Electric & Hybrid Vehicle Technology • July 2021 • Extreme machine

An electric racing series that pushes the boundaries of performance over the harshest terrains was going to demand a special vehicle. EHVTI talks to the engineers behind the Extreme E Odyssey 21 e-SUV

If there’s a motorsport oxymoron, a sustainable racing series is surely it. But, Extreme E is far from a traditional motorsport series. Electric SUVs race at 10-mile-long ‘X Prix’ events at five remote global locations as diverse as rainforests, deserts, the Arctic and on ocean islands, their whereabouts chosen to highlight the environmental challenges facing society. In planning for over three years before the first round erupted in a storm of dust clouds in January 2021, the unique series needed a unique racer.

The all-electric Odyssey 21 is such a car. A 557PS four-wheel-drive SUV underpinned by a niobium-reinforced steel-alloy tubular frame topped with a unique Bcomp natural flax fiber composite body, it is capable of 0-62mph in 4.5 seconds. Built by Spark Racing Technology (SRT) who is responsible for the Gen1 and Gen2 Formula E race cars, the common specification is shared between competitors and allows for individual team powertrain and body development.

Each SUV takes a week to build and it will come as no surprise that such a demanding series necessitates components far removed from a road car. “The electric powertrain components are 100% different,” states Nicolas Wertans, SRT chairman. “All the components are bespoke for racing purposes and the more extreme conditions.”

In addition to the infrastructure carbon savings, instead of flying the racers to the X Prix locations, Extreme E loads them onto the RMS Saint Helena to cut transport emissions. The ex- Royal Mail cargo vessel serves as a mobile paddock, with an on-board laboratory for scientists to conduct environmental work in the regions the series visits. It might be diesel-powered, but the ship still saves two-thirds of the emissions generated by flying.

Designed by Williams Advanced Engineering (WAE), the mid-mounted lithium-ion battery has 3,600 cells and delivers a maximum power of 400kW. The identical 54kWh batteries – with 40kWh of usable energy – employ 800V technology, and the battery management system runs WAE hardware and software. A massive 920Nm of torque can be balanced between the dual 250kW front and rear electric motors at the push of a button, allowing drivers to maximize energy efficiency to the wheels.

“Simplicity, serviceability, and modularity were key features,” reports Glen Pascoe, principal engineer at Williams Advanced Engineering. “Commercially available cells were designed into a pack to align with both the race format and the vehicle performance duty cycle. Working with limited space in the car, we had to meet very tough power and mass performance targets to deliver a bespoke battery pack design in under 12 months. The stored energy figure is a consequence of the race duty cycle and the peak power demand required, balanced against the usual targets relating to cost, mass, and complexity,” he explains.

“Although the cells are used in automotive applications, they’re not actively cooled on this vehicle. Instead, they’re conditioned between vehicle runs. An air-conditioning system is connected to the rear of the vehicle and air, which is cooler than ambient conditions, is passed through the battery. To minimize mass, we reduced the number of components, and simplified several operational aspects for ease of use in remote environments.” The batteries weigh under 400kg each; the car weighs 1,650kg.

Encased in a carbon fiber composite enclosure, one crucial design element was easy access. “We’ve designed the batteries to provide easy access to components, and if servicing or replacement is required during the battery’s two-year life span, we can support that (on a road vehicle battery, we’d be working to a 10-year life span),” says Pascoe. “A dedicated field service team is trained to replace components and offer support – either on a glacier or in a jungle! An ability to lift the lid and see the major elements reduces inspection times and fault diagnosis during development, as well as build and rebuild time.”

“Intense engineering and iterations with our suppliers ensure the electric powertrain components withstand the increased race and climate punishments,” Wertans says. “Identifying specific needs early in the program has been critical,” agrees Pascoe. “We employed simulation, strict internal design standards for vibration inputs and carried out physical prototype testing on the battery pack ahead of the first vehicle run. We also carried out ingress testing using proven methods and in-house electronics component durability testing of our battery management system, cell monitoring, vehicle control module and telematics. We have an extensive design validation plan for every new WAE battery system and we carry forward the learning from our previous projects. Extreme E will benefit all future WAE projects.”

Extreme conditions present more exaggerated challenges. “High-altitudes create specific electric isolation resistance needs,” Pascoe says. “Additional challenges are dust, off-road terrains, high temperatures, humidity, jumps and vibration. We also had to develop dedicated interconnects for the motors, individually mated to the battery, to allow the vehicle to run on a single powertrain if required.”

“Compared to an electric production vehicle, the biggest difference was the tougher shock and vibration profiles, which we addressed by rigorous physical test programs. We also carried out more battery level testing ahead of vehicle level tests, similar to those of an electric production vehicle.”

The exaggerated requirements are more unusual than other motorsport disciplines – as such the car’s suspension has 385mm of wheel travel and has to cope with gradients of up to 130% – but WAE is used to dealing with harsher conditions.

“There were no obstacles that we were not already familiar with,” reports Pascoe. “However, the environments and the logistics of test and race events provided additional challenges. General lack of Wi-Fi in remote locations means battery experts travel to the tests and work independently from our HQ team. This placed increased emphasis on quick decisions and diagnosis at test events by the team on the ground and follow-up learning from the factory support for the next test. New travel experiences for the team as well as planning early to deliver freight ready for sea travel and undertaking test events held with international Covid-19 restrictions also had to be dealt with.”

The remote locations Extreme E visits present recharging and power issues, but it also has a zero-emission solution for this. Harnessing solar and water power, hydrogen fuel cell generators provided by AFC Energy pump clean energy into the electric SUVs off the grid. The bespoke ‘H-Power’ system has been created especially for the series, powering rapid Vital EV Solutions and Kempower DC T800-series mobile chargers. According to Extreme E, the combined use of battery storage and zero-emission car charging provide more than a 95% reduction in carbon emissions. It is working with Allcot to off set the series’ carbon footprint, aiming to achieve net-zero by the end of its first season. A second-life electric bus battery from Zenobe runs the utility power for the broadcast, race and event control and the media center.

“Huge torque, power and very demanding duty cycles compared with other motorsport electric vehicles testing regimes created challenges,” Wertans says. “Our challenge was to build a car that could face all the variations in surface and terrain that will be thrown its way,” states Théophile Gouzin, SRT technical director. “The torque and power density from the powertrain is a breakthrough: we’re getting huge figures from a small package, which means lighter weight, space savings and improved weight distribution. This innovation is transferable from race-car to road – ultimately benefiting the consumer and the sustainable mobility cause.”