A
system and method for improving the performance of a
hybrid power supply apparatus comprising a power generating device, such as a fuel
cell, and a
primary energy storage device, such as a battery. The purpose of the invention is to provide an
equalization charge to the battery from a source other than the fuel
cell when the battery achieves a predetermined
state of charge condition, thereby avoiding the need to operate the fuel
cell in a low
power output mode. When the predetermined
state of charge condition is detected by a controller, the fuel cell is shut-down. In one aspect of the invention the
equalization charge is provided to the battery by a
secondary energy storage device, such as a plurality of capacitors or secondary batteries. The predetermined
state of charge condition may be satisfied, for example, when the state of charge of the battery exceeds a predetermined threshold, such as 80% of the battery's storage capacity, for a predetermined period of time. In some aspects of the invention, the
secondary energy storage device may also be connectable to the load. Preferably the
system also includes a DC /
DC converter for regulating current flow between the fuel cell and the storage devices.