Detecting a remaining battery capacity and a battery remaining capacity circuit

A battery circuit, comprising

• a secondary battery,
• a capacitor selectively coupled to a load,
• a monitor circuit coupled to terminals of the secondary battery,
• at least one switch connecting the secondary battery and the capacitor, wherein
• when the monitor circuit measures a voltage of the secondary battery, the capacitor supplies current to the load, and the secondary battery is in an open state and does not supply current to the load.

A method of measuring a remaining capacity of a secondary battery in a battery circuit and supplying a current to an external load outside the battery circuit comprising:

• selectively connecting the secondary battery to a capacitor via a first switch, the secondary battery charging the capacitor when connected to the capacitor when a potential difference exists between corresponding terminals of the secondary battery and the capacitor;
• selectively connecting the capacitor to an external load via a second switch;
• measuring a terminal voltage of the capacitor with a capacitor voltage monitor circuit coupled across terminals of the capacitor,
• measuring a terminal voltage of the capacitor with the capacitor voltage monitor circuit after the first switch is first turned ON and then OFF to connect and then disconnect the secondary battery and the capacitor;
• and
• supplying a current to the external load outside the battery circuit.