Abstract: A non-aqueous electrolyte secondary battery system includes a non-aqueous electrolyte secondary battery and a charging control system which has a function of detecting the voltage of the non-aqueous electrolyte secondary battery and disconnecting a charging circuit. The non-aqueous electrolytic solution contains a non-aqueous solvent having a viscosity of 0.6 cP or less at 25° C. in an amount of 35 to 80 vol % inclusive as a non-aqueous solvent and also contains hexamethylene diisocyanate, and the charging control system stops charging when the potential of the positive electrode of the non-aqueous electrolyte secondary battery is 4.35 to 4.6 V inclusive based on lithium. Thus the non-aqueous electrolyte secondary battery system equipped with the non-aqueous electrolyte secondary battery having high charging potential and excellent high-temperature cycling characteristics can be provided.