Battery State Estimation Using Surface SOC and Dynamic Voltage Models
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Solution Overview
Problem
Existing battery state estimation methods, particularly for electric vehicles, struggle to accurately reflect dynamic changes in battery states during charging or discharging, leading to increased estimation errors.
Innovation Solution
A battery management system that includes a processor for estimating a surface state of charge (SOC) and terminal voltage by using kinetics and diffusion coefficients based on temperature and current measurements, incorporating a memory to store correspondence relationships for these coefficients, and models to estimate open circuit voltage, overpotential, and ohmic resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an equivalent circuit model using SOC is used to estimate terminal voltage, then the estimation is suitable for static battery states, but the current effect cannot be reflected in dynamic states leading to increased estimation error
Solution Approach 1:
The patent segments the terminal voltage estimation into two distinct components: open circuit voltage (estimated using equivalent circuit model with SOC) and current effect voltage (estimated using overpotential and ohmic resistance models). This segmentation allows each component to be optimized for its specific function while maintaining overall accuracy in both static and dynamic states.
Solution Approach 2:
The patent introduces dynamic parameters (overpotential and ohmic resistance) that adapt to changing battery conditions during charging and discharging. These dynamic parameters allow the model to reflect real-time current effects and concentration changes, making the estimation suitable for dynamic states while maintaining static state accuracy.
2Device complexity
If only open circuit voltage model is used, then the model is simple to implement, but it cannot reflect concentration changes in dynamic charging/discharging states
Solution Approach 1:
The patent segments the voltage estimation model into distinct components: open circuit voltage (simple equivalent circuit model), overpotential (concentration changes), and ohmic resistance (current effects). This segmentation maintains relative simplicity while capturing dynamic effects that a single unified model would miss.
Solution Approach 2:
The patent introduces additional parameters (overpotential and ohmic resistance) that change with battery state, allowing the model to adapt to dynamic conditions. These parameters are calculated based on measurable quantities (current, SOC) and physical principles, maintaining model tractability while improving accuracy.
Data Source
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AI summary
A battery apparatus receives a measured current of a battery, and estimates a surface SOC representing a potential at an electrode surface of the battery based on a plurality of parameters including a first parameter determined based on the measured current and a second parameter determined based on an SOC of the battery.