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

May/June 2023 | E-Mobility Engineering 29 Dossier | WAE EVR separate motors and inverters, and evaluated the packaging implications of that type of integration, and we have also investigated fully integrated motor- inverter solutions.” At the time of writing, the powertrain on the baseline EVRwas a fully integrated package with two inverters and two motors – one pairing for each rear-wheel drive. This gives fully independent torque vectoring to both the rear-left and rear- right wheels, althoughWAE is happy to integrate all-wheel drive on request thanks to the space available in the front of the chassis. DC power passes from the battery to the large, cylindrical enclosure on the back of the vehicle, and within that housing the three-phase current is able to run from the inverters to the motors via busbars, without the need for cabling (and hence without any of the weight, copper losses or potential points of failure that these could represent). “It also saves us the complexity and weight of all the additional HV connectors that separate inverter- motor installations need,” McCaw says. “Right now, with the standard EVR, there are four silver connectors coming out of the back of the battery pack, which enable a DC supply from either side of the battery pack – two from the left and two from the right.” installed at the back, although many users are in fact expected to decline the mass and complexity of AC-DC onboard chargers and opt for fast DC charging instead, or to use a comparatively lighter 400-800 V DC-DC for slower DC charging stations, as many EVs in future are expected to integrate this type of converter as standard. “In fact, at present the modules are assembled together in what we call a split-pack architecture, which allows us to cut this 800 V pack in half when we’re charging, so it becomes two 400 V packs linked in parallel,” McCaw explains. “That allows us to charge at 400 V without needing a 400-800 V DC-DC. That’s going to be a critical battery r&d route for us, because there’s an industry-wide problem of compatibility between charging stations. “It’s not like IC-engined cars, where you know every petrol nozzle is going to fit; there needs to be compatibility and communication between the vehicle and the charger, and making that possible on a global scale is something OEMs are struggling with. Fortunately, some test facilities in Europe are installing what are effectively banks of charging stations from all the suppliers they can, so that when big OEMs or smaller teams like ours turn up, there are about 15-20 different chargers for us to test compatibility with.” Battery thermal management A standardwater-glycol system is used to cool the EVR’s packs, rather than immersion cooling or the dielectrics that would entail. AlthoughWAE has plenty of experience in immersion cooling, it opted for thismore tried and tested thermal management approach that had been validatedwith the batterymodule’s design. Modules are installed back-to-back to allow sharing of cooling plates between them, as is increasingly common in the EV world, although WAE also installs a system of valves throughout the plates and passages to change the direction and routes the coolant takes. The system also allows coolant pressure to be concentrated at different levels of the pack and modules, so that the BMS can reroute and focus cooling as necessary. For final heat exchange, radiators are likely to be installed at locations chosen for their aesthetics and aerodynamics as much as thermal efficiency. A front radiator has been shown on display versions of the EVR, but as it and other EVs typically no longer integrate a frontal IC engine, this is entirely a style point and not at all necessary. “Rather than sticking a radiator at the front and having coolant hoses running the length of the EV back to the battery pack and powertrain, it would perhaps make more sense to have multiple smaller radiators dotted around the rear of the vehicle, potentially taking air from underneath the car and from the wheel arches, saving weight and avoiding potential failure points by using very short coolant lines,” McCaw says. Integrated powertrain “As I said, we’ve gone through maybe eight different powertrain configurations, and to do that we approached a considerable number of powertrain suppliers who were offering different things,” he continues. “We’ve looked at several set-ups that had Packaging the inverters in a cylindrical shape was vital to ensuring that the motors, inverters and transmissions could all be combined in a single housing