Battery Pack Bus Bar Welding Sequence for Stress Reduction
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Solution Overview
Problem
The existing methods for welding bus bars to electrodes in battery packs often result in low welding strength, leading to detachment issues or stress on the bus bar, and can damage the battery cell due to excessive heat.
Innovation Solution
A manufacturing method where the bus bar is welded to one electrode, then to another in an intermediate region, and finally in an end region, allowing for deformation and reducing stress, and using laser irradiation away from the edge of the holes to achieve a fillet weld without damaging the battery cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If welding strength between the bus bar and the electrodes is increased, then the connection reliability is improved, but the stress on the bus bar during welding increases
Solution Approach 1:
The welding process is divided into three distinct stages: first welding one end region, then welding the intermediate region, and finally welding the other end region. This segmentation of the welding sequence allows the bus bar to deform progressively without accumulating excessive stress, while still achieving strong connections at all locations.
Solution Approach 2:
The intermediate region is welded first as a preliminary action before welding the end regions. This preliminary welding creates anchor points that guide the deformation process, allowing the bus bar to flex appropriately during subsequent end region welding without generating excessive stress.
2Strength
If the heat of the weld is increased to strengthen the connection, then the welding strength is improved, but the battery cell is damaged
Solution Approach 1:
The welding heat application is segmented into three sequential zones: first end region, intermediate region, and second end region. By distributing the heat input across these separate zones rather than applying high heat all at once, the total thermal energy affecting the battery cell is reduced, preventing heat damage while still achieving strong welds.
Solution Approach 2:
Different welding parameters and heat inputs are applied to different regions of the bus bar. The intermediate region receives welding heat first to create stable anchor points, while the end regions receive controlled heat input later. This localized approach to heat application ensures adequate welding strength without overheating the battery cell.
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 enhances welding strength while minimizing stress and heat transfer to the battery cell, preventing damage and ensuring a strong, durable connection.
Implementation Method 1
the bus bar may be irradiated by laser at a position away from an edge of one of the holes, and irradiation by the laser may be stopped when the bus bar melts up to the edge
Data Source
AI summary
Disclosed is a manufacturing method of a battery pack in which multiple battery cells are stacked, and electrodes of adjacent battery cells of the battery cells are connected by a bus bar, the bus bar having two holes that are smaller than the electrodes, and the bus bar being disposed such that the holes overlap the electrodes respectively. The manufacturing method includes welding the bus bar and one of the electrodes, then welding the bus bar and another one of the electrodes in an intermediate region between the two holes of the bus bar, and subsequently welding the bus bar and the other one of the electrodes in an end region adjacent to the intermediate region of the bus bar.