Battery Management Micro Short Circuit Detection via SOC Comparison
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Solution Overview
Problem
It is challenging to accurately determine the occurrence of micro short circuits in series-connected batteries due to variations in battery deterioration and measurement errors, making it difficult to identify the cause of voltage differences between batteries.
Innovation Solution
A management apparatus comprising a voltage detection unit, a current detection unit, and a control unit that estimates the state of charge (SOC) using both open circuit voltage (OCV) and current integration methods, comparing the results to determine if a micro short circuit is present.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage measurement and equalization control are performed in series-connected batteries, then voltage variation can be managed, but it becomes difficult to accurately identify the cause of voltage differences (micro short circuit vs. deterioration vs. measurement error)
Solution Approach 1:
The patent segments the voltage variation analysis by introducing a differential voltage concept. Instead of analyzing absolute voltage values which are affected by deterioration and measurement errors, the system segments the analysis into: (1) individual battery voltage measurements, (2) differential voltage calculations between adjacent batteries, and (3) threshold-based anomaly detection. This segmentation isolates the micro short circuit detection from other sources of voltage variation.
Solution Approach 2:
The patent introduces differential voltage as an intermediary parameter to detect micro short circuits. Rather than directly comparing absolute voltage values between batteries (which are affected by deterioration and measurement errors), the system uses differential voltage (the voltage difference between adjacent batteries) as an intermediary indicator. This intermediary parameter amplifies the effect of micro short circuits while canceling out common-mode errors from deterioration and measurement uncertainties.
2Duration of action of moving object
If multiple batteries with different deterioration levels are connected in series, then system capacity is maintained through partial replacement, but voltage differences increase making micro short circuit detection more difficult
Solution Approach 1:
The patent inverts the detection approach by not looking for absolute voltage deviations from a reference value (which would be affected by different deterioration levels), but rather looking for abnormal voltage differences between adjacent batteries. Instead of asking 'is this battery's voltage normal?', the system asks 'is the voltage difference between this battery and its neighbor abnormal?'. This inversion makes the detection insensitive to overall deterioration levels while remaining sensitive to micro short circuits.
Solution Approach 2:
The patent changes the detection parameter from absolute voltage to differential voltage. By transforming the measurement parameter from V_i (absolute voltage of battery i) to ΔV_i = V_i - V_(i-1) (differential voltage between adjacent batteries), the system makes the detection robust against deterioration-induced voltage shifts while maintaining sensitivity to micro short circuits. The parameter change effectively filters out low-frequency deterioration effects while preserving high-frequency fault signals.
Data Source
AI summary
A voltage detection unit detects voltage between both ends of a power storage unit. A current detection unit detects current flowing through the power storage unit. A control unit estimates a state of charge (SOC) of the power storage unit using an open circuit voltage (OCV) method based on the voltage detected by the voltage detection unit and estimates the SOC of the power storage unit using a current integration method based on the current detected by the current detection unit. The control unit compares the SOC estimated using the OCV method with the SOC estimated using the current integration method to determine whether micro short circuit occurs in the power storage unit.