Wiring Module Bus Bar Cross Section Optimization
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Solution Overview
Problem
Existing wiring modules are inadequate for serially connecting multiple power storage devices in parallel, leading to increased heat generation and weight due to uneven current density across bus bars, which limits the capacity and efficiency of power storage modules in electric vehicles.
Innovation Solution
A wiring module design with bus bars featuring varying cross-sectional areas to optimize current density, where the n-th linking portion has the largest area, reducing heat generation and weight, while maintaining efficient series connections of power storage devices by using 2n electrode connection portions and 2n-1 linking portions, with specific configurations to manage heat and manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a bus bar with uniform cross-sectional area is used to connect multiple power storage devices in series, then the structure is simple and easy to manufacture, but the current density is uneven leading to increased heat generation
Solution Approach 1:
The bus bar is designed with varying cross-sectional areas at different locations. Specifically, the cross-sectional area at the n-th linking portion is made larger than at other linking portions, creating local quality variations that match the current density distribution. This allows the bus bar to have optimal electrical properties at each section while maintaining manufacturing feasibility.
Solution Approach 2:
The cross-sectional area parameter of the bus bar is changed along its length rather than remaining uniform. By adjusting the cross-sectional area parameter to be largest at the n-th linking portion, the design optimizes current distribution and reduces heat generation at critical locations while keeping the overall structure manufacturable.
2Temperature
If the cross-sectional area of the n-th linking portion is increased to reduce heat generation, then heat generation is reduced, but the weight of the bus bar increases
Solution Approach 1:
Instead of uniformly increasing the cross-sectional area throughout the bus bar, the design applies local quality enhancement only at the n-th linking portion where current density is highest. This targeted approach reduces heat generation at the critical location while minimizing the overall weight increase compared to a uniform thickening design.
Solution Approach 2:
The design applies partial action by increasing the cross-sectional area only at specific linking portions (particularly the n-th portion) rather than throughout the entire bus bar. This partial enhancement is sufficient to address the heat generation problem at critical locations without the excessive weight penalty of a completely uniform thick bus bar.
3Productivity
If multiple bus bars are used to connect power storage devices in parallel sets, then the capacity and efficiency of the power storage module are improved, but the device complexity increases
Solution Approach 1:
The bus bar design with varying cross-sectional areas serves multiple functions: it connects power storage devices in series, handles uneven current density distribution, and reduces heat generation at critical points. This multi-functional design allows a single bus bar configuration to address multiple requirements, reducing the need for additional specialized components and simplifying the overall wiring module complexity.
Solution Approach 2:
The design merges the series connection function with the current density management function into a single bus bar structure. By combining these functions rather than using separate components, the design achieves improved capacity and efficiency while avoiding the complexity increase that would result from multiple separate wiring solutions.
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
The solution effectively reduces heat generation and weight while maintaining high current density, enhancing the capacity and efficiency of power storage modules by optimizing bus bar design and electrode connection configurations, thereby improving the overall performance of power storage modules in electric vehicles.
Implementation Method 1
the current density of the n-th linking portion that links the n-th electrode connection portion and the (n+1)-th electrode connection portion is larger than that of the other linking portions. For this reason, there is a concern that the amount of heat generated may increase during energization.
Implementation Method 2
the cross-sectional area of the n-th linking portion is set to be larger than the cross-sectional areas of the other linking portions. Accordingly, the electrical resistance of the n-th linking portion can be made smaller than those of the other linking portions.
Data Source
AI summary
A plurality of sets of power storage devices each formed by connecting a plurality of power storage devices in parallel are connected in series. A wiring module that is arranged on a plurality of power storage devices each having electrode terminals, the wiring module including: a plurality of connection bus bars each connected to a corresponding electrode terminal and each having 2n (n is a natural number greater than or equal to 2) electrode connection portions; and an insulating protector that houses the plurality of connection bus bars. In each of the plurality of connection bus bars, the cross-sectional areas of the second electrode connection portion from the right of the connection bus bar and the third electrode connection portion from the right of the connection bus bar are set to be larger than the cross-sectional areas of the other electrode connection portions.