Control apparatus for a fuel cell generating system

In a hybrid fuel cell generating system, a fuel cell (3) supplies electrical power to a variable load (5) and is provided with back-up power by means of a storage battery (6). The surplus output of the fuel cell (3) is used to recharge the battery (6) under light load conditions. In order to avoid damage to the battery (6) during recharging, the output power (7,8,9,10) and current (4,16,17,18) of the fuel cell are controlled by means of a signal (Ifc) generated by controller (15) in dependence on a comparison of the measured values of battery current (11,12) and voltage (13) with preset values (14) determined in accordance with a predetermined characteristic related to the charge level of the battery as calculated by the controller (15).