Lithium-Ion Battery Thermal Model Using Finite Difference Method
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Solution Overview
Problem
Current thermal models for lithium-ion batteries in electric vehicles either fail to accurately simulate internal temperature distributions due to complexity or are too simplistic, leading to potential thermal runaway and safety issues.
Innovation Solution
A method and system for building a thermal model of power lithium-ion batteries based on an electrochemical mechanism, involving discretization of the second-order partial differential heat conduction equation using the finite differential method, dynamic working condition tests, and identification of electrochemical parameters to estimate surface temperatures and verify model accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a thermal model based on internal mechanism is used to accurately simulate heat generation law and internal temperature distribution, then measurement precision is improved, but device complexity increases and calculation amount becomes too large for practical use
Solution Approach 1:
The patent segments the continuous heat conduction equation into discrete nodes using the finite difference method. The battery thermal field is divided into multiple calculation nodes, allowing the complex partial differential equation to be transformed into a system of algebraic equations that can be solved iteratively, thus reducing computational complexity while maintaining accuracy.
Solution Approach 2:
The patent introduces an equivalent thermal circuit model as an intermediary between the complex internal mechanism model and the simple equivalent circuit model. This intermediary model uses thermal resistance and thermal capacitance elements to represent heat transfer processes, enabling accurate temperature prediction with reduced computational burden.
2Device complexity
If a thermal model based on equivalent circuit is used to simplify calculation, then device complexity is reduced, but measurement precision deteriorates and internal temperature distribution cannot be accurately acquired
Solution Approach 1:
The patent changes the mathematical parameters by transforming the continuous heat conduction partial differential equation into discrete difference equations through the finite difference method. This parameter transformation allows the model to maintain high accuracy while reducing computational complexity, as the discrete form can be solved more efficiently than the continuous form.
3Measurement precision
If the finite differential method is used to discretize the heat conduction equation, then measurement precision is improved and internal temperature distribution accuracy is enhanced, but calculation amount increases
Solution Approach 1:
The patent implements a dynamic solution approach where the finite difference equations are solved iteratively at each time step. The model adapts to changing thermal conditions by updating temperature values at each node dynamically, allowing accurate prediction of transient thermal behavior while maintaining reasonable computational efficiency through incremental solving.
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
This approach improves the reliability and safety of battery packs by accurately estimating heat generation and temperature distribution, reducing computational complexity while ensuring model accuracy, and is suitable for batteries of any shape.
Implementation Method 1
discretizing a second order partial differential heat conduction equation of a power lithium-ion battery according to a finite differential method
Implementation Method 2
A thermal model of a power lithium-ion battery based on an electrochemical mechanism
Implementation Method 3
calculating an internal discharging resistance R(t) of the battery at each measured discharging moment
Data Source
AI summary
A method and system for building a thermal model of a power lithium-ion battery based on an electrochemical mechanism. The method includes: discretizing a second order partial differential heat conduction equation of a power lithium-ion battery according to a finite differential method, thereby building a thermal model of the power lithium-ion battery; carrying out a dynamic working condition test by using a cylindrical power lithium-ion battery selected as an object, thereby acquiring experimental data such as a temperature, a current, a voltage, and a temperature of a surface of the battery; identifying an electrochemical parameter of the power lithium-ion battery according to an optimal parameter algorithm by using test data acquired in a dynamic working condition, thereby building a thermal model of the power lithium-ion battery; and verifying accuracy of the thermal model of the power lithium-ion battery by using test data acquired in another dynamic working condition.