Battery Impedance Ratio Analysis for High-Rate Deterioration Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods fail to accurately distinguish between deterioration by aging and high-rate deterioration in secondary batteries, leading to inadequate control measures, particularly in lithium-ion batteries where metal lithium precipitation can occur due to uneven salt concentration during high-current charging and discharging.
Innovation Solution
A method involving a controller that monitors voltage, current, and temperature changes in a secondary battery, calculates impedance for different frequency bands using Fourier transform, and estimates high-rate deterioration by comparing impedance ratios between specific frequency bands, allowing for accurate differentiation between aging and high-rate deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional impedance measurement methods are used, then general battery deterioration can be detected, but high-rate deterioration cannot be accurately distinguished from aging deterioration
Solution Approach 1:
The patent segments the impedance spectrum into multiple frequency bands (low frequency band including DC resistance and reaction resistance, and high frequency band including diffusion resistance). By analyzing impedance characteristics in each segmented frequency band separately, the method can distinguish between aging deterioration (affecting all bands) and high-rate deterioration (primarily affecting low frequency band), thereby resolving the inability to differentiate deterioration types.
Solution Approach 2:
The patent introduces a new dimension of analysis by comparing impedance ratios across different frequency bands rather than relying on a single impedance value. The key indicator is the ratio of low frequency impedance to high frequency impedance, which provides an additional diagnostic dimension that enables differentiation between deterioration mechanisms that appear similar in conventional single-point measurements.
2Productivity
If high-rate deterioration is not detected, then battery can continue operating, but metal lithium precipitation and reduced overcharging resistance occur
Solution Approach 1:
The patent implements preliminary detection of high-rate deterioration by continuously monitoring impedance ratios across frequency bands before critical failure occurs. The controller calculates the impedance ratio and compares it against predetermined thresholds to identify high-rate deterioration in its early stages, enabling preventive control actions to be taken before metal lithium precipitation or safety issues develop.
Solution Approach 2:
The patent establishes a feedback mechanism where the controller continuously monitors impedance characteristics, detects high-rate deterioration through impedance ratio changes, and responds by adjusting battery operation (such as limiting charging/discharging rates). This closed-loop feedback system ensures battery safety while maintaining productivity by allowing operation within safe parameters.
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 enables precise estimation of high-rate deterioration, preventing potential issues like reduced resistance against overcharging and metal lithium precipitation by restricting battery usage when high-rate deterioration is detected, thus enhancing safety and performance.
Implementation Method 1
carries out frequency conversion of the voltage and the current during the prescribed period of the secondary battery stored in the memory and calculating an impedance for each frequency band
Data Source
AI summary
A method of estimating a deteriorated state of a battery mounted on a vehicle includes first to third steps. The first step is a step of obtaining a voltage value and a current value of the battery a plurality of times during a data acquisition period and storing the values in a memory. The second step is a step of subjecting the voltage value and the current value during the data acquisition period stored in the memory to Fourier transform and calculating an impedance component for each frequency band based on the voltage value and the current value subjected to Fourier transform. The third step is a step of estimating high-rate deterioration of the battery by comparing a ratio E between a medium-frequency impedance ZM and a low-frequency impedance ZL2 with a reference value K.