Preparation before spot welding

Before spot welding the 18650 battery, proper preparation is key to ensuring weld quality. Firstly, cleaning and deburring the battery is a step that cannot be ignored. These impurities can affect the welding effect, as grease and oxides can remain on the battery surface. It is recommended to use an alcohol cotton pad to gently wipe the positive and negative electrodes of the battery, keeping the surface clean and stain-free. If the battery pole has burrs, you can use fine sandpaper (400 mesh or more) to lightly sand it, but be careful not to over-polish it that can cause the pole to become thinner.

Secondly, the setting of the spot welder is a crucial factor affecting the weld quality. The voltage and pulse time should be adjusted according to the thickness of the nickel sheet and the type of battery. In general, it is recommended to use 3.5V with a pulse time of 5ms for nickel sheets with a thickness of 0.15mm, while nickel sheets with a thickness of 0.2mm need to be increased to 4V, and the pulse time is extended to 7ms. According to data from a battery manufacturing plant in Hong Kong, improper parameter settings can lead to a weld defect rate of up to 30%.

When it comes to tool preparation, the choice of nickel sheet is just as important as the quality of the spot welding pen. The nickel sheet must be made of materials with a purity of at least 99% to ensure electrical conductivity and weld strength. For spot welding pens, it is recommended to choose models with copper nibs, as they have excellent thermal conductivity and durability. Here is a list of common tools:

• Nickel sheet (0.15mm/0.2mm thickness)
• Spot welding pen (copper nib)
• Insulating tape
• Alcohol Cotton Pad
• Fine sandpaper (400 mesh or more)

Basic Principles of Spot Welding

The core principle of spot welding is the resistive thermal effect, that is, the localized high heat is generated by a large current in a short time, and the nickel sheet and battery electrode are fused. When an electric current flows through the contact point between the nickel sheet and the battery electrode, a large amount of thermal energy is generated due to the presence of contact resistance, causing the metals to fuse together. This method has a smaller heat-affected zone than traditional welding, effectively protecting the integrity of the body.

The spot welding process can be divided into three stages: pre-pressing, welding, and retention. During the pre-press stage, a slight pressure is applied to the nickel sheet through a spot welding pen to ensure good contact. It energizes the welding stage to generate high heat. The holding stage maintains pressure even after the power supply is cut off, allowing the molten metal to cool and solidify. According to the technical manual, time management at each stage is very important, especially the welding stage is too short, leading to welding defects, and too long will damage the battery.

Specific Steps for Spot Welding

Cutting and positioning the nickel sheet is the first step in spot welding. The nickel sheet should be cut to the appropriate width (usually 5-8mm) and ensure it is long enough to cover the battery electrodes. When positioning, it is necessary to ensure that the nickel sheet is in full contact with the battery electrodes without any gaps. When using multiple layers of nickel sheets, it is recommended to spot weld the bottom layer first and then layer on top of it to reduce heat buildup.

Proper use of spot welding pens is key to ensuring weld quality. The nib should be held securely and the nib should be perpendicular to the battery surface to avoid tilting or uneven welding. The intensity and time control of spot welding should be adjusted according to the thickness of the nickel sheet, generally 2-3kg is recommended, and the time should be controlled to 5-10ms. According to measurement data from a maintenance workshop in Hong Kong, insufficient strength can reduce welding strength by more than 40%.

Attention should also be paid to the placement of the spot weld joints. To distribute stress and improve overall strength, it is recommended to use a staggered arrangement where adjacent solder joints are not on the same straight line. Each cell electrode should have at least 3-4 solder joints, and the solder joint spacing should be constant (about 5mm). Here are some common solder joint placement patterns:

Common spot welding problems and solutions

Weak point welding is the most common problem encountered by beginners, mainly due to improper parameter settings and contamination of the nickel sheet surface. The solution is to re-clean the nickel and battery electrodes and adjust the voltage and pulse time of the spot welding machine. If the problem persists, try increasing the number of solder joints or switching to a thicker nickel sheet.

Overheating of the battery can cause damage, causing security issues. During the spot welding process, it is recommended to leave an interval of 10-15 seconds to allow the battery to dissipate heat.18650 スポット溶接機If you frequently overheat during use, you can check if the cooling system of the spot welder is working properly.

Nickel burnthrough is usually caused by too long a pulse time or too high a current. The solution is to reduce the voltage or shorten the pulse time and ensure that the spot weld tip is clean and free of oxidation. Spot welding machine failures can be caused by unstable power supplies or aging internal components, so regular maintenance and the use of a stabilized power supply are recommended.リチウムイオン電池 構造

Inspection and maintenance after spot welding

Spot weld hardness testing is the final step to ensure weld quality. Use tweezers to gently pull on the nickel sheet and observe for any looseness. If the solder joint falls off easily, it will need to be spot welded again. In addition, a multimeter can be used to measure the resistance between solder joints, and the normal value should be less than 10 mΩ.

Battery protection is equally important. After spot welding, it is recommended to cover the solder joints with insulating tape to avoid short circuits. For long-term storage, the battery should be placed in a dry environment and the solder joints should be checked regularly for oxidation.

Advanced skills: multi-layer nickel sheet spot welding, special material spot welding

Multilayer nickel spot welding should be done in layers, and each layer should be cooled after welding before moving on to the next layer. Spot welding of special materials (for example, nickel-plated steel strips) requires adjustment of parameters, usually increasing the voltage by 10-15%. Tests from Hong Kong suppliers have shown that the optimal welding parameters for nickel-plated steel strips are 4.5V voltage and 8ms pulse time.

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