Abstract: A battery-powered electrical device with a rechargeable battery pack and a means for preventing excessive discharge of the cells in the battery pack. Each cell is characterized by a voltage-value V.sub.end at which it is desirable to terminate discharge of the cell. The cells are divided into a number of mutually exclusive subsets s.sub.i having N.sub.i cells. The device comprises means for measuring the series voltage V.sub.i across each subset s.sub.i, and interrupting the current to the device if the condition V.sub.i .ltoreq.n.sub.i .times.V.sub.end is met in any of the subsets s.sub.i.

Abstract: Apparatus for charging a battery (5) includes a battery 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 resistive strain gauge (15) for monitoring mechanical deformation of the battery is attached to an elastic surface within the battery compartment, against which surface the battery is pressed when it is located in the battery compartment. In a particular embodiment, one of the electrodes (9) is a sprung metallic sheet and the elastic surface is located on this sheet.

Abstract: Apparatus for recharging a battery, comprising a compartment which holds the battery so that its electrical terminals are in contact with a pair of electrodes. The electrodes are connectable to the poles of a controllable source of electrical energy. In the compartment a ferromagnetic body is positioned so as to be subjected to mechanical stress in response to mechanical deformation of the battery. An electrical device monitors the magnetic permeability .mu. of the ferromagnetic body by measuring the self-inductance of a coil surrounding at least a portion of the ferromagnetic body. The .mu. of the ferromagnetic body changes by magnetostrictive effects arising from mechanical stress of the ferromagnetic body in response to mechanical deformation of the battery (5) during charging. Expansion of the battery can be used as an indicator that charging has been completed, and that the battery should be disconnected from the source of electrical energy.

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.

Abstract: A charging device for charging a rechargeable battery including a current supplier for supplying charging current to a battery having an initial temperature at the beginning of the supply of charging current, a selector for selecting an end temperature based on a temperature range the initial temperature is in and a current terminator for terminating the supply of charging current when a battery reaches the end temperature. A rechargeable battery including a strain gauge having a temperature coefficient differing from a temperature coefficient of the battery housing is also provided.