The difference between different spot welding materials

The difference between different spot welding materials

As we all know, the common materials for battery pack welding are pure nickel, nickel-plated steel bars. Apart from that, copper and nickel-plated copper, aluminum have also been used for battery pack connections. Here, the differences between these materials will be listed.

Resistance welding: Lithium battery pack, 18650/21700/26650/32650, the connection between the connecting piece and the battery is resistance spot welding. Therefore, the resistance of the material is greater and welding is easier.

1. The comparison of internal resistance of these materials is nickel-plated steel>pure nickel>aluminum>copper=copper=copper-plated copper, therefore, nickel-plated steel is more reliable in terms of spot welding effect and stability.
2. Current-carrying capacity: The internal resistance is small, and the current-carrying capacity is greater, so, copper > red copper with nickel plating > aluminum > pure nickel > nickel-plated steel.

• The following is a reference to the calculation formula of the over-current capacity:

The over-current capacity of pure nickel is: 10A/mm2.

For example, pure nickel with a thickness of 0.15mm * 7mm wide, to calculate the ability to withstand the current of pure nickel, it is recommended to use its maximum continuous current resistance of 10 * 0.15 * 7 = 10.5A;

For nickel-plated steel strips, its overcurrent capacity: 7A / mm2, for copper strip, its flow capacity: 30A/mm2.

For easier memory, nickel-plated steel strip is 0.7 times that of pure nickel, and copper is 3 times that of pure nickel.

The above formula is for reference only, and should also be based on the charging/discharging time and the structural design of the package for the ability to withstand the nickel strip current.

3. Product stability: pure nickel>nickel-plated steel=nickel-plated copper>aluminum>copper

For example, if the lithium-ion battery pack is often used in a very humid environment, nickel plating is easy to rust, copper and aluminum are easily oxidized, But pure nickel will not. This is also one of the preferred advantages of pure nickel.

4. Price: pure nickel>nickel-plated copper>copper>>nickel-plated steel>aluminum

So we know from above that pure nickel is a good material in terms of product stability, but the cost is too expensive, and the welding requirements are a little higher than nickel-plated steel materials , you need to add cuts or dents to the product to improve welding;

Copper is a good material for current overcurrent, and the price is also very good, but it is difficult to solder, to solve this problem, you can use the solution of copper-nickel welding. nickel and copper are welded together. Nickel is used for spot welding, and copper is used for for over-current.

For nickel-plated copper, it is the same as copper, the nickel layer can delay the aluminum oxide is the cheapest, and the product is also very light, but its welding ability is not good, it also needs to be welded by copper-nickel welding weld. Nickel-plated steel is common, inexpensive, and easy to weld, but is more prone to rust. Each material has its advantages and disadvantages, you should choose the material base according to your needs, such as function, price, etc.