Battery State Estimation Using Impedance Slope Angle
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Solution Overview
Problem
Existing battery state estimating apparatuses face challenges in accurately estimating the charge amount of batteries independently of their degradation state, as the impedance of a battery varies with degradation, making it complex to determine the state of charge (SOC) and state of health (SOH).
Innovation Solution
A battery state estimating apparatus that calculates the ratio of a predetermined feature amount from the complex impedance and uses this ratio in conjunction with the integrated current value to estimate the charge amount, eliminating the influence of degradation state and temperature dependence, by employing components such as an acquirer, calculator, and estimator to process the impedance data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the impedance of the battery is used to estimate the charge amount, then the charge amount can be detected, but the estimation accuracy deteriorates due to battery degradation
Solution Approach 1:
The patent transforms the impedance estimation approach by changing from using absolute impedance values to using the slope angle of the impedance characteristic line. This parameter transformation makes the estimation independent of battery degradation, as the slope angle remains consistent between new and degraded batteries at the same charge level.
Solution Approach 2:
The patent introduces the slope angle as an intermediary parameter between the impedance characteristics and the charge amount estimation. This intermediary eliminates the direct influence of degradation on the estimation, allowing accurate charge detection without needing to account for degradation state.
2Measurement precision
If the degradation state is considered to improve charge amount estimation accuracy, then the estimation becomes more accurate, but the process complexity increases
Solution Approach 1:
The patent extracts and eliminates the degradation-related variables from the estimation process. By using only the slope angle of the impedance characteristic, the method removes the need to measure or estimate degradation state, thereby maintaining accuracy while simplifying the process.
Solution Approach 2:
The patent changes the estimation parameter from impedance magnitude (which degrades with battery aging) to impedance slope angle (which remains stable). This parameter substitution eliminates the need for degradation compensation calculations, reducing process complexity while maintaining accuracy.
Data Source
AI summary
A battery state estimating apparatus is provided with: an acquirer configured to obtain a complex impedance of a battery; a calculator configured to calculate a ratio of a variation of a predetermined feature amount regarding the complex impedance; and an estimator configured to estimate a charge amount of the battery on the basis of the ratio of the variation of the predetermined feature amount with respect to an integrated current value, which is an integrated value of an electric current flowing through the battery.