Battery Module Rebalancing via Dynamic Charge Current Control
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Solution Overview
Problem
Conventional methods for rebalancing batteries in vehicles during operation are inefficient, requiring precise low-rate constant-current overcharge and long durations, which can degrade vehicle performance and reduce battery life, especially in hybrid and fuel cell vehicles that are not configured for such control during charging.
Innovation Solution
A system and method that includes a controller to determine when to initiate and end a rebalancing mode by modifying the target state of charge of the battery, allowing for rebalancing during vehicle operation, particularly in cruise control modes, to reduce SOC divergence and improve charge current control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional low-rate constant-current overcharge is used for battery rebalancing, then module SOC divergence is reduced, but the rebalancing process requires long duration (5 hours or more) and precise current control
Solution Approach 1:
The system implements periodic action by alternating between rebalancing mode and normal operating mode. During rebalancing mode, the battery is charged at a higher rate to reduce SOC divergence, then switched to normal mode. This cycling approach enables effective rebalancing without requiring continuously long charging periods, thus reducing total loss of time while maintaining reliability.
Solution Approach 2:
The system applies dynamics by dynamically adjusting the charge rate based on real-time SOC measurements. The controller monitors module SOC levels and automatically modulates the charge current between low-rate (for precision) and high-rate (for speed) modes. This dynamic adaptation resolves the contradiction by optimizing both rebalancing effectiveness and time efficiency through adaptive control.
2Reliability
If low-rate constant-current overcharge is used for battery rebalancing, then module SOC divergence is reduced, but precise control of charge current (1 to 2 Amperes) is required which complicates the control system
Solution Approach 1:
The system applies partial action by using low-rate constant-current charging only when and where needed for rebalancing, rather than continuously. The controller selectively activates precise current control only during rebalancing mode when SOC divergence exists, and switches to normal operating mode otherwise. This reduces device complexity by limiting precise control requirements to specific conditions rather than requiring constant precision.
Solution Approach 2:
The control system is segmented into distinct operational modes: rebalancing mode and normal operating mode. Each mode has its own control characteristics - rebalancing mode uses precise low-rate control when needed, while normal mode uses standard control. This segmentation allows the system to maintain reliability during rebalancing without requiring the entire system to operate at high precision continuously, thereby reducing overall device complexity.
3Duration of action of moving object
If battery rebalancing is performed during vehicle operation, then operating range is maintained, but vehicle performance may degrade due to charge control requirements
Solution Approach 1:
The system uses periodic action by alternating between rebalancing mode and normal operating mode during vehicle operation. During rebalancing mode, the battery is charged to reduce SOC divergence while the vehicle operates. The system periodically switches to normal mode for optimal performance. This periodic switching allows the vehicle to maintain operating range through rebalancing without sustained performance degradation, as normal mode restores full performance capabilities.
Solution Approach 2:
The system ensures continuity of useful action by performing rebalancing during normal vehicle operation rather than requiring vehicle shutdown or separate charging sessions. The battery management system continuously monitors SOC divergence and initiates rebalancing charges during operation when conditions are favorable. This continuous monitoring and opportunistic rebalancing maintains operating range without requiring vehicle downtime, while minimizing impact on performance by limiting rebalancing to appropriate conditions.
Data Source
AI summary
A system and method for rebalancing a battery in a vehicle during vehicle operation, the battery including a plurality of modules, is provided. The method may include determining when an automatic rebalance mode start condition is satisfied, modifying a target state of charge for the battery at least in part in response to the start condition being satisfied such that the target state of charge is raised from a standard operating value to a rebalance value, operating the vehicle with the target state of charge at the rebalance value, determining when an automatic rebalance mode end condition or an interrupt condition is satisfied, and modifying the target state of charge in response to the automatic rebalance mode end condition or the interrupt condition being satisfied such that the target state of charge is lowered from the rebalance value to the standard operating value.