Parallel Battery Bus Control for Imbalanced Cell Foldback
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Solution Overview
Problem
Secondary battery systems face capacity degradation due to imbalanced aging of batteries, temperature variations, and manufacturing inconsistencies, leading to reduced energy capacity and performance.
Innovation Solution
A battery system with a battery management system (BMS) that monitors operating limits, initiates a foldback operation, and disconnects imbalanced batteries from the bus to maximize system capacity by redistributing current to remaining batteries within safe limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If all secondary batteries operate in parallel without individual monitoring, then the system structure is simple, but imbalanced aging and temperature variations cause capacity degradation and reduced energy capacity
Solution Approach 1:
The patent segments the battery system into individually monitored battery units, with each battery having its voltage, current, and temperature monitored separately. The BMS divides the system into manageable segments (battery groups) that can be independently controlled, allowing the system to handle imbalanced conditions while maintaining overall functionality.
Solution Approach 2:
The patent implements continuous feedback monitoring through the BMS that tracks voltage, current, and temperature of each battery in real-time. When imbalanced conditions are detected (such as a battery reaching voltage limits or excessive temperature), the system provides feedback signals to adjust current distribution, preventing capacity degradation while maintaining simple operational control.
2Power
If the system operates at maximum current capacity, then power output is maximized, but imbalanced batteries reach operating limits causing foldback operations that reduce overall system capacity
Solution Approach 1:
The patent implements dynamic current distribution where the BMS continuously adjusts current allocation to each battery based on real-time conditions. When some batteries approach their operating limits, the system dynamically redistributes current to maintain maximum overall power output without triggering foldback operations, thereby extending discharge time while preserving power capability.
Solution Approach 2:
The patent changes operational parameters by monitoring voltage, current, and temperature thresholds for each battery and adjusting current distribution accordingly. When imbalanced conditions are detected, the system modifies current parameters dynamically to prevent any single battery from limiting the system's power output or discharge duration.
3Device complexity
If temperature variations among batteries are not addressed, then cooling system is simpler, but high-temperature batteries degrade faster causing imbalanced aging and reduced system capacity
Solution Approach 1:
The patent implements preliminary monitoring and intervention for temperature management. The BMS continuously monitors battery temperatures and takes preventive action by adjusting current distribution before excessive heat buildup occurs. This preliminary action prevents thermal runaway and imbalanced aging without requiring complex active cooling systems.
Data Source
AI summary
A battery system includes a plurality of batteries including a plurality of chargeable battery cells, and a bus to which the plurality of batteries are selectively connected in parallel. A battery management system monitors operating limits of the chargeable battery cells of the plurality of batteries, generates a signal indicating that an operating limit of a chargeable battery cell of a battery among the plurality of batteries is being reached for a foldback operation of the battery, and initiates the foldback operation. A controller is configured to generate a signal to disconnect the battery associated with the signal of the battery management system from the bus.