A low-power protective circuit includes a detection unit that intermittently detects a voltage across a secondary battery; a battery management unit that includes a buffer memory device and a processor and determines, based on a value of the voltage, whether the secondary battery needs to be charged; a switch circuit that establishes or breaks electrical continuity between a host system and the secondary battery; a switch control unit that turns on or off the switch circuit in accordance with the judgment made by the battery management unit; a switch that controls supply of power supply voltage from the secondary battery to the battery management unit; and a power controller that intermittently stops supply of the power supply voltage to the battery management unit by turning off the switch.