CONTRUCTION OF BATTERY CHARGE CONTROL FOR PHOTOVOLTAIC SYSTEMS
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Photovoltaic Systems
Abstract:
This paper describes a microcontroller based charge controller using PWM (pulse width modulation) technique. This PWM technique is employed by the PIC16F877 microcontroller. The microcontroller is to charge a 12V battery using 80W solar panel. The main feature of this charge controller is dusk to dawn operation; it switches „on‟ the load (the light) at dusk (evening) and switches off at dawn (morning). During day time, the load is disconnected from the battery and the battery is to be recharged with current from the solar panel. When the battery is at full charge (14.7V), the charging current becomes “pulsed” interrupted by the PIC16F877. “Battery Full” will be displayed on the liquid crystal display (LCD). An inbuilt analog to digital converter (ADC) is used to determine voltage level of the battery and the solar panel voltage. The hardware design, software implementation, and flow chart of the program are also discussed in this paper. Keywords: Charge controller, battery, microcontroller, pulse width modulation, photovoltaic.
Introduction
As the source of conventional energy deplete day by day, resorting to alternative sources, energy like solar energy has become the need of the hour. Solar energy can be used to generate power in two-ways; solar thermal conversion and solar electric (photovoltaic) conversion. Solar thermal is employed in heating of fluids to produce steam to derive turbines for large scale centralized generation while solar electric (photovoltaic) which is considered in this paper, is the direct conversion of sunlight into electricity through photocells. Photovoltaic (PV) production becomes double every two years, increasing by an average of 48 percent each year since 2002 [2] . For this reason, it has become the world’s fastest growing energy technology.Photovoltaic Systems
A charge controller is an essential part of nearly all power systems that charge batteries, whether the power source is PV, wind, hydro e.tc [3] . A PV system consists of a PV array which converts sunlight to direct – current electricity, a control system which regulates the battery charging and operation of the load, energy storage in the form of secondary batteries and loads. A charge controller is one of the functional and reliable components of PV system.Photovoltaic Systems
The main function of a charge controller in a PV system is to keep batteries properly charged and safe for the long term, and to protect it from deep discharging [3] , without a charge controller, the battery will overcharge. Absence of charge controller in PV system results in high maintenance cost including frequent battery replacement. Hence, a charge controller is important to prevent battery overcharging excessively, over discharging, reverse current flow at night and to prolong the life of the batteries in a PV system.Photovoltaic Systems