Lithium Ion Battery State Determination via Partial Charge-Discharge and Relaxation Analysis
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Solution Overview
Problem
Existing methods for determining the state of lithium ion secondary batteries, such as preparing deterioration maps or actual measurements, require significant labor, time, and cannot accurately assess battery deterioration in real-use conditions without full charging and discharging, especially for batteries used in HEVs and EVs.
Innovation Solution
A method that estimates the entire charge-discharge curve from fragmentary curves by analyzing the resistance through the relaxation process after current interruption, allowing for the calculation of battery state without full charging, using partial charge-discharge curves and considering resistance values to predict future deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If full charge and discharge measurements are performed to accurately assess battery deterioration, then measurement precision is improved, but loss of time and productivity deteriorate due to the lengthy charging/discharging cycles required
Solution Approach 1:
The patent applies partial action by performing only partial charge and discharge cycles (e.g., charging from 30% to 70% SOC) instead of complete cycles. This allows acquisition of sufficient charge-discharge curve data for deterioration assessment without the time penalty of full cycles, directly resolving the contradiction between measurement precision and time loss
Solution Approach 2:
The patent performs preliminary actions by conducting multiple partial charge-discharge cycles and accumulating charge-discharge curve data before performing the actual deterioration assessment. This preliminary data collection during normal battery operation enables accurate assessment without requiring dedicated full charge-discharge testing time
2Measurement precision
If actual measurement methods are used to grasp battery state, then measurement precision is improved, but ease of operation deteriorates because full charge and discharge must be performed which is not feasible for batteries used in HEVs and EVs
Solution Approach 1:
The patent enables operation under real-use conditions by performing measurements during partial charge-discharge cycles that occur naturally in HEV and EV operation. This eliminates the need to force full charge-discharge cycles, making the measurement method easy to operate in actual service conditions while maintaining precision through proper analysis of the partial cycle data
Solution Approach 2:
The patent makes the battery system self-sufficient by utilizing its own normal operating cycles (partial charge-discharge) to generate the measurement data needed for deterioration assessment. No external full charge-discharge testing infrastructure is required, as the battery's regular service operation provides sufficient data when analyzed with the proposed method
3Ease of operation
If deterioration maps are prepared in advance to assess battery state, then ease of operation is improved, but manufacturing precision deteriorates due to the extensive labor and time required to prepare comprehensive maps
Solution Approach 1:
The patent creates a simplified copy of the deterioration assessment process by using charge-discharge curve data from partial cycles instead of requiring comprehensive deterioration maps prepared from extensive full cycle testing. The curve data serves as a sufficient proxy that maintains assessment accuracy while eliminating the labor-intensive map preparation process
Solution Approach 2:
The patent changes the assessment parameters from requiring complete charge-discharge curves (as in traditional map methods) to utilizing partial charge-discharge curve data combined with resistance analysis. This parameter change maintains the ability to assess deterioration accurately while dramatically reducing the data collection and processing requirements for creating assessment tools
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
Enables the accurate assessment of battery deterioration and future performance without full charging, reducing labor and time requirements, and allows for effective suppression of future deterioration through controlled charging strategies.
Implementation Method 1
grasping a resistance value of the lithium ion secondary battery on a basis of a relaxation process of a terminal voltage after interrupting a charging current during charging or a discharge current during discharging
Data Source
AI summary
Provided is a method for determining a battery state of a lithium ion secondary battery that allows for understand a deterioration state of the battery without performing full charging of the battery.To estimate an entire image of a charge-discharge curve on the basis of a fragmentary charge-discharge curve by analyzing a relaxation process after the electric current interruption to grasp the resistance of a battery and taking into consideration a resulting resistance value.Specifically, a method for determining a battery state of a lithium ion secondary battery includes: a partial charge-discharge curve calculating step of acquiring, by partial charge or partial discharge, a partial charge-discharge curve which is a part of a charge-discharge curve, and calculating a positive electrode partial charge-discharge curve and a negative electrode partial charge-discharge curve; a resistance grasping step of grasping a resistance value of the lithium ion secondary battery on a basis of a relaxation process of a terminal voltage after interrupting a charging current during charging or a discharge current during discharging; and a charge-discharge curve calculating step of taking into consideration the resistance value thus acquired, and acquiring a calculation charge-discharge curve prepared by calculating an entire image on a basis of the partial charge-discharge curve.