31 Furthermore, aluminium comes with a significantly lower melting point than steel. While Fellten has never had a fire break out in or around one of its packs, and judges that such instances are far rarer in the EV world than social media lets on, it also judges steel as providing a desirable minimum level of fire tolerance and hence safety. “We always think with the worst-case scenario in mind, and that has dictated a lot of what we’ve done on the enclosure end. With the XP-1 pack and several others we’ve made, we go with a 3 mm-thick steel base, with 1.5 mm steel for the upper section, and those are joined by sheets around the middle of the pack,” Hazell says. “That allows us to build the modules into the enclosure base easily and then put the lid section on, and as that goes together, the cooling plates all tie throughout the battery pack and bolt to the housing walls to make it rigid. As we’ve taken this approach to the cooling plates that allows for modular pack assembly, we can also connect a section of plates, modules and busbars together, which then gets lifted and lowered into the pack; then build the next section and lower it alongside the first one, installing them part by part, with the connection of each series coming afterwards.” Regardless of the approach taken with modular construction, the pack is designed with a split down the middle, such that the positive and negative are never connected (an approach similarly taken by Xerotech, as seen in EME 22, November/December 2022) until the final stages of assembly, during which the safety disconnect devices are installed last. “That saves our team or end-users’ technicians from having to work with huge quantities of safety gear on. Trying to work nuts and bolts with massive, HVprotective gloves on is extremely difficult, and the risk of someone dropping tiny, metal components into a battery pack is actually really high,” Hazell notes. “In both the XP-1’s pack and our 55 kWh pack, the HV plate is at the very top section of the modules, so it can be pre-assembled before the lid goes on. That plate constitutes the BMS, contactor controller and the pre-charge system. As the lid lowers on, there are two bolting locations in the HV plate, corresponding to the positive and negative terminals that run up into the lid from the lower part of the pack, so the moment where the lid goes on is the only point in the entire assembly process where HV gloves are needed. After that, the pack can be delivered to the installer or taken for testing.” Future Fellten’s principle aim with Morgan, as with many customers, has been to enable a non-EV company to move into the EV space, without that company needing to dilute its focus away from its own specialisations with new skill requirements, such as battery manufacturing, BMS design or charge protocol programming. “The XP-1 may be a prototype, but Morgan now knows it can make the transition into EVs quite easily, should it decide to. It’s a similar experience to that we had before, with BMW and their Classic Mini,” Hazell recounts. “There was no way BMW was going to develop a Classic Mini retrofit solution. It was never going to be costeffective. But, with us, we’ve been able to produce the Mini system, supply it all to Recharge Heritage with the BMW branding on it, and bring it to market with the BMW wings. “There are other companies we’re working with, and a similar thread runs through them all in that they are long-established companies, which produce vehicles but need to start thinking about EVs, and they’re missing either the time, the resources or the staffing to just switch from combustion to electric powertrains. It’s a different world, but we can take care of the electrical, technical aspects for them, and they get to focus on building beautiful vehicles.” Indeed, the XP-1 has received positive reviews, and is now in testing until mid-to-late 2025, with the ball in Morgan’s court as to whether it will focus on producing this electric design or another in series. In the meantime, Fellten is ramping up its capacity for module and pack manufacturing, touting significant room for further cost-optimisation across its present and planned facilities, and it plans to target overseas markets in the US and elsewhere. These will not just be limited to conversion systems, however, as Fellten’s customer base also includes energy banks for a solar-powered car-recharging park, being made by 3ti. “The 3ti system will be a containerised, IP-rated, interlinkable pack system that can be dropped into a car park wherever EVs need to be driven, parked and charged at short notice,” Hazell says. “Simultaneously, we’re working on a product called the Charge Qube, which is a 100 kWh Euro-pallet-sized battery pack with CCS rapid charging in and out. One day, that could be taken to race tracks along with the Caterham to do two full recharges of the car on track. “Our next big in-house project is going to be a 50 kWh pack for Caterham, which will show how we can build something for the higher-performance sports-car world rather than the classic-car world.” E-Mobility Engineering | July/August 2024 Key suppliers for Fellten’s 33kWh pack Battery modules: DFD Energy Cells: DFD Energy BMS hardware: Orion BMS software: Brill Power Cell-monitoring sensor module: Metis Engineering Charging control module: IoTecha Wiring harness design software: Cadonix Washers: Nord-Lock Inverter: iNetic
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