Battery Cell Voltage Drop Screening for Early Low-Voltage Defects
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Solution Overview
Problem
Current methods for detecting low voltage defects in lithium secondary batteries are time-consuming and lack sufficient detection power, making it difficult to distinguish good battery cells from defective ones within a reasonable timeframe.
Innovation Solution
A method involving setting a reference time point after a shipping charge to measure a first voltage, followed by a second voltage measurement with a temporal interval longer than the self-discharge suppression period, and determining low voltage defects by comparing the voltage difference with a reference value (+3 to +6 sigma in a normal distribution of voltage drop amounts for normal sample battery cell groups, using microvolt-resolution instruments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage measurements are taken at multiple time points (1 day, 8 days, 14 days) to distinguish good battery cells from defective ones, then detection accuracy is improved, but detection time becomes excessively long
Solution Approach 1:
The patent changes the measurement parameters by using microvolt-resolution instruments to detect voltage differences at a single time point (1 day) rather than requiring multiple time points. By detecting voltage drop amounts in the microvolt range and comparing against a reference value (+3 to +6 sigma), the method achieves high detection accuracy without the time penalty of extended monitoring periods.
2Productivity
If voltage measurements are taken early (before 14 days) to reduce detection time, then detection speed is improved, but detection power decreases making it difficult to distinguish defective cells
Solution Approach 1:
The patent replaces the mechanical/time-based differentiation approach (waiting 14 days for voltage divergence) with an instrumental/electrical approach (using microvolt-resolution measurement). By substituting extended time monitoring with high-resolution voltage measurement at an earlier time point, the method achieves both faster detection speed and maintained detection power.
Solution Approach 2:
The patent creates a reference model by measuring voltage drop amounts of normal battery cells and establishing a statistical baseline (+3 to +6 sigma). This reference copying approach allows early detection by comparing defective cells against the established normal pattern, enabling reliable differentiation without waiting for natural voltage divergence over 14 days.
3Ease of manufacture
If standard voltage measurement resolution is used, then measurement simplicity is maintained, but voltage drop amount dispersion among good battery cells cannot be minimized
Solution Approach 1:
The patent changes the measurement resolution parameter from standard voltage measurement to microvolt-resolution measurement. This parameter change enables detection of subtle voltage drop differences among good battery cells, minimizing dispersion and allowing reliable identification of defective cells while maintaining procedural simplicity through automated measurement and statistical comparison.
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 significantly reduces the time required for detecting low voltage defects and improves detection power by minimizing voltage drop amount dispersion among good battery cells, thereby clearly distinguishing good from defective products.
Implementation Method 1
measuring a second voltage of the battery cell with a temporal interval longer than a period at which a self-discharge of the battery cell is suppressed
Data Source
AI summary
The present technology provides a method of detecting a battery cell having a low voltage defect, including: setting a reference time point when a voltage of a battery is stabilized after a shipping charge, and measuring a first voltage of a battery cell at the reference time point; measuring a second voltage of the battery cell with a temporal interval longer than a period at which a self discharge of the battery cell is suppressed; and determining whether the battery cell has a low voltage defect by comparing a difference (ΔOCV) between the first voltage and the second voltage with a reference value, wherein the reference value is +3 sigma (σ) to +6 sigma (σ) in a normal distribution of a voltage drop amount obtained by the measuring of the first voltage and the measuring of the second voltage for a plurality of normal sample battery cell groups.