This paper describes the improvement of originally proposed solar-cell circuit model applicable to more various different size solar panels including for home solar power generation system. Optimization of resistor values and transistor model selection of the equivalent circuit enables application to larger solar-cells which generate higher voltage and higher current. This circuit model is useful for total circuit simulation of electric system whose power is supplied by solar cells. Especially, it is useful for MPPT (Maximum Power Point Tracking) design to extract maximum solar electric power. Using these equivalent circuits connected to step-up converter or SEPIC(Single Ended Primary Inductance Converter) type step-up/down converter, maximum power point operation of solar-cells can be designed by circuit simulation.