Photovoltaic system generates electricity by the direct conversion of the sun's energy and it is a modular system because it is built out of several pieces of elements. The theoretical studies of PV and modeling techniques using equivalent electric circuits carried out and the characteristics of PV cell have been investigated. The new model of PV implemented in pspice program, the optimum voltage was (17volt) and optimum current was (4.41Ampere). This model is used in the DC-DC converter which has the following characteristics, the variable output voltage is (1.5V-12V), switching frequency (20 kHz), duty cycle (0.1- 0.7) and the output power (1W- 41.6W), the system has been design and tested by pspice program. The application of PV and battery implement in the DC-DC converter, the results of the converter simulation obtained from both two input show a good agreement.