Let’s Talk about Battery Spot Welders

Posted on Jul 29, 2021

battery spot welder

Battery spot welders connect metal plates to the contact points (terminals) of the battery. This method has been used for many decades and is still very common today. In this article, we will explain the process and how this type of welder works. Hope you will walk away with some tips on how to use it after reading this article.

What is a Battery Spot Welder?

Welding strips on the batteries to build the battery pack is a common technique for both DIY machinists and professional manufacturers. This process requires the battery spot welder to be carried out. Typically, battery interconnects are made of nickel strips, ideally designed with bifurcations and protrusions, and then welded using parallel gap or step welding methods.


DIY Battery Spot Welder, Darkkevind

To improve power handling capabilities and reduce losses, battery pack manufacturers are looking for ways to connect more conductive interconnects while trying to reduce costs by simplifying design. To obtain the best and reproducible results, the quality of the welding head, electrode, and power source is of great importance.


Automatic Battery Pack Production Line, Shenzhen JXC Mechanical & Equipment

Why Weld Batteries?

Battery packs are increasingly used to drive portable electric tools, such as electric bicycles, and electric hybrid vehicles. In these applications, the cells are connected in series or parallel to achieve the required voltage and capacity. Based on the battery design, there are bagged, square and cylindrical batteries. The connection quality affects the function and performance of the entire energy storage system.
 

Battery Types and Welding Methods

The connecting process is a challenge because it combines highly conductive materials that vary in thickness. The common energy storage methods include lead-acid, nickel-cadmium, nickel-metal hydride, sodium-nickel, and lithium-ion batteries. Usually, spot welding, projection welding, or ultrasonic and laser welding are used to combine batteries, with spot welding being the most common method.
 

How does it Work?

The first takeaway of battery spot welding is that the process does not need any filler material. It involves pressure and heat applying to the welding area. A copper-alloy electrode transmits current through the material so that it melts and fuses the parts. The current is off while the pressure maintains to solidify the weld and so the joint forms. Usually, the current only runs in a flash whereas the pressure stays a bit longer.
 

Why Copper?

Copper (or copper-based alloys) is the standard material for electrodes because of its high thermal conductivity and low electrical resistance. This feature ensures that heat is generated preferentially in the welding material rather than the electrode. In addition, copper is an ideal material to concentrate heat in the metal.
 

What Materials does it Process?

Steel and low-carbon steel are ideal materials for spot welding. These materials have lower thermal conductivity but higher electrical resistance than copper. Therefore, welding is easier to conduct on them. However, high-carbon steel is not that suitable since it forms hard but brittle welds that are easy to break. On the other hand, galvanized steel needs a higher current to weld.

As for zinc alloys, copper electrodes can quickly deteriorate the surface and reduce the welding efficiency accordingly. Welding zinc-coated steel is possible, but the electrode must be replaced or trimmed regularly. Other materials that can be spot welded include nickel, aluminum, and titanium. Although aluminum has thermal conductivity and resistance similar to copper, it has a lower melting point, which makes welding feasible. Due to its low resistance, very high currents are required though.
 

Battery Spot Welder Pros & Cons

It can provide reliable results and form long-lasting welds. Because it uses the current flowing through the electrodes, there is no need for filler material. On this note, it is a cost-saving option. The other advantage is that the welding area is restricted. It only takes place exactly where the tip of the electrode makes contact. Therefore, the energy is focused and heat generation reduced.

Speaking of the disadvantages, this method is not suitable for all materials, and the cost is relatively higher for mass-production lines when dealing with small-scale projects. Besides the cost issue, the welding quality is a concern if the process is not conducted properly. If the heat and pressure are not high enough, the joints will not be strong enough and hence susceptible to vibration or cracks. Last but not least, it does not work well for irregular protrusions or hard-to-reach locations.
 

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