Power supply system, electric vehicle with power supply system mounted thereon, and method of charging storage battery included in power supply system

An electric vehicle having a motor rotated by electric energy and means for transmitting a rotational force of said motor to an axle, thereby producing a driving force for said vehicle,

• said electric vehicle having a power supply system mounted thereon, said power supply system comprising a stack of fuel cells and a storage battery, wherein at least either one of said stack of fuel cells and said storage battery supplies electric power to said motor, said power supply system further comprising:
• an electric current detector that detects at least two electric currents selected among three different current values, that is, a storage battery-electric current output from said storage battery, a fuel cells-electric current output from said stack of fuel cells, and an overall electric current that is a sum of the storage battery-electric current and the fuel cells-electric current;
• remaining charge determining unit the determines a remaining charge of said storage battery, based on a relationship between the at least two electric currents out of the three different electric current values, which is obtainable from the result of measurement by said electric current detector;
• and
• charging means that, when the remaining charge of said storage battery determined by said remaining charge determining means is not greater than a predetermined first level at the time of stopping operation of said power supply system, causes said storage battery to be continuously charged by said stack of fuel cells until the remaining charge of said storage battery reaches a predetermined second level.

In a power supply system comprising a stack of fuel cells and a storage battery, wherein at least either one of said stack of fuel cells and said storage battery supplies electric power to a loading, a method of enabling said stack of fuel cells to charge said storage battery, said method comprising the steps of:

• (a) detecting at least two electric currents selected among three different current values, that is, a storage battery-electric current output from said storage battery, a fuel cells-electric current output from said stack of fuel cells, and an overall electric current that is a sum of the storage battery-electric current and the fuel cells-electric current;
• (b) determining a remaining charge of said storage battery, based on a relationship between the at least two electric currents out of the three different electric current values, which is obtainable from the result of measurement in step (a);
• and
• (c) causing said storage battery to be continuously charged by said stack of fuel cells until the remaining charge of said storage battery reaches a predetermined second level, when the remaining charge of said storage battery determined in said step (b) is not greater than a predetermined first level at the time of stopping operation of said power supply system.