Battery Pack Assembly Pressure Control for Short Circuit Detection
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Solution Overview
Problem
Existing battery pack assembly methods require extended periods for short-circuit testing to identify and remove single cells with conductive foreign matter, which affects workability and efficiency.
Innovation Solution
A manufacturing method involving restraining single cells at a maximum compression contact pressure slightly higher than the maximum restraint contact pressure, followed by a standing period and short-circuit testing to differentiate and remove cells with potential shorts in a shorter timeframe.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the compression contact pressure is increased to improve workability during assembly, then the single cells can be more easily restrained by the restraining member, but the separator may be damaged and conductive foreign matter may pass through causing future shorts
Solution Approach 1:
The patent applies preliminary compression at a controlled pressure (0.8≦Pd/Pc≦0.9) before final assembly to pre-compress the electrode body and remove excess electrolyte. This preliminary action improves workability during subsequent restraint operations while controlling the compression force to prevent separator damage, thus resolving the contradiction between ease of operation and reliability.
2Reliability
If the single cells are restrained at maximum restraint contact pressure for an extended period to ensure reliability, then potential shorts can be detected, but the testing time and production cycle are significantly increased
Solution Approach 1:
The patent performs preliminary compression before assembly that creates optimal conditions for detecting potential shorts. By compressing the electrode body in advance and removing excess electrolyte, the test conditions are prepared beforehand, allowing reliable detection of conductive foreign matter with a shorter standing period (1-7 days) rather than requiring extended testing, thus reducing time loss while maintaining reliability.
Solution Approach 2:
The patent changes the compression pressure parameter during different stages: using higher compression contact pressure (Pc) during preliminary compression to improve workability and detect defects, then transitioning to maximum restraint contact pressure (Pd) for final assembly where Pd/Pc ratio is controlled between 0.8-0.9. This parameter change allows reliable defect detection with reduced testing time.
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 method improves workability during assembly, allows for timely identification and removal of cells with conductive foreign matter, and reduces the duration of short-circuit testing, ensuring the battery pack's reliability.
Implementation Method 1
the assembled single cells are supercompressed in the stacking direction beforehand to improve workability. This is because workability is improved when the single cells are restrained by a restraining member or the like, as a result of the dimension (thickness) of the single cells being reduced beforehand by supercompressing them
Implementation Method 2
the highest maximum contact pressure, of pressure that is applied in the thickness direction of the separator and the electrode plate that form the electrode body housed in the single cells by the restraining member and is distributed in the spreading direction of the separator and the electrode plate, is the maximum restraint contact pressure
Data Source
AI summary
A manufacturing method of a battery pack includes a restraining process of restraining single cells at a maximum restraint contact pressure Pd of the battery pack in a complete state, after compressing the single cells at a maximum compression contact pressure Pc that satisfies 0.8≦Pd/Pc≦0.9, with respect to the maximum restraint contact pressure Pd; a standing process of then leaving the single cells to stand for a predetermined number of days in an electrically open state; and a short-circuit testing process of then testing for an internal short in the single cells.