NOVELTY - Power supply comprises battery pack, fuel cell, hydrogen fuel tank, and controller. The battery pack is capable of providing power output of 20-1000 kW. The fuel cell is capable of providing power output of 0.2-20 kW. The hydrogen fuel than has rated capacity based on miles of travel at an average city fuel economy rating where the rated capacity in miles is equal to 4.5-18 times the fuel cell maximum power rating in kW.    USE - Used as battery for plug-in hybrid electric vehicle.    ADVANTAGE - Less expensive catalysts are required to provide the majority of the needed power output. The configuration allows the group(s) that receive oxidant and fuel having higher concentration to use lower catalyst loadings than the group(s) that were to operate at oxidant and fuel compositions with purge gas concentration at lower oxidant and fuel compositions. It is small fuel cell allowing for high ranges without large number of batteries while the batteries provide for high power output without large fuel cell.    DETAILED DESCRIPTION - Power supply comprises battery pack, fuel cell, hydrogen fuel tank, and controller. The battery pack is capable of providing power output of 20-1000 kW. The fuel cell is capable of providing power output of 0.2-20 kW. The hydrogen fuel than has rated capacity based on miles of travel at an average city fuel economy rating where the rated capacity in miles is equal to 4.5-18 times the fuel cell maximum power rating in kW. The controller uses the power output of the battery pack to provide the high power needs of the vehicle and uses the fuel cell as battery charger to charge the battery pack.    INDEPENDENT CLAIMS are included for:    (a) fuel cell power system using air separator to supplement a stored electrolysis oxygen supply comprising pressurized regenerative fuel cell, electrolysis oxygen tank, air separated oxygen tank, air separator, hydrogen storage tank, liquid fuel storage tank, and controller. The regenerative fuel cell is capable of producing hydrogen through hydrolysis of water, and produces electrical power through electrochemical reactions of the oxygen and fuel. The electrolysis oxygen tank storage stores oxygen (0.2-100 kg). The air-separated oxygen tank separates air into oxygen stream(s) with purity not less than 50 wt.% oxygen. The liquid fuel storage tank contains liquid fuel. The pressurized regenerative fuel cell operates at greater than 5 bars of pressure;and    (b) regenerative fuel cell system comprising pressurized regenerative fuel cell, pressurized electrolysis oxygen tank, pressurized hydrogen storage tank, and line with one end connecting the bottom of the hydrogen tank and second end connected to the oxygen tank.    DESCRIPTION OF DRAWING(S) - The figure shows a condensed equilibrating tank equilibrating the pressure between hydrogen and oxygen tank on the vehicle.