A battery pack comprising: a plurality of series connection units forming a series connection, each of the plurality of series connection units comprising a plurality of battery cells , wherein the plurality of battery cells in each of the plurality of series connection units are connected in parallel; a voltage detecting module configured to detect a voltage signal of a high-voltage side of each of the plurality of series connection units; a battery control module configured to receive the voltage signal detected by the voltage detecting module and determine a voltage of each of the plurality of series connection units; a disconnection detecting module configured to determine whether the plurality of battery cells in each of the plurality of series connection units has been disconnected based on the voltage of each of the plurality of series connection units, the disconnection detecting module comprising a time calculating means for providing time data; and a determining means configured to determine whether said plurality of battery cells in each of said plurality of series connection units has been disconnected; the battery pack having an output voltage of at least 56 V; and the disconnection detecting module comprising: - a slope calculation means configured to determine a slope of the voltage of each of the plurality of series connection units relative to the time data; and - wherein said determining means is configured to determine whether the plurality of battery cells in each of the plurality of series connection units has been disconnected based on said slope of the voltage of each of the plurality of series connection units relative to said time data. a plurality of series connection units forming a series connection, each of the plurality of series connection units comprising a plurality of battery cells , wherein the plurality of battery cells in each of the plurality of series connection units are connected in parallel; a voltage detecting module configured to detect a voltage signal of a high-voltage side of each of the plurality of series connection units; a battery control module configured to receive the voltage signal detected by the voltage detecting module and determine a voltage of each of the plurality of series connection units; a disconnection detecting module configured to determine whether the plurality of battery cells in each of the plurality of series connection units has been disconnected based on the voltage of each of the plurality of series connection units, the disconnection detecting module comprising a time calculating means for providing time data; and a determining means configured to determine whether said plurality of battery cells in each of said plurality of series connection units has been disconnected; the battery pack having an output voltage of at least 56 V; and the disconnection detecting module comprising: - a slope calculation means configured to determine a slope of the voltage of each of the plurality of series connection units relative to the time data; and - wherein said determining means is configured to determine whether the plurality of battery cells in each of the plurality of series connection units has been disconnected based on said slope of the voltage of each of the plurality of series connection units relative to said time data. - a slope calculation means configured to determine a slope of the voltage of each of the plurality of series connection units relative to the time data; and - wherein said determining means is configured to determine whether the plurality of battery cells in each of the plurality of series connection units has been disconnected based on said slope of the voltage of each of the plurality of series connection units relative to said time data. <EOS>