A secondary battery system (200; 250), comprising: a plurality of lithium ion batteries (110; 210; 230, 240); a plurality of battery controllers (120; 220) arranged to control charge and discharge of the respective lithium ion batteries; a total controller (101; 201) arranged to control the entire system; a plurality of ammeters (112; 212) arranged to detect a charge current and a discharge current of the respective lithium ion batteries; and a plurality of voltmeters (111; 211) arranged to detect a voltage of the respective lithium ion batteries; the secondary battery system being characterized by comprising determination means arranged to obtain, for each of the lithium ion batteries after the lithium ion battery has been rested for an overnight rest period after an end of charge and discharge, direct current resistance of the lithium ion battery at a time of charge and direct current resistance of the lithium ion battery at a time of discharge on the basis of a current value and a voltage value detected by the ammeter and the voltmeter, to calculate a value of a ratio of the direct current resistance of the lithium ion battery at the time of discharge to the direct current resistance of the lithium ion battery at the time of charge, and to determine, when the calculated value decreases to be equal to or smaller than 1.05, that the condition has occurred of a temporary increase in the direct current resistance of the lithium ion battery caused by charge and discharge with a large current density; and the total controller outputs, when the determination means determines the temporary increase in the direct current resistance of the lithium ion battery, a signal for stopping a use of the lithium ion battery for at least 200 hours via its battery controller, to thereby suspend the charge and discharge of the lithium ion battery. a plurality of lithium ion batteries (110; 210; 230, 240); a plurality of battery controllers (120; 220) arranged to control charge and discharge of the respective lithium ion batteries; a total controller (101; 201) arranged to control the entire system; a plurality of ammeters (112; 212) arranged to detect a charge current and a discharge current of the respective lithium ion batteries; and a plurality of voltmeters (111; 211) arranged to detect a voltage of the respective lithium ion batteries; the secondary battery system being characterized by comprising determination means arranged to obtain, for each of the lithium ion batteries after the lithium ion battery has been rested for an overnight rest period after an end of charge and discharge, direct current resistance of the lithium ion battery at a time of charge and direct current resistance of the lithium ion battery at a time of discharge on the basis of a current value and a voltage value detected by the ammeter and the voltmeter, to calculate a value of a ratio of the direct current resistance of the lithium ion battery at the time of discharge to the direct current resistance of the lithium ion battery at the time of charge, and to determine, when the calculated value decreases to be equal to or smaller than 1.05, that the condition has occurred of a temporary increase in the direct current resistance of the lithium ion battery caused by charge and discharge with a large current density; and the total controller outputs, when the determination means determines the temporary increase in the direct current resistance of the lithium ion battery, a signal for stopping a use of the lithium ion battery for at least 200 hours via its battery controller, to thereby suspend the charge and discharge of the lithium ion battery.