Individual Cell Testing for Multi-Cell Battery Packs
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Solution Overview
Problem
Accurate battery pack testing is challenging due to the potential for one or more unhealthy cells to inaccurately indicate the health of the entire battery pack, leading to incorrect life performance predictions, as existing methods test the battery as a single entity rather than at the individual cell level.
Innovation Solution
A method is provided to assess the operating characteristics of individual cells in a multi-cell battery by selecting cells offline for testing, using spare cells or external power sources to maintain battery functionality, and evaluating their efficiency through charging and discharging processes, including data acquisition on charge acceptance, discharge characteristics, and recharge parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the battery pack is tested as a single entity, then the testing process is simple and quick, but the measurement precision of individual cell health is poor
Solution Approach 1:
The battery pack is segmented into individual cells for separate testing. The system isolates each cell from the battery pack to perform independent charge/discharge cycles, enabling precise measurement of individual cell health characteristics without interference from other cells.
Solution Approach 2:
Individual cells are extracted from the battery pack configuration for dedicated testing. The cell under test is electrically disconnected from the battery pack and connected to external charging/discharging equipment, allowing independent assessment of cell health while the battery pack remains operational with remaining cells.
2Measurement precision
If individual cells are tested offline, then the measurement precision of cell characteristics is improved, but the productivity of battery operation is reduced
Solution Approach 1:
The system performs preliminary identification of cells requiring testing, then schedules offline testing during periods when the battery pack can operate with reduced capacity or use alternative power sources. This allows precise cell characterization to be completed in advance of when the data is needed for battery management decisions.
Solution Approach 2:
External charging and discharging equipment serves as an intermediary between the cell under test and the power source/load. This intermediary system enables precise control of charge/discharge cycles for accurate cell characterization while the battery pack itself remains in service, minimizing impact on operational productivity.
3Measurement precision
If all cells are tested simultaneously, then the assessment completeness of battery health is improved, but the loss of time for testing increases
Solution Approach 1:
The system implements periodic testing of individual cells rather than simultaneous testing of all cells. Cells are selected for testing based on their operational history, voltage deviations, or temperature anomalies, and are tested at scheduled intervals. This periodic approach ensures comprehensive battery health assessment over time while minimizing the time any individual cell is taken offline.
Solution Approach 2:
The system tests only the subset of cells that require assessment based on diagnostic criteria, rather than testing all cells simultaneously. This partial action approach focuses resources on cells showing signs of potential issues, achieving sufficient battery health assessment completeness without the time penalty of testing every cell.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for precise evaluation of individual cell health and longevity, enabling accurate prediction of battery pack performance and maintenance, reducing the risk of misidentifying healthy cells as unhealthy and improving overall battery management.
Implementation Method 1
the cell is charged to a known state
Implementation Method 2
the cell is discharged to a known state so that the capacity of the cell can be ascertained
Data Source
AI summary
Embodiments of the invention relate to a multi-cell battery, and individual evaluation of the battery cells. Each cell is individually removed or disconnected from the battery. An adjustable cell charger and an adjustable cell load are mapped to the disconnected cell. As the charger charges the cell, an associated sensor validates acceptance of the charge. As the cell load discharges the cell, the sensor measures discharge characteristics. Operating efficiency of the selected cell is evaluated based on the measured charge acceptance and discharge characteristics.