Lithium-ion batteries are considered key technological components of electromobility and stationary storage systems due to their high efficiency and storage capacity. Intensive R&D activities have recently led to an increase in their performance and a reduction in charging times. At the same time, however, unit sales are falling by up to 20 percent per year.

The proportion of manual workstations in the production of battery packs has so far made cost-attractive production in large quantities difficult. For example, the condition of individual Li-ion cells is still largely checked manually using measuring devices both when they are dispatched from cell production and when they are received in battery pack assembly. This is time-consuming and sometimes leads to incorrect measurement results due to operating errors. This process can now be fully automated in order to cope with the increasing demand forecast for the coming years.

Autonomous control of all relevant parameters
Schunk has developed an integrated gripper system that actively uses its strategically exposed "closest-to-the-part" position to autonomously perform all the process steps required for handling and quality control: The gripper gently picks up the prismatic Li-ion cell and moves it to a defined inspection position within the gripper during the handling process. There, the cell is identified and geometrically measured fully automatically using a barcode or data matrix code.

At the same time, the temperature and curvature of the cell surface as well as important electrical parameters are determined: Open-circuit voltage to determine the state of charge (SOC), internal cell resistance, insulation resistance, impedance at two frequencies to determine the capacity.

The processed information can be made available in real time to the system control, ERP systems and higher-level database systems via Ethernet TCP/IP using an integrated PC system at the gripper module level. Evaluations of faulty or deviating modules can be automatically documented there and, if necessary, sent directly to the supplier as a defect report.

The data curves can be displayed separately in the visualization. Information for product and process improvement can be obtained from the analysis of the measurement data. Once the fully integrated quality control has been completed, the gripper inserts the cell into the appropriate line in module production or places the cell in the cell manufacturer's shipping tray. NIO parts are automatically ejected.

Modular concept for individual process design
The battery cell gripper can be connected to various robot or gantry systems via standardized mechanical interfaces. It is controlled via digital I/O. Thanks to the modular concept and freely configurable control loops, both the type and scope of the individual test procedures can be defined individually. Additional measurements and evaluations can also be integrated on request. The modular sensor concept and configurable control loops ensure flexible application options. Cycle times of less than two seconds are possible at peak times.