E-Mobility Engineering 014 l InoBat Auto dossier l In Conversation: Brandon Fisher l Battery monitoring focus l Supercapacitor applications insight l Green-G ecarry digest l Lithium-sulphur batteries insight l Cell-to-pack batteries focus

materials that break down under thermal stress and release phase- change materials that could extinguish a fire,” he says. “Certainly the F500 additive used in fire extinguishers in Formula E is promising. Progressive chemicals like that are very capable, but you have to have some really serious damage to a battery for them to come into their own.” Cell format impacts Not all cell formats are well-suited to either cell-to-pack or cell-to-chassis battery construction, with pouch cells in particular lacking inherent structural strength and requiring additional support that also allows for their expansion and contraction during charging and discharging. Prismatic and cylindrical cells feature a robust aluminium or steel alloy housing, respectively, whereas the housing of pouch cells is made of less stable composite foils. Larger cylindrical or prismatic cells will be better suited to the application, the vehicle technology and engineering services specialist says. “Our initial analysis with the 21700 cylindrical cell is that stacked tolerances could become a significant barrier to reliable repeatability in manufacturing.” While cylindrical format cells can be made in large energy capacities and large physical sizes, most are small, and as the technology for mass producing the jellyroll anode, separator and cathode structure is very well understood, the other formats are playing catch-up when it comes to economies of scale, our EV consultant and battery manufacturer points out. “If you are churning out a vehicle every 5 minutes, that means you have 5 minutes to make the battery… and you have a few seconds to make each cell,” he says. “For cell-to-pack and cell-to-chassis construction you need a large capacity cell, and certainly large pouch and prismatic cells are available, and Focus | Cell-to-pack batteries Crash safety implications Crash safety affects all aspects of battery design, and the cell-to-pack and cell-to-chassis concepts provide the opportunity to get the battery components into a better place than can usually be achieved when working with a single large battery pack mass, the specialist EV builder notes. “You are able to get the batteries lower in the vehicle, typically, improving the weight distribution, the inertia of the battery system in impact, and you are getting away from the extremities of the vehicle,” he says. Whether a module-to-chassis or cell- to-chassis design will perform better in a crash than a standalone battery pack – in a skateboard configuration, for example – depends on the details of the design. “As with module-to-pack designs, the cells must be packaged away from any crash or impact zones,” the lithium metal battery manufacturer says. “Vehicle development engineers can assess the intrusion of a crash into the battery enclosure space, which is a limiting factor on the available space to package the batteries, especially in the y axis or the width of the battery pack,” the expert says. “The worst crash generally is the side pole impact. That is a very difficult test to pass, from a legislative perspective, because you have a high level of intrusion through a sill section and into the battery enclosure,” the specialist EV builder says. “When you have a standalone battery pack bolted into a chassis, typically you will end up with the mounting structure being relatively close to the extremity of the vehicle, and it therefore comes into the impact fairly early. “When you are building an integrated module- or cell-to-chassis solution you have the opportunity for a much greater deformation area before you get into battery deformation.” That said, the elimination of battery housings and module components call for new developments of structural elements, notes the adhesives and thermal management materials expert. “Even if the vehicle chassis itself remains undamaged, the crash impact can affect the cells, causing damage to interfaces or in-cell structures and potentially leading to severe thermal runaway events. Additional safety measures will be necessary to protect battery cells in vehicle-to-chassis concepts,” the adhesives and materials expert says. The EV consultant and battery maker concurs. In addition to fuses and interconnects that break when certain mechanical stress levels are exceeded, advanced materials will play even more important parts than they do now. “We are getting to a point where over the next few years you will start seeing Some suppliers of cell-to-pack and cell-to-chassis batteries Germany Henkel AG +49 211 7970 www.henkel.com Japan Panasonic +81 6 6908 1121 www.holdings.panasonic/global South Korea LG Energy Solution +82 2 3777 1114 www.lgensol.com/en/index Samsung SDI +82 55 380 2334 www.samsungsdi.com/automotive-battery/index.html SK Innovation +82 2 2121 5114 www.eng.skinnovation.com/main.asp UK Silver Power Systems – www.silverpowersystems.com USA BYD North America +1 213 748 3980 www.en.byd.com C4V +1 607 224 2225 www.chargecccv.com Sion Power +1 520 799 7500 www.sionpower.com 68 Summer 2022 | E-Mobility Engineering