Patent GB-1141518-A (GB)
Title: Accumulator cell containing at least one control electrode in addition to the main electrodes
IPC: G01R31/36
Filed: 1966-12-05
Abstract: 1,141,518. Accumulators. VARTA A.G. 5 Dec., 1966 [10 Dec., 1965], No. 54292/66. Heading H1B. [Also in Division H2] An accumulator cell contains, in addition to the main electrodes, at least one "bi-functional" (see below) control electrode, the capacities and initial states of charge of the main electrodes being so adjusted that on termination of charge and/or discharge of the cell there occurs a change in the potential difference between the control electrode and a main electrode to which it is connected through a suitable resistance, which change may be used to operate switchgear. The control electrode may be connected to the negative or the positive main electrode, or via a switch to either at will, or a pair may be connected one to each main electrode. Only one cell in a battery need be so equipped. The change of potential in the control electrode may be associated with its functioning as an oxygen-generating or hydrogen-generating electrode, or as an oxygen-reducing or hydrogenreducing electrode for gases generated at a main electrode. This ability to perform electrochemical oxidation reactions on anodic polarization and electrochemical reduction reactions on cathodic polarization is meant by the term "bi-functional". Which of these functions the control electrode performs is determined by the capacities and initial states of charge of the main electrodes, each of which may be provided with a charge reserve and/or a discharge reserve and/or an antipolar additive. A number of such combinations are described, and illustrated in Figs. 1, la, 3, 3a, 5, 7, 9, 11, 13, 15 and 17 (not shown), wherein 5 designates the control electrode, 6, 6a and 6b resistances, and 2 and 10 charge reserves, 7 and 8 discharge reserves and 11 and 4 antipolar additives in negative and positive electrodes respectively. In cells containing 2+4, 2+7+4, 10, and 2+ 11 + 8, 5 is connected to the negative electrode; in cells containing 2+4, 2+7+4, and 10, 5 is connected to the positive electrode; in cells containing 27+4 or 8, 5 is connected by a switch to either; and in a cell containing 2 + 4 a pair of electrodes 5 are used. Switchgear is described in which the potential difference is fed by a potentiometer to a voltage sensitive switch which interrupts or reduces the charge or discharge current when a predetermined potential difference is reached. The voltage sensitive switch may comprise a transistor relay which, when the predetermined voltage is exceeded during charging, energizes an impulse relay which operates a slave relay which disconnects the charging device, switches over to a voltmeter which indicates that the cell or battery is charged, and switches over the contacts to the transistor relay to reverse the polarity. A further switch may be closed to connect a current-consuming device; when the discharge is terminated the transistor relay operates again to de-energize the slave relay and switch the accumulator to charge. The system is said to be suitable for Ni(OH) 2 /Cd, Ni(OH) 2 /Zn, AgO/Cd or AgO/Zn alkaline cells, or PbO 2 /Pb acid cells.