Vehicular power supply system

Abstract

A vehicular power supply system is provided, which is equipped with a two-battery power supply system including a lithium-ion battery and a lead battery, and can securely supply the lead battery with power without fail even when the lithium-ion battery is disconnected by a relay. The vehicular power supply system comprises: a lead battery; a lithium-ion battery that can be charged and discharges at a voltage higher than the lead battery's voltage; a step-down DC-DC converter that is connected between the lead battery and the lithium-ion battery and whose output voltage is controllable; a generator connected with the step-down DC-DC converter and the lithium-ion battery; a lithium-ion battery SOC detection means for detecting a state of charge of the lithium-ion battery; a relay for the lithium-ion battery by which the battery is connected to or disconnected from the generator and the step-down DC-DC converter; and a control means, based on the state of charge of the lithium-ion battery, for taking control of switching on and off the relay for the lithium-ion battery.

Dependencies are inferred from the claim text.