Technology in Formula E

* since season 8 (2021/22) - before 200 / 235 kW

The lithium-ion battery from Williams Advanced Engineering (WAE) weighs around 284 kilograms and is located in the rear of the car and can store up to 51 kWh of energy. However, a certain amount of energy is intended for the "zero laps" before and after the race (known as outlap & inlap) and as an emergency reserve, which is why the drivers actually only have 40 kWh available during the race. This corresponds to the capacity of around 500 laptops or 6,500 smartphone batteries.

In seasons 1 to 4 (2014 to 2018), Formula E already relied on a unit battery from Williams Advanced Engineering (WAE) with 28 kWh of usable energy. This, however, this did not provide enough energy for a full race distance. Therefore, towards the middle of the race, drivers had to switch to a second car with a fully charged battery after just over 20 minutes. With the introduction of the second generation of cars at the start of the 2018/19 season, which had a battery from McLaren Advanced Technologies (MAT), these pit stops became obsolete. The drivers had 52 kWh of energy at their disposal. However, this battery was more than 100 kg heavier than its successor.

Since the battery operates in a comparatively small temperature window, it has to be cooled constantly. In racing trim, the airstream is sufficient for this. In the garage, however, the mechanics have to install air pumps and containers with dry ice in front of the side box. The radiator in the right-hand side box cools the battery, its counterpart on the left-hand side the electric motor.

The drivetrain - consisting of the motor, gearbox, and inverter - is the only area of the Formula E car in which manufacturers are allowed to develop freely, alongside the rear suspension and software.

While the battery can only output direct current, the mostly three-phase AC electric motors require a very precisely frequency-tuned alternating current input to convert the available energy into power and transmit it to the drive axle through the gearbox. The manufacturers are allowed to determine the number of gears themselves. The inverter is responsible for converting the energy and creating this voltage profile as the centerpiece between the battery and electric motor.

The driver can choose from various power settings via a rotary control on the steering wheel. For example, there are settings for the shakedown (max. 130 kW), qualifying (max. 350 kW), the race (max. 300 kW - formerly 220), or the attack mode (350 kW - formerly 235).

During recuperation, the energy recovery during "coasting" and braking, the drivetrain can operate in the opposite direction: Drive axle >>> motor >>> inverter >>> battery. Up to 600 kW can be recuperated (350 kW on the rear axle, 250 with the standardized front motor). The recovery process in the braking zones through "lift and coast" is one of the most complex tasks for drivers during a Formula E race, although they have been supported by the vehicle's software since 2018 with the "brake-by-wire" system. With good recuperation work during the race, a driver can extend the range of their battery by almost 20 percent.

With the exception of the powertrain (motor, gearbox, inverter, and rear suspension) and the control electronics, there is a general development ban in Formula E. For cost reasons, no work can be done on any other vehicle parts in the foreseeable future.

A few months before the start of a new season, the powertrains are homologated by the FIA. Once a manufacturer passes the mandatory crash tests, which must meet the standards of Formula 1, they may no longer make any changes to the hardware of the vehicles. Only software adaptations are still possible afterwards. The software is continuously developed throughout the season.

In order to save costs, all powertrains are homologated on a two-season cycle in Formula E. Manufacturers will thus have to use the same hardware in the 2023 and 2024 seasons.