Battery Module Capacity Screening by Lowest Cell Voltage
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Solution Overview
Problem
In large energy storage systems, particularly those using lithium ion batteries, it is difficult to efficiently measure the capacity of all cells and modules due to the impracticality of standard periodic inspections, leading to challenges in maintaining the health and performance of the system.
Innovation Solution
A method involving the use of a voltage sensor to identify the module with the lowest voltage value within a bank, which is correlated with the cell having the lowest capacity, allowing for targeted capacity measurements to be performed efficiently, either during charge/discharge cycles or through historical voltage data analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If all cells and modules are measured for capacity in large energy storage systems, then measurement precision is improved, but productivity deteriorates due to the impracticality of measuring all 800-1600 cells in systems mounted on cargo containers
Solution Approach 1:
The patent segments the large energy storage system into banks, modules, and cells hierarchically. Instead of measuring all cells uniformly, the system divides them into groups and applies different measurement strategies to different segments based on their voltage characteristics, thereby improving maintenance efficiency while maintaining necessary measurement precision.
Solution Approach 2:
The patent applies local quality by identifying cells with abnormal voltage characteristics (lowest voltage values) and performing detailed capacity measurements only on those specific cells rather than all cells uniformly. This targeted approach focuses measurement resources on areas most likely to have degradation issues.
2Reliability
If standard periodic inspection methods are applied to all modules, then reliability is improved through comprehensive monitoring, but device complexity increases making the maintenance system impractical for large-scale deployments
Solution Approach 1:
The patent applies partial action by performing complete capacity measurements only on selected cells with abnormal voltage characteristics, while using simpler voltage-based screening for the majority of cells. This selective approach maintains reliability for critical cells while reducing overall system complexity.
Solution Approach 2:
The system uses the existing voltage monitoring infrastructure to automatically identify candidate cells for detailed measurement, reducing the need for complex external inspection systems. The voltage data already being collected serves the dual purpose of operational monitoring and maintenance triage.
3Productivity
If voltage-based identification is used to target cells for capacity measurement, then productivity is improved by reducing the number of measurements needed, but measurement precision may deteriorate if the voltage-capacity correlation is not reliable
Solution Approach 1:
The patent uses voltage measurement as a preliminary screening step to identify candidate cells before performing detailed capacity measurements. This preliminary action filters out cells that are likely healthy based on voltage characteristics, ensuring that detailed measurements are performed only on cells that need them, thereby maintaining precision while improving productivity.
Solution Approach 2:
The system uses voltage measurement results as feedback to guide subsequent capacity measurement decisions. Cells showing abnormal voltage patterns trigger detailed capacity measurements, while normal voltage readings allow cells to be excluded from further measurement, creating a feedback loop that optimizes measurement resource allocation.
Data Source
AI summary
A maintenance method for a power storage system wherein: in a bank in which multiple modules, each comprising multiple lithium-ion battery cells connected to each other, are serially connected, a voltage sensor measures voltage values of the cells; a module containing a cell having the lowest voltage value in the hank is identified; and the capacity of the identified module or of the cell having the lowest voltage value is measured.