Abstract: The present invention can be embodied in a power source having internal redundancy for allowing continued operation of a load such as an electric vehicle, as well as related methods. The power source comprises a first plurality of fuel cell stacks, a second plurality of fuel cells, and a third plurality of bypass devices. Each power converter can receive input electrical power from one of the fuel cell stacks and generates output electrical power at a predetermined output voltage. The power converters can be connected in series between terminals of the power source. Each bypass device can be coupled to one of the power converters for providing a current path if the power converter is unable to provide output electrical power. Each power converter can have selectable output voltages for increasing its output voltage if one of the power converters is not supplying power for the power source.