Achieving Controlled and Efficient Storage Power Replenishing in a Solar Energy System

Abstract

In a solar energy system, the stored power is replenished via charging. It is important that the process be controlled, as overcharging can be destructive to the battery. To do this, a charge controller is required. It is an electronic device used to transfer the electrical energy available from a solar panel to the battery, allowing current to flow from the panel to the battery when it is not fully charged while disconnecting the battery from the solar panel when it reaches a preset threshold value, thus, maintaining the battery voltage at a level suitable to keep the battery in full charge state. Most charge controllers are imported. In this paper, a charge controller is developed locally for the purpose of controlling the charging activity of the battery in the solar energy system. It incorporates a PIC16F72 microcontroller, the system’s brain and also manager of its operation. The charge state of the battery is determined by converting the taken analog samples of the battery voltage into digital values. Current flow is allowed into the battery under charge from the solar panel, this leads to a steady increase in voltage across the battery until it reaches an upper threshold value set in the source code embedded in the microcontroller. A MOSFET was used as the switching device in the controller and the microcontroller displays the battery voltage on a liquid crystal display. The circuit was tested using simulation software and the results were excellent. A prototype was constructed using a bread board and tested, thereafter the circuit was transferred to a printed circuit board layout.