Abstract: Apparatus for recharging a battery includes a compartment for accommodating the battery in a manner such that its electrical terminals are in contact with a pair of electrodes. The electrodes are connectable to respective poles of a controllable source of electrical energy. A strain gauge is positioned so as to make contact with a wall of the battery when the battery is in place in the compartment. The strain gauge includes a foil which carries a resistive element, each of the two extremities of the resistive element being connected to an electrical device via a separate contact wire, whereby the coefficient of thermal expansion of the strain gauge is substantially equal to that of the wall of the battery. The material of one of the contact wires, at its juncture with the resistive element, has a different Seebeck coefficient to the material of the other contact wire at its juncture with the respective element.