CONTRUCTION OF BATTERY CHARGE CONTROL FOR PHOTOVOLTAIC SYSTEMS
Background of the study
A charge controller is an essential part of any alternative energy system. In its simplest form, a charge controller’s job is to make sure the power (such as a solar panel) ‘plays nice’ with the load (such as a battery). The simplest implementation of this is a single diode placed in between a solar panel and battery. This ensures that the battery does not discharge into solar panel at night. A more sophisticated implementation will be adding the ability for the charge controller to disconnect the solar panel when the batteries are fully charged in order to prevent over-charging damage to the batteries (James and Dunlop, 1991).
The current version of the open source free charge controller is a converter for charging batteries, A bulk converter steps down voltage from a higher voltage level to a lower voltage level. In this case, it would step voltage down from the 18volts of a solar panel to the 12volts of a battery (Harrington and Dunlop, 1992). Since the converter is software controlled, it can be programmed to charge any battery chemistry, change it drive frequency to achieve maximum conversion efficiency as well as implement MPPT to allow a solar panel to deliver maximum power, all without any changes to hardware (Robert and Isaac, 2007). A charge controller also called charge regulator or battery regulator limits the rate at which electric current is added to or drawn from electric batteries. It prevents over charging and may prevent over voltage, which can reduce battery performance or life span, or may pose a safety risk. It may also prevent completely draining (deep discharging) a battery, or perform controlled discharges, depending on the battery technology, to protect battery life.
The term charge controller or charge regulator may refer to either a stand-alone device, or control circuitry integrated within a battery pack, battery-power device, or recharger (Dunlop, 1991; Harrington and Dunlop, 1992).
