A method of operating a power adapter for a load, the power adapter including a fuel cell system including a fuel supply and a fuel cell stack, the power adapter also including an energy storage device electrically connected to the fuel cell system, wherein the fuel supply comprises a fuel generator comprising a fuel storage composition storing fuel in a chemically bound form that thermolyses at a decomposition temperature to generate fuel, the method comprising: determining a connectivity state of an auxiliary power source with the energy storage device; determining a connectivity state of a load with the fuel cell system; selecting a power adapter operation mode based on the connection states of the auxiliary power source and the load, the operation modes comprising: an auxiliary mode when the auxiliary power source is connected to the energy storage device and the load is connected to the fuel cell system, comprising: providing power from the auxiliary power source to the load, providing power to the fuel cell system, preheating the fuel storage composition to a temperature lower than the decomposition temperature with power from the auxiliary power source, measuring a parameter of the fuel cell system indicative of power generation from the fuel cell system, and ceasing energy production when the measured parameter indicates power generation by cooling the fuel supply below the decomposition temperature; a fuel cell mode when the auxiliary power source is disconnected from the energy storage device and the load is connected to the fuel cell system, comprising: providing fuel to the fuel cell stack from the fuel supply, generating power from the fuel by the fuel cell stack, and providing the generated power to the load; wherein the measured parameter is indicative of energy generation when the fuel supply temperature exceeds a decomposition temperature of a fuel storage composition of the fuel supply. determining a connectivity state of an auxiliary power source with the energy storage device; determining a connectivity state of a load with the fuel cell system; selecting a power adapter operation mode based on the connection states of the auxiliary power source and the load, the operation modes comprising: an auxiliary mode when the auxiliary power source is connected to the energy storage device and the load is connected to the fuel cell system, comprising: providing power from the auxiliary power source to the load, providing power to the fuel cell system, preheating the fuel storage composition to a temperature lower than the decomposition temperature with power from the auxiliary power source, measuring a parameter of the fuel cell system indicative of power generation from the fuel cell system, and ceasing energy production when the measured parameter indicates power generation by cooling the fuel supply below the decomposition temperature; a fuel cell mode when the auxiliary power source is disconnected from the energy storage device and the load is connected to the fuel cell system, comprising: providing fuel to the fuel cell stack from the fuel supply, generating power from the fuel by the fuel cell stack, and providing the generated power to the load; an auxiliary mode when the auxiliary power source is connected to the energy storage device and the load is connected to the fuel cell system, comprising: providing power from the auxiliary power source to the load, providing power to the fuel cell system, preheating the fuel storage composition to a temperature lower than the decomposition temperature with power from the auxiliary power source, measuring a parameter of the fuel cell system indicative of power generation from the fuel cell system, and ceasing energy production when the measured parameter indicates power generation by cooling the fuel supply below the decomposition temperature; a fuel cell mode when the auxiliary power source is disconnected from the energy storage device and the load is connected to the fuel cell system, comprising: providing fuel to the fuel cell stack from the fuel supply, generating power from the fuel by the fuel cell stack, and providing the generated power to the load; wherein the measured parameter is indicative of energy generation when the fuel supply temperature exceeds a decomposition temperature of a fuel storage composition of the fuel supply.