Energy Storage Life Estimation Using Nth-Degree Resistance Functions
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Solution Overview
Problem
Conventional methods for estimating the residual life of energy storage devices, such as lithium-ion batteries, face challenges in accurately predicting the variation of DC resistance over time due to uncertainties in the empirical formula's exponent value, leading to incorrect estimation of the residual life.
Innovation Solution
A life estimating apparatus that acquires a relational expression using an Nth-degree function (N≥3) or exponential function of the accumulated use period to estimate the residual life of energy storage devices, allowing for accurate prediction of resistance value changes and subsequent residual life calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an Nth-degree function (N<3) or exponential function is used to model resistance variation, then the residual life estimation accuracy is improved, but the complexity of the relational expression increases
Solution Approach 1:
The patent changes the mathematical parameters of the relational expression by using Nth-degree functions where N≥3 or exponential functions instead of conventional lower-degree polynomials. This parameter change enables accurate modeling of the non-linear resistance variation over accumulated use period, directly improving residual life estimation accuracy while accepting increased expression complexity as a necessary trade-off.
2Ease of operation
If a simple empirical formula is used for resistance variation, then the ease of calculation is improved, but the accuracy of residual life estimation deteriorates
Solution Approach 1:
The patent transitions from simple empirical formulas with low-degree polynomials to more sophisticated Nth-degree functions (N≥3) or exponential functions. This parameter change in the mathematical model captures the complex non-linear behavior of resistance variation over time, significantly improving estimation accuracy despite requiring more complex calculations.
Solution Approach 2:
The patent creates a more accurate mathematical copy of the actual resistance variation process by using higher-degree functions that better replicate the non-linear degradation behavior. This improved mathematical model serves as a more faithful copy of the physical phenomenon, enabling accurate residual life prediction.
Data Source
AI summary
A life estimating apparatus estimating a residual life that is of a usable accumulated residual period of an energy storage device, the life estimating apparatus includes: a relational expression acquisition unit that acquires a relational expression, in which a resistance value of a DC resistance or an AC resistance of the energy storage device at an accumulated use period elapsed time point that is of an accumulated value of a use period of the energy storage device is given by an expression including a term of a function of the accumulated use period; and a residual life estimating unit that estimates the residual life of the energy storage device using the acquired relational expression. When a value in which the resistance value in the relational expression is differentiated by the accumulated use period twice becomes a positive value, the relational expression acquisition unit sets the accumulated use period to a relational expression acquisition period, and acquires the relational expression obtained from a relationship between the resistance value and the accumulated use period up to the relational expression acquisition period elapsed time point.