Battery Pack Welding: Tips for Improving Tab-to-Terminal Connections

How would we survive without battery packs? Whether to power our latest portable electronic device, power tool, or hybrid/electric vehicle, the removable battery pack is essential to our everyday lives. Tab-to-terminal connection is one of the key battery pack welding applications. Manufacturers need equipment, systems, and automated lines that meet quality and production requirements for these products. Resistance and laser technologies are both good options for integration into production lines, either as standalone units or for automated operation.

Battery pack manufacturing systems for welding tabs to terminals

Today’s battery packs come in a variety of configurations and battery types – cylindrical, prismatic, ultra-capacitor, and pouch. Typical configurations are shown below.

The critical process step for battery pack welding is joining the individual batteries together using a collector plate which consists of tabs for the individual cells to be welded to both the positive and negative terminals. Many packs also need a smaller number of collector plate-to-bussbar connections.

Selecting the appropriate battery pack welding technology to weld battery tabs involves many considerations, including materials to be joined, joint geometry, weld access, cycle time and budget, as well as manufacturing flow and production requirements.

Fiber laser welding

The laser welding process is non-contact, has no consumables, and offers instantaneous welding once the laser is positioned at the weld point location. Furthermore, you can closely control and optimize the weld size and location on the part for strength and conductivity. You can also tailor the motion options to the manufacturing environment.

Fiber lasers can be used to weld battery tabs on prismatic, cylindrical, pouch, and ultra-capacitor battery types. The tab thickness can vary from 0.006-0.08-inch for both aluminum and copper tab material, depending on the size of the battery. The fiber laser can weld many material combinations, including aluminum to aluminum, aluminum to steel, copper to steel, and copper to aluminum. The figure above shows examples of fiber laser welding of common dissimilar materials combinations for tab-to-terminal welding.

Resistance welding

Resistance welding is the most cost-effective method to weld battery tabs, using both DC inverter closed loop and capacitor discharge power supplies. With fast rise times, closed loop feedback control, polarity switching, and options for displacement and force sensing, the process can be finely tuned and monitored to ensure both high quality and yield.

Resistance welding is a great 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.

For nickel tab thicknesses up to 0.0070-inch, the tab can be welded as is, with no modification. For thicker tabs, one should place a slot and projections in the tab as part of the stamping process to prevent electrical shunting and excessive electrode wear.

So which technology is best for my application?

Table 1 offers some guidelines on the available methods and a few parameters that can help choose the right option for a specific application. Table 2 provides an overview of battery pack joining applications and key components of joining solutions required.

*Material and material thickness dependent

Complete production solution must deliver and support the required product flow

There are a variety of system solutions available for battery pack manufacturing. The system must take into consideration how the pack is loaded and unloaded, how the un-welded parts are held prior and during welding, and whether and to what level the system reports data and information to the supervisory control software. Here’s what has to be included:

• Enclosures
• Motion
• Tooling (for laser welding only)
• Communication
• Process monitoring

See below for pictures of integrated systems for battery pack welding, including (left to right) a conveyor fed automation cell, a laser tab welding system with fire suppression deployment, and a resistance welding system.

For more information read our Battery Industry Capabilities Brochure.