Battery String Bypass Control for Fault-Tolerant Voltage Equalization
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Solution Overview
Problem
Existing battery systems in electric vehicles face challenges in achieving high capacity and reliability with minimal installation space and cost, particularly due to redundancy requirements for fault tolerance, leading to inefficiencies and range reduction when faults occur.
Innovation Solution
A method that allows individual battery cells or modules to be connected and disconnected independently, using software-based control to manage voltage equalization and bypass faulty components, maintaining system operation with minimal hardware additions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant battery modules are added to achieve fault tolerance, then reliability is improved, but installation space and cost increase
Solution Approach 1:
The battery system is divided into multiple independent strings, each with its own battery modules and cells. This segmentation allows individual strings to be isolated and bypassed when faults occur, while other strings continue to provide power. The system achieves fault tolerance through architectural segmentation rather than physical redundancy of entire battery modules.
Solution Approach 2:
The invention extracts and removes faulty battery cells from the system by bypassing them through coupling devices. When a fault is detected in a specific battery cell, that cell is electrically isolated and taken out of the active circuit, allowing the rest of the system to continue operating without the defective component.
2Power
If battery modules are connected in parallel to increase capacity, then power availability is improved, but installation space increases
Solution Approach 1:
The battery system uses multiple strings connected in parallel, with each string containing battery modules. This segmented architecture provides power redundancy and capacity distribution without requiring complete parallel duplication of entire battery modules, optimizing space utilization while maintaining power availability.
Solution Approach 2:
The patent transitions from a single-dimension battery configuration to a multi-dimensional architecture with multiple strings arranged in parallel. This dimensional expansion allows the system to achieve higher power capacity and fault tolerance by distributing battery cells across multiple independent pathways rather than simply increasing the size of a single battery module.
3Reliability
If faulty battery cells are bypassed to maintain system operation, then reliability is improved, but capacity is reduced due to loss of intact cells
Solution Approach 1:
The battery system is segmented into multiple independent strings, allowing isolation of faults to specific cells or modules within individual strings. This segmentation prevents fault propagation to other strings, maintaining overall system capacity by keeping healthy strings fully operational while only affecting the minimal necessary components in the faulty string.
Solution Approach 2:
The invention extracts only the specific faulty battery cells from the system through bypass circuits, rather than removing entire battery modules or strings. This selective extraction minimizes the loss of functional battery capacity by isolating and removing only the defective components while preserving all intact cells in other strings and even in the same string if possible.
4Reliability
If voltage equalization is performed by discharging intact strings, then reliability is improved, but energy is lost
Solution Approach 1:
The battery management system continuously monitors voltage levels across all strings and battery cells, providing feedback control for voltage equalization. When voltage imbalances are detected, the system selectively discharges or charges specific strings or modules to restore voltage equilibrium, minimizing unnecessary energy loss by acting only when and where needed rather than continuous equalization.
Data Source
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AI summary
The invention relates to a method for operating a battery system (10). The battery system (10) comprises several parallel-connected strings (12), each of which has at least one battery module (18, 20, 22, 23). In the at least one battery module (18, 20, 22, 23), several battery cells (24, 26, 28, 30) are connected in series (34) and/or in parallel. The strings (12) can be connected and disconnected from one another. Individual battery cells (24, 26, 28, 30) and/or individual battery cell packs (38), each comprising several parallel-connected battery cells (24, 26, 28, 30), can be connected and disconnected from one another and can be bridged.The procedure comprises at least the following steps: - Detecting a fault in a battery cell (24, 26, 28, 30); - Disconnecting and bypassing the faulty battery cell (24, 26, 28, 30) and/or the faulty battery cell pack (38) containing the faulty battery cell (24, 26, 28, 30); - Disconnecting the faulty string (12) containing the faulty battery cell (24, 26, 28, 30) and/or the faulty battery cell pack (38); - Comparing the string voltage of the faulty string (12) with the string voltage of the respective intact strings (12) in which no faults were detected; - Discharging the intact strings (12) if voltage differences between the strings (12) exceed a voltage threshold.