Cylindrical Battery Module Bus Bar Welding for Stable Diagonal Bonding
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Solution Overview
Problem
Conventional resistance welding methods for cylindrical secondary battery modules suffer from poor welding quality due to high reactive current, leading to damage from high-temperature vibrations and impacts, particularly in 2-point welding, and uneven growth of welding nuggets in the 4-point method.
Innovation Solution
A cylindrical secondary battery module design with welding portions spaced farther apart, using a polarity switching type welding process where four welding portions are connected diagonally, with primary and secondary welding voltages of different magnitudes and supply times, applied in opposite directions to reduce reactive current and enhance bonding stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If welding portions are located close to each other to connect bus bar to electrode terminals, then connectivity is achieved, but reactive current increases causing welding quality deterioration and easy breakage
Solution Approach 1:
The patent applies asymmetry by positioning welding portions at diagonally opposite corners of the bus bar rather than symmetrically close positions. This asymmetric diagonal arrangement increases the distance between welding portions, reducing reactive current while maintaining electrical connectivity. The welding portions are specifically located at four corners with diagonal connections, creating an asymmetric current path that minimizes harmful reactive current effects.
Solution Approach 2:
The patent transitions from a one-dimensional linear arrangement of welding portions to a two-dimensional diagonal arrangement across the bus bar surface. By utilizing the diagonal dimension and spacing welding portions at opposite corners, the current path is optimized to reduce reactive current while maintaining effective electrical connection between bus bar and electrode terminals.
2Ease of manufacture
If 2-point welding method is used to simplify the welding process, then manufacturing complexity is reduced, but welding portion breaks easily under high temperature and vibration
Solution Approach 1:
The patent combines multiple welding portions (four diagonal corners) into a unified welding structure that functions as an integrated connection system. By merging the welding portions at all four corners with diagonal connections, the overall welding assembly achieves enhanced strength and durability under high temperature and vibration, while maintaining relative manufacturing simplicity through consistent welding methodology across all portions.
Solution Approach 2:
The patent enhances welding portion strength by utilizing the diagonal dimension and spatial arrangement of four corners rather than a simple linear two-point connection. This dimensional expansion creates a more robust welding structure that better resists high temperature and vibration stresses while maintaining ease of manufacture through standardized welding procedures.
3Reliability
If 4-point welding method is used to improve connectivity, then electrical connection is enhanced, but reactive current causes uneven welding nugget growth and flying on base material surface
Solution Approach 1:
The patent applies asymmetry by positioning welding portions at diagonally opposite corners rather than symmetrically close positions. This asymmetric diagonal arrangement balances the current distribution across the bus bar, preventing uneven welding nugget growth and reducing flying on the base material surface while maintaining enhanced electrical connection through the four-point diagonal configuration.
Solution Approach 2:
The patent improves welding nugget uniformity by utilizing the diagonal dimension and spacing welding portions at opposite corners of the bus bar. This two-dimensional diagonal arrangement creates more uniform current distribution and heat generation across welding portions, eliminating uneven nugget growth and reducing surface flying while maintaining enhanced electrical connectivity.
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 reduces reactive current, improves welding quality, and prevents bus bar damage from vibrations and impacts, resulting in stronger and more reliable connections between the bus bar and electrode terminals.
Implementation Method 1
bonded by partially melting the bus bar with heat generated by the resistance by flowing current while pressing the bus bar and the electrode terminal with a welding rod
Implementation Method 2
resistance welding is commonly used to minimize deformation of an electrode terminal of the secondary battery cell
Data Source
AI summary
A cylindrical secondary battery module includes a plurality of cylindrical secondary battery cells having an electrode assembly and an electrolyte accommodated therein; a cell frame in which the plurality of cylindrical secondary battery cells are disposed; and a bus bar coupled to each of a plurality of cylindrical secondary battery cells and having a plurality of welding portions thereon. Among the plurality of welding portions, the welding portions spaced apart at larger intervals are welded to each other.