Battery State Estimation Using Dual-Frequency Impedance
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Solution Overview
Problem
Existing battery state estimation methods require a significant amount of time to measure complex impedance, making timely acquisition of battery state difficult, especially in low-frequency bands where measurements are prolonged.
Innovation Solution
The method estimates battery state by measuring complex impedance using only two frequencies in the low-frequency band (0.1 Hz or less), allowing for faster measurement times of around 10 seconds to 100 seconds, and utilizes the real component instead of the imaginary component when there is a correlation between them, providing flexibility in selecting measurement frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex impedance measurement is performed in the low-frequency band (0.1 Hz or less) to accurately estimate battery state, then measurement precision is improved, but measurement time is significantly prolonged
Solution Approach 1:
The patent applies partial action by measuring complex impedance at only two specific frequencies (0.01 Hz and 0.1 Hz) within the low-frequency band, rather than performing comprehensive measurements across the entire diffusion region. This selective measurement approach captures the essential battery state information while significantly reducing the measurement time from what would be required for full-spectrum analysis.
2Productivity
If measurement frequencies are reduced to speed up battery state estimation, then productivity is improved, but measurement precision deteriorates
Solution Approach 1:
The patent changes the measurement parameters by selecting two specific frequencies (0.01 Hz and 0.1 Hz) that are optimized for both speed and accuracy. By carefully choosing these frequency parameters within the low-frequency band, the system achieves rapid measurement (completing the diffusion region assessment in just two steps) while maintaining sufficient precision to accurately estimate battery state and temperature.
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 reduces the time required for estimating battery state and temperature, enabling more accurate and efficient battery state monitoring, particularly in nickel-metal hydride rechargeable batteries, by limiting measurements to two frequencies within the diffusion region.
Implementation Method 1
the power supply unit applies an alternating current signal having a measurement frequency ranging from 0.5 mHz or greater to less than 10 mHz to the rechargeable battery
Implementation Method 2
the complex impedance measurement unit measures a complex impedance of the rechargeable battery based on an alternating current signal applied by the power supply unit
Implementation Method 3
a temperature measurement unit configured to measure a temperature of the rechargeable battery
Data Source
Figure 1
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AI summary
A battery state estimation device (30) for estimating a charged electric charge quantity of a rechargeable battery (10) includes an impedance measurement unit (43) configured to measure a plurality of complex impedances of the rechargeable battery (10) by supplying measurement power to the rechargeable battery (10), a parameter calculation unit (45) configured to calculate a parameter that includes a ratio of a difference between measurement angular velocities of two complex impedances in a diffusion region among the measured complex impedances to a difference between components of the two complex impedances, and an electric charge quantity estimation unit (46) configured to estimate a charged electric charge quantity of the rechargeable battery (10) based on the calculated parameter and preset correlated information between the charged electric charge quantity of the rechargeable battery (10) and the parameter.