14 Future-oriented fastening solutions for electromobility By Andreas Blecher, Team Manager Marketing, EJOT SE & Co. KG In the emerging field of electromobility, EJOT focuses on developing and producing highly specialized functional and fastening elements tailored to the unique demands of high-voltage batteries and power electronics. For these complex projects, EJOT leverages advanced manufacturing technologies and robust application engineering support to deliver customized solutions to its customers. High-voltage battery The drive battery is the energy source of an electric vehicle and, depending on its design, comprises multiple battery modules interconnected by solid copper conductor rails. The objective is to establish a durable electrical connection with minimal contact resistance between conductors. This connection endures particularly challenging conditions, such as vibrations during driving and temperature fluctuations from charging and discharging cycles. To ensure the integrity of the screw joint and its resistance to vibrations, customers can utilize simulation software and benefit from the comprehensive support of EJOT’s in-house APPLITEC laboratory. Here, the clamp loads of the connection are evaluated under varying temperatures and vibration tests simulate operational stresses. Another critical requirement, which results from the high electrical load on the connection, is the necessary touch protection of the screw. Although the screw itself is not an electrical conductor, it can become conductive upon contact, posing potentially severe risks. To address this, EJOT combines its expertise in plastic injection molding with metal forming capabilities. This results in screws encapsulated with plastic at both the head and tip (Fig. 1). The plastic overmolding is meticulously designed to ensure maximum safety during operation, maintenance and repairs. To achieve the required electrical insulation, EJOT can also design the required clearance and creepage distances. Furthermore, each overmolded screw undergoes a 100 % dielectric strength test at 4,000 volts during production to ensure optimal safety. To seal the battery housing of an electric vehicle, the battery cover is fastened onto the hollow aluminum profile of the battery frame. An established technology for this demanding joining task is the so-called “Flow Drill Screw” (FDS®), originally developed for body-in-white structures (Fig. 2). A significant challenge is ensuring a reliable seal to protect the sensitive internal components of the battery from harsh environmental conditions. To achieve a durable and secure VOLTtec® Insulated Screw for high-voltage applications ● Ensures electrical connectivity ● Provides electrical insulation ● Offers vibration resistance FDS® with aluminum sealing washer ● Head-side sealing function ● Joining process with one-sided accessibility ● Facilitates easy disassembly and recycling Fig. 1 Fig. 2
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