OEM&Lieferant Ausgabe 2/2020

114 Battery systems Customised joining concepts for battery systems By Heinrich Georg Homrighausen, Head of Business Development Industry, EJOT GmbH & Co. KG The controversy over whether combustion engines, fuel cells or electric vehicles are the better choice has been steered after many discussions and perhaps also through political decisions derived from them – at least for the time being. And when market-leading OEMs clearly choose a battery strategy, this gives the market an extreme dynamic. It is exciting to see how electromobility is constantly evolving in almost every detail. Hundreds of thousands of engineers and scientists worldwide are working to optimise the systems. The battery is the detail of elec- tromobility which is crucial for the ecological and economic suitability of this type of drive. And due to its range and ease of charging, the cost-intensive battery becomes the key deci- sion-making criterion for buyers for or against electric vehicles. Crash safety and fire protection are two of the most important requirements that every manufacturer, regardless of design strategies, must meet. The joining technology has the task of durably connecting the battery compo- nents, even if they are made of very different materials. The challenges for joining techno- logy are assessed below using three applica- tion examples from the fastening technology specialist EJOT. A large number of joining processes are used in battery systems, detachable and non-de- tachable. The first application shows the possibilities of detachable screw connections in the area of the battery box cover. A va- riant of the EJOT FDS ® screw is used here, a flow-drilling fastening element for detacha- ble high-strength sheet metal connections which usually does not require any com- ponent preparation, such as pre-drilling or punching. FDS ® screws have proven them- selves millions of times in body-in-white construction. Due to the increased thread engagement in the formed draught, a high- strength screw joint without any undesirable swarfs is created. The special feature of this battery cover screw connection is the pre-assembled em- bossed aluminium sealing washer, which en- sures an under-head seal at the cover. The sealing function is given by the surface of the aluminium washer. In this application, pre-drilling of the clamping part is indispen- sable. Thanks to the embossed assembly of washer and screw, the components are rot- atable and captive. Protection of the battery interior from moisture and dirt is ensured and the screws can be loosened for mainte- nance purposes without any problems. An additional sealing of the screw head is not necessary. An important criterion for the OEMs, the global availability of the joining technology, is guaranteed by the manufac- turer and its licensees. The second example from the field of battery systems is the EJOWELD ® process, friction welding with a friction element. This process offers the possibility to join composite ma- terial with robot-controlled friction welding equipment without any pre-treatment. The battery frame box has a base which, in this example, is made of aluminium for weight reasons. In a multi-stage installation process, the aluminium is penetrated, the surface of the steel material is activated, the friction element as well as the base sheet are plasticised and finally the welding is formed. There are no intermetallic phases and a tight joint, since the lower joining material is not penetrated. And since the production of the entire bat- tery system is ultimately measured by its CO² footprint, this technology offers significant advantages over the alternative method of resistance spot welding due to its low energy balance … Continue reading … https://t1p.de/9vtw Images: © EJOT EJOT GmbH & Co. KG Heinrich Georg Homrighausen Head of Business Development Industry EJOT fastening solutions for battery systems S H A R E