Deformation detecting sensor for sealed secondary battery

A deformation detecting sensor for a sealed secondary battery used with a unit cell, battery module and battery pack of the sealed secondary battery, comprising:

• a magnetic resin layer;
• and
• a magnetic sensor;
• wherein the magnetic resin layer is stuck to the unit cell, the battery module or both;
• wherein the magnetic resin layer comprises a matrix composed of a resin component and a magnetic filler that is dispersed in the matrix;
• wherein the magnetic sensor is attached to an inside wall or an outside wall of a package case;
• wherein the magnetic sensor is capable of detecting a change in magnetic field that is caused by the magnetic resin layer, and
• wherein the magnetic filler is unevenly distributed in the thickness direction of the magnetic resin layer and the concentration of the magnetic filler is made higher on the magnetic sensor side than on the unit cell side.