A data storage device and a method for operating the data storage device are disclosed. The data storage device may include an interface receiving a command and data from a host, a cache temporarily storing the received data, a memory non-temporarily storing the data stored in the cache, and a controller controlling the memory and the cache based on the command received from the host. The command may include charge rate of a battery supplying a power to the data storage device. The controller may determine whether or not the data storage device is an idle state, and determine an active operation mode of the data storage device based on the charge rate of the battery, when the data storage device is the idle state.