Apparatus and method to apply voltage to fuel cell stack from high voltage system for usage during diagnostic tests

A fuel cell charging system comprising:

• a fuel cell stack having a fuel cell stack voltage between fuel cell stack terminals, the fuel cell stack voltage being at a first voltage during normal fuel cell operation;
• a high voltage electrical system operating at a first DC operating voltage, the first DC operating voltage being higher than the first voltage of the fuel cell stack;
• a boost converter in electrical connection with the fuel cell stack and the high voltage electrical system, the boost converter transferring electrical power from the fuel cell stack to the high voltage electrical system during normal fuel cell operation;
• a stack charging component in electrical connection with the fuel cell stack and the high voltage electrical system and which steps down the first DC operating voltage of the high voltage electrical system to a second DC operating voltage that is lower than the first DC operating voltage, the stack charging component further applying the second DC operating voltage to the fuel cell stack as a charging voltage;
• and
• a FCS controller operable to disable the boost converter and enable the stack charging component to apply the second DC operating voltage to the fuel cell stack.