Battery SOC Tracking via Equivalent Circuit Model Selection
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Solution Overview
Problem
Accurate estimation of battery state of charge (SOC), state of health (SOH), and remaining useful life (RUL) is challenging due to varying battery capacity with age, usage patterns, and temperature, requiring adaptive modeling and online parameter identification across temperature changes and SOC variations.
Innovation Solution
A method and system that store a library of equivalent circuit models, select a model based on operational mode, and calculate SOC using the selected model, incorporating hysteresis modeling and recursive filtering to improve estimation accuracy and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single equivalent circuit model is used for battery SOC estimation, then the device complexity is reduced, but the measurement precision deteriorates due to varying battery characteristics across different operational modes and temperatures
Solution Approach 1:
The patent divides the battery modeling into multiple equivalent circuit models, each representing different operational modes (e.g., charging, discharging, resting states). This segmentation allows the system to select the appropriate model for current conditions, improving SOC estimation accuracy without requiring a single overly complex model to handle all scenarios
Solution Approach 2:
The patent implements dynamic model selection based on real-time operational conditions. The system monitors battery state and automatically switches between different equivalent circuit models according to the current operational mode and temperature, making the modeling approach adaptive rather than static
2Adaptability or versatility
If multiple equivalent circuit models are maintained for different operational modes, then the adaptability improves, but the loss of time increases due to model selection overhead
Solution Approach 1:
The patent pre-establishes multiple equivalent circuit models for different operational modes before runtime. By having models ready in advance rather than generating them dynamically, the system eliminates model creation time during operation and only incurs minimal selection overhead
Solution Approach 2:
The system continuously monitors battery operational parameters and uses this feedback to determine the current operational mode. This real-time feedback mechanism enables automatic model selection that responds to changing conditions without manual intervention, reducing delays associated with model switching
3Reliability
If equivalent circuit models are updated to reflect battery aging and capacity changes, then the reliability improves, but the difficulty of detecting and measuring increases due to varying parameters
Solution Approach 1:
The patent accounts for battery aging by allowing equivalent circuit model parameters (such as resistance and capacitance values) to change over time. The system updates these parameters based on observed battery behavior and capacity degradation, maintaining model accuracy throughout the battery lifecycle without requiring complete remodeling
Solution Approach 2:
The system performs self-calibration by monitoring its own estimation errors and adjusting model parameters accordingly. This self-service capability allows the battery management system to maintain reliability over time without requiring external recalibration or complex measurement procedures
Data Source
AI summary
A method includes calculating a first estimated state of charge (SOC) of a battery at a first time, receiving a voltage value representing a measured voltage across the battery at a second time, calculating a filter gain at the second time, and calculating a second estimated SOC of the battery at the second time based on the first estimated SOC, the voltage value, and the filter gain. Another method includes storing, in a memory, a library of equivalent circuit models representing a battery, determining an operational mode of a battery based on a load associated with the battery, selecting one of the equivalent circuit models based on the determined operational mode, and calculating a state of charge of charge (SOC) of the battery using the selected equivalent circuit model.