If you’re like me, you could fill a bathtub with batteries and battery packs for all of the devices in your life; they have become an integral part of everyday living. With all of this, however, comes the need to manufacture batteries and battery packs to power our connected world.
Materials joining requirements for battery manufacturing depend on the specific type, size and capacity of the battery as well as the specific application. Will you be joining internal terminal connections, performing battery can and fill plug sealing, making tab to terminal connections, or welding external electrical connections?
I thought it might be helpful for me to give people some guidance on selecting and using the right technology for these applications. I’ll cover resistance, micro-TIG, and laser welding. I’ve also offered a table summarizing when and where to use each technology.
Resistance welding – tried and true
Resistance welding has been used in the battery industry for nearly 40 years. Some great new advances have really improved process control for battery welding, including DC inverter power supplies with basic closed-loop electrical modes; polarity switching for capacitor discharge supplies; and most recently, displacement and electrode force measurement.
Resistance welding is the most cost-effective method for joining tabs on a wide range of battery types and sizes, using both DC inverter closed loop and capacitor discharge power supplies. It’s an excellent choice for welding nickel tab material up to 0.015-inch thickness, and nickel or steel clad copper tab material to around 0.012-inch thickness to a wide variety of terminal materials.
Tungsten inert gas welding (TIG) welding – great for welding copper
Tungsten inert gas (TIG) welding, also known as gas tungsten arc welding, has long been the most preferred method for challenging nonferrous welding applications. With the addition of great new high frequency power supplies with increased low current control and arc stability, the technology has segued into what’s known as micro-TIG welding.
This non-contact process enables much finer welding and is really useful for copper joining, so it's a good solution for buss bar welding that would normally require a brazing material for resistance welding or a large power laser welder. Butt, fillet, and lap welds are possible up to and beyond thickness of 0.02-inches copper. When welding copper using micro-TIG, it is extremely important to use a pulsation function that creates a finished weld without porosity.
Laser welding – use for high speed seam sealing, tabs and buss bars
Laser welding for batteries is still kind of the new kid on the block, introduced in volume into the manufacturing marketplace in the mid-1980s. Two laser types are a good choice for battery applications: pulsed Nd:YAG and fiber.
Lasers are most often used for high speed seam and plug sealing of battery cans, offering significant advantages over mechanical clinching and adhesive methods. Figure 1 shows a few examples of seam welding of aluminum cans, including a weld cross section, and ball and plug sealing application examples.
For tab and buss bar joining, laser welding offers a high degree of flexibility, welding both thin and thick tab materials, materials such as copper, aluminum, steel and nickel, as well as some dissimilar material combinations. Welding tabs or terminal connections to buss bars generally does not require as much penetration or heat input control as the tab to terminal welds.
How to choose?
Resistance, microTIG and laser technologies each have pluses and minuses for battery joining applications. Table 1 offers a few guidelines on the available methods and the parameters you should look at when examining their suitability for your battery application.