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Solar Car Battery Management System and Solar Array
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 crosscountry 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
Batteries
Thirteen lithium polymer batteries from Electrovaya were chosen for the solar car.
Battery and Temperature Protection
System PCB Design
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.
Differential Amplifier PCB Design
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.
Battery and Temperature Protection
System PCB Board
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.
Zhenming Zhang EE ’05
ADVISOR:
Professor Jay Zemel
DEMO TIMES:
Thursday, April 21st, 2005
9:30AM, 10AM, 10:30AM and
11:30 AM
GROUP 7
Solar Array Module Layout
Differential Amplifier PCB Board