A battery device is provided. The battery device includes: a battery module, a protection device, a battery management circuit, and a battery protection circuit. The battery module includes one or more battery cells. The battery management circuit is for managing the protection device and charging and discharging of the battery module. When the battery device is in a charging mode, the battery protection circuit periodically checks and calculates a direct current internal resistance (DCIR) of the battery module, and determines a current operation temperature of the battery module and a temperature range corresponding to the current operation temperature. When the battery protection circuit determines that the DCIR is greater than a predetermined multiple of a first threshold corresponding to the temperature range, the battery protection circuit informs the battery management circuit to cut off the protection device.