Battery Cell Balancing Across Pack Strings Without Long Rest Times
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Solution Overview
Problem
Battery cells in vehicles develop imbalances in electrical characteristics such as charge capacities, states of charge, discharge rates, impedances, and voltages due to cell replacements or additions, affecting performance and service life, and long rest times are impractical for autonomous vehicles.
Innovation Solution
A method and system for charge balancing across multiple battery cells involving battery pack and string controllers that calculate balance points and instruct cell balancing systems to equalize energy levels, using sensors and controllers to monitor and adjust cell states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If long rest times are used for charge balancing, then balancing accuracy is improved, but vehicle operational continuity deteriorates
Solution Approach 1:
The system performs preliminary charge balancing calculations during vehicle operation using real-time electrical parameters, preparing balance points in advance rather than waiting for rest periods. This allows the vehicle to maintain operational continuity while achieving accurate balancing through pre-calculated balance points that account for cell characteristics and operational requirements.
Solution Approach 2:
The battery management system performs self-balancing calculations and adjustments during normal operation without requiring external intervention or vehicle shutdown. The controller continuously monitors electrical parameters and automatically executes balancing routines, enabling the system to maintain both operational continuity and balancing accuracy through autonomous real-time management.
2Productivity
If real-time balancing calculations are performed during operation, then vehicle operational continuity is maintained, but calculation accuracy may deteriorate due to dynamic conditions
Solution Approach 1:
The system implements continuous feedback loops where the controller monitors electrical parameters (voltage, current, temperature) in real-time and adjusts balance point calculations dynamically. This feedback mechanism ensures that balancing calculations remain accurate despite changing operational conditions, maintaining both vehicle continuity and calculation precision through adaptive real-time adjustments.
Solution Approach 2:
The balancing system transitions from static pre-rest calculations to dynamic real-time calculations that adapt to changing vehicle operational conditions. The controller continuously updates balance points based on current electrical parameters, cell states, and operational requirements, enabling accurate balancing during motion without requiring vehicle shutdown.
3Quantity of substance
If multiple battery packs with different cell characteristics are connected in series, then system voltage and energy capacity are increased, but charge balancing complexity increases
Solution Approach 1:
The system divides the multi-pack battery system into individual battery pack segments, each with its own controller that calculates balance points independently based on its specific cell characteristics. This segmentation approach simplifies the overall balancing complexity by treating each pack as a manageable unit while the central coordinator integrates them to achieve system-wide balancing, maintaining both high energy capacity and manageable complexity.
Data Source
AI summary
Embodiments include methods and systems for charge balancing in a battery system having a string of battery packs that each include a plurality of battery cells. Aspects include obtaining electrical parameters for each of the plurality of battery cells and calculating a battery pack balance point for each of the battery packs in the string. Aspects also include instructing a cell balancing system to execute a cell charge balancing routine to balance each of the plurality of battery cells of each battery pack to the battery pack balance point corresponding to the battery pack, calculating a string balance point for the string of battery packs based on the battery pack balance points, and instructing the cell balancing system of each battery pack to balance the plurality of battery cells of the battery pack to the string balance point.