Simulated Battery Modeling for Temperature and Degradation Accuracy
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Solution Overview
Problem
Existing methods struggle to accurately reproduce the characteristics of rechargeable batteries, particularly under varying conditions of temperature and degradation, when connected to a load and repeatedly charged and discharged.
Innovation Solution
A simulation battery construction device that recognizes complex impedance measurements of rechargeable batteries, identifies parameter values for a rechargeable battery model using IIR and FIR transfer functions, and calculates a time series of voltage simulating the battery's output, allowing for accurate simulation under various conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a capacitor with several 100 F to several 1000 F capacitance value is used to explain transient response waveform, then the time constant element can reproduce battery voltage behavior for a few or more seconds, but such values are not compatible with AC impedance and equivalent circuit model used for evaluating AC characteristics
Solution Approach 1:
The invention segments the internal resistance into multiple time constant elements (RC circuits), where each element represents different time scales of battery behavior. This segmentation allows the model to capture both transient response (using larger capacitance values for longer time constants) and AC impedance characteristics (using smaller capacitance values for shorter time constants) simultaneously, resolving the contradiction between duration and reliability.
2Ease of manufacture
If internal resistance is treated as mere DC resistance applying Ohm's law, then calculation is simplified, but it cannot accurately reproduce battery voltage behavior where complicated chemical reactions occur in intertwined manner
Solution Approach 1:
The invention changes the parameters of the equivalent circuit model by introducing multiple time constant elements with different resistance and capacitance values. This allows the model to transition from a simple DC resistance model to a complex dynamic model that captures the intertwined chemical reactions (electrode reactions, SEI reactions, ion diffusion) while maintaining computational tractability through systematic parameter identification.
3Measurement precision
If dedicated device such as frequency response analyzer is used to measure AC impedance, then accurate measurement of Warburg resistance is achieved, but it requires specialized equipment not available in practical operating conditions
Solution Approach 1:
The invention creates a virtual copy of the battery's electrical characteristics through an equivalent circuit model. Instead of requiring physical measurement equipment like frequency response analyzers, the model replicates the battery's AC impedance behavior and Warburg resistance characteristics through mathematical relationships, allowing accurate representation of these properties using only standard voltage and current measurements from practical operating conditions.
4Ease of operation
If only voltage, current, and temperature are measured as basic information in practical use, then measurement is simple and practical, but the internal resistance variation depending on temperature conditions or degradation cannot be accurately captured
Solution Approach 1:
The invention implements feedback by continuously updating the equivalent circuit model parameters based on measured voltage, current, and temperature data. The model uses these measurements to identify and adjust the resistance and capacitance values of the time constant elements, thereby capturing the variation of internal resistance with temperature conditions and degradation state while maintaining measurement simplicity.
Data Source
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AI summary
Provided are a device and the like that can improve the accuracy in reproduction of the characteristics of a rechargeable battery by a simulation battery under various conditions. Parameters P(n0,n1,n2) of a rechargeable battery model at each of different temperatures T(nl) at each of different degradation degrees D(n2) are determined. The values of the parameters P(n0,n1,n2) of the rechargeable battery model are identified based on a measurement result of a complex impedance Z of a rechargeable battery 220. The rechargeable battery model expresses an impedance of an internal resistance of the rechargeable battery 220 with transfer functions representing the IIR and FIR systems, respectively. Further, a voltage command value Vcmd(t) in the case where a current command value Icmd(t) is input to a rechargeable battery model corresponding to the identifier id(m0), temperature T(m1), and degradation degree D(m2) of the virtual rechargeable battery to be simulated by a simulation battery 20 is calculated, and a voltage V(t) according thereto is applied to the designated apparatus 200 or its load by the simulation battery 20.