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Posted on Aug 18, 20206
Spot welding of tapes and tabs on the battery to interconnect the batteries and larger battery pack components is a common production technique that requires specialized machinery, usually called a battery spot welder. Typically, battery interconnects are made of nickel strips, ideally designed with bifurcations and protrusions, and then resistance-welded using parallel gap or step welding methods. To obtain the best and reproducible results, such methods depend on the quality of the welding head, electrode, and power source.
To continuously improve power handling capabilities and reduce losses, high-end battery pack manufacturers are looking for ways to connect more conductive interconnects (such as aluminum and copper), while trying to reduce costs by simplifying interconnect design. Because the interconnection lines are too conductive, such requirements usually negate the possibility of using resistance welding methods. In this article, we will tell you everything you need to know about battery spot welders!
Cylindrical batteries combined into battery packs are increasingly used to drive portable electric tools, electric bicycles, electric and hybrid vehicles, for example. The battery is composed of many components. The basic component is a battery connected in series or parallel to achieve the required voltage and capacity. According to the type of battery design, there are mainly bagged, square and cylindrical batteries. The quality of the connection between each battery and the bus will affect the function and performance of the entire energy storage system. Connecting batteries is a challenge because of the need to combine different materials that usually have high conductivity with a combination of variable thickness. Due to the energy storage method, lead-acid, nickel-cadmium, nickel-metal hydride, sodium-nickel, and the most commonly used lithium-ion batteries are distinguished. Usually spot welding and projection welding resistance welding, ultrasonic and laser welding are used to combine batteries into groups, and mechanical methods are rarely used.
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Battery spot welders usually connect metal plates to the contact points of the battery. This method has been used for many decades and is still very common today. Battery spot welding is a form of resistance welding and is one of the oldest welding processes. Using a pointed electrode to generate the opposite force can heat the metal sheet and then easily connect it. The shape of the electrode used in this process determines various welding factors such as current, heat generation, and welding nugget size.
During the welding process of a battery spot welder, two or more pieces of metal are welded together without using any filler material.
The process involves applying pressure and heat to the welding area using a shaped copper alloy electrode that transmits current through the weldment. The material melts to fuse the parts. At this time, the current is turned off to maintain the pressure of the electrode, and the molten "nugget" solidifies to form a joint. The current generates welding heat, and the current is transferred to the workpiece through the copper alloy electrode. Copper is used for electrodes because copper has higher thermal conductivity and lower electrical resistance than most other metals, ensuring that heat is generated preferentially in the workpiece rather than the electrode. The amount of heat depends on the thermal conductivity and resistance of the metal and the time the current is applied.
The battery spot welder works by conduction heating, which is generated by electric current. The traditional battery spot welding machine places two copper alloy electrodes to fix the two metal sheets together. Copper has high thermal conductivity and low electrical resistance and is an ideal way to concentrate heat in the metal rather than in the electrode itself. Electric current flows through the electrodes, generating concentrated heat to melt the metal. The melting causes the two pieces of metal to stick together at that location. The current only runs for a short time, because once the metal pieces are fused, the current is no longer needed. However, the electrode will continue to apply pressure until the molten metal solidifies into a strong joint. The weld is repeated at regular intervals to effectively connect the two parts.
Owing to its lower thermal conductivity and higher electrical resistance, welding is easier for steel to find, and low carbon steel is better suited for battery find welders. However, steel with a high carbon content appears to form a hard and brittle microstructure that is vulnerable to low cracking strength or cracks in the weld.
Galvanized steel needs a higher welding current than non-coated steel. Similarly, for zinc alloys, copper electrodes can quickly deteriorate the surface and reduce the efficiency of the welding operation. While spot-welding zinc-coated steel, the electrode must be replaced regularly or the electrode tip surface must be trimmed. During this case, the cutter extracts the infected material so that the surface of the copper is clean and the electrode is reshaped. Certain materials widely used for battery spot welders include stainless steel, nickel alloys and titanium. While thermal conductivity and resistance of aluminum are similar to copper, aluminum has a lower melting point, which means it can be soldered. Due to its low resistance, however, very high currents are required when welding aluminum.
Battery spot welders can provide reliable results and form long-lasting welds. Because the battery spot welder uses the current flowing through the electrodes, there is no need for metal welding materials. This is a fast process that can make your project run smoothly. A large amount of energy can cause welding to occur without applying excessive heat to other areas of the metal.
This resistance welding method is not appropriate for all types of metals, so it can restrict the possibilities of the project. You will need a MIG or TIG arc welder with the appropriate accessories mounted. When you just need to use the device for small tasks, the price would be high. When the current or heat is not good enough, the joints cannot be repaired properly over time, so it is vital to have the appropriate settings. It may also be difficult to place the electrodes well on irregular protrusions or hard-to - reach locations.
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