Key technical points for assembling 18650 lithium battery pack using spot welding machine.

Key technical points for assembling 18650 lithium battery pack using spot welding machine.

Spot welding machines are widely used in the assembly process of 18650 lithium battery packs by using pulse AC welding. During assembly, it is responsible for tightly connecting various welding components, such as nickel sheets and battery cells, nickel sheets and nickel sheets, nickel sheets and protective plates, and composite nickel sheets and battery cells, through spot welding technology. The quality of spot welding has a direct impact on the appearance and circuit performance of batteries, and may even threaten the safety of batteries, such as risks of short circuits.

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Function and Operation 1: Preparation before Spot Welding - Selection and Repair of Welding Electrode Heads
The size of the welding electrode head and the distance between the two electrode heads have a significant impact on the welding quality. The thickness and material of the welded workpiece also have a significant impact on the selection of welding parameters. Therefore, when selecting welding electrode heads, it is necessary to consider the thickness, material, and required welding parameters of the battery and battery cells. To ensure welding quality, the spacing between electrode tips should usually be adjusted to about 3mm. In addition, selecting the appropriate shape of the welding head and carefully grinding the contact area with a fine file or sandpaper to maintain the flatness and smoothness of the welding head is also an indispensable preparation work before spot welding.

Firstly, turn on the power switch and carefully check if the device is operating normally.
Next, it is necessary to confirm whether the spot welding surfaces of the two welding needles are on the same horizontal line. At the same time, it is necessary to check whether the spot welding surface of the spot welding needle is oxidized, burnt black, or mushroom shaped. If these problems exist, sandpaper or sand belt should be used to polish the spot welding needle until the surface is smooth and free of oxides.

After confirming that the spot welding machine is operating normally and that there is no oxidation or mushroom shaped phenomenon on the spot welding needle, the current, height of the spot welding needle to the welding surface, and air pressure parameters can be adjusted. The goal of debugging is to ensure that the products produced by spot welding meet the following requirements: no explosion or blackening of the welding points; The nickel sheet of the positive electrode of the square aluminum shell battery can withstand a tensile force of at least 3Kg, and the nickel sheet of the negative electrode can withstand a tensile force of at least 1.5Kg; The nickel sheet on the protective plate can withstand a tensile force of at least 1.5Kg; For 18650 cylindrical batteries, both the positive and negative nickel plates can withstand a tensile force of at least 3Kg. If these requirements are not met, the parameters need to be re debugged until the requirements are met.

After the battery spot welding machine is debugged, the actual spot welding operation can be carried out. When spot welding the positive electrode of an aluminum shell battery, align the protective plate with the nickel sheet connected to the battery cell with the composite aluminum nickel strip on the positive electrode of the battery cell, and then start the spot welding machine to spot weld at two different positions (note that the same spot welding point cannot be repeatedly spot welded twice). At the same time, it is necessary to ensure that the number of effective solder joints formed by the positive electrode reaches four. For spot welding of the negative electrode, simply align the nickel strip with the negative electrode of the battery cell and start the spot welding machine for one spot welding. The effective number of spot welding points for the negative electrode is two.

4.2 When spot welding 18650 cylindrical batteries, nickel sheets should be placed at the positive and negative terminals of the battery, and spot welding should be performed twice at different positions of the positive and negative electrodes (note that the same spot welding should not be repeated twice). At the same time, it is necessary to ensure that the positive and negative electrodes each form four effective welding points.

4.3 When spot welding the protective plate, the nickel plate should be placed on the nickel plated steel plate on top of it, and then the spot welding machine should be started for operation. Meanwhile, it is necessary to ensure the formation of at least two effective solder joints.

When performing spot welding work, the height and stability of various parameters between the spot welding machine and the workpiece should be maintained. If it is found that the spot welding surfaces of the two welding needles are not on the same horizontal line, the welding needles should be adjusted in a timely manner to ensure that they are in the same horizontal position. In addition, every hour, sandpaper and sand belt should be used to perform maintenance polishing on the spot welding needle (sandpaper should be parallel to the surfaces of the two welding needles to maintain the flatness of the spot welding surface; sand belt should wrap around the spot welding needle for polishing), in order to remove the oxides generated during the previous welding process. However, during the maintenance period, if any phenomena such as explosion, blackening of welding points, virtual welding, or oxidation of spot welding needles are found during spot welding operations, the spot welding needles should be immediately polished and maintained.