Characterization of LiFePO4 cells for Formula SAE’s driverless vehicle using climate tests

One of the most crucial aspects in driverless vehicles is represented by the electric actuators that move steering wheel and brake pedal. These motors require an amount of power that the classic 12 V automotive battery can’t usually supply. For this reason, this work aims at studying a high-performance, safe, and compact battery pack for a driverless Formula SAE vehicle developed by the Firenze Race Team (FRT). The chemistry chosen for the battery cells is LiFePO4 because is considered one of the safest solutions in case of overheating, high discharge current and thus high temperature conditions. The latter scenario is extremely common in Formula SAE vehicles because of the high speed at which actuators must operate. In this work, a temperature-based characterization of the single cells composing the battery pack has been performed to validate the performances of the proposed energy storage solution. The tests involve constant current charge and discharge profile at different operating temperatures. Furthermore, Electrochemical Impedance Spectroscopy (EIS) measurements have been taken for every cell for the sake of a thorough characterization. The results provide a preliminary analysis useful to predict the battery behaviour during the Formula SAE race.