Lithium-Ion Battery Safe-State Detection From Discharge Curve Shifts
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Solution Overview
Problem
Existing methods for detecting the safe state of lithium-ion secondary batteries only determine an unsafe state after or immediately before the battery enters that state, failing to provide timely detection of potential safety issues.
Innovation Solution
A method that calculates the absolute value of the differential coefficient of a discharge curve from which a voltage equivalent to a voltage drop is removed, determining a first battery voltage when the degree of increase in the absolute value exceeds a threshold, and identifying a second battery voltage at the start of oxidation heat increase, to detect the safe state of the battery based on the second battery voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional temperature sensing methods are used to detect battery safety, then the system can detect abnormal temperature changes, but it only determines unsafe state after or immediately before the battery enters unsafe state
Solution Approach 1:
The patent performs preliminary actions by calculating the differential coefficient of the discharge curve and comparing it with reference values before the battery actually enters unsafe state. This allows prediction of potential safety issues in advance, enabling preventive measures to be taken before thermal runaway occurs, thus resolving the contradiction between detection accuracy and detection timing.
2Loss of time
If the battery is monitored continuously to detect unsafe state early, then detection timing is improved, but the complexity of the detection system increases
Solution Approach 1:
The patent replaces complex multi-sensor monitoring systems with a simplified computational approach using voltage-time data from existing battery management systems. By calculating differential coefficients and comparing with reference values, the system achieves early unsafe state detection without adding complex hardware, thus resolving the contradiction between detection timing and system complexity.
Data Source
AI summary
A safe state detection method for a lithium-ion secondary battery, includes: calculating an absolute value of a differential coefficient of a discharge curve from which a voltage equivalent to a voltage drop of the lithium-ion secondary battery is removed; determining a first battery voltage when the degree of increase in the absolute value of the differential coefficient is greater than a threshold value; determining a second battery voltage at a start of an increase in oxidation heat in response to the first battery voltage, the oxidation heat being heat generated inside the lithium-ion secondary battery when the lithium-ion secondary battery is overcharged; and detecting a safe state of the lithium-ion secondary battery, based on the determined second battery voltage.