Int. J. of Thermal & Environmental Engineering Volume 7, No. 1 (2014) 17-24 * Corresponding author. E-mail: hattia@aurak.ae © 2014 International Association for Sharing Knowledge and Sustainability DOI: 10.5383/ijtee.07.01.003 17 Portable Solar Charger with Controlled Charging Current for Mobile Phone Devices Hussain A. Attia*, Beza Negash Getu, Hasan Ghadban, Ahmed K. Abu Mustafa Electronics and Communications Engineering Department, American University of Ras Al Khaimah, UAE Abstract In this paper, we design, construct as well as test and analyze an electronic circuit that can be used as a solar portable charger for mobile phone devices using the solar energy as a source of electric power. A suitable small size solar cell panel is selected that is easy to carry to any locations farther from city electric grids. The alternative use of the solar energy as power source is helpful in outdoor emergency situations and avoids the traditional way of waiting beside an electrical sockets or outlets for charging. We suggest here a special electronic design and construction with an important merit related to controlling battery charging currents. Software verification and simulations, laboratory experiments on the circuit, practical testing to the charging capabilities; all these are discussed in this paper. Keywords: Solar power; photovoltaic; solar panel; mobile phone; portable charger; mobile battery; charging current 1. Introduction Recently various types of chargers that utilize the solar energy as a source of power are emerging. They might have variations in their design, construction, time and cost of work and the type of components used in the prototypes but their overall purpose is charging cell phone or other wireless devices [1]-[5]. However, they have differences in their merits that motivate us to present a new design with special merit related to controlling the battery charging current. The charging circuits are used to charge Lead Acid, NiCd or other types of batteries. The circuits harvest solar energy to charge rechargeable batteries for various applications. The electronic circuits often use solar panels consisting of few or several solar cells, standard voltage regulator integrated circuits (IC) chips, transistors, Zener diodes, diodes and resistors all of them used to regulate the output voltage and charging currents. Through our research, we have made special attention to the design specifications for the circuits designed previously. The first design in [2] was made from an IC and it completely depends on Maximum Power Point Tracking (MPPT) algorithm to deliver the charging power of a mobile battery. Other design in [3] represents a solar charger for battery 3.7 V @ 2000mAh, the design and construction again depends on integrated circuits as a main part of the controlling circuit. The circuit diagram for a project presented by Colin Mitchell in 2005 [4] showed a solar charger. The problem faced by this circuit is due to the output levels (the output current is 15 mA) whereas the necessary minimum current for charging battery is often 75 mA although it has an output voltage of 5 Volts. Other design in [5] is a shunt-mode charge controlled solar charger. This circuit has been used to prevent the battery from overcharging and this procedure is done by interrupting the flow of current by the charge controller when the battery reaches full voltage. Due to the high voltage output which is 18 Volts and the greater number of solar cells (36 cells), it may be difficult to adopt this design for a mobile phone charger. Here, we investigate a complete design and construction for an electronic circuit that will be used for charging mobile devices. This paper starts with description of the original designed circuit and it’s components in Section II. In Section III, a complete analysis to the presented design will be given. The experimental work and the practical testing results to the constructed circuit will be explained in Section IV. The paper concludes with the explanation of the important merits of our design in Section V.