Design of The Ohio State University Electric Race Car

The aim of this paper is to document a three year process of product development of the Formula Lightning_tm electric race car constructed at the Ohio State University. Today interest in electric vehicles (EV's) is growing, due to the technological advances in recent years, but also in part due to recent legislation which mandates the introduction of ‘zero emission vehicles’ in California before the end of the century. The definition of ‘zero emission vehicle’ is: a vehicle which does not emit any pollutants during operation. Technologically, the only near term vehicle which meets this definition is an EV. One of the most difficult problems of electric racing is that the usable energy in a given set of batteries is not as easily determined as the amount of fuel in a tank. Also, the motor controllers may limit power output as battery voltage drops, further decreasing the amount of usable energy in a battery set. Batteries have energy capacity which is a function of battery state of charge, time and battery life. This complex relationship makes the state of charge (SOC) of the battery pack a very difficult quantity to measure. In a vehicle, as the energy in the batteries is depleted, the battery bus voltage decreases to the controller minimum voltage. Determining the usable amount of energy in a given battery set is contingent upon knowing the history of the batteries, current draw, and a reasonable model of the batteries' charge and discharge characteristics. The energy storage problem is one of many which were overcome during the development of this vehicle. Many existing mature technologies, such as a manual transmission, were investigated as potential solutions to the new problems of electric vehicle development. A systems approach was taken to develop the vehicle as a set of coexisting subsystems. The success of the vehicle is a testament to the integration of these separate battery, motor, and mechanical systems.