The invention relates to a fault managing method for a low-voltage storage battery of a pure electric automobile. A whole automobile controller confirms that a storage battery fault exists and lightens a storage battery fault lamp on an instrument according to fault information, when any one of the following four fault conditions is met: a DCDC (Direct Current to Direct Current) converter feeds back information that a storage battery is in a fault state at present to the whole automobile controller; a voltage-collecting sensor at a storage battery end is abnormal; a voltage at the storage battery end is abnormal; and an output circuit of the DCDC converter is abnormal. The fault managing method for the low-voltage storage battery provided by the invention is used for monitoring the state of the low-voltage storage battery of the pure electric automobile and is used for determining set DCDC output voltage according to feedback information from the DCDC, a charger, a storage battery temperature sensor and the like and timely opening DCDC to charge the storage battery. Meanwhile, a set of fault managing method for monitoring the storage battery is developed. If a fault happens, the storage battery fault lamp on the instrument lights up to remind a driver of repairing the automobile as soon as possible.