This specification describes a system and method for controlling the voltage produced by a fuel cell. The system involves providing a bypass line between an air exhaust from the fuel cell and an air inlet of the fuel cell. At least one controllable device is configured to allow the flow rate through the bypass line to be altered. A controller is provided to control the controllable device. The method involves varying the rate of recirculation of air exhaust to air inlet so as to provide a desired change in fuel cell voltage.

A redox flow battery system includes an anolyte having a first ionic species in solution; a catholyte having a second ionic species in solution, where the redox flow battery system is configured to reduce the first ionic species in the anolyte and oxidize the second ionic species in the catholyte during charging; a first electrode in contact with the anolyte, where the first electrode includes channels for collection of particles of reduced metallic impurities in the anolyte; a second electrode in contact with the catholyte; and a separator separating the anolyte from the catholyte. A method of reducing metallic impurities in an anolyte of a redox flow battery system includes reducing the metallic impurities in the anolyte; collecting particles of the reduced metallic impurities; and removing the collected particles using a cleaning solution.

A fuel cell system includes: an external load connected to a fuel cell; an electric power adjusting unit configured to adjust a generated electric power of the fuel cell in accordance with electric power consumption of the external load; a humidity control unit configured to control humidity of an electrolyte membrane in the fuel cell on the basis of the generated electric power of the fuel cell; an output voltage detecting unit configured to detect an output voltage of the fuel cell; and a cross leakage determining unit configured to cause the humidity control unit to increase the humidity of the electrolyte membrane when the fuel cell generates the electric power, the cross leakage determining unit being configured to determine whether a cross leakage amount increases or not on the basis of a change in the output voltage at that time.

A voltage synchronization method and system are provided. The system includes a main controller that is configured to determine whether voltage synchronization is possible. When the voltage synchronization is determined to be possible, the main controller is configured to transmit a voltage synchronization command to a plurality of auxiliary controllers. The plurality of auxiliary controllers are configured to adjust sensed voltages based on an output voltage of a fuel cell stack when the transmitted voltage synchronization command is received.

One embodiment is a redox flow battery system that includes an anolyte; a catholyte; an anolyte tank configured for holding at least a portion of the anolyte; a catholyte tank configured for holding at least a portion of the catholyte; a primary redox flow battery arrangement, and a second redox flow battery arrangement. The primary and secondary redox flow battery arrangements share the anolyte and catholyte tanks and each includes a first half-cell including a first electrode in contact with the anolyte, a second half-cell including a second electrode in contact with the catholyte, a separator separating the first half-cell from the second half-cell, an anolyte pump, and a catholyte pump. The peak power delivery capacity of the secondary redox flow battery arrangement is less than the peak power delivery capacity of the primary redox flow battery arrangement.

A method of operating a fuel cell assembly comprising a plurality of fuel cells connected together for collectively providing power to a load, each fuel cell including an anode and a cathode, the method comprising selectively providing an electrical connection between the anode and the cathode of at least one of the fuel cells of the assembly for lowering the voltage across the fuel cell independent of the load.

A direct isopropanol fuel cell adapted for use in ambient conditions and utilizing as fuel isopropanol and water preferably with isopropanol at relatively high concentrations representing 30% to 90% isopropanol.

A diagnostic system for determining the cathode gas quality of a fuel cell system has a fuel cell stack, with a diagnostic fuel cell which can be connected at the cathode side to a cathode supply line and at the anode side to an anode supply line of the fuel cell system. The diagnostic system furthermore comprises a detection unit which is configured to detect a measured value or the measured value time curve of the diagnostic fuel cell operating with the cathode gas provided via the cathode supply line and with the anode gas provided via the anode supply line. The present disclosure moreover relates to a fuel cell system having a diagnostic system, and to a corresponding method.

A method of improving the electrical performance of an operating fuel cell catalyst-containing cathode in a fuel cell connected to an electrical load by: reducing the flow of air to the cathode; disconnecting the load from the fuel cell; connecting a potentiostat to the fuel cell; cycling an applied voltage, current, or power to the fuel cell one or more times; disconnecting the potentiostat from the fuel cell; reconnecting the load to the fuel cell; and resuming the flow of air to the cathode.

This specification describes a system and method for controlling the voltage produced by a fuel cell. The system involves providing a bypass line between an air exhaust from the fuel cell and an air inlet of the fuel cell. At least one controllable device is configured to allow the flow rate through the bypass line to be altered. A controller is provided to control the controllable device. The method involves varying the rate of recirculation of air exhaust to air inlet so as to provide a desired change in fuel cell voltage.