Battery Cell Voltage Correction for Minute Short-Circuit Detection
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Solution Overview
Problem
Existing methods for detecting minute short circuits in battery cells are less accurate due to variations in state-of-charge (SOC) and state-of-health (SOH) among cells, leading to inconsistent voltage differences and reduced detection accuracy under non-uniform conditions.
Innovation Solution
A management device with a voltage detector and controller that calculates voltage differences using a representative voltage based on a SOC-OCV curve, applying a linear function to estimate initial capacitance and derive open-circuit voltage, allowing for accurate abnormality detection regardless of SOC or SOH variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the average voltage method is used to detect minute short circuits, then the detection process is simple, but the detection accuracy deteriorates when SOC or SOH varies among cells
Solution Approach 1:
The patent changes the detection parameters by introducing SOC-based voltage correction. Instead of using raw voltage differences, the system calculates corrected voltage differences by subtracting the expected voltage variation (based on SOC and reference voltage characteristics) from the actual voltage difference. This parameter transformation enables accurate detection across varying SOC conditions while maintaining a relatively simple detection framework.
2Measurement precision
If the determination threshold is corrected based on SOC or DOD, then the detection accuracy is improved, but the device complexity increases due to additional correction calculations
Solution Approach 1:
The patent introduces an intermediary approach by using a reference voltage value (Vref) that represents the expected voltage characteristic at a given SOC. This reference voltage acts as a mediator between the actual cell voltages and the determination threshold, simplifying the correction process. The system calculates a corrected voltage difference by comparing actual voltages against this reference, avoiding the need for complex SOC-specific threshold tables while maintaining high detection accuracy.
3Measurement precision
If more detailed determination conditions are created for long-term operation, then the detection accuracy is improved, but the device complexity and operational complexity increase
Solution Approach 1:
The patent creates a universal detection framework that works across all SOC and SOH conditions through SOC-based voltage correction. Instead of creating separate determination conditions for different operating phases (early, mid, late life), the system uses a single corrected voltage difference calculation that adapts to varying conditions through the SOC-dependent reference voltage. This universal approach maintains high detection accuracy throughout the battery's lifecycle without requiring multiple condition sets.
Data Source
AI summary
Provided is a controller configured: to calculate, among voltages detected from a plurality of cells, a voltage difference between the voltage detected from one cell of the plurality of cells, the one cell to be detected, and a representative voltage at each of a first time and a second time, the representative voltage based on the voltage detected from at least one cell of the plurality of cells, the at least one cell to be compared; and when a discrepancy between the voltage difference at the first time and the voltage difference at the second time is equal to or more than a threshold, to determine that an abnormality has occurred in the one cell to be detected. The controller refers to a state-of-charge versus open-circuit-voltage (SOC-OCV) curve of the one cell to be detected in accordance with a state-of-health (SOH) of the one cell to be detected, so as to estimate an SOC as initial capacitance reference of the one cell to be detected in correspondence to the voltage detected from the one cell to be detected. The controller introduces a linear function using an SOC as initial capacitance reference as an input variable, using an OCV as an output variable, and having a predetermined inclination, and applies the SOC as initial capacitance reference of the one cell to be detected that the controller has estimated to the linear function, so as to derive an OCV. Then, in place of the voltage detected from the one cell to be detected, the controller uses the OCV that the controller has derived, so as to calculate the voltage difference at the first time and the voltage difference at the second time.