Bus Bar Projection Structure for Cell Swelling Load Relief
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Solution Overview
Problem
The increasing capacity of cells in a cell stack leads to swelling, which increases the load on the connecting parts between the bus bar and the cells, causing instability in the welding process, higher electrical resistance, and increased production costs due to the need for multiple dies for plates with different projections.
Innovation Solution
A bus bar with a projection structure featuring first and second inclined parts that align with a predetermined interval, allowing for flexibility and gap control, enabling the use of the same die for production and reducing the load on connecting parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If projections having different sizes are provided on plates to prevent gaps between stacked plates, then gap prevention is achieved, but production cost increases due to the need for multiple dies
Solution Approach 1:
The projection is designed with asymmetric geometry where the inclined surface is positioned only on one side of the projection, creating a tapered shape. This asymmetric design allows the projection to effectively bridge gaps between stacked plates while maintaining a uniform shape that can be produced with a single die, thus preventing gaps without increasing production cost
Solution Approach 2:
The projection features a curved inclined surface that gradually tapers from the base to the tip. This curvature allows the projection to conform to and bridge irregular gaps between stacked plates more effectively than a straight-sided projection, while the overall shape remains simple enough for single-die production
2Reliability
If projections are added to increase bus bar flexibility and absorb swelling loads, then connection reliability improves, but gaps between stacked plates are created hindering welding
Solution Approach 1:
The projection is positioned locally between the joint parts rather than being distributed throughout the bus bar. This localized placement provides the necessary flexibility and load absorption capability at critical stress points while maintaining flat, gap-free surfaces on the main bus bar bodies that are suitable for stable welding operations
Solution Approach 2:
The bus bar is segmented into functional zones: joint parts for welding connections, projection structures for flexibility and load absorption, and flat intermediate sections for stable stacking and welding. This segmentation allows each zone to optimize its function without compromising the others
3Power
If cell capacity is increased to provide higher output voltage, then power output improves, but cell swelling increases the load on connecting parts
Solution Approach 1:
The projection structures are pre-configured in the bus bar design to act as cushioning elements that will absorb and mitigate the swelling forces generated by high-capacity cells. These projections are positioned to engage with the cell surfaces and provide a compliant interface that protects the rigid joint parts from excessive mechanical loads
Data Source
AI summary
A bus bar has: a first joint part connected to an output terminal of the first cell; a second joint part connected to an output terminal of the second cell; and a projection that is disposed between the first joint part and the second joint part and protrudes in a stacking direction in which the cells and the bus bar are stacked. The projection has a first inclined part extending from the first joint part and has a second inclined part extending from the second joint part. The first inclined part and the second inclined part are arranged in such a manner that the first inclined part and the second inclined part are aligned with a predetermined interval W and that the predetermined interval gradually becomes wider from a first end side toward a second end side.