In the battery spot welding process, spot welding failure sometimes occurs. If it cannot be solved, it will cause serious quality problems in the finished battery packs. So, what is the main cause of spot welding failure?
Figure 1. Automatic Battery Spot Welder for Lithium Ion Batteries
There are six major factors that affect the quality of battery spot welding, including welding current, welding time, spot welding electrode & electrode holder, spot welding electrode pressure, cell-to-cell busbar and spot welding resistance.
Among them, welding current, welding time and spot welding electrode pressure can be controlled by adjusting the battery spot welding machine, but these parameters must be optimized and adjusted according to actual conditions.
In addition, the biggest variables are caused by spot welding electrodes and cell-to-cell busbars. The material, thickness, structure, shape, flatness, cleanliness, etc. of the cell-to-cell busbar will directly affect the quality of battery spot welding. Generally speaking, for pure nickel battery tabs with a thickness greater than or equal to 0.2mm, slotting and bumping are usually recommended.
Changes in the contact surface between the battery spot welding machine electrodes and the cell-to-cell busbar, as well as changes in the pressure between the two, will cause changes in welding resistance. Changes in Joule heat in the battery spot welding process will obviously affect the spot welding quality. Therefore, it is important to control the shape, grinding frequency and replacement time of the battery spot welding machine electrodes to make sure these are under control.
Table 1 shows the main cause of spot welding failures in the battery spot welding process.
Table 1 Main Cause of Spot Welding Failure
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NO. |
Spot Welding Failure |
Main Causes |
|
1 |
Welding spot burn-through |
Possible cause 1: The welding current is too large. |
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Possible cause 2: Poor contact of spot welding electrodes. |
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Possible cause 3: The pressure of the spot welding electrode is too small. |
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Possible cause 4: Contaminants on the spot welding electrodes or battery tabs. |
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Possible cause 5: The battery tabs are defective. |
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Possible cause 6: The thickness and material of the battery tabs vary greatly. |
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2 |
Too much spatter during spot welding |
Possible cause 1: The welding current is too large. |
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Possible cause 2: The spot welding electrode is welded to the edge of the battery tabs. |
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Possible cause 3: Contaminants on the spot welding electrodes or battery tabs. |
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Possible cause 4: The pressure of the spot welding electrode is too small. |
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Possible cause 5: The thickness and material of the battery tabs vary greatly. |
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3 |
The welding spot indentation is too large |
Possible cause 1: The spot welding electrode pressure is too high. |
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Possible cause 2: The needle tip of the spot welding electrode is too thin or deformed. |
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Possible cause 3: The surface of the battery tabs is uneven. |
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4 |
The welding spot is too small or the fastness is poor |
Possible cause 1: The welding current is too small. |
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Possible cause 2: The welding current was diverted during spot welding. |
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Possible cause 3: Spot welding time is too short. |
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Possible cause 4: Poor contact of spot welding circuit. |
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Possible cause 5: The spot welding electrodes pressure is too high. |
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Possible cause 6: Contaminants on the spot welding electrodes or battery tabs. |
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Possible cause 7: The thickness and material of the battery tabs vary greatly. |
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5 |
There are burn marks or scratches on the welding spots |
Possible cause 1: The spot welding electrode pressure is too high. |
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Possible cause 2: The battery tabs are defective. |
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Possible cause 3: The pressure of the spot welding electrode is too small. |
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Possible cause 4: Contaminants on the spot welding electrodes. |
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Possible cause 5: The spot welding electrode needles are ground roughly. |
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Possible cause 6: The spot welding electrodes are not cooled well, resulting in needle sticking. |
WinAck Group can provide complete battery spot welder solutions. Come by, contact us for a solution that can help you succeed. For better batteries, Win & Ack!
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