A device and method for determining the state of charge of an object, such as an electrochemical battery cell. The device includes a state of charge sensor having a primary magnet that creates a primary magnetic field, and at least one magnetic field sensing element. The sensitivity axes of the sensing elements are substantially perpendicular to the direction of polarization of the primary magnet. The primary magnet and the sensing elements are placed in the proximity of the object, and magnetic fields resulting from the magnetic susceptibility of the object are measured by the sensing elements. The sensing elements output an electrical signal from which the state of charge of the object can be determined.
