TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Method: In transitioning electrochemical cell stack, the act of transitioning comprises: turning off a voltage converter that receives a voltage from the stack and reconfiguring the voltage converter to provide a voltage to the stack during the electrochemical cell pumping mode. It further comprises: turning on the voltage converter after the reconfiguration of the voltage converter. It further comprises: determining whether the stack has transitioned into the electrochemical pumping mode based on a voltage of the stack. It further comprises: disconnecting a load from the stack prior to the halting of the oxidant flow. It further comprises: disconnecting a load from the stack after the voltage decreases below the predefined threshold. It further comprises: continuing the communication of the fuel flow in the anode chamber during the halting of the oxidant flow and the monitoring of the voltage of the stack. It further comprises: replacing the fuel flow in the anode chamber with a hydrocarbon flow in the anode chamber during the halting of the oxidant and the monitoring of the voltage of the stack. Preferred System: The system further comprises: a voltage converter to receive a voltage generated by the stack when the stack is in the power producing mode, where the control subsystem is adapted to turn off the voltage converter and subsequently reconfigure the voltage converter to provide a voltage to the stack during the electrochemical cell pumping mode. The control subsystem is adapted to turn on the voltage converter after the reconfiguration of the voltage converter. The control subsystem is adapted to determine whether the stack has transitioned into the electrochemical pumping mode based on a voltage of the stack. The control subsystem is adapted to disconnect a load from the stack prior to the halting of the oxidant flow. The control subsystem is adapted to disconnect a load from the stack after the voltage decreases below the predefined threshold. The control subsystem is adapted to continue the communication of the fuel flow in the anode chamber during the halting of the oxidant flow and the monitoring of the voltage of the stack. The control subsystem is adapted to halt the communication of the fuel flow in the anode chamber and communicate a hydrocarbon flow in the anode chamber during the halting of the oxidant flow and the monitoring of the voltage of the stack.