Mixed Battery Pack Control for Capacity Mismatch
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Solution Overview
Problem
In electrified vehicles, replacing an entire traction battery pack when only some cells experience diminished performance is inefficient and costly, as it does not utilize the remaining cells' capacity effectively.
Innovation Solution
A vehicle system with a controller that determines the state of charge (SOC) and operating range for both original and new cells, adjusts the SOC of new cells to match the maximum value of the original cells, and balances them separately to maintain the battery's performance and capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the entire traction battery is replaced when one or more cells experience diminished performance, then the vehicle maintains reliable operation, but the cost increases and resources are wasted
Solution Approach 1:
The battery pack is divided into individual replaceable cells rather than requiring replacement of the entire battery assembly. The system identifies and replaces only the specific cell(s) with diminished performance while retaining functional cells, thereby reducing waste and cost while maintaining overall system reliability
Solution Approach 2:
The system adjusts the state of charge (SOC) parameters and operating ranges for replacement cells to match the characteristics of original cells. By modifying SOC thresholds and balance parameters, the system ensures seamless integration of replacement cells with varying capacity characteristics, maintaining reliable operation without requiring full battery replacement
2Quantity of substance
If replacement cells with greater capacity are installed, then the battery capacity increases, but the SOC alignment with original cells becomes mismatched
Solution Approach 1:
The system dynamically adjusts SOC parameters including maximum SOC thresholds, minimum SOC thresholds, and balance SOC values for replacement cells based on their capacity characteristics. This parameter adaptation allows cells with greater capacity to operate in harmony with original cells, maintaining precise SOC alignment across the mixed battery pack
Solution Approach 2:
The SOC management system operates dynamically, continuously monitoring and adjusting SOC targets for individual cells based on their capacity, age, and performance characteristics. This dynamic adjustment ensures that replacement cells with varying capacities maintain proper SOC alignment with original cells throughout operation
3Productivity
If separate balancing is performed for original and replacement cells, then the capacity utilization is optimized, but the control complexity increases
Solution Approach 1:
The battery management system segments cell monitoring and balancing operations, treating replacement cells and original cells as separate groups with distinct parameters. This segmentation enables optimized capacity utilization for each cell type while managing control complexity through modular, cell-group-based control strategies
Solution Approach 2:
The system applies localized control parameters specific to each cell group (original cells vs. replacement cells), including group-specific SOC thresholds, balance targets, and capacity factors. This local quality approach optimizes capacity utilization for each cell type while keeping the overall control architecture manageable through group-based rather than fully individualized control
Data Source
AI summary
A vehicle system is provided with a battery and a controller. The battery includes a first module having a first capacity and a second module. The controller programmed to responsive to indication that the second module has been replaced by a new module with a second capacity that is greater than the first capacity for a corresponding state of charge (SOC), adjust a second SOC of the new module such that a maximum SOC value of the new module aligns with a maximum SOC value of the first module. The controller is further programmed to balance the first module and the new module separately.