Power source apparatus for vehicle

A power source apparatus, which is mounted to a vehicle, comprising:

• an alternator;
• a constant voltage control section configured to adjust a voltage of electric power generated by the alternator to a set voltage;
• a lead-acid battery electrically connected to the alternator;
• a secondary battery, electrically connected in parallel to the lead-acid battery, having an energy density that is higher than an energy density of the lead-acid battery, the secondary battery being a non-aqueous electrolyte type composed of positive electrode active material and negative electrode active material, the positive electrode active material being made of lithium metal composite oxide, and the negative electrode active material being made of one selected from lithium titanium oxide, carbon, graphite, alloy containing silicon, and alloy containing tin;
• a rectifying section placed between the lead-acid battery and the secondary battery so that a forward current direction of the rectifying section becomes a direction from the lead-acid battery to the secondary battery, and the rectifying section having a barrier voltage to the current flowing in the forward direction through the rectifying section;
• an open and close section, connected in parallel to the rectifying section, configured to electrically connect the alternator with the secondary battery and disconnect the alternator from the secondary battery;
• an open and close control section configured to (i) instruct the open and close section to close the electrical connection between the alternator and the secondary battery when the secondary battery is charged with electric power generated by the alternator, and (ii) instruct the open and close section to open the electrical connection between the alternator and the secondary battery when the rectifying section performs the rectifying operation;
• and
• a protection control section configured to protect the secondary battery from overcharge by controlling a charging capacity to the secondary battery and to protect the secondary battery from over discharge by controlling a discharging capacity from the secondary battery so that a residual capacity of the secondary battery becomes within a range of 10% to 90% of a state of charge (SOC) of the secondary battery, and the protection control section outputs, to the constant voltage control section, an instruction signal which instructs the constant voltage control section to reduce the set voltage in order to control the charging capacity to the secondary battery,
• wherein an open circuit voltage and an internal resistance of the lead-acid battery and an open circuit voltage and an internal resistance of the secondary battery are determined in order to satisfy the following conditions (a′), (b′), and (C′):
• (a′) an equal voltage point, at which the open circuit voltage of the secondary battery is equal to a subtracted voltage obtained by subtracting the barrier voltage of the rectifying section from the open circuit voltage of the lead-acid battery, is present within a range of 88% to 100% of a state of charge (SOC) of the lead-acid battery and within the range of 10% to 90% of the SOC of the secondary battery;
• (b′) the open circuit voltage of the secondary battery is higher than the subtracted voltage of the lead-acid battery at an upper limit side from the equal voltage point within the range of 10% to 90% of the SOC of the secondary battery;
• and
• (c′) a terminal voltage of the secondary battery when a maximum charging current flows in the secondary battery is not more than the set voltage which is set by the constant voltage control section, and
• wherein, when an engine of the vehicle restarts, the protection control section instructs the open and close section to disconnect the starter motor from the secondary battery and the electrical load in order to stably supply the constant voltage to the electrical load.