POWER SUPPLY SYSTEM AND STORAGE BATTERY CHARGE CONTROL METHOD

A power supply system has: an energy conversion unit that converts natural energy to electric energy; an electricity storage unit; a supply control unit that controls supply of electric energy to the electricity storage unit; an instruction unit that stops the supply of the electric energy by the supply control unit when a terminal voltage of the electricity storage unit becomes equal to or higher than a charge-stopping voltage set in advance and starts the supply of electric energy when the terminal voltage of the electricity storage unit becomes equal to or lower than a charge-starting voltage, in order to alternately repeat a charge period during which the electric energy is supplied to the electricity storage unit and a suspension period during which the supply of the electric energy to the electricity storage unit is stopped; and an information acquisition unit that acquires, as charge information, a charge electric quantity charged to the electricity storage unit during each of the charge periods, wherein the instruction unit causes the supply control unit to supply the electric energy to the electricity storage unit during a charge-continuation period which starts from a force-in start timing based on a timing when charge information satisfies a judgment condition set in advance and which expires upon elapse of a charge-continuation time set in advance.