University of Pennsylvania Department of Electrical and Systems Engineering ABSTRACT: Solar racing has increased in popularity over the past few years due to the greater frequency of solar competitions. Most competitions are designed to be fun and promote awareness of alternative energy and new technologies. The North American Solar Challenge is a cross- country race, starting from Austin, Texas and ending in Calgary, Canada specifically aimed at college level competition. Penn Solar Racing is creating a new car to enter in the 2005 North American Solar Challenge. In order to race, each solar powered vehicle stores energy from solar cells in a battery pack and uses this energy to power a motor. This project will allow Penn Solar Racing to effectively compete against other teams in the North American Solar Challenge while minimizing cost. Minimizing cost will be accomplished by selecting appropriate batteries and solar cells and designing a battery protection system and solar array to be constructed by students. AUTHORS: Michael Ashley EE ’05 Zhenming Zhang EE ’05 ADVISOR : Professor Jay Zemel DEMO TIMES : Thursday, April 21 st, :30AM, 10AM, 10:30AM and 11:30 AM GROUP 7 Solar Car Battery Management System and Solar Array Batteries Thirteen lithium polymer batteries from Electrovaya were chosen for the solar car. Battery Protection System The battery protection system monitors the batteries used by the solar car for overvoltage, undervoltage, overtemperature and overcurrent conditions. The battery protection system is made of 13 differential amplifiers and two PIC microcontrollers, one to monitor battery voltages and current and another to monitor battery temperatures. If the battery conditions exceed desired values, the PICs disconnect the batteries from the electrical systems of the solar car. Overvoltage and Undervoltage Protection The voltage from the differential amplifiers is sent to a PIC 16F777 Microcontroller. The analog voltage of the batteries is converted to a digital value using 13 A/D converters in the PIC. Overtemperature Protection The batteries contain built in temperature sensors. The analog voltage from the temperature sensors is converted to a digital value using 13 A/D converters in the PIC. Overcurrent Protection A Hall Effect current sensor measures how much current is passing through the batteries. A 50 Amp fuse will also be used for overcurrent protection. Solar Array Five Hundred polycrystalline silicon solar cells were donated by Mitsubishi Electric to comprise the solar array. Solar Array The solar array is divided into five sections. Each section contains several smaller modules which allow cells to be wired together and placed on the car. Modules are of similar size and can be replaced during the race with spare modules if cells on the car are damaged. Differential Amplifier PCB Design Battery and Temperature Protection System PCB Design Differential Amplifier PCB Board Battery and Temperature Protection System PCB Board Solar Array Module Layout