30 weaved) and the Arcadia software from Cadonix, which many OEMs use for designing and testing. “On top of that, the overall approach to this facility means we’ll get to standardise our cell stock, our busbars, our cable stock, our software. People say it’s not cost-effective to build modules in the UK, but we see a huge cost-saving opportunity via just-in-time [JIT] manufacturing, as we won’t need to hold masses of stock,” Hazell adds. “We will build modules as and when we need to, and then the modules in the packs will be fresher – they won’t have sat rocking on a container ship for six weeks, so they will be of a better quality.” Early-stage CAD of new Fellten modules will include simulations of up to 20 G crashes for safety rating the designs. Once built, each new pack will go through comprehensive charge/ discharge cycling, as machinery for rapid charging and discharging is already present at the company’s plant, and include one 100 kW rig and another 400 kW system. “We can cycle each module and pack contextually, based on BMS data, meaning we can limit based on the DC out or constant current out, or tailor the peaks and troughs of the cycle to match, for instance, someone taking a pack meant for a Porsche 911 and pushing it really hard on a track,” Hazell says. “That will also help us get our BMS profile dead on, to limit the batteries at the right time and smoothly, so drivers never feel a hard limit coming in.” Some of these cycles will be performed with the pack lid removed and a thermal camera pointed at the modules to detect hotspots in the busbars or elsewhere. As some shorter busbars may feature flexible joints – composed of multiple, thin, ultrasonically-welded layers – to compensate for the lower resistances, it will be critical to check there are no contaminants or damage that risk causing performance losses later in the pack’s life. As Fellten looks towards R100 certification, it will begin crash- or crush-testing modules, as well as shake tests, fire tests, dead short tests, and over-charge and over-discharge tests. Pack assembly Today, the pack enclosure is made from steel, with Fellten having avoided the more lightweight aluminium for several reasons. For one, the company has found that building packs from aluminium eventually mandates using very thick sheets of it to achieve the ideal structural strength. “Additionally, from a crash-safety perspective, steel is a better choice,” Hazell adds. “Most OEMs don’t need to worry too much about what the pack is made from as they will just sling their packs under the vehicle floor, and then when the crash inevitably comes from the front, rear or side, there is low to zero risk of a pack deforming or flying into a driver or passenger. But, with retrofitted EVs, the battery pack is more likely in the front or rear, so you need to build an extra degree of crash resistance into the pack, so that if the pack takes a knock, it withstands the impact and doesn’t deform or move too much.” Fellten has simulated virtual crash tests of up to 20 G to visualise how the pack and its mounts distort against hard shocks, and to determine the best material and design approaches to minimise the chance of a thermal event or other hazardous consequences. Some customers of the 55 kWh pack have chosen to perform full crash scenarios to validate that it will remain in one piece without any significant deformation (even if the test car itself is destroyed). July/August 2024 | E-Mobility Engineering Dossier | Fellten Morgan XP-1 Fellten’s next plans are to construct a new, 15,000 ft2 facility for pack manufacturing, with a stock-control warehouse and a module-manufacturing centre to follow
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