The effect of tire pressure on battery and brake performance in electric vehicles

In this thesis study, the effects of tire pressure levels on braking performance and battery energy consumption were experimentally investigated in electric vehicles equipped with a Tire Pressure Monitoring System (TPMS). The research covers tests performed at different tire pressures (20 psi, 25 psi, 28 psi, 30 psi, 32 psi, 35 psi). The experimental work was conducted on an L7e-class four-wheeled electric vehicle in accordance with the (EU) 168/2013 and (EU) 134/2014 regulations. Braking performance tests were performed on dry, wet, and thermally damped brake conditions in compliance with ECE R78 regulation, while battery energy consumption tests were conducted in accordance with Annex 7 of (EU) 134/2014. Braking distance and Mean Fully Developed Deceleration (MFDD) values were measured using a VBOX Sport data acquisition system, while tire pressures were continuously monitored through TPMS. The test results revealed that a tire pressure of 28 psi provided the best overall performance in terms of both braking and energy efficiency. In dry and wet braking tests, the 28 psi setting resulted in the shortest stopping distance and the highest deceleration values. In the thermally damped brake tests, all pressure levels met the regulatory requirements, yet 28 psi maintained the most stable braking performance. In the battery consumption tests, the 28 psi pressure resulted in the lowest energy usage due to reduced rolling resistance. In conclusion, a nominal tire pressure of 28 psi was determined to be the optimum value for ensuring both safe braking and energy efficiency in electric vehicles. The contribution of TPMS in maintaining this value is critical for driving safety and battery life.