A deterioration degree determining system (100, 200) configured to determine a deterioration degree of a battery of a vehicle, the deterioration degree determining system (100, 200) comprising: a relay (21, 22, 23, 24) which is inserted into electric power pathways of the vehicle; an electric power pathway controller which is mounted on the vehicle and is configured to control electric power pathways, by turning on/off the relay (21, 22, 23, 24); a communication part (120, 220) which is mounted on the vehicle and is configured to perform data communications with a remote monitoring center external to the vehicle, the remote monitoring center monitoring the deterioration degree of the battery of the vehicle and having a database for determining deterioration degree; an electric component activating part (130, 350) which is located in the remote monitoring center and is configured to activate, via the communication part (120, 220), a non-driving series electric component of the vehicle by using electric power of the battery; a charge characteristic value obtaining part (140, 370) which is located in the remote monitoring center and is configured to obtain, via the communication part (120, 220), a charge characteristic value of the battery during a period of time in which a charge state of the battery is increased to a designated degree by charging the battery after the battery is discharged for a designated period of time by causing the electric component activating part (130, 350) to activate the non-driving series electric component, the battery being charged by electric power generated by an electric generator of the vehicle; and a deterioration degree determining part (150, 380) which is located in the remote monitoring center and is configured to determine the deterioration degree of the battery by using the database based on the charge characteristic value obtained by the charge characteristic value obtaining part (140, 370); wherein an electric power pathway controller is configured to control electric power pathways among the battery, the electric generator, the non-driving series electric component and a driving series electric component, and wherein the electric power pathway controller is configured to shut off electric power from the electric generator to the battery and the non-driving series electric component and to supply the electric power generated by the electric generator to a driving series electric component while the battery is being discharged by supplying the electric power to the non-driving series electric component which is being activated by the electric component activating part (130, 350). a relay (21, 22, 23, 24) which is inserted into electric power pathways of the vehicle; an electric power pathway controller which is mounted on the vehicle and is configured to control electric power pathways, by turning on/off the relay (21, 22, 23, 24); a communication part (120, 220) which is mounted on the vehicle and is configured to perform data communications with a remote monitoring center external to the vehicle, the remote monitoring center monitoring the deterioration degree of the battery of the vehicle and having a database for determining deterioration degree; an electric component activating part (130, 350) which is located in the remote monitoring center and is configured to activate, via the communication part (120, 220), a non-driving series electric component of the vehicle by using electric power of the battery; a charge characteristic value obtaining part (140, 370) which is located in the remote monitoring center and is configured to obtain, via the communication part (120, 220), a charge characteristic value of the battery during a period of time in which a charge state of the battery is increased to a designated degree by charging the battery after the battery is discharged for a designated period of time by causing the electric component activating part (130, 350) to activate the non-driving series electric component, the battery being charged by electric power generated by an electric generator of the vehicle; and a deterioration degree determining part (150, 380) which is located in the remote monitoring center and is configured to determine the deterioration degree of the battery by using the database based on the charge characteristic value obtained by the charge characteristic value obtaining part (140, 370); wherein an electric power pathway controller is configured to control electric power pathways among the battery, the electric generator, the non-driving series electric component and a driving series electric component, and wherein the electric power pathway controller is configured to shut off electric power from the electric generator to the battery and the non-driving series electric component and to supply the electric power generated by the electric generator to a driving series electric component while the battery is being discharged by supplying the electric power to the non-driving series electric component which is being activated by the electric component activating part (130, 350).