Battery Pack Uniform Aging via Temperature-Based Charge Control
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Solution Overview
Problem
Existing battery packs with stacked thin battery cells face challenges in maintaining uniform deterioration rates, leading to inefficient replacement and high management costs when one cell deteriorates more than others, as they are not economical to replace the entire pack for a single faulty cell.
Innovation Solution
The battery pack design involves a configuration where the temperature of one unit cell is set to be lower than another, with the states of charge or open-circuit voltage of the first unit cell being less than that of the second unit cell, using a temperature detecting unit and charge control to maintain these conditions, ensuring equalized deterioration rates by controlling the charging process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If all unit cells are charged to the same state of charge, then charging efficiency is improved, but deterioration rates become non-uniform leading to premature replacement
Solution Approach 1:
The patent applies local quality by setting different target states of charge for different unit cells based on their individual characteristics. Specifically, unit cells with higher temperatures are charged to lower states of charge, while cooler unit cells are charged to higher states of charge. This differentiated charging strategy compensates for temperature-induced deterioration differences, ensuring uniform aging across all cells while maintaining efficient charging operations.
2Manufacturing precision
If the battery pack is disassembled to replace a single deteriorated cell, then replacement precision is improved, but labor cost and time increase substantially
Solution Approach 1:
The patent implements preliminary action by proactively controlling the charging states of unit cells to prevent deterioration differences from occurring in the first place. Through continuous temperature monitoring and differentiated charging control, the system ensures all cells age uniformly, eliminating the need for selective replacement. This preventive approach avoids the time-consuming disassembly and reassembly processes that would be required to replace individual cells.
3Reliability
If the entire battery pack is replaced when one cell deteriorates, then reliability is improved, but economic efficiency deteriorates
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the target state of charge parameter for each unit cell based on its temperature. This parameter adjustment ensures uniform deterioration rates across all cells, allowing the entire battery pack to reach its end-of-life simultaneously. Consequently, the battery pack can be replaced as a complete unit at the optimal time, maintaining high reliability while avoiding the economic waste of replacing functional cells along with deteriorated ones.
Data Source
AI summary
A battery pack having a plurality of electrically connected unit cells and configured so that the cells degrade at similar rates is provided. The battery pack may comprise a first unit cell and a second unit cell, wherein a temperature of the second unit cell is lower than the first unit cell. A condition of the first cell, such as states of charge or an open circuit voltage is set so that the condition of the first unit cell is less than a corresponding condition of the second unit cell. The unit cells may be thin battery cells stacked in a thickness direction of the thin battery cells, and the first unit cell may be located on an inner side of the second unit cell as viewed in a stacked direction. A temperature detecting unit may detect a temperature of each of the first and second unit cells and a charge control unit may be configured to control charging of the plurality of unit cells according to the temperatures of the first and second unit cells. With this configuration, even when the temperatures of the unit cells are not uniform, the rates of deterioration of the unit cells are equalized as much as possible.