Fraunhofer Institute research scientists use an electric racing car to present novel solutions for battery management and electronic sensor systems, together with an industry partner.

EVE, a racing car with a very quiet engine, goes from 0 to 100 in 3.6 seconds. EVE is powered by two electric motors, one for each rear wheel. With a maximum output of 60 kilowatts, the e-racer gets going at 4500 rotations per minute. The sprinter can reach a top speed of 140 km/h, and has a range of 22 km thanks to two lithium polymer batteries, with a combined capacity of 8 kWh.

Electrical engineering students from the e-racing team at the Hochschule Esslingen University of Applied Sciences designed the 300-kg car, and they have already competed in it at the international Formula Student Electric (FSE) race in Italy. Scientists from the Fraunhofer Institute for Integrated Circuits IIS in Erlangen developed the entire electronic sensor system in close collaboration with Seuffer GmbH & Co.KG, an industry partner.

Besides wheels, brakes, damper unit, batteries, and electric motors, EVE is equipped with numerous sensors. These include braking pressure, crash, temperature and acceleration sensors as well as sensors that monitor the accelerator and brake pedals, speed, steering angle, wheel speed and power. These last six functions could all be performed by HallinOne® sensors developed by Fraunhofer IIS, 3D magnetic-field sensors that are already a standard feature in washing machines, where they are used to determine the position and orientation of the drum.

The two electronic sensors attached at the sides of the batteries use 3D magnetic-field sensor technology developed by Fraunhofer IIS to measure the magnetic field generated by the flow of electrical current and thus to determine the battery’s level of charge. What’s special about this is that the contactless sensors measure both the current that flows from the battery to the engine and the current that flows back again when the vehicle brakes. The integrated sensor system is able to eliminate disturbances and foreign magnetic fields, thus guaranteeing very precise measurements. A further advantage is that the system is also able to measure other aspects of the battery such as its voltage and temperature. The data is collected and sent to the power control unit (PCU) and the battery management system (BMS), which controls the charging and discharging processes.

Battery running times and battery life are limiting factors for all electric vehicles. The BMS tackles this problem by determining the impedance spectrum of all battery cells and constantly testing whether the cells are functioning properly. This allows cells’ condition, current capacity and potential service life to be ascertained and running times to be predicted more accurately.