Battery Pack Lap Weld Joint with Arc Spot Welding
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Solution Overview
Problem
Battery packs in hybrid and electric vehicles and mobile devices face increased conduction loss and heat generation due to high connection resistance between battery cells, leading to degradation and reduced lifespan, as existing methods fail to achieve optimal welding quality and low electric resistance.
Innovation Solution
A battery pack design using a copper connecting metallic plate for lap weld joints between positive and negative electrodes, with specific thickness and nickel plating conditions to form a strong, low-resistance weld, employing arc spot welding to ensure good welding quality and high tensile strength while minimizing electric resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional welding methods are used to connect battery cells, then the battery pack can be assembled, but the connection resistance is large leading to increased conduction loss and heat generation
Solution Approach 1:
The patent changes the welding parameters by specifying a weld penetration depth that exceeds the thickness of the copper connecting plate, creating a through-weld that directly connects the positive and negative electrodes. This parameter change reduces contact resistance and improves electrical conductivity, thereby reducing conduction loss in the battery pack.
2Strength
If the weld penetration depth is too shallow, then the welding process is faster and easier, but the welding quality is poor and tensile strength is insufficient
Solution Approach 1:
The patent specifies that the weld penetration depth should be greater than the thickness of the copper connecting plate to ensure adequate weld strength. This parameter specification guarantees that the weld joint achieves sufficient tensile strength while maintaining manufacturing feasibility through controlled arc spot welding parameters.
3Reliability
If copper is used as the connecting metallic plate material, then the electric resistance is low and cost is reduced, but the welding difficulty increases compared to nickel
Solution Approach 1:
The patent replaces conventional resistance welding (which relies on Joule heating and mechanical pressure) with arc spot welding. This substitution is necessary because copper's high electrical conductivity makes it resistant to Joule heating, but arc welding provides the intense localized heat needed to melt and fuse copper effectively, achieving reliable welds despite copper's welding difficulties.
4Manufacturing precision
If the weld penetration depth exceeds the copper plate thickness, then the welding quality improves, but there is a risk of welding through to the back surface affecting corrosion resistance
Solution Approach 1:
The patent specifies that the weld penetration depth should be greater than the copper plate thickness to ensure adequate weld strength, but the nickel plating on the back surface provides corrosion protection. The through-weld design accepts that the copper will be exposed internally, while the external corrosion-resistant nickel layer remains intact, balancing welding quality with corrosion resistance.
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 significantly reduces electric resistance between electrodes, minimizing power loss during charging and discharging, extending the battery pack's lifespan and reducing manufacturing costs by using copper, which is cheaper and easier to weld than nickel.
Implementation Method 1
applying arc spot welding to each of a position on the connecting metallic plate above the positive electrode and another position on the connecting metallic plate above the negative electrode
Data Source
AI summary
A battery pack with a reduced resistance connection arrangement in which battery cells are arranged in rows in an insulating case and an electrode of each battery cell is coupled to an electrode of another battery cell through a connecting metallic plate. The connecting metallic plate is made of copper and is disposed on a positive electrode of one battery cell and a negative electrode of another battery cell to form a lap joint. Welds are formed in predetermined positions on the connecting metallic plate above the positive and negative electrodes by arc spot welding. The electrodes are formed of nickel-coated steel. The depth h of weld penetration in the weld is greater than the thickness T1 of the connecting metallic plate and smaller than the thickness T1 plus the thickness T2 of one of the electrodes, that is, T1<h≦(T1+T2×4/5).