Battery Cell Voltage Compensation for Short-Circuit Detection
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Solution Overview
Problem
Current methods for detecting minute short circuits in lithium-ion batteries during the equalization process are delayed and complex, as they rely on capacity adjustment time and require different determination processes during idle and non-idle periods, making it difficult to distinguish between voltage drops caused by energy transfer and actual short circuits.
Innovation Solution
A management device with a voltage detector and controller that calculates voltage differences between representative and target cell voltages, applying a compensation value for energy transfer changes during equalization, allowing for accurate abnormality determination regardless of the equalization process status.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cell discharge is performed during equalization to prevent voltage difference expansion, then safety is improved, but detection accuracy of minute short circuits deteriorates because the discharge current masks the voltage difference caused by short circuits
Solution Approach 1:
The patent applies preliminary action by performing abnormality determination before the equalization process begins. Specifically, the controller determines cell abnormality based on voltage differences measured at a first time point (before equalization) and compares it with voltage differences at a second time point (after equalization). This allows detection to occur in advance, preventing the masking effect of equalization discharge current while still maintaining safety through timely detection.
2Measurement precision
If abnormality determination is performed only after equalization process, then detection reliability is improved by avoiding false positives from energy transfer, but detection speed deteriorates causing time delay from abnormality occurrence to detection
Solution Approach 1:
The patent performs preliminary abnormality determination at a first time point before the equalization process starts. The controller measures voltage differences among cells before equalization begins, then performs the same determination after equalization completes at a second time point. This dual timing approach enables early detection while maintaining reliability through comparison, reducing the time delay from abnormality occurrence to detection.
Solution Approach 2:
The patent uses feedback by comparing voltage difference data from two different time points. The controller determines abnormality at the first time point, then repeats the determination at the second time point after equalization. By comparing the results and analyzing changes in voltage differences, the system provides feedback that confirms detection reliability while enabling timely alerting of abnormalities.
3Measurement precision
If different determination processes are used for idle and non-idle periods, then detection accuracy is improved by accounting for equalization effects, but system complexity increases due to multiple determination standards and additional calculations
Solution Approach 1:
The patent applies universality by using a single, unified abnormality determination process that works for both idle and non-idle periods. The controller consistently performs voltage difference measurement and comparison logic regardless of whether equalization is occurring. This universal approach maintains detection accuracy by using the same reliable methodology in all operational states, while reducing system complexity by eliminating the need for separate determination standards and conditional logic branches.
Data Source
AI summary
A controller executes an equalization process of equalizing capacities of a plurality of cells, and a cell abnormality determination process of, of detected voltages of the plurality of cells, calculating a voltage difference between a representative voltage based on the detected voltage of at least one cell to be compared and the detected voltage of one cell to be detected at a first time and a second time, and when a difference between the two voltage differences is greater than or equal to a threshold value, determining that the cell to be detected is abnormal. In the case of executing the cell abnormality determination process during the equalization process, the controller provides the detected voltage of a target cell to be subjected to the equalization process with a compensation value corresponding to a voltage change based on energy transfer in the target cell due to the equalization process between the first time and the second time, and calculates the voltage difference at the second time.