Design And Implementation Of A Solar Battery Charger

Recent technological developments in thin-film photovoltaics (PVs), such as amorphous silicon and hybrid dye sensitized/PV cells, are leading to new generations of portable solar arrays. These new arrays are lightweight, durable, flexible, and have been reported to achieve power efficiencies of up to 10%. Since the emergence of these flexible and foldable solar arrays, there has become a need to develop solar battery chargers for more portable batteries, such as Nickel metal hydride (NiMH) and Lithium-ion (Li-ion) batteries for military and consumer applications. This paper describes the development of a solar battery charger for Li-ion batteries. Two electrical engineering technology undergraduate students formed a senior design project team to design and implement a solar battery charger. A senior design project is an integral part of the undergraduate engineering technology degree program requirements at Northern Illinois University. All students are required to complete a two-semester long (4 credit hours) senior design project. Charging a battery requires a regulated dc voltage. However, the voltage supplied by a solar panel can vary significantly depending upon the day, time, weather condition and irradiation from the sun. In order to charge the battery with a regulated voltage, a dc-dc converter is connected between the solar panel and the battery. The main components in the solar battery charger are standard Photovoltaic solar panels (PV), a deep cycle rechargeable battery, a SingleEnded Primary Inductance Converter (SEPIC) converter and a controller. Different types of rechargeable battery were considered including lead acid, Nickel Cadmium (NiCd), Nickel metal hydride (NiMH) and Lithium ion (Li-ion) batteries. Among these batteries, Li-ion batteries have the highest energy density and relatively low self-discharge rates and no memory effect. A BB2588 Li-ion battery from Bren-Tronics, Inc is used for this project. The SEPIC converter is a type of dc-dc converter that is able to convert unregulated input voltage into either a higher or lower output voltage. This allows the solar panel to charge the battery with a wider range of output voltage, thus flexibility is increased. Experimental results of the solar battery charger are evaluated.