Car power source apparatus

A car power source apparatus comprising:

• a battery having a plurality of battery modules connected in series on the positive and negative sides of a reference node, and
• a voltage detection circuit for detecting the voltage of one or a plurality of battery modules with respect to the reference node of the battery;
• wherein the reference node of the battery is connected to the voltage detection circuit via a reference connection line, voltage detection nodes of the battery are connected to the voltage detection circuit via voltage detection lines, and voltage detection node voltages are detected by the voltage detection circuit to determine battery module voltages;
• and
• wherein the voltage detection circuit has detection switches connected in voltage detection lines, the voltage detection circuit detects voltage detection node voltages with the detection switches in the OFF state, and reference connection line open circuit is detected from those detected voltages.