BATTERY PEAKING UNIT FOR FUEL CELL POWER PLANTS

1437888 Battery boosted supply systems; control of AC motors UNITED AIRCRAFT CORP 16 May 1974 [18 June 1973 (2)] 21839/74 Headings H2H and H2J A system for supplying power to a load comprises a fuel cell 10, a battery 20 connectable in parallel with the fuel cell via a switch 24 and a circuit for supplying a pulse to the switch when the voltage of the fuel cell falls below a predetermined value, the pulse causing closure of the switch to connect the battery to the load for the duration of the pulse. The load may be a motor, the high starting current of which causes a fall in the voltage of the fuel cell. This fall in voltage is detected by a comparator 32 connected to a monostable multi vibrator 38 which supplies a pulse of a pre-set duration of between one half and five seconds to the transistor switch 24 via an optical isolator 48 and an amplifier 50. The transistor is switched on for the duration of the pulse to enable the battery to provide current to an inverter 16 which supplies the load. When the battery voltage is low, a voltage controlled oscillator 60 produces pulses which turn on a thyristor 56 to enable the battery to be charged by a rectifier 54, the oscillator being switched off when the battery voltage reaches a predetermined value. When the transistor 24 is switched on to connect the battery to the inverter, the oscillator is turned off to prevent charging of the battery.