ELECTRIC VEHICLE 2.0

BEHIND THE SECOND WAVE OF WE INVESTIGATE THE TECHNOLOGY COMBUSTION EVS SET TO CHALLENGE THE INTERNAL- ESTABLISHMENT LIKE NEVER BEFORE

AS automotive historians will know, electric-vehicle (EV) technology dates back to the dawn of the automobile age and only power and range limitations saw electric vehicles lose favour to those equipped with an internalcombustion engine (ICE). EVS remained a fringe tech until the development of power-dense lithium-ion battery packs over the last decade began to make electric propulsion a realistic prospect.

From 2010, the race to bring EVS into mass production intensi ed, with even a South African company, Optimal Energy, entering the fray with its Joule. Unfortunately, many start-ups foundered along the way, including that local one, and it was only the big automotive brands such as Nissan (with its Leaf) and BMW (i3) that were successful with their rst wave of ground-breaking vehicles. Because of their size and range limitations, however, they have remained predominantly city cars.

California based start-up, Tesla, should therefore be applauded for pioneering uncompromised, full-electric luxury cars from as early as 2012 with the Model S. The rm has been so successful that major automotive rms have had to take note. One such OEM is Jaguar, which recently launched its I-pace EV. I attended the launch in Portugal ( nd out how it drives on page 100) and spent some time with vehicle-engineering manager, David Shaw, to understand the leap in technology that enabled this second generation of electric luxury cars.

While the first Nissan Leaf was built on an adapted conventional chassis, it was the BMW i3, designed from the ground up as an EV, which first featured a radically different platform. Still, the i3 is a city car and the luxury-car segment has very different requirements, including a longer wheelbase for more interior space, and a more elegant and sporty persona.

Achieving the I-pace’s shape was therefore equally driven by engineering and styling requirements. Its heavy battery pack is located centrally below the occupants, giving it a low centre of gravity that aids handling and results in a high body torsional rigidity of 36 knm/ degree. With a compact drivetrain on each axle, the wheelbase could be stretched to 2 990 mm (an F-pace’s wheelbase is 2 874 mm), allowing for increased interior space while having an overall length of only 4 682 mm, only 12 mm longer than the XE midsize sedan. The result is a compact luxury vehicle with more interior space than larger competitors and there is even a small luggage space under the bonnet (27 litres) to complement the large boot (656 litres).

Battery technology – specifically issues of cost, mass and energy density – has had the largest influence on the prospects of a luxury EV making it into production. In the case of the I-pace, Jaguar decided on pouch lithium-ion cells. This complicates packaging because the cell dimensions change slightly with variations in temperature and electrical load. To keep the battery pack rattle-free while allowing slight cell movement meant applying a special coating to the outside of the cells where they touch.

Another big challenge is the battery pack’s thermal management. With an optimum operating range between 20 and 28 degrees Celsius, you need liquid cooling and heating to maintain these parameters. Extreme climates pose a severe risk to the battery pack and the thermal-management system stays active when the vehicle is parked to monitor the cell temperatures. According to Shaw, the batteries’ large mass (thermal inertia), as well as their isolation from the environment, allows the vehicle to be parked for extended periods in extreme temperatures before the thermal management needs to start protecting the cells.

During charging, the battery-control module has to balance the charge in each cell. It uses resistors to dispose of small amounts of excess energy in order to limit the state of charge of “overachieving” cells during the closing stages of the charging process.

The I-pace’s battery pack won’t accept any further charge when it is at 100% and the system shuts down regenerative braking through the electric motors, forcing the driver to employ the mechanical brakes.