28 November/December 2023 | E-Mobility Engineering forming the fluid connectors between each module’s main coolant ports. Doing without plumbing harnesses helps with pack compactness, and optimises the cooling headers by ensuring sufficient water passage with low pressure drop. “Our L-shaped busbars connect electrically and geometrically at the side, eliminating the need for wire harnesses inside and outside the modules,” Dr Flannery adds. An outside ladder frame is then bolted onto the four corners of the module stack for rigidity, including a top piece for further protection. The busbars are strapped about the sides of the module stack to electrically connect the modules in series, and then after some QC checks, the stack is lifted by an electric crane designed and built inhouse, and lowered into a pack enclosure. The sheet metal for the pack enclosures and busbars is cut inhouse to allow flexible and fast supply of different pack sizes. “Take three Hibernium packs with 19, 20 and 21 modules, and all three will need different housing sizes and sheet metals,” Dr Flannery notes. “So battery manufacturers relying on third parties for sheet metal often find scalability stops at the pack level.” A Trumpf TruFlow 4000 laser is among the laser-cutting machines in Xerotech’s sheet metal factory, although Dr Flannery anticipates moving to other production methods as volumes increase, including press tooling and turret punching machinery. Once cut to size, the metal sheets are folded, formed and welded together to form enclosure sub-assemblies for packs and BDUs, after which they are painted in Xerotech’s signature white. “Having all this in-house means that for critical projects, we can turn a production pack around from scratch in less than 16 hours, and as standard we offer customers a prototype lead time of about 4 to 5 weeks, compared with 3 to 6 months at absolute best for most pack manufacturers,” Dr Flannery says. “If we really push ourselves, we can make a prototype in 2 or 3 days, and working our own sheet metal is the biggest enabler of that. “We expect our current facilities, once scaled up over the next 12 months, to have an initial capacity of 0.4 GWh of pack assembly; then the future facility we’re planning here in Ireland will be somewhere between 2 and 4 GWh, with a US facility to follow at some point.” The pack enclosure typically comes as two aluminium pieces. One is a five-sided sub-frame that is folded, formed and welded to form the core box shape; the second is the lid, bolted on top. The BDU is normally also welded onto the pack housing’s front end, so its lid, also bolted on, can be considered a third piece. “Other packs usually have big flange connections outside their boxes, but that means you then need to transfer loads from the stack, through the inside of the box, so you add a lot of structural membranes through the housing, which adds cost, complexity and weight,” Dr Flannery comments. “Bolting directly to the sub-frame instead makes for a compact housing that serves purely as an environmental bubble, not a structural one.” Although most of the packs have been made from Al 5254 (with powder-coated paint), Xerotech’s standard-issue Hibernium enclosure is now steel, a change made to improve manufacturability and welding throughput – key factors in scalability, particularly regarding plans to move to robotic welding next year. Steels also have higher melting points than aluminiums, meaning greater safety against thermal runaways. Dossier | Xerotech battery system Some key suppliers Processors: Texas Instruments Connectors: Amphenol Industrial adhesives: HB Fuller 21700 cylindrical cells: Molicel 21700 cylindrical cells: various Inorganic electrolyte cells: Innolith Vents: WL Gore CFD: Ansys Battery test cyclers: Neware Temperature test chambers: Weiss Technik Coordinate measuring machines: Aberlink Additional measuring equipment: Insize Additive printers: Prusa Additive printers: Bambu Injection moulding machines: FANUC CNC milling machines: Z-MaT CNC control and automation solutions: Mazak Laser cutting machines: Trumpf In the pack assembly area, modules are stacked on top of each other and structurally bound using (orange) ladder frames, with busbars also installed outside for electrical connections
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