Patent GB-1304092-A (GB)
IPC: H01M8/04858
Filed: 1970-02-13
Abstract: 1304092 Automatic control of fuel cells ROBERT BOSCH GmbH 13 Feb 1970 [15 Feb  1969] 7022/70 Heading G3R [Also in Division H1] A fuel cell unit comprises two fuel cells 1, an oxygen bottle 3 and control valve 14, a fuel/ electrolyte reservoir 4 having outputs controlled by pumps 5 and an input controlled by an oxygen outlet valve 16, and an electronic control device 2 which receives signals of the output voltage and current of the unit (from members 11, 12), of the temperature of the cells (from thermistors 22) and of the electrode potentials of the cells (from specially prepared and individual cells fitted into fuel cells), the unit being maintained in its optimum operating condition by the action of the device 2 to control the following regulating processes: - (1) actuation of the pumps 5 by a temperature controller 21, for a period determined by an electronic time switch 27, when the temperature exceeds a nominal value at which the cells are to be maintained, (2) actuation of the pumps 5 by a potential monitor 28 when the electrode potential falls below a pre-set value and valve 16 has been opened (see process (4) below), (3) actuation of the pumps 5 by the switch 27 at time intervals controlled by the power output of the unit, this action only occurring if the operating temperature is below the nominal value and thus process (1) does not occur, or if the electrode potential is such that process (2) does not occur, (4) opening of the valve 16, for a period determined by the time switch 27, at time intervals determined by the power output of the unit and/or the electrode potential according to whether the latter falls below the pre-set value or the former exceeds a pre-set value. If neither of these two conditions occurs the valve 16 is opened at fixed time intervals by the switch 27, and (5) operation of a conventional switching voltage regulator 26 to maintain the output voltage of the unit at a predetermined value. In addition to the above processes, the device 2 also serves to switch a current limiting resistor 30 in series with the load if the power taken from the unit exceeds an upper limit; to regulate an electronically controlled load circuit 24 which rapidly brings the cells to their working temperature; and to isolate the unit from the (normal) load and switch off the whole control system by way of a relay 29, in the event of:- (a) processes (2) and (4) failing to restore the electrode potential to its pre-set value or (b) process (1) failing to restore the cell temperature to its nominal value, a condition which is detected by an excess temperature monitor 31. The setting of the controller 21 is dependent on the setting of an output stage switch 20, whereby each power output of the unit )over a specific range) has a corresponding optimum working temperature, and vice versa. A heating current controller 25 operates in conjunction with members 21, 24 to obtain the maximum permissible current for the prevailing temperature during rapid heating of the cells. The method of putting the unit into operation and rapid heating-up is described. The special cells for measuring the electrode potential have a high sensitivity attained by reducing the catalyst content of the electrodes to about 40% of the customary quantity.