NOVELTY - Operating devices provided by on-board flex-fuel hydrogen generator comprises: providing at least one parallel autothermal (ATR) reformers for producing hydrogen and carbon monoxide from e.g. biofuels; providing one automatic control system comprising e.g. flow meters/controllers (52); providing stream of ATR reformer's inlet fuel mixture comprising e.g. oxidant; reacting stream of inlet fuel mixture over catalysts with system's own heat and electricity; providing e.g. at least one vessel/manifold (10A); providing at least one flow control curve; and reacting startup reactants over catalysts.    USE - The method is useful for operating devices provided by an on-board flex-fuel hydrogen generator which is used: in a system that is used by itself as a driving device for automobile, lawn mower, fork lift truck, diesel truck, bus, and motorcycle, and in a system to generate and store electricity as a standalone distributed mobile or portable stationary power station, where a standalone distributed power station is used to power an electric car, truck, motorcycle, forklift truck, electric utility vehicle, battery charger and backup power generator; and in internal combustion engine or gas turbines (all claimed).    ADVANTAGE - The method provides an improved on-board hydrogen generator, which has long reformer life without coke formation, and can successfully produce hydrogen from hydrocarbons and/or biofuels in an efficient and effective manner.    DETAILED DESCRIPTION - Operating devices provided by an on-board flex-fuel hydrogen generator comprises: providing at least one parallel autothermal (ATR) reformers for producing hydrogen and carbon monoxide from hydrocarbons and/or biofuels over the supported and/or unsupported platinum group catalysts; providing one automatic control system comprising a control computer and/or microprocessors, flow meters/controllers (52), valves, pumps, sensors and thermocouples; providing a stream of the ATR reformer's inlet fuel mixture comprising at least one oxidant, one fuel and one water/steam comprising reactant supply including liquid fuel loop, gas fuel loop, water supply loop, air supply loop, water electrolyzer loop, exhaust gas recycle loop, water recycle loop or reformate recycle loop; reacting the stream of the inlet fuel mixture over the catalysts inside the ATR reformer with the system's own heat and electricity to produce a reformate containing hydrogen and carbon monoxide from fuels; providing at least one vessel/manifold (10A) for storing the condensed water for the reformers and also the produced dry reformate from the ATR reformers at 1-100 atmospheres for the downstream internal combustion engine/gas turbines (11); providing at least one flow control curve for regulating each reactant's flow rate by the pressure of the storage vessels, where the control curves which are stored in the control computer and/or in the microprocessors should provide precisely an inlet fuel mixture to the reformers at the specified oxygen/carbon, water/carbon and carbon dioxide/carbon ratios; and reacting the startup reactants over the catalysts to start or restart rapidly the ATR reformers without external heat and electricity, where at least two startup reactants are fuels, air, engine/gas turbine's recycle exhaust gas, hydrogen/oxygen gases from electrolyzer (5), and recycle reformate. An INDEPENDENT CLAIM is also included for an on-board flex-fuel hydrogen generator providing device comprising: at least one parallel autothermal reformer for producing hydrogen and carbon monoxide from hydrocarbons and/or biofuels; one automatic control system comprising a control computer and/or microprocessors, flow meters/controllers, valves, pumps, sensors and thermocouples; a stream of the ATR reformer's inlet fuel mixture comprising at least one oxidant, one fuel and one water/steam comprising the reactant supply group including liquid fuel loop, gas fuel loop, water supply loop, air supply loop, water electrolyzer loop, exhaust gas recycle loop, water recycle loop or reformate recycle loop; at least one vessel/manifold for storing the condensed water and the produced dry reformate from the ATR reformers at 1-100 atmospheres; and at least one flow control curve which is stored in the control computer and/or microprocessors for regulating directly each reactant's flow rate by the pressure of the reformate storage vessels, and which provide precisely an inlet fuel mixture to the reformers at the specified oxygen/carbon, water/carbon and carbon dioxide/carbon ratios.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of system comprising the flex-fuel hydrogen generator, internal combustion engine/gas turbine and electric generator.    Electrolyzer (5)    Manifold (10A)    Engine/gas turbine (11)    Flow meter/controllers (52)    Filter (54)