<；P>；PROBLEM TO BE SOLVED: To provide an oxygen concentrator capable of enhancing the convenience by having identification tag ID codes and charged state detection means in individual rechargeable batteries so that a discharged battery can be confirmed and changed with a full-charged battery. <；P>；SOLUTION: The rechargeable batteries of the oxygen concentrator have discernible unique ID codes respectively, and a plurality of the rechargeable batteries are connected to a power supply feeding terminal. The oxygen concentrator comprises an ID code discriminating means juxtaposed with the power supply feeding terminal for discriminating tags, and the detection means disposed in the respective rechargeable batteries for detecting the charged state of the rechargeable batteries. If the detection means detects a discharged battery, a command to stop discharge is output to the discharged rechargeable battery from the ID code discriminated by the tag discrimination means, and the discharged battery is changed with a rechargeable battery before discharge, so that the electric power is fed via the power supply feeding terminal. <；P>；COPYRIGHT: (C)2009,JPO&INPIT
