The option to disconnect from the utility company using a renewable energy system (e.g. photovoltaic system), is known as “Off-grid”. In this type of system, the use of electric power depends a 100% on photovoltaic batteries to operate. These batteries will be charged by the photovoltaic modules during sunny days. The charge controller protects the batteries against overcharging and over-discharging by controlling the flow of current from the photovoltaic modules to the batteries. The design of an “Off-grid” photovoltaic system is different from that of an interconnected system since all the electrical equipment that is fed from the batteries has to be accounted for in order to correctly choose the capacity and the total number of batteries and corresponding components.