Apparatus for preventing overdischarge of battery used for electric vehicle

摘要

To provide an electric vehicle in which a low voltage power obtained by conversion from a high voltage power of a running power source composed of a secondary battery by a DC-DC convertor is supplied to an operation control unit and electric equipment loads such as a lamp and is also used to charge a low voltage secondary battery, in which the running power source and the low voltage secondary battery are prevented from being over-discharged even when a main switch is left in the on-state. A low voltage power VR outputted from a DC-DC convertor 6 is supplied to an exciting winding 8a of a relay and is also supplied to a low voltage secondary battery 7 through a diode 14. The low voltage power VR is supplied to low voltage loads 5 through a contact 8b of the relay. The DC-DC convertor 6 is so constructed that the output of the low voltage power is stopped when the output voltage is reduced to a value less than a specified range due to the reduction in the battery capacity of the running power source 2. In the case where the battery capacity of the running power source 2 is reduced when the main switch 9 is left in the on-state, the output of the DC-DC convertor 6 is stopped, and the contact 8b of the relay is opened for preventing over-discharge of the low voltage secondary battery 7.