System and method for periodically charging sub-battery for an electric vehicle based on the SOC discharge rate

• US 9,413,182 B2
• Filed: 06/28/2013
• Issued: 08/09/2016
• Est. Priority Date: 12/18/2012
• Status: Active Grant

• Current Assignee: Hyundai Motor Company (Hyundai Motor Group)
• Original Assignee: Hyundai Motor Company (Hyundai Motor Group)
• Inventors: Park, Jun Yeon
• Primary Examiner(s): Grant, Robert
• Assistant Examiner(s): TRISCHLER, JOHN T
• Application Number:
  US13/930,780
• Publication Number:
  US 20140167680A1
• Time in Patent Office: 1,138 Days
• Field of Search: 320/103, 320/104
• US Class Current: 1/1
• CPC Class Codes: B60L 2210/12 Buck converters
• CPC Class Codes: B60L 2240/545 Temperature
• CPC Class Codes: B60L 2240/547 Voltage
• CPC Class Codes: B60L 2240/549 Current
• CPC Class Codes: B60L 2240/80 Time limits
• CPC Class Codes: B60L 2250/10 by alarm
• CPC Class Codes: B60L 3/0015 Prevention of collisions
• CPC Class Codes: B60L 3/0046 relating to electric energy storage systems, e.g. batteries or capacitors
• CPC Class Codes: B60L 3/04 Cutting off the power supply under fault conditions protective devices and circuit arrangements in general H01H; H02H
• CPC Class Codes: B60L 58/13 Maintaining the SoC within a determined range
• CPC Class Codes: B60L 58/14 Preventing excessive discharging
• CPC Class Codes: B60L 58/16 responding to battery ageing, e.g. to the number of charging cycles or the state of health [SoH]
• CPC Class Codes: B60L 58/20 having different nominal voltages
• CPC Class Codes: H02J 2310/48 for electric vehicles [EV] or hybrid vehicles [HEV]
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: H02J 7/342 The other DC source being a battery actively interacting with the first one, i.e. battery to battery charging with circuits for polarity protection H02J7/0034
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility

Abstract

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.

Claims

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

then

a 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, wherein

the 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; and

setting 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.