In a power supply
system using various kinds of storage batteries such as a
large capacity storage battery or a small capacity storage battery, an
electric power path is complicated, which may increase failures such as a
short circuit trouble. There is a problem in that, when a
short circuit trouble between storage batteries occurs, damage to a smaller capacity storage battery is serious. Accordingly, in a power supply
system according to the present invention, the relationship among voltages, current capacities, and
electric power capacities of various kinds of storage batteries such as a
large capacity storage battery or a small capacity storage battery is defined so that damage to the storage batteries may be minimized even when malfunction occurs in, for example, switching a switch, and energy transfers from a higher
voltage storage device.