E-Mobility Engineering 019 | In conversation: Stephen Lambert l WAE EVR l Battery case materials focus l Quality control insight l Clipper Automotive Clipper Cab digest l Optimising battery chemistries insight l Powertrain testing focus

28 May/June 2023 | E-Mobility Engineering want within the next few years, and in return they can supply us with unique cell chemistries that are still in the development stages, and not yet necessarily a COTS system available to others,” McCaw says. “When faced with the trade-off between energy and power in cells, we’ve tended towards a chemistry that can deliver a consistently high rate of power, and that’s best for their life cycle given how they will be used. Our motorsport background made us look into certain pouch-type cells that have a very high power output, but they don’t have the life cycles and durability that a road-oriented vehicle like the EVR does.” Various cell types were therefore evaluated against expected drive cycles, with WAE’s vehicle dynamics team simulating how they would perform within known power cycles (such as fast laps around the Nurburgring race track), then cycling the cells through those simulated routines in test rigs to directly observe the rates at which their capacities degraded after, say, 1000 simulated laps of the Nurburgring. “Energy and range can’t be ignored of course,” McCaw says. “Plenty of drivers will want to drive for a couple of hours per day, so 80-90 kWh was ideal to ensure the kinds of 400-500 km between charges we anticipated.” The BMS has been optimised through pack simulations and digital twinning to determine how the lives of the cells can bemaximised through balancing of voltages, currents, temperatures and other parameters. Predictive analytics are embedded into the system to reprofile its charging, discharging and balancing behaviours after 10-20% of the cells’ expected lifetime, in order to improve the longevity of the overall pack against the usage characteristics up to that point. The pack is designed to a nominal 800 V (ranging from around 900 V at a high SoC down to roughly 550 V at low SoCs) to match charging infrastructures and howWAE sees recharging stations evolving. A COTS onboard charger is extender integrated, so we’ve installed hydrogen fuel tanks where traditionally a cross-over suspension architecture would go.” Wheels Like the crash tubes, the wheels vary between versions of the EVR. For instance, the skateboard has been displayed with carbon rimwheels, for their aesthetic qualities. “We know we’re going to be selling these cars at six- figure prices and above, so the styling and perceived value of these products becomes important from a design perspective,” McCaw says. “However, some drivers will want to take their sports EVs out to tracks, and they’ll want the rolling mass to be as light as possible. Some magnesiumwheels also offer good weight efficiency.” In addition to wheel and rimmaterials, the size of the wheel is also likely to vary, with a major consideration during development having been the size of the smallest wheel that WAE would be willing to offer on the EVR. Track- focused hypercar drivers for instance will probably not care for the 21-23 in rims that auto stylists insist on pushing; they will more often opt for smaller wheels, which then places constraints on the braking package, especially with regard to the discs at the front. “Obviously, at this level of technology, CCM-R discs [carbon ceramic material brakes produced originally for the racing market] with six-pot calipers are what’s expected, and that will mean that going anywhere below 19 in wheels will become very challenging,” McCaw says. Pack-to-body battery The EVR’s battery pack is built around 21700 lithium-ion cylindrical cells, as well as a module design supplied by Hyperbat that WAE has tested and validated in-house. “It’s a semi- structural module carrier inside the pack, with a composite housing around the pack, and that all creates a very rigid structure for the battery which ties into the composite tub and the rear metal structure,” McCaw says. “By using the pack as a semi- structural member – or in a ‘pack- to-body’ configuration as we call it sometimes – we avoid the weight of a dedicated metallic pack housing.” WAE also anticipates that using 21700 cylindrical cells will help it avoid major changes to its manufacturing and integration lines in the future, given that this form factor is widely expected to remain a standard for many years to come. The exact cathode and anode chemistries remain undisclosed, although WAE describes the cell as a new one supplied by an organisation with whom the company collaborates. “We provide themwith forecasts of what the EV market is likely to The battery pack’s cooling plates and passages feature valves that can be actuated to alter the direction and routes of liquid coolant