Battery Cell Rebalancing via Temperature-Limited Discharge
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Solution Overview
Problem
Hybrid/electric vehicle batteries face charge imbalances as cells age, leading to increased workload and heat generation during rebalancing, which can result in overheating and reduced performance.
Innovation Solution
A controller is programmed to dynamically adjust the number of cells for simultaneous discharge based on temperature, adjusting the upper charge threshold to manage charge rebalancing, ensuring that only a maximum number of cells are discharged at a time to prevent overheating, thereby maintaining optimal charge distribution within the battery array.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all cells in the battery array are discharged simultaneously to rebalance charge, then charge rebalancing is achieved, but heat generation increases causing overheating
Solution Approach 1:
The battery array is divided into multiple cell groups, with only a subset of cells discharged simultaneously rather than all cells. This segmentation of the discharge process limits the total heat generation at any given time while still achieving charge rebalancing across the full array over multiple cycles.
Solution Approach 2:
The charge rebalancing is performed in periodic cycles rather than continuously. The controller selectively discharges cells in alternating phases, allowing heat to dissipate between discharge events and preventing cumulative overheating while maintaining effective rebalancing over time.
2Temperature
If the number of cells for simultaneous discharge is limited to prevent overheating, then temperature control is improved, but charge rebalancing efficiency decreases
Solution Approach 1:
The controller dynamically adjusts the number of cells discharged simultaneously based on real-time temperature conditions and charge state assessments. When temperature is low, more cells can be discharged; when temperature rises, the number of active discharge cells is reduced, optimizing both temperature control and rebalancing efficiency adaptively.
Solution Approach 2:
The system changes operational parameters by varying the upper charge threshold values and the number of cells discharged in each phase. By adjusting these parameters based on temperature and charge state, the system maintains effective rebalancing while preventing overheating through controlled parameter modification rather than fixed limitations.
3Productivity
If multiple cells are discharged simultaneously to improve rebalancing speed, then productivity increases, but heat generation increases causing harmful thermal effects
Solution Approach 1:
The battery array is divided into multiple cell groups, with only a subset of cells discharged simultaneously rather than all cells. This segmentation of the discharge process limits the total heat generation at any given time while still achieving charge rebalancing across the full array over multiple cycles.
Solution Approach 2:
The controller acts as an intermediary that manages the discharge process by selectively activating only the necessary number of cells based on temperature conditions. This intermediary control prevents excessive heat generation by mediating between the need for fast rebalancing and the thermal constraints of the system.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively rebalances the battery cells while preventing overheating, extending the battery's lifespan and maintaining efficient vehicle performance by optimizing the discharge process based on temperature and charge thresholds.
Implementation Method 1
The battery has an array of cells that are configured to deliver electrical power to the electric machine
Implementation Method 2
charge imbalance as cells age, leading to increased workload and heat generation during rebalancing
Data Source
AI summary
A vehicle includes an electric machine, a battery, and a controller. The electric machine is configured to deliver power to wheels to drive the vehicle. The battery has an array of cells that are configured to deliver electrical power to the electric machine. The controller is programmed to, in response to a charge imbalance within the array of cells, simultaneously discharge a number of cells within the array based on a temperature of the controller.