Battery Cell Diagnosis Using Q-V Fitting for Plateau Voltage Profiles
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Solution Overview
Problem
Existing battery degradation monitoring techniques, such as Differential Voltage Analysis (DVA), struggle to accurately diagnose degradation in battery cells with voltage plateau characteristics due to the difficulty in detecting peaks in the Q-dV/dQ profile, necessitating a more precise and non-destructive method for estimating degradation parameters.
Innovation Solution
A battery diagnosis apparatus and method that generates Q-V, normalized Q-V, and Q-dV/dQ profiles to identify a cut-off reference point, applies a profile fitting factor using a curve fitting algorithm, and determines degradation parameters through a linear regression model without disassembling the battery cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Differential Voltage_analysis (DVA) is used to monitor battery degradation, then degradation can be detected through external parameter observation, but accurate diagnosis becomes difficult for battery cells with voltage plateau characteristics due to inability to detect peaks in Q-dV/dQ profile
Solution Approach 1:
The patent segments the Q-V profile into multiple sections based on voltage ranges, and further segments the differential voltage curve into multiple sections. By analyzing each segment separately and identifying local maximum points in specific sections, the method overcomes the limitation of无法 detecting peaks in voltage plateau regions, thereby resolving the contradiction between degradation detection accuracy and peak detection difficulty
Solution Approach 2:
The patent applies different analysis strategies to different sections of the differential voltage curve. Specifically, it identifies local maximum points in certain sections and uses differential capacity in other sections, rather than applying a uniform peak detection method throughout. This localized approach allows accurate degradation monitoring even in voltage plateau regions where traditional peak detection fails
2Ease of operation
If traditional DVA methods are applied to battery cells with voltage plateau characteristic, then the analysis process becomes simplified, but the degradation parameter estimation becomes inaccurate
Solution Approach 1:
The patent changes the analysis parameters by introducing section-based differential voltage analysis and differential capacity analysis at different voltage ranges. Instead of relying solely on peak detection in the entire Q-dV/dQ profile, the method uses multiple parameters (local maximum points in different sections, differential capacity values) to accurately estimate degradation parameters while maintaining operational simplicity
Data Source
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AI summary
There are provided a battery diagnosis apparatus, a battery pack, an electric vehicle and a battery diagnosis method. The battery diagnosis apparatus includes a control circuit configured to generate a Q-V profile, a normalized Q-V profile and a Q-dV/dQ profile based on capacity-voltage relationship data of a battery cell acquired by a data acquisition unit. The control circuit identifies a cut-off reference point located in a reference capacity range from the Q-dV/dQ profile. The control circuit determines a profile fitting factor associated with a Q-V profile of interest that is a higher capacity side part of the normalized Q-V profile on the basis of a capacity value of the cut-off reference point. The control circuit determines at least one degradation parameter of the battery cell based on the profile fitting factor.