The Understanding of Traceability and Quality Assurance for Battery Pack Repair During Assembly

Sammanfattning

Traceability and quality assurance during repair refers to the control of the workflow to ensure that the repaired product has the best possible quality. During the assembly of electric vehicle batteries, deviations may occur that warrant repairs to avoid scrapping of the battery. It is the study of this master’s thesis to understand the traceability and quality assurance requirements during a repair process in order to facilitate repairs for electric vehicle batteries. The studied company was Scania’s main battery assembly in Södertälje. The company assembles battery cells they receive from a supplier along with several other components into modules, layers and packs that will then act as the power supply for Scania’s electric trucks. The focus was on the major components (modules, layers and packs) as they are considered the most essential. To garner an understanding of traceability and quality assurance for repairs during assembly, three research questions were used to create an overview of these aspects. This overview was created by conducting a literature review and then supplementing it by interviewing experts internally at Scania. This allowed for an understanding of what aspects are relevant according to the literature and how they are actualized in Scania’s current operations. Scania’s current battery operations and repair process was analyzed in order to understand the current state. A problem analysis was then performed to understand what deviations occur, how they pertain to traceability and quality assurance and the repair process can be managed. Based on the literature and interviews, thermal management of the battery is central in order to ensure longevity of the battery. For a repair process, this means that thermal management is a key aspect to consider from a quality assurance point of view. The physical environment itself is also relevant to consider. Keeping the repair environment clean minimizes the risk of hazards such as short circuits. Furthermore, regulatory and internal requirements by the manufacturer mandates that each battery should be tested for quality and safety where several of these parameters are required to be documented in a publicly accessible ledger called a digital passport. As the repairs take place during the assembly procedure, there is a variability of how much the assembly line can be used if the battery can leave and reenter the assembly line via special stations. By utilizing Miltenburg’s model for manufacturing investments, this variability is evaluated based on Miltenburg’s concept of manufacturing levers and outputs. The proposed action for Scania is to utilize the functionality of the line and strive for entire layer replacements when repairing faulty modules in a pack. By doing so, Scania leverages the automatic assembly of components which yields better results compared to a manual repair process. The company should also invest in their production support systems that enable traceability so that component replacement can successfully be logged, which is something that is currently not possible.