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.

Abstract: An electrochemical cell comprising a negative electrode whose electrochemically active material includes an intermetallic compound which can form a hydride with hydrogen, the cell comprising an electrolyte of a solution of at least one alkali hydroxide in water, the negative electrode being provided with a discharge buffer by introducing a quantity of an alkali metal, alkaline earth metal or aluminium into the cell before the cell is sealed, the quantity corresponding to the desired quantity of hydrogen in the negative electrode in the uncharged condition of the cell.

Abstract: An electrochemical cell comprising a negative electrode whose electrochemically active material includes an intermetallic compound which can form a hydride with hydrogen, the cell comprising an electrolyte of a solution of at least one alkali hydroxide in water, the negative electrode being provided with a discharge buffer by introducing a quantity of an alkali metal, alkaline earth metal or aluminum into the cell before the cell is sealed, the quantity corresponding to the desired quantity of hydrogen in the negative electrode in the uncharged condition of the cell.

Abstract: Electrochemical cell comprising at least one electrode consisting of a substrate made of porous material which is impregnated with an electrochemically active material, highly efficient and high-speed gas reactions occurring at the electrode because of the fact that the substrate is impregnated in accordance with a pattern such that a portion of substrate surfaces contains free metal.

Abstract: An electrochemical cell having a negative electrode comprising a compound derived from LaNi.sub.5, in which La is optionally substituted by a plateau pressure-increasing element and in which Ni is substituted entirely or partly by a plateau pressure-reducing element, for example, Co and/or Cu, with the object of considerably reducing volume steps and hence crack formation of the intermetallic compound during charging and discharging.Moreover, the corrosion of the intermetallic compound is counteracted by adding small quantities of Al, Cr and/or Si, which metals enhance the formation of a protecting oxide layer.