Plug connections for electrical contacting of modules in the battery pack offer several advantages. However, until now it was only possible to assemble them manually – an obstacle for large batch sizes. Liebherr, together with KOSTAL Kontakt Systeme GmbH, has developed an innovative solution for the automation of the plugging process.

The modules installed in the high-voltage battery must be electrically contacted with each other. Currently, screw connections with busbars made of copper material are predominantly used for this. It is also possible to use plug connections with flexible lines or busbars.

Advantages of plug connections

Compared with screwed and rigid busbars, plug connections with flexible cables offer a number of advantages:

• Easy assembly: Only the plug and counterpart have to be connected. This also facilitates the disassembly of the modules in the battery pack during later servicing, for a second life or for battery recycling. The flexible lines can also compensate positioning tolerances in the battery modules of several millimeters.
• Safety: Normed, touch-protected contact parts mean that no danger is presented by exposed electrical high-volt contacts.
• Robustness in practice: If there are strong vibrations in the vehicle, screwed busbars can detach themselves. The flexible lines with the plug connections are able to compensate for these vibrations.

Challenge: the automation of limp parts

For these reasons, there is growing interest from manufacturers in pluggable connections. However, since the automated assembly of soft components presents an engineering challenge, this has till now still been carried out manually. This can cause a bottleneck in production if batch sizes increase. The problem is that the parts have low resistance against shape changes. They already become very highly deformed as a result of even small stresses, such as their own weight. These changes in shape are often a rejection criterion for the automation of handling or assembly processes.

Innovative automation solution by Liebherr

Liebherr has developed a unique solution for this to enable the automated, process reliable, plugging of module connections. Two cooperating robots each grip one end of the cable and carry out the plugging process synchronously with temporally and geometrically coordinated movements. Using a 2D camera, the robot detects the real position of the slots, thus enabling positioning tolerances to be compensated. The actual, mechanical plugging process is performed using a pneumatic cylinder. A spring assembly limits the force transfer to the module, plug and plug lock to secure the position (CPA). Finally, process reliable monitoring is performed by a stop position sensor. Liebherr can also solve the laying of the cables in the desired position and geometry using suitable cable bend grips.

About the Liebherr Group

The Liebherr Group is a family-run technology company with a highly diversified product portfolio. The company is one of the largest construction equipment manufacturers in the world. It also provides high-quality and user-oriented products and services in a wide range of other areas. The Liebherr Group includes over 140 companies across all continents. In 2020, it employed around 48,000 staff and achieved combined revenues of over 10.3 billion euros. Liebherr was founded in Kirchdorf an der Iller in Southern Germany in 1949. Since then, the employees have been pursuing the goal of achieving continuous technological innovation, and bringing industry-leading solutions to its customers.