Patent ID: 7777453

Claim:
A car power source apparatus comprising: a battery array having a plurality of battery units connected in series via connection nodes; an over-charge and over-discharge detection circuit that detects over-charge and over-discharge conditions by measuring voltage of the plurality of battery units that make up said battery array; selection switches that sequentially input connection node voltages for each of the plurality of battery units to said over-charge and over-discharge detection circuit; a reference voltage circuit that inputs reference voltages to said over-charge and over-discharge detection circuit when said selection switches are not inputting connection node voltages; and a control circuit that controls said selection switches on and off and controls input of reference voltages from said reference voltage circuit to said over-charge and over-discharge detection circuit, wherein said control circuit controls said selection switches to input each connection node voltage of the plurality of battery units to said over-charge and over-discharge detection circuit to determine for each of the plurality of battery units over-charge and over-discharge conditions; said control circuit controls said selection switches to a state that does not input connection node voltages to said over-charge and over-discharge detection circuit; said control circuit controls the input of reference voltages from said reference voltage circuit to said over-charge and over-discharge detection circuit to confirm proper operation of said over-charge and over-discharge detection circuit; and the reference voltage is a maximum reference voltage greater than the over-charge voltage for detection of a battery unit over-charge condition or a minimum reference voltage less than the over-discharge voltage for detection of a battery unit over-discharge condition.