Formula E has always been a test bed for electric vehicle innovations. Let’s look at the technology innovations happening in the latest season of this electric race.

The final two races of the fifth season take place in Red Hook in Brooklyn, NY (Figure 1). There are 22 drivers and 11 teams with electric vehicles that can accelerate from 0 to 100km/h in 2.8 seconds.

Figure 1 A view from the stands at the Formula E Red Hook racetrack in Brooklyn, NY (Image courtesy of Maria Guerra)

Here are some of the technology improvements that have been achieved during the last two seasons:

The battery

All Gen2 Formula E cars are powered by McLaren Applied Technologies batteries (previously provided by Williams Advanced Engineering). The batteries have doubled the energy storage capacity of Gen 1. Therefore Gen 2 drivers are now able to complete a full race in a single car instead of changing vehicles mid-race.

The battery currently sits inside the monocoque chassis and it uses a greater number of cylindrical battery cells. Table 1 shows a comparison of the battery specifications between the two generations ever used in Formula E:

Table 1

In this fifth season, the driver is able to use an extra hit of power using the “attack mode.” To fire up attack mode, drivers will need to arm their car, drive off the racing line, and through the activation zone. As a reward for taking a slower line through the corner, they’ll be able to collect an extra 25 kW of power. Drivers that secure the extra speed, can use it for a few laps when they want to race harder, giving them the edge to keep ahead of the competition.

The state of charge (SoC) of the battery is a substantial factor when using attack mode because the amount of torque that is used by regenerative braking system (regen) depends of different battery factors such as SoC and temperature (Figure 2).

Figure 2 McLaren’s battery charger screen (Image courtesy of Maria Guerra)

Brakes

Gen 2 cars have a new electronic brake-by-wire system that allows greater electronic control of the rear brakes, which would improve the feel for the drivers and maximize the regenerative braking system.

Glycerin generators

Every Gen 2 car is still powered by glycerin fuel generators, a 100% renewable glycerin fuel. The generators are based on standard production diesel engines – a Cummins KTA50 to be precise – that have been adapted with Aquafuel Research’s patented technology to run on glycerin.

Powertrain

Each team can develop their own powertrain and that is where most of the innovation happens. Maximizing the efficiency of certain components (e.g. the inverter, the motor, etc.) can make the difference between winning or losing.

“In the case of the Venturi team, the powertrain has been made by a collaboration between ZF and Rohm (Figure 3). For the fifth season, ZF is providing the Inverter but Rohm components are still used inside this inverter (e.g. SiC modules). This inverter is now located as low as possible inside the back end of the car (near to the e-motor),” said Venturi’s powertrain designer Louis-Marie Blondel.

Figure 3 The Venturi team checking the car before the race (Image courtesy of Maria Guerra)

He added, “There are two main differences between the last two generation of powertrains: power and lifetime. We have to use more power, so we had to increase our powertrain efficiency more than the previous powertrain to stay competitive. The more power you have, the more you lose if the efficiency is not good. And as we have to use the same car for all the season, the powertrain will also have to complete more mileage. We are not allowed to change powertrain during the season as we want because of FIA regulations. So, the powertrain needs also to be more reliable. If not, we have to face penalties.”

All these technological advances taking place every season will allow Formula E to help push forward the development of clean, sustainable energy.

Maria Guerra is an electrical engineer and freelance technology writer.