From Cells to Road-Ready Packs: How EV Batteries Are Made

Automakers and their suppliers use many individual parts and pieces when building an electric car.

One of the most complicated and unique is an electric vehicle battery. Made from thousands of smaller components, the EV battery pack must be a single integrated power source that delivers energy in a prescribed manner at a specified rate, all while doing so safely and consistently. To meet these needs, the EV battery manufacturing process requires more than just stacking a bunch of cells into a box. The process includes cell preparation, battery module assembly, pack construction, structural connections, wiring hooks, testing, and quality control at every step of the way.

Cells Are Checked & Modules Are Built

The process begins with incoming cells. These batteries are typically inspected by the manufacturer for size, voltage, resistance, and other issues. Cells that pass inspection are then either sent to or sorted into groups or assortments, depending on the final application. This is important because tolerances may vary slightly between cells, and this difference can affect performance, charge rates, and longevity later on.

The next step in battery pack manufacturing is to make the modules. In this phase, cells go from being in groups to being put into a single plastic or metal frame to create a module. This is where the physical mounting of cells can occur, as well as the welding, bonding, busbar connections, insulation, and sensors used. Cells must be positioned with precise alignment and location to operate properly, and small mistakes or errors can lead to large issues later on, including shorts, dead spots in the battery, or reduced performance and life.

Battery Packs Are Constructed

With the modules complete, they can be put into the pack or case that will hold them for the remainder of their lifespan. This is the final module case, typically called a pack or tray. This process will also have a battery tray assembly that needs to occur before the modules go in. The tray is there to help with structure and holding the modules in place. It can be made from metal, composite, or plastic and may have cooling channels, mounting points, insulation, and other features included. In the EV battery manufacturing step, the individual modules are placed in the tray or case. The trays are made to hold, seal, support, and cool the modules that are within them.

Battery packs also require that the modules and cells inside them are connected to busbars, sensors, power cables, contactors, and the battery management system. Again, as before, we also have thermal components and control systems that ensure heat is removed effectively during charge and discharge periods, and that the entire system is sealed to prevent water, dirt, and other particles from entering and causing issues with the electrical or chemical operation of the cells and modules.

Assembly Lines Are Full of Automation

Newer electric car battery manufacturers are starting to use automation to help out with their production, so things are done the same way every time. Welds are consistent, adhesives are in the right spot and quantity, force and torque are all where they need to be, etc. Unmanned warehouse logistics systems are being put in place that can automatically find and deliver ordered parts to nearby robots or station areas. These parts that are in the stations before and after, and used to access all the areas of the individual module or pack, are then inspected, recorded, and confirmed. Humans are usually reserved for tasks that require skill, troubleshooting, or design work rather than the manufacturing of the assembly that is built from a controlled and programmed design program, such as in an assembly line making products.

A contemporary battery pack assembly line may involve several linked automatic stations, plus associated inspection systems and software. Cameras and sensors could help verify the placement of parts, while other automated equipment does electrical testing and searches for possible defects.

Validation Outside the Vehicle

Since EV ranges continue to lengthen and operating environments vary widely, it no longer matters if the battery works when it leaves the factory. The customer expects the battery to perform well in extreme hot and cold temperatures. The customer expects the battery to function properly after thousands of charging cycles. The customer expects the battery to work flawlessly over gravel, cracked pavement, and other rough driving conditions. These targets get harder to achieve every time an automaker decides on a smaller, higher-powered, application-tuned battery, and as the EV market continues to ramp up, enhancing production quality with an array of inspection, testing, and automation techniques should remain a priority.