Battery Pack Cell Connector Segmentation for Welding
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Solution Overview
Problem
The existing methods for connecting battery cells in hand-held power tools face challenges with parasitic shunts and inefficient resistance spot welding due to high contact resistance and conductivity requirements, leading to unstable and inefficient connections.
Innovation Solution
The use of separate conductors with overlapping cross-sectional areas connected via welding at specific points, allowing for high conductivity and controlled resistance spot welding, reducing parasitic shunts and enhancing connection quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cell connector has high conductivity to reduce parasitic shunt, then the welding process becomes less controllable due to increased shunt current, but low conductivity is needed for efficient resistance spot welding
Solution Approach 1:
The cell connector is divided into multiple separate conductors (at least two) instead of using a single solid connector. This segmentation reduces the parasitic shunt effect during welding while maintaining high overall conductivity for current flow, thereby resolving the contradiction between connection stability and welding process controllability
Solution Approach 2:
The conductors are arranged with overlapping cross-sectional areas in the non-welded area between battery cells, creating local variations in conductivity. This local quality optimization allows the connector to have high conductivity where needed (between cells) while minimizing shunt paths during welding operations
2Productivity
If resistance spot welding is used to connect cell connectors, then the joining process is efficient and controllable, but parasitic shunt current flows through the join partners reducing welding efficiency
Solution Approach 1:
The cell connector is divided into multiple separate conductors (at least two) instead of using a single solid connector. This segmentation reduces the parasitic shunt effect during welding while maintaining high overall conductivity for current flow, thereby resolving the contradiction between connection stability and welding process controllability
Solution Approach 2:
The conductors are arranged with overlapping cross-sectional areas in the non-welded area between battery cells, creating local variations in conductivity. This local quality optimization allows the connector to have high conductivity where needed (between cells) while minimizing shunt paths during welding operations
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 results in a battery pack with low conductor resistance, improved process controllability, and high-quality connections, effectively addressing the issues of parasitic shunts and conductivity in battery cell connections.
Implementation Method 1
a welding current is applied in a locally limited area, the Joule heating which accompanies this causing a melting of the join partners in the area of a so-called weld nugget
Implementation Method 2
The process is designed here in such a way that the largest electrical resistance, and thus the greatest heating, occurs in the area of the joint
Data Source
AI summary
A battery pack for a hand-held power tool including a battery pack housing, the battery pack housing accommodating at least two battery cells, and at least one cell connector for connecting the battery cells in parallel and/or in series, the cell connector being connected to a pole of the first battery cell and to a pole of the second battery cell using a welding method, the cell connector including at least two at least partially overlapping, current-carrying cross-sectional areas in an unwelded area between the battery cells.