Battery Management System Shorted Cell Detection
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Solution Overview
Problem
Existing battery management systems lack effective methods to detect shorted battery cells within a battery pack, which can lead to reduced performance and potential safety issues such as explosions due to sudden voltage drops.
Innovation Solution
A battery management system that includes a sensing unit to measure cell voltages and currents, a Main Control Unit (MCU) to determine State of Charge (SOC) and identify shorted cells by comparing SOC difference values with predefined reference values, and a controller to alert the Engine Control Unit (ECU) for display and potential action.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If battery management systems monitor cell voltages and currents, then charging and discharging control is improved, but the ability to detect shorted battery cells remains insufficient
Solution Approach 1:
The system performs preliminary SOC measurements at multiple time points (first SOC, second SOC after predetermined time, third SOC) before making a determination. By measuring SOCs at different stages and comparing the differences, the system can predict and detect shorted cells before they cause safety hazards, rather than waiting for voltage drop symptoms to appear.
Solution Approach 2:
The system continuously monitors SOC changes and compares the first difference value (between maximum and individual second SOCs) and second difference value (between first and second SOCs of individual cells) against reference values. This feedback mechanism allows the determination unit to identify shorted cells based on abnormal SOC deviation patterns, improving detection accuracy beyond simple voltage monitoring.
2Measurement precision
If the system monitors all battery cells continuously, then detection accuracy is improved, but system complexity and computational load increase
Solution Approach 1:
The system applies a two-stage detection approach: first compares the first difference value against a first reference value, and only if that threshold is not exceeded, proceeds to compare the second difference value against a second reference value. This partial action approach maintains high detection accuracy while reducing unnecessary computational operations and system complexity.
Solution Approach 2:
The system uses different reference values (first reference value and second reference value) for different detection stages and different SOC difference metrics. By changing the threshold parameters based on the detection stage and the type of SOC difference being analyzed, the system optimizes the balance between detection sensitivity and system complexity.
Data Source
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AI summary
A BMS and driving method, the BMS including a sensing unit sensing voltages and currents of battery cells and an MCU determining an SOC of the battery cells and controlling charging and discharging based on cell voltages and currents of the battery cells, wherein the MCU includes an SOC measurer measuring first SOCs and, after a predetermined duration, second SOCs of the battery cells; and a controller determining whether a first difference value between a maximum second SOC value and the second SOCs of each battery cell is greater than a first reference value or determining whether a second difference value between the first and second SOCs of respective battery cells is greater than a second reference value, and determining which battery cell is shorted when the first difference value is greater than the first reference value or when the second difference value is greater than the second reference value.