Protection device used in battery pack, battery pack and vehicle

A battery pack comprising a plurality of batteries, and a protecting device being disposed between two adjacent batteries and comprising:

• a first connecting assembly, electrically connected with a housing of a first battery of the two adjacent batteries, wherein the housing of the first battery has a same polarity as one electrode of the first battery;
• a second connecting assembly, electrically connected with a housing of a second battery of the two adjacent batteries, and the second connecting assembly being opposite to the first connecting assembly, wherein the housing of the second battery has a same polarity as one electrode of the second battery and has a same polarity as the housing of the first battery;
• and
• a conductive connecting assembly, electrically connected with terminals of the first battery and the second battery, and selectively and electrically connected with the first connecting assembly and the second connecting assembly, respectively, to form an overload protection circuit,
• wherein the protection device comprises a normal state and an alarm state,
• when the protection device is in the normal state, the first connecting assembly and the second connecting assembly are spaced apart, and the overload protection circuit is open;
• and
• when the protection device is in the alarm state, at least one of the first connecting assembly and the second connecting assembly moves to be electrically connected with each other and the overload protection circuit is closed to form a short circuit among the first and second connecting assemblies, the conductive connecting assembly and one of the two adjacent batteries and to cause a main loop current of the battery pack to be cut off.