【正文】 quired. In the method disclosed in Patent Document 1,the output voltage and the voltage set value are pared with each other by a discharge time and discharge state of the battery is detected by the magnitude relation there between to control the operation of the ,when the power supply capacity of the battery power source is low,the power supply capacity will be lost,thereby stopping the power supply from the this case,because charging of the battery power source is started after the interruptible power source returns ,and the rescue operation is conducted upon pletion of the charging,the elevator cannot be carried to the nearest floor to perform rescue operation in the case of an abnormal situation of the interruptible power a result,the passengers remain trapped in the elevator. Moreover,when the interruptible power source is stopped due to disaster like as in the hybrid elevator,it is necessary for the backup power source to ensure the minimum power supply capacity for enabling minimum operation. Consequently,because a margin bees necessary in the capacity of the backup power source,a large power accumulator is necessary. In addition,the minimum voltage used for calculating the power supply capacity has a margin,in view of the life , the value of the actual power supply capacity is smaller than the that of the primary power supply capacity of the power accumulator.Disclosure of invention An object of the present invention is to provide a power source system capable of realizing at least the minimum backup function ,increasing the life duration of a power accumulator,and reducing the size of the power accumulator by temporarily improving the power supply capacity of a power accumulator when an interruptible power source is stopped by disaster or the present invention also provide a power supply control method of the power source system ,a power supply control program Of the power source system and a puter readable recoding medium having power supply control program Of the power source system recoded thereon. A power source system according to an aspect of the present invention has:a power unit for supplying power to a load service。a power accumulator for supplying the power to a load service in place of the power unit when the power unit is stopped,and a controller for controlling power supply from the power accumulator to a load service。wherein the controller sets an operable voltage,which is determined as an output voltage foe ending discharge of the power accumulator,at a first voltage when the power unit is operated,and sets the operable voltage at a second voltage lower than the first voltage when the power unit is stopped ,thereby increasing the power supplied to the load device by the power accumulator. According to the power source system described above,the power supply capacity of the power accumulator can be improved by reducing the operable voltage of the power accumulator when the power unit is stopped,the operable voltage being set during the normal operation of the power ,because the operable voltage of the power accumulator is reduced after the power unit is stopped,and the number of the times that the power accumulator is overdischarged duo to the decrease in the operable voltage can be prevented from increasing.,the life duration of the power accumulator can be addition,the size of the power accumulator can be reduced because it is not necessary to increase the capacity of the power accumulator beforehand in the light of an increase in power supply when the power unit is stopped.Brief description pf the drawings[ ] is a block diagram showing a configuration of a power source system according to Embodiment 1 of the present invention.Best Mode For Carrying the invention.(Embodiment 1) is a block diagram showing a configuration of a power source system according to Embodiment 1 of the present shown in ,a power source system 10 according to the present invention has an interruptible power source 100,a load device 200,a power accumulator 300,a charge|discharge control device 400,a power supply control device 500,and an electric control unit 600. The interruptible power source 100 is ,for example ,a mercial power source,such as a generator having an engine as a source of power. The power accumulator 300 stores surplus power from the interruptible power source 100 and regenerative electric power generated by the load device 200,and supplies the stored electric power to the load device 200 according to power accumulator 300 is configured by connecting N number of electric power accumulation element blocks B1,B2,......BN in of the electric power accumulation element blocks B1,B2,......BN is configured electrically connecting a plurality of electrical storage elements 301 alkaline storage battery such as a nickel hydride battery ,an organic battery such as a lithiumion battery ,and an electrical double layer capacitor can be used as each of the electrical storage elements 301 .Note that the number N of electric power accumulation element blocks and the the number of the electrical storage elements 301 are not particularly limited. The power accumulator 300 has a predetermined range of operating voltage determined beforehand ,so that the battery characteristics,life duration and reliability of the power accumulator 300 are not voltage,which is the minimum voltage (final voltage) of this operating voltage range is the voltage for ending discharge of the power accumulator 300 .During the normal operation ,when the output voltage of the power accumulator 300 falls below the operable voltage,discharge of the power accumulator 300。namely,power supply from he power accumulator 300,is ,power supply from the power accumulator 300 is possible until the output voltage of the power accumulator 300 falls below the operable voltage。namely,by reducing the operable this case,the power accumulator 300 is overdischarged tem