Patent ID: 8583307

Claim:
A power supply system for an electrically powered vehicle mounted with a motor for generating power to drive the vehicle, comprising: a main power storage device; an electric power feeding line for supplying electric power to an inverter that controls and drives said motor; a first voltage converter provided between said electric power feeding line and said main power storage device and configured to convert voltage bidirectionally; a plurality of sub power storage devices provided in parallel to each other; a second voltage converter provided between said plurality of sub power storage devices and said electric power feeding line and configured to convert voltage between one of said plurality of sub power storage devices and said electric power feeding line bidirectionally; a connection unit provided between said plurality of sub power storage devices and said second voltage converter and configured to control connection and disconnection between said plurality of sub power storage devices and said second voltage converter; and a control device operative in a first mode for controlling said connection unit to connect a selected sub power storage device selected sequentially from said plurality of sub power storage devices to said second voltage converter and also disconnect the sub power storage device other than said selected sub power storage device from said second voltage converter, and operative in a second mode for controlling said connection unit to disconnect each of said plurality of sub power storage devices from said second voltage converter, said control device including: a first determination unit configured to detect a first state where a residual capacity of said selected sub power storage device currently in use is smaller than a first reference value set in advance, when no sub power storage device replaceable with said selected sub power storage device currently in use is left in said first mode; a second determination unit configured to generate a disconnection request for giving an instruction to shift said first mode to said second mode, depending on a vehicle state of said electrically powered vehicle, when said first determination unit detects said first state; and a third determination unit configured to generate said disconnection request regardless of said vehicle state, when no sub power storage device replaceable with said selected sub power storage device currently in use is left in said first mode and a second state is detected where the residual capacity of said selected sub power storage device falls below a second reference value smaller than said first reference value.