Fractional Battery Model for Internal-Temperature Cell Impedance
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Solution Overview
Problem
Existing battery cell impedance modeling methods using temperature sensors are inaccurate due to the sensors being thermally well-connected but spaced apart from the battery core, leading to low-pass behavior and dependence on ambient temperature, resulting in inaccurate cell temperature measurements.
Innovation Solution
A fractional battery model is used to extend the cell impedance model by incorporating a temperature model that predicts cell internal temperature based on power dissipation, ambient temperature, and external temperature measurements, optimizing model parameters to minimize voltage differences and improve temperature accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a temperature sensor is thermally well-connected to the battery cell but spaced apart from the core, then the sensor can be easily installed and thermally connected, but the measured temperature is inaccurate due to low-pass behavior and dependence on ambient temperature
Solution Approach 1:
The patent introduces a thermal model as an intermediary between the easily measurable external temperature and the difficult-to-measure internal temperature. The model uses the external temperature sensor readings combined with power dissipation data to calculate and predict the internal cell temperature, effectively mediating the measurement problem without requiring direct physical contact with the cell core
Solution Approach 2:
The patent replaces the mechanical/physical measurement approach (direct temperature sensing at the cell core) with a computational/electrical approach. Instead of physically placing a sensor inside the cell, the system uses electrical measurements (power dissipation, current, voltage) combined with thermal modeling to determine internal temperature, substituting a complex physical measurement system with a computational solution
2Device complexity
If the cell impedance model uses measured external temperature, then the model is simple to implement, but the model accuracy is reduced due to inaccurate temperature representation
Solution Approach 1:
The patent changes the temperature parameter from directly measured external temperature to model-calculated internal temperature. By transforming the temperature parameter through thermal modeling that incorporates power dissipation and external temperature, the model uses a more accurate temperature representation that reflects actual internal cell conditions, thereby improving impedance determination accuracy
3Measurement precision
If a temperature sensor is placed inside the battery cell core, then accurate internal temperature measurement is achieved, but the installation complexity and invasiveness increase significantly
Solution Approach 1:
The thermal model serves as an intermediary that translates easily obtainable external measurements into accurate internal temperature estimates, avoiding the need for invasive internal sensing while achieving the same measurement precision goal
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 method provides a more accurate determination of cell impedance by accounting for internal temperature variations, enhancing the model's ability to simulate battery behavior and predict current or power provision without violating operating limits.
Implementation Method 1
a progression of the internal cell temperature is determined for the time steps of the measurement time series based on a predetermined temperature model as a function of the respective measured cell external temperature or the measured ambient temperature and a power dissipation
Data Source
AI summary
A method for providing a cell impedance model for a battery cell based on an equivalent circuit model with components having temperature-dependent component values and configured to model a terminal voltage and/or a cell impedance by providing a measurement time series of measured values in time steps, where the measured values each comprise a measured terminal voltage, a measured cell current, a measured cell external temperature, or a measured ambient temperature, and performing an optimization method for the model parameters of the cell impedance model. In each iteration, on a provisionally parameterized cell impedance model, a progression of the cell internal temperature is determined for the time steps, and the model parameters of the cell impedance model are optimized for the time steps by minimizing an entirety of the voltage differences between the measured terminal voltage and a terminal voltage modeled with the cell impedance model.