Gas-Liquid Dynamic Model for Battery Open Circuit Voltage Estimation
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Solution Overview
Problem
Current battery models, such as equivalent circuit models and electrochemical models, are complex and computationally intensive, making real-time estimation of open circuit voltage (OCV) challenging, especially in electric vehicles, due to their complexity and time-consuming calculations, which leads to inaccurate OCV estimation and uncertainty in remaining mileage.
Innovation Solution
A gas-liquid dynamic model is used to estimate OCV, incorporating battery temperature and simplifying the estimation process, with equations that reflect the nonlinear battery charging and discharging processes, and utilize a genetic algorithm for parameter identification, allowing for real-time estimation on a single-chip microcomputer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electrochemical model is used to describe battery charge discharge process, then estimation accuracy is improved, but computational complexity increases making real-time estimation difficult
Solution Approach 1:
The patent extracts only the essential polarization characteristics from the complex electrochemical model, isolating the key dynamic behavior (voltage lag phenomenon) while removing unnecessary computational complexity. This allows retaining accuracy for OCV estimation without the heavy computational burden of full electrochemical models.
Solution Approach 2:
The patent creates a simplified analytical copy of the electrochemical model's essential behavior using closed-form mathematical equations. This analytical solution replicates the voltage relaxation characteristics without requiring numerical integration or complex state equations, enabling real-time calculation on MCUs.
2Productivity
If equivalent circuit model is used to simplify calculation, then computational speed is improved, but estimation accuracy deteriorates
Solution Approach 1:
The patent transforms the equivalent circuit model parameters into temperature-dependent functions with explicit analytical expressions. By changing parameters from fixed values to temperature-varying analytical functions, the model maintains simplicity for fast calculation while improving accuracy across different operating conditions.
Solution Approach 2:
The patent introduces dynamic temperature compensation into the equivalent circuit model, allowing parameters to adapt to changing battery conditions. This dynamic adjustment enables the simplified model to track the more complex electrochemical behavior across varying temperatures and states of charge.
3Measurement precision
If intelligent algorithm is combined with equivalent circuit model to ensure accuracy, then estimation precision is improved, but computational burden increases making real-time estimation difficult
Solution Approach 1:
The patent replaces expensive, computationally intensive intelligent algorithms with inexpensive analytical solutions based on closed-form mathematical equations. These analytical expressions provide sufficient accuracy without requiring the heavy computational resources of neural networks or optimization algorithms.
Solution Approach 2:
The patent substitutes the iterative, optimization-based intelligent algorithms with direct analytical calculations. By replacing the mechanical iterative process with closed-form mathematical expressions, the system achieves the same estimation accuracy with dramatically reduced computational complexity suitable for real-time MCU implementation.
4Ease of manufacture
If existing battery models are used, then implementation is simple, but they cannot accurately describe nonlinear battery processes and temperature characteristics
Solution Approach 1:
The patent creates a composite model that combines the simplicity of equivalent circuit models with the physical accuracy of electrochemical models. By integrating temperature-dependent analytical parameters into the equivalent circuit framework, the model achieves both ease of implementation and accurate representation of nonlinear battery behavior and temperature effects.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a simple, accurate, and robust method for OCV estimation that is decoupled from time, reducing computational errors and enabling real-time estimation on a single-chip microcomputer, with improved robustness and accuracy, reflecting temperature characteristics and describing battery terminal voltage lag.
Implementation Method 1
the principle of gas dissolution/precipitation is equivalent to the polarization effect of the battery
Data Source
AI summary
A method and device for estimating an open circuit voltage of a battery based on a gas-liquid dynamic model, includes the following steps: deriving an undetermined equation for estimating the open circuit voltage according to a gas-liquid dynamic model; identifying the estimation equation parameters according to experimental data; designing a method for estimating the open circuit voltage according to the complete equation for estimating open circuit voltage and calculating to obtain an estimated value of the open circuit voltage. The estimation equation of open circuit voltage includes the battery temperature. The experimental data includes open circuit voltages under different currents, terminal voltages and temperatures, optimal values of undetermined parameters of the equation for estimating open circuit voltage are identified with an identification method, and the optimal values of undetermined parameters are substituted into the undetermined equation for estimating open circuit voltage in the deriving step to obtain a complete equation.