E-Mobility Engineering 016 l Aurora Powertrains eSled dossier l In Conversation: Thomas de Lange l Automated manufacturing focus l Torque sensing insight l Battery Show Europe 2022 report l Sodium batteries insight l User interfaces focus

and just having the DC fast charger, but not everywhere has a DC HV plug available,” Autioniemi comments. “It would have made the eSled less expensive, but then fleet customers would have had to buy at least a few fast-charging stations, so it would have made the overall cost of owning our system higher for them.” As a final point, the eSled’s charging inlet, which is designed to the CCS Combo 2 standard, does not have the kind of hinged cover typical of charging input connectors; if it did, it would provide a point at which snow can pile up, melt and then trickle into the interior of the OBC or elsewhere in the EV. The eSled therefore uses charger covers that are removed entirely and reattached by way of interference fit, with a brush typically available nearby for users to manually clear excess snow. “Both the cover and the charging pistol render the connector airtight the future,” Autioniemi says. “We tried other charging controllers, and there are certainly high-quality ones available, but again they were all just too big for our EV. Our VCCU on the other hand is the size of a credit card; it’s something of a game-changer for smaller high- end EVs, especially since a lot of OBCs out there don’t come with a charging control and comms system.” The OBC is 3.3 kW as standard, and runs on its own embedded software, although 6.6 kW AC and fast DC charging are also available. As with the rest of the powertrain, size and weight were the most vital constraints on Aurora’s choice of solution, and 3.3 kW was the lowest charging rate it was willing to install to ensure each eSled can be used for at least two or three guided tours per day. A slow trickle charge of 100-220 W can be used overnight if desired. “Given our space limitations, we had thought about omitting the OBC when installed, ensuring that precipitation can’t sneak in that way so long as the user is reasonably diligent,” Autioniemi says. “Also, at the back of the connector is a small drain-and-hose design feature, so that if water still somehow gets in, it flows into the drain by gravity or centrifugal force, and is guided back outside the EV again.” Drive unit The eSled runs on a single electric motor mounted beneath the handlebars and at the front of the track, where it directly drives the sprocket at the front of the transmission system, which in turn drives a belt connected to the track’s forwardmost wheel. A fixed gear reduction ratio of anywhere between 3:1 and 2:1 can be installed in the transmission, depending on a customer’s torque requirements. The e-motor is an axial flux permanent magnet machine. Aurora’s charging inlets are designed without hinged covers, to prevent ice pooling and cracking around or beyond the CCS Combo 2 connector 32 Winter 2022 | E-Mobility Engineering