Battery Cell Equalizer Using SEPIC Converter Stages
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Solution Overview
Problem
Battery charging systems for series-connected cells often lead to overcharging or undercharging due to manufacturing and aging variations, necessitating a method to efficiently equalize charge levels across cells while preventing overcharging.
Innovation Solution
A battery charging system with converter stages configured to transfer charge from cells with excess energy to those with deficits, using a SEPIC converter configuration where cells with the highest charge are in a source configuration and those with the lowest are in a sink configuration, dynamically adjusting as needed to balance all cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional charging is used for series-connected battery cells, then charging simplicity is maintained, but charge balance deteriorates leading to overcharging or undercharging of individual cells
Solution Approach 1:
The charging system is segmented into multiple converter stages, with each stage associated with a specific battery cell. Each converter stage can independently control charge transfer to or from its associated cell, enabling individualized charge management while maintaining overall system functionality through modular architecture
Solution Approach 2:
The converter stages are configured to dynamically switch between source and sink modes based on real-time charge state assessment. The system continuously monitors cell voltages and reconfigures which cells charge others, allowing adaptive charge equalization that responds to changing battery conditions during the charging process
2Reliability
If charge equalization is implemented to prevent overcharging, then cell safety is improved, but charging time increases due to energy transfer between cells
Solution Approach 1:
The charge equalization process occurs continuously during the charging operation rather than as a separate post-charging step. Converter stages actively transfer energy between cells in real-time as the battery pack charges, ensuring that equalization and primary charging happen simultaneously without adding time penalty
Solution Approach 2:
The converter stages act as intermediary devices between the main charging source and individual battery cells. They enable direct energy transfer from higher-charged cells to lower-charged cells through the conversion circuitry, facilitating rapid equalization that minimizes time loss while preventing overcharging through controlled energy redistribution
3Measurement precision
If individual converter stages are assigned to each cell for precise control, then charge precision is improved, but device complexity increases
Solution Approach 1:
Each converter stage is designed as a multi-functional module that can operate in multiple modes: charging its associated cell from the main source, receiving charge from other cells, or transferring charge to other cells. This universal design allows the same hardware architecture to perform diverse charge management functions, reducing overall system complexity despite the presence of multiple converter stages
Solution Approach 2:
The system merges the functions of charge reception, charge storage, and charge distribution into integrated converter stage modules. Each converter stage combines voltage conversion capability with bidirectional energy transfer functionality, consolidating multiple control functions into unified control logic that manages the entire battery pack through coordinated stage operation
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 reduces overcharging risks while ensuring all cells reach the desired charge level, maintaining balance during charging and discharging, and improving battery pack utilization.
Implementation Method 1
discharging the cell with the greatest charge excess to charge, with a voltage converter, the cell with the greatest charge deficit. The voltage converter is a SEPIC voltage converter.
Implementation Method 2
a battery system comprising a plurality of battery cells coupled in series
Data Source
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AI summary
A method of operating a battery system includes a plurality of battery cells (24,26,28,30) coupled in series. The plurality of cells (24,26,28,30) includes at least three battery cells coupled in series. The method includes determining a cell with the greatest charge excess of the plurality of battery cells (24,26,28,30). The method further includes determining a cell with the greatest charge deficit of the plurality of battery cells (24,26,28,30). The method further includes discharging the cell with the greatest charge excess to charge, with a voltage converter, the cell with the greatest charge deficit.