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Provided is a system method for periodically charging a sub-battery for an electric vehicle. In this method, an SOC self-discharge rate of the sub-battery is calculated. An LDC output voltage and a charging time of the sub-battery are set using the SOC self-discharge rate of the sub-battery and info

Provided is a system method for periodically charging a sub-battery for an electric vehicle. In this method, an SOC self-discharge rate of the sub-battery is calculated. An LDC output voltage and a charging time of the sub-battery are set using the SOC self-discharge rate of the sub-battery and information received from an IBS. It is determined whether or not an SOC of a main battery is equal to or greater than a set value. Periodic charging is performed on the sub-battery through an operation of an LDC when the SOC of the main battery is equal to or greater than the set value.

대표청구항 ▼

1. A method for periodically charging a sub-battery for an electric vehicle, consisting of: a first step of calculating, by a controller, a State of Charge (SOC) discharge rate of the sub-battery after charging the sub-battery by compulsory driving a Low Voltage DC-DC Converter (LDC) and discharging

1. A method for periodically charging a sub-battery for an electric vehicle, consisting of: a first step of calculating, by a controller, a State of Charge (SOC) discharge rate of the sub-battery after charging the sub-battery by compulsory driving a Low Voltage DC-DC Converter (LDC) and discharging the sub-battery, which has been charged by the compulsory driving of the LDC, into a reference electronic load value;thereafter, a second step of setting, by the controller, the LDC output voltage and a charging time of the sub-battery using the SOC discharge rate of the sub-battery and information received from an Intelligent Battery Sensor (IBS);a third step of determining, by the controller, whether or not an SOC of a main battery is equal to or greater than a set value; and thena fourth step of performing, by the controller, periodic charging of the sub-battery through an operation of an LDC when the SOC of the main battery is equal to or greater than the set value. 2. The method of claim 1, wherein the SOC discharge rate of the sub-battery is calculated from the Equation below: SOC Discharge Rate=(Initial SOC of Sub-Battery−SOC after Compulsory Discharging of Sub-Battery)/Compulsory Discharging Time of Sub-Battery, whereinthe initial SOC of the sub-battery is an SOC value of the sub-battery charged through the compulsory driving of the LDC. 3. The method of claim 1, wherein the reference electronic load value is a sum of a vehicle's own load. 4. The method of claim 1, wherein the compulsory driving of the LDC is performed after a reservation charging operation for charging the sub-battery at a predetermined time. 5. The method of claim 1, further consisting of: stopping an operation of an in-vehicle main relay and electronic load before the periodic charging of the sub-battery is performed. 6. The method of claim 1, further consisting of: informing a user by an alarming unit when either an in-vehicle main relay or an electronic load operates before the periodic charging of the sub-battery is performed. 7. The method of claim 1, wherein the setting of the LDC output voltage and the charging time of the sub-battery comprises: calculating a State of Health (SOH) of the sub-battery using the SOC self-discharge rate of the sub-battery and the information received from the IBS; andsetting the LDC output voltage and the charging time of the sub-battery according to the SOH of the sub-battery. 8. The method of claim 1, wherein the information received from the IBS comprises at least one of an internal temperature and an SOC of the sub-battery, a load resistance value detection, and a voltage. 9. The method of claim 1, further consisting of: determining whether or not the sub-battery needs to be replaced after the setting of the LDC output voltage and the charging time of the sub-battery. 10. The method of claim 9, wherein the determining of whether or not the sub-battery needs to be replaced comprises using the charging time and an SOH of the sub-battery, and a consumption of the main battery due to the periodic charging of the sub-battery. 11. The method of claim 9, wherein when it is determined that the sub-battery needs to be replaced, further comprising informing a user of the charging time and an SOH of the sub-battery, and a consumption of the main battery due to the periodic charging of the sub-battery.