implements self-service by having the assembled battery assess its own components' degradation states. The control unit orchestrates measurements where healthy battery modules within the same assembled battery are used to measure the impedance characteristics of modules being assessed. This self-diagnostic capability eliminates the need for external assessment equipment and simplifies the overall system while maintaining high measurement precision.
2Ease of operation
If conventional capacity difference method is used to assess degradation, then the ease of operation is improved, but the measurement precision deteriorates when variations in degradation are small
Solution Approach 1:
The patent applies parameter changes by shifting from measuring capacity differences to measuring impedance characteristics (specifically differential capacitance) for degradation assessment. Impedance measurements are performed at multiple frequencies to capture the electrochemical state of battery modules more sensitively. This parameter transformation enables detection of subtle degradation variations that capacity measurements cannot detect, while the control unit automatically processes these measurements to maintain operational simplicity.
Solution Approach 2:
The patent replaces the mechanical/disassembly-based assessment method with an electrical measurement system. Instead of physically removing and testing individual modules, the control unit uses electrical impedance spectroscopy to assess degradation in-situ. This substitution maintains ease of operation through automated control while dramatically improving measurement precision by detecting electrochemical changes before they manifest as capacity differences.
3Productivity
If assembled battery is discharged to lower limit SOC for assessment, then the productivity is improved by enabling in-situ assessment, but the duration of action increases due to additional discharge cycles
Solution Approach 1:
The patent applies partial action by performing impedance measurements at specific state-of-charge ranges rather than requiring complete discharge to the lower limit SOC. The control unit can conduct degradation assessments at intermediate SOC levels where impedance characteristics remain informative. This partial measurement approach maintains productivity by avoiding full discharge cycles while still achieving accurate degradation assessment, thereby reducing the additional time required.
Solution Approach 2:
The patent implements preliminary action by performing degradation assessments during normal battery operation before the battery reaches its discharge lower limit. The control unit monitors impedance characteristics continuously or at regular intervals during regular charge-discharge cycles, enabling early detection of degradation without requiring the battery to be discharged to extreme levels. This preliminary assessment approach maintains productivity while minimizing additional cycle time.
Data Source
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AI summary
A degradation degree assessment device for a secondary battery (1) is to assess a degree of degradation of a secondary battery (2) and includes a battery characteristic acquisition unit (61), a capacity estimation unit (62), and an assessment unit (63). The battery characteristic acquisition unit (61) acquires a battery characteristic relating to a voltage transition of the secondary battery (2) in a predetermined voltage section. The assessment unit (63) assesses the degree of degradation of the secondary battery (2) based on the battery characteristic acquired by the battery characteristic acquisition unit (61) or based on a battery characteristic-related value computed on the basis of the battery characteristic.