Vehicle Battery Capacity Decay Detection via SOC Difference
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Solution Overview
Problem
The existing systems for hybrid and electric vehicles fail to accurately estimate battery capacity over time, leading to inefficient operation and potential vehicle performance issues due to aging batteries, as they rely on outdated control strategies that do not account for changes in battery health and capacity decay.
Innovation Solution
A vehicle power system with a controller that updates battery capacity estimates based on differences between current-based and voltage-based estimates of state of charge, using integration of battery current and open-circuit voltage measurements, and selects appropriate characteristic curves to adjust battery operation, thereby providing a more accurate battery age indicator and adjusting control strategies to maintain optimal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the controller uses a fixed battery capacity estimate for operation, then the control strategy is simple to implement, but the battery operation becomes inefficient as the battery ages and capacity decays
Solution Approach 1:
The battery capacity estimate is transformed from a fixed value to a dynamic parameter that automatically updates based on measured SOC differences. The controller continuously monitors the difference between current-based SOC estimates and voltage-based SOC estimates, and adjusts the capacity estimate when this difference exceeds a threshold, enabling the system to adapt to battery aging without complex manual intervention
Solution Approach 2:
The system performs self-diagnosis and self-adjustment by using its own operational data (current measurements and voltage measurements) to detect capacity decay and update the capacity estimate. The controller compares SOC values derived from different measurement methods and automatically corrects the capacity estimate when degradation is detected, eliminating the need for external calibration or manual intervention
2Productivity
If the controller continuously updates battery capacity estimates, then the battery operation efficiency is maintained, but the control system complexity increases
Solution Approach 1:
The controller implements a feedback mechanism where the difference between current-based SOC estimates and voltage-based SOC estimates serves as the feedback signal. When this difference exceeds a predetermined threshold, the system triggers a capacity estimate update. This feedback-based approach ensures updates occur only when necessary, maintaining efficiency while avoiding unnecessary computational overhead
Solution Approach 2:
The system changes the battery capacity estimate parameter only when the SOC difference threshold is exceeded, rather than continuously updating it. This selective parameter change approach maintains operational efficiency by updating the capacity estimate only when actual degradation is detected, reducing unnecessary computational operations and system complexity
3Device complexity
If the controller uses outdated battery capacity values, then the control strategy remains simple, but measurement precision of battery health status deteriorates
Solution Approach 1:
The controller performs preliminary detection of capacity decay by continuously monitoring SOC differences between current-based and voltage-based estimates. When the difference exceeds the threshold, the system proactively updates the capacity estimate before significant performance degradation occurs, ensuring accurate battery health information is available for subsequent control decisions
Solution Approach 2:
The battery capacity estimate transitions from a static, outdated value to a dynamic parameter that automatically reflects current battery health status. The system continuously monitors operational data and adjusts the capacity estimate in real-time based on detected SOC differences, ensuring the control strategy always uses accurate battery health information without requiring complex external monitoring systems
Data Source
AI summary
A vehicle includes a traction battery. A controller is configured to operate the traction battery according to a capacity estimate. The capacity estimate is based on a difference between a current-based estimation and a voltage-based estimation of a change in battery state of charge over a time interval. The difference is evaluated over a predetermined number of time intervals. When more than a predetermined percentage of the differences exceed a threshold, the capacity estimate is updated based on an average of the differences.