Rechargeable battery system

A rechargeable battery system that controls charge/discharge of a lithium ion rechargeable battery, includes: an internal resistance detection means that detects or estimates an internal resistance value indicating an internal resistance at the lithium ion rechargeable battery; and a discharge control means that executes control so as to set a discharge suspension period while the lithium ion rechargeable battery is discharged if the internal resistance value detected via the internal resistance detection means during discharge of the lithium ion rechargeable battery exceeds a first threshold value.