E-Mobility Engineering 015 l EMotive Scarab off-road truck dossier l In Conversation: Giulio Ornella l Hall effect and magnetic sensors focus l Challenge of batteries for heavy-duty EVs l Alpha Motor Corporation digest l Automated charging insight l HVAC systems focus

system, and Williams describes the one that has been selected as a very high power specification inverter that is well- suited to off-highway applications. Smart power distribution EMotive is also designing its own HV power distribution interface module. This will draw power from the battery packs and deliver it to the motors via the inverter, as well as to various electric power take-offs for accessories and payload systems. It will also send power from the onboard generator/range extender into the battery packs to top up their charge. “The power distribution module is just a way of managing the power in a way that maximises the amount we can handle,” Williams notes. “Off-the- shelf systems are very limited as to how many kilowatts we can put into them from onboard generators and so on, so we are looking to develop our own solution.” In terms of componentry, the interface module will consist essentially of a set of HV, high-current contactors run by the master controller in concert with the battery management system, he explains. The low-voltage system also features intelligent power distribution in the form of a solid-state module from ETA Energy Technology that integrates semiconductor switches with a power management capability. The switches are MOSFETs, each of which functions as a relay and a circuit breaker/fuse. “We don’t have a conventional standard bank of fuses and relays; their functions are all handled by the MOSFETs and software fusing, which is very configurable,” Williams explains. “It’s an intelligent module in its own right. No more flash relays; it’s all done on timed circuits.” The module is much more controllable than conventional fuses and relays, Williams says, and allows systems engineers to set any thresholds they need for the fusing. turning and in which direction, what the torque loading is and how much weight it is carrying.” Detailed design and testing of the system is due in the next phase of the Scarab’s development, Williams adds. “We are essentially building all the technology in at this level, not just for traction control but for future control options as well, such as autonomy,” he says. “The platform will have interfaces in the architecture that will allow an autonomous platform to sit above it. We want to make sure we hit the market with the latest technology.” Battery packs and electrical architecture Meanwhile, the company is working with Webasto on the battery system. This is based on the latter’s commercial vehicle CV Standard Pack, which features lithium-ion prismatic cells using nickel- rich NMC chemistry and comes in 35 kWh modules that can be connected to form larger packs, either in series or parallel depending on the required voltage and capacity. “We would look to have a number of those batteries as standard, and then we can multiply them up to 175 kWh in total,” Williams says. “You can get a huge amount of power out of them as well. We looked at supercapacitors, thinking that in some applications we might need a large peak of power, but the batteries will provide it on their own.” Between the battery and the motors is a multiple inverter system, with an inverter per motor for a total of six. They are all supplied by Curtis Instruments, fed by a power distribution module and managed by a master controller through a CAN bus. “The master controller is the brains of the vehicle and will control all the tractive effort through algorithms, as well as interfacing with the battery management system,” Williams explains. Changing to a high-voltage electrical system will also require a new inverter “You can change the inrush currents, for example. It’s all part of the more intelligent system architecture that we’re going for really, with an eye to future-proofing.” Regan notes, “It also means that when a circuit blows we will pick it up via our telemetry. And we can then talk to the driver, investigate what is going on and even remotely reset it.” In addition to the solid-state power electronics, there are also computer chips and comms hardware in the module that enable its data to be uploaded to the cloud. Also, the power management architecture will include a separate DC-DC converter that will take in 800 V DC and supply 24 V DC to open and close the battery pack’s HV contactors and to power the vehicle’s lights and other standard automotive ancillaries. The final major HV device will be a DC onboard charger capable of delivering 22 kW to the battery. “We are designing in suitable components to meet our power demands,” Williams says. “With an off-road vehicle, we have not just great extremes in terms of how much power we need, there are many variables as well in between, whereas on-highway applications have fairly straightforward Specifications Scarab off-road truck Maximumgross weight: 12 t Kerbweight: 4.5-5 t Payload: up to 5.5 t Drive system: 6x6 with in-wheel motors and two-stage reduction hubs Maximumwheel torque: 6000 Nm Power: target of 75 kW per wheel continuous, 150 kW per wheel peak Maximum speed: 30 mph (62 mph projected) Battery capacity: 35-175 kWh depending on number of battery packs Voltage: 48 V for development vehicle, 800 V for production 28 Autumn 2022 | E-Mobility Engineering