An electrical device system having a battery pack, an electrical device, and a charging device, includes: a current detecting unit that detects a battery current flowing through the battery during a charge to or a discharge from the battery; a battery state detecting unit that detects at least one of a battery voltage and a temperature of a heat generating unit; and a determining unit that estimates an amount of change in at least one of the battery voltage and the temperature of the heat generating unit, based on the battery current, and calculates an amount of actual change in at least one of the battery voltage and the temperature of the heat generating unit, wherein the determining unit determines that the current detecting unit is abnormal, when the difference between the calculated amount of actual change and the estimated amount of change is a default value or more.