Traction Battery Subpack Switching for Cycle-Life-Preserving Discharge
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Solution Overview
Problem
Existing electrified vehicles face challenges in efficiently managing the charging and discharging of traction battery packs, particularly those with lithium metal anodes, which can degrade quickly due to high discharge rates, and there is a need for methods to prolong their cycle life.
Innovation Solution
A method involving a traction battery pack divided into subpacks, where a switching system electrically isolates and connects different subpacks for separate charging and discharging, allowing dynamic control based on vehicle state and load demands, with lithium metal anodes in both subpacks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high discharge rates are used to power electric machines and loads, then power delivery is improved, but battery cycle life deteriorates due to quick degradation of lithium metal anodes
Solution Approach 1:
The battery pack is divided into multiple independent subpacks (first subpack, second subpack) that can be charged and discharged separately. This segmentation allows different subpacks to operate at different rates - one subpack can be discharged at high rate while another is charged or rested, thereby maintaining power delivery capability while extending overall battery cycle life by avoiding continuous high-rate discharge of all cells.
2Reliability
If the battery pack is divided into subpacks with separate charging and discharging, then battery cycle life is extended, but device complexity increases due to switching system requirements
Solution Approach 1:
The switching system is designed to perform multiple functions: it can connect subpacks in series for high-voltage operation, connect them in parallel for increased capacity, isolate individual subpacks for separate charging/discharging, and reconfigure connections based on operational requirements. This multi-functionality justifies the added complexity by providing versatile battery management capabilities that extend cycle life while maintaining operational flexibility.
Data Source
AI summary
A traction battery pack operating method includes charging a traction battery pack of an electrified vehicle. The charging includes charging a first subpack of battery cells together with a second subpack of battery cells. The method can discharge the first subpack separately from the second subpack. The method can include during the discharging, maintaining at least one switch in an open state to electrically isolate the first subpack from the second subpack.