Patent ID: 7318971

Claim:
A fuel cell system having a fuel cell generating section comprising at least one fuel cell for generating electric power by an electrochemical reaction between a fuel gas containing hydrogen and an oxidizing gas containing oxygen, fuel gas supply means for supplying a flow of fuel gas to said fuel cell generating section and oxidizing gas supply means for supplying a flow of oxidizing gas to said fuel cell generating section, wherein said system comprises: a controllable electric power source; control means for controlling a moisture content condition within said fuel cell generating section by adjusting said value of electric current generated by said fuel cell generating section, detecting a first condition whereby a value of total electric power generated by said system exceeds a required value and a second condition whereby said total value of electric power is less than said required value, and reducing an amount of electric power generated by said controllable electric power source when said first condition is detected and for increasing said amount of electric power generated by said controllable electric power source when said second condition is detected; and moisture diagnosis means for diagnosing said moisture content condition of said fuel cell generating section, wherein said control means performs control of said value of electric current based upon diagnosis results obtained by said moisture diagnosis means, wherein said control means performs control to supply a part of said electric power generated by said fuel cell generating section to be stored in said electrical energy storage device when said first condition is detected and to obtain electric power from said electrical energy storage device, to supplement said electric power generated by said fuel cell generating section, when said second condition is detected, and wherein said control means comprises means for judging, based on said diagnosis results, whether a value of moisture content within said fuel cell generating section is below a predetermined lower limit, and for applying control to increase said value of electric current generated by said fuel cell generating section when said moisture content value is found to be below said lower limit.