Charging device of vehicle, control method thereof, vehicle, and control method of vehicle

Abstract

Provided are a charging device for a vehicle, a control method thereof, a vehicle, and a control method thereof. The charging device for a vehicle includes a third switching element disposed between a first battery and a second battery and configured to electrically connect or disconnect the first battery and the second battery, a first switching element configured to supply or cut off a charging current supplied from the outside to the first battery, a second switching element configured to supply or cut off a charging current supplied from the outside to the second battery, and a controller configured to control the first switching element, the second switching element, and the third switching element so as to selectively charge at least one of the first battery and the second battery.

Description

[0001] Cross-references to related applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2020-0083094, filed on July 6, 2020, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] This disclosure relates to a vehicle, and more specifically, to an apparatus and method for charging a battery in a vehicle. Background Technology

[0004] As the development of environmentally friendly vehicles (such as electric or hybrid vehicles) accelerates, the mileage of these vehicles is also increasing.

[0005] Battery capacity has increased significantly, allowing for a range of hundreds of kilometers on a single charge. To enable faster charging at this increased capacity, battery voltage is also being developed from 400V to 800V. However, most currently available high-speed chargers only respond to 400V batteries and, in many cases, do not support 800V batteries. Despite the increasing availability of 800V high-speed chargers, 400V high-speed chargers still dominate the market.

[0006] Therefore, environmentally friendly vehicles equipped with 800V batteries must be able to be charged using both 400V and 800V high-speed chargers. To achieve this, the voltage of the 400V charger is typically boosted inside the vehicle to charge the 800V battery.

[0007] To increase the voltage of the 400V charger inside the vehicle, a boost converter must be provided. This process can generate noise, which can lead to charging failures. Furthermore, providing a filter to block the noise may increase the vehicle's price. Summary of the Invention

[0008] One aspect of this disclosure is enabling a vehicle to accommodate multiple external chargers with different charging voltages without using a separate boost converter.

[0009] Other aspects of this disclosure will be set forth in part in the description which follows, and will be apparent in part from the description, or may be learned by practice of this disclosure.

[0010] According to one aspect of this disclosure, a charging device for a vehicle may include: a third switching element disposed between a first battery and a second battery, configured to electrically connect or disconnect the first battery and the second battery; a first switching element configured to supply or disconnect charging current supplied from an external source to the first battery; a second switching element configured to supply or disconnect charging current supplied from an external source to the second battery; and a controller configured to control the on / off switching of the first switching element, the second switching element, and the third switching element to selectively charge each or all of the first battery and the second battery.

[0011] The controller can be configured to variably adjust the amount of charging current supplied to each of the first and second batteries so that the amount of charge on the first and second batteries is equal to that on each other.

[0012] The first switching element may include a first transistor configured to regulate the supply of charging current. The second switching element may include a second transistor configured to regulate the supply of charging current.

[0013] The first switching element may further include a first relay configured to control the supply or interruption of the charging current. The second switching element may further include a second relay configured to control the supply or interruption of the charging current.

[0014] The controller can be configured to control the first battery and the second battery to charge as a single battery by turning on the third switching element and turning off the first switching element and the second switching element.

[0015] The controller can be configured to control the independent charging of the first and second batteries by disconnecting the third switching element and connecting the first and second switching elements.

[0016] The controller can be configured to control the independent charging of only one of the first and second batteries by disconnecting the third switching element and turning on one of the first and second switching elements, and disconnecting the other.

[0017] The controller can be configured to control a first switching element, a second switching element, and a third switching element such that each or all of the first and second batteries is selectively charged in response to the charging capacity of an external charger supplying charging current.

[0018] According to another aspect of this disclosure, in a method for controlling a charging device for a vehicle, the charging device includes: a third switching element disposed between a first battery and a second battery, configured to electrically connect or disconnect the first battery and the second battery; a first switching element configured to supply or disconnect charging current supplied from an external source to the first battery; and a second switching element configured to supply or disconnect charging current supplied from an external source to the second battery. The method may include a controller identifying the charging capacity of an external charger supplying the charging current; and the controller controlling the first, second, and third switching elements to selectively charge each or all of the first and second batteries in response to the charging capacity of the external charger.

[0019] The method may further include variably adjusting the magnitude of the charging current supplied to each of the first and second batteries by the controller, such that the charge amount of the first and second batteries is equal to that of each other.

[0020] The first switching element may include a first transistor configured to regulate the supply of charging current. The second switching element may include a second transistor configured to regulate the supply of charging current.

[0021] The first switching element may further include a first relay configured to control the supply or interruption of the charging current. The second switching element may further include a second relay configured to control the supply or interruption of the charging current.

[0022] The method may also include: controlling the first battery and the second battery to be charged as a single battery by the controller by turning on the third switching element and turning off the first switching element and the second switching element.

[0023] The method may further include: controlling the independent charging of the first battery and the second battery by the controller disconnecting the third switching element and connecting the first switching element and the second switching element.

[0024] The method may further include: controlling only one of the first battery and the second battery to charge independently by the controller by disconnecting the third switching element and turning on one of the first switching element and the second switching element and disconnecting the other.

[0025] According to one aspect of this disclosure, a vehicle may include: a first battery and a second battery; a third switching element disposed between the first battery and the second battery and configured to electrically connect or disconnect the first battery and the second battery; a first switching element configured to supply or disconnect charging current supplied from an external source to the first battery; a second switching element configured to supply or disconnect charging current supplied from an external source to the second battery; and a controller configured to control the on / off state of the first switching element, the second switching element and the third switching element to selectively charge each or all of the first battery and the second battery.

[0026] According to another aspect of this disclosure, in a method of controlling a vehicle, the vehicle includes: a first battery and a second battery; a third switching element disposed between the first battery and the second battery and configured to electrically connect or disconnect the first battery and the second battery; a first switching element configured to supply or disconnect charging current supplied from an external source to the first battery; and a second switching element configured to supply or disconnect charging current supplied from an external source to the second battery. The method may include a controller identifying the charging capacity of an external charger supplying the charging current; and the controller controlling the first, second, and third switching elements to selectively charge each or all of the first and second batteries in response to the charging capacity of the external charger. Attached Figure Description

[0027] These and / or other aspects of this disclosure will become apparent and more readily understood from the following description of embodiments in conjunction with the accompanying drawings.

[0028] Figure 1 This is a diagram illustrating one form of charging device for a vehicle according to the present disclosure.

[0029] Figure 2 This is a diagram illustrating charging control in response to an external high-speed charger of 400V level in a charging device for a vehicle according to one form of the present disclosure.

[0030] Figure 3 This is a diagram illustrating charging control in response to an external high-speed charger of 800V level in a charging device for a vehicle according to one form of the present disclosure.

[0031] Figure 4 This is a diagram illustrating one form of vehicle charging method and charging device for a vehicle according to the present disclosure. Detailed Implementation

[0032] Figure 1 This is a diagram illustrating some forms of charging devices for vehicles according to the present disclosure.

[0033] Reference Figure 1Reference numeral 102 indicates an external high-speed charger disposed outside the vehicle. The external high-speed charger 102 is electrically connected to a charging device for a vehicle according to an embodiment of the present disclosure via a charging cable connector and a high-voltage relay assembly 120. The high-voltage relay assembly 120 may include a current sensor 110 for detecting the magnitude of the current flowing through two high-voltage relays RL4 and RL5 and the (+) terminal respectively connected to the (+) and (-) terminals of the external high-speed charger 102. When the external high-speed charger 102 and the charger for a vehicle according to an embodiment of the present disclosure are connected via the charging cable connector, the two high-voltage relays RL4 and RL5 of the high-voltage relay assembly 102 are activated to provide current.

[0034] A charging device for vehicles can be provided to charge the high-voltage batteries 104 and 106 located in the vehicle. Figure 1 The high-voltage batteries 104 and 106 shown are composed of two 400V high-voltage batteries 104 and 106. A third high-voltage relay RL3, acting as a third switching element, can be positioned between the two 400V high-voltage batteries 104 and 106, i.e., between the first high-voltage battery 104 and the second high-voltage battery 106. Therefore, when the third high-voltage relay RL3 is open, the two 400V high-voltage batteries 104 and 106 are electrically isolated from each other and function as discrete 400V batteries. Conversely, when the third high-voltage relay RL3 is closed, the two 400V high-voltage batteries 104 and 106 are electrically connected to each other and function as 800V batteries.

[0035] The first high-voltage battery 104 can be charged independently by the first high-voltage relay RL1 and the first transistor IGBT1, which constitute the first switching element. That is, when the first high-voltage relay RL1 and the first transistor IGBT1 are turned on and the third high-voltage relay RL3, the second high-voltage relay RL2, and the second transistor IGBT2 are turned off, the first high-voltage battery 104 is charged independently. The first switching element can be configured by a combination of the first high-voltage relay RL1 and the first transistor IGBT1, or it can be configured by only the first transistor IGBT1.

[0036] The second high-voltage battery 106 can be charged independently via the second high-voltage relay RL2 and the second transistor IGBT2, which constitute the second switching element. That is, when the second high-voltage relay RL2 and the second transistor IGBT2 are turned on while the third high-voltage relay RL3, the first high-voltage relay RL1, and the first transistor IGBT1 are turned off, the second high-voltage battery 106 is charged independently. The second switching element can be composed of a combination of the second high-voltage relay RL2 and the second transistor IGBT2, or it can be composed of only the second transistor IGBT2.

[0037] When the first high-voltage relay RL1, the first transistor IGBT1, the second high-voltage relay RL2, and the second transistor IGBT2 are turned on while the third high-voltage relay RL3 is turned off, the first high-voltage battery 104 and the second high-voltage battery 106 can be charged independently.

[0038] When only the third high-voltage relay RL3 is turned on, while the first high-voltage relay RL1, the first transistor IGBT1, the second high-voltage relay RL2, and the second transistor IGBT2 are turned off, the first high-voltage battery 104 and the second high-voltage battery 106 are connected in series to charge as an 800V battery.

[0039] The first transistor IGBT1 and the second transistor IGBT2 are insulated-gate bipolar transistors (IGBTs), which are high-power switches. Under the control of the battery management system 112, which acts as a controller, the first transistor IGBT1 can be controlled by the gate voltage V1 supplied through the regulator 114. Under the control of the battery management system 112, the second transistor IGBT2 can also be controlled by the gate voltage V2 supplied through another regulator 116.

[0040] The operating regions of the first transistor IGBT1 and the second transistor IGBT2 can be divided into a linear region, a saturation region, and a cutoff region, respectively. In embodiments of this disclosure, each of the first transistor IGBT1 and the second transistor IGBT2 is operated in the saturation region and the cutoff region using the magnitudes of gate voltages V1 and V2, and the first transistor IGBT1 and the second transistor IGBT2 are used only as on / off switches. The magnitude of the current flowing through each of the first transistor IGBT1 and the second transistor IGBT2 is adjusted by operating each of the first transistor IGBT1 and the second transistor IGBT2 in the linear region using the magnitudes of gate voltages V1 and V2. As described above, adjusting the magnitude of the current flowing through each of the first transistor IGBT1 and the second transistor IGBT2 is to equally (uniformly) charge the first high-voltage battery 104 and the second high-voltage battery 106 by equally controlling the amount of current flowing to the first high-voltage battery 104 and the second high-voltage battery 106.

[0041] exist Figure 1 In this circuit, current sensor 110 can measure the magnitude of the charging current Icharge supplied through the (+) terminal of the external high-speed charger 102. Another current sensor 108 can measure the magnitude of the current flowing through the current path between the first high-voltage relay RL1 and the (+) electrode of the second high-voltage battery 106 (see [link]). Figure 2 and Figure 3 (I2 in the middle).

[0042] The vehicle charging device according to this embodiment can charge 800V high-voltage batteries 104 and 106 independently as two 400V high-voltage batteries 104 and 106. Most external high-speed chargers currently in use are 400V models, and the availability of 800V external high-speed chargers is increasing for faster charging. The vehicle charging device according to this embodiment can charge 800V high-voltage batteries 104 and 106 independently as two 400V high-voltage batteries 104 and 106 to accommodate both 400V and 800V external high-speed chargers.

[0043] In vehicles according to embodiments of this disclosure, reference will be made to... Figures 2 to 4 The changes in the charging method based on the capacity of the external high-speed charger 102 are described in detail.

[0044] Figure 2 This is a diagram illustrating charging control in response to a 400V-class external high-speed charger in certain forms of charging devices for vehicles according to this disclosure. Figure 2 The external high-speed charger 102 shown is a 400V model. In this case, the charging device for the vehicle according to the embodiment divides the 800V high-voltage batteries 104 and 106 into two 400V high-voltage batteries 104 and 106, and performs independent charging on the two 400V high-voltage batteries 104 and 106.

[0045] like Figure 2 As shown, the first high-voltage relay RL1, the first transistor IGBT1, the second high-voltage relay RL2, and the second transistor IGBT2 are turned on, while the third high-voltage relay RL3 is turned off. Through this control, the first high-voltage battery 104 and the second high-voltage battery 106 are independently charged as 400V batteries.

[0046] The first high-voltage battery 104 and the second high-voltage battery 106 can be charged using the charging current Icharge supplied from the external high-speed charger 102. Figure 2 In this case, the charging current Icharge can be supplied by dividing the battery into a first high-voltage battery 104 and a second high-voltage battery 106. Ideally, the first current I1 supplied to the first high-voltage battery 104 and the second current I2 supplied to the second high-voltage battery 106 should be the same. However, due to the physical characteristics of the current path, the first current I1 and the second current I2 may not be the same. When the first current I1 supplied to the first high-voltage battery 104 and the second current I2 supplied to the second high-voltage battery 106 are not equal, an imbalance may occur between the battery cells of the first high-voltage battery 104 and the second high-voltage battery 106.

[0047] Therefore, in the charging device for a vehicle in this embodiment, by adjusting the gate voltages V1 and V2 of each of the first transistor IGBT1 and the second transistor IGBT2, the magnitude of the current flowing through each of the first transistor IGBT1 and the second transistor IGBT2 is adjusted, thereby equally controlling the first current I1 supplied to the first high-voltage battery 104 and the second current I2 supplied to the second high-voltage battery 106. At this time, both gate voltages V1 and V2 are greater than 0V to turn on the first transistor IGBT1 and the second transistor IGBT2. However, in order to adjust each of the first current I1 and the second current I2 to have the same magnitude (I1 = I2), each of the gate voltages V1 and V2 can have different voltage levels greater than 0V. When I1 > I2, the magnitudes of the gate voltages V1 and V2 can be adjusted so that V1 < V2 to make I1 = I2. Conversely, when I1 < I2, the magnitudes of the gate voltages V1 and V2 can be adjusted so that V1 > V2 to make I1 = I2.

[0048] The relationship between the charging current Icharge, the first current I1, and the second current I2 can be expressed as Icharge = I1 + I2. Therefore, the second current I2 is I2 = Icharge - I1. Thus, the two current sensors 108 and 110 can independently measure the charging current Icharge, the first current I1, and the second current I2.

[0049] Figure 3 This is a diagram illustrating some forms of charging devices for vehicles according to the present disclosure, in response to charging control by an 800V-class external high-speed charger. Figure 3 The external high-speed charger 102 shown is an 800V-class model. In this case, the charging device for the vehicle according to the embodiment can charge as one 800V-class high-voltage battery 104 or 106 without distinguishing between 800V-class high-voltage batteries 104 and 106.

[0050] like Figure 3 As shown, when only the third high-voltage relay RL3 is turned on, while the first high-voltage relay RL1, the first transistor IGBT1, the second high-voltage relay RL2, and the second transistor IGBT2 are turned off, the first high-voltage battery 104 and the second high-voltage battery 106 are connected in series to be charged as an 800V battery.

[0051] Since both the first transistor IGBT1 and the second transistor IGBT2 are off, there is no need for current control by adjusting the gate voltages V1 and V2. Therefore, the gate voltages V1 and V2 are both 0V at this time. In addition, the charging current Icharge supplied from the external high-speed charger 102 is sequentially supplied to the second high-voltage battery 106 and the first high-voltage battery 104 to charge the first high-voltage battery 104 and the second high-voltage battery 106.

[0052] In response to an 800V-class external high-speed charger 102, if with Figure 3 The high-voltage batteries 104 and 106 are charged in the same way as shown, but when an imbalance in charging is found between the first high-voltage battery 104 and the second high-voltage battery 106, as described above... Figure 1 As mentioned in the description, only the first high-voltage relay RL1 and the first transistor IGBT1 are turned on to charge only the first high-voltage battery 104. Conversely, by turning on only the second high-voltage relay RL2 and the second transistor IGBT2 to charge only the second high-voltage battery 106, the charging imbalance between the first high-voltage battery 104 and the second high-voltage battery 106 can be eliminated.

[0053] Figure 4 The diagram illustrates some forms of vehicle charging methods and charging devices for vehicles disclosed herein.

[0054] The battery management system 112 can identify whether the external high-speed charger 102 is electrically connected to the vehicle (402) via a plug-in.

[0055] When the external high-speed charger 102 is electrically connected to the vehicle via a plug, the battery management system 112 can identify whether the charging voltage of the external high-speed charger 102 is 400V or 800V (404).

[0056] When the charging voltage of the external high-speed charger 102 is determined to be 400V, the battery management system 112 can be activated, allowing each of the first high-voltage battery 104 and the second high-voltage battery 106 to be independently charged to a 400V level battery (412) via subsequent switching control. That is, in this case, as referenced... Figure 2 As described, the battery management system 112 can turn on the first high-voltage relay RL1 and the second high-voltage relay RL2, turn off the third high-voltage relay RL3, and make each gate voltage V1 and V2 greater than 0V, thereby charging each of the first high-voltage battery 104 and the second high-voltage battery 106 independently as a 400V-class battery.

[0057] When the first current I1 used to charge the first high-voltage battery 104 and the second current I2 used to charge the second high-voltage battery 106 are the same (yes in 414), the battery management system 112 maintains each gate voltage V1 and V2 at a value greater than 0V so as to continue to charge the first high-voltage battery 104 and the second high-voltage battery 106 independently (416).

[0058] When the first current I1 used to charge the first high-voltage battery 104 and the second current I2 used to charge the second high-voltage battery 106 are different (not in 414), the battery management system 112 can adjust (variate) each of the gate voltages V1 and V2 to a specific value greater than 0V so that the magnitudes of the first current I1 and the second current I2 become the same. By adjusting (variing) the first current I1 and the second current I2, the first high-voltage battery 104 and the second high-voltage battery 106 are charged uniformly (418).

[0059] In operation 404, when the charging voltage of the external high-speed charger 102 is determined to be 800V, the battery management system 112 can begin charging as 800V-class high-voltage batteries 104 and 106 without requiring subsequent switching control to separate the 800V-class high-voltage batteries 104 and 106 (422). That is, in this case, as referenced... Figure 3 As described, the battery management system 112 can disconnect the first high-voltage relay RL1 and the second high-voltage relay RL2, turn on the third high-voltage relay RL3, and maintain each gate voltage V1 and V2 at 0V so that both the first transistor IGBT1 and the second transistor IGBT2 are turned off (422).

[0060] When the desired charging of high-voltage batteries 104 and 106 is completed through this charging (yes in 430), the battery management system 112 can complete the charging of high-voltage batteries 104 and 106.

[0061] According to embodiments of this disclosure, a vehicle can respond to multiple external chargers with different charging voltages without the need for a separate boost converter.

[0062] The disclosed embodiments are merely examples of technical ideas, and those skilled in the art will understand that various modifications, alterations, and substitutions can be made without departing from their essential characteristics. Therefore, the exemplary embodiments and drawings disclosed above are not intended to limit the technical ideas, but rather to describe the spirit of the technology, and the scope of the technical ideas is not limited by the embodiments and drawings. The scope of protection should be interpreted by the appended claims, and all technical ideas within the equivalent scope should be interpreted as included within the scope of the claims.

Claims

1. A charging device for a vehicle, the charging device comprising: A third switching element is disposed between the first battery and the second battery, and the third switching element is configured to electrically connect or disconnect the first battery and the second battery. A first switching element is configured to supply or cut off charging current supplied from the outside to the first battery; The second switching element is configured to supply or cut off the charging current supplied from the outside to the second battery; as well as The controller is configured to control the first switching element, the second switching element, and the third switching element to selectively charge at least one of the first battery and the second battery. The first switching element includes a first transistor configured to regulate the supply of charging current; as well as The second switching element includes a second transistor configured to regulate the supply of charging current. By adjusting the gate voltage of each of the first transistor and the second transistor, the magnitude of the current flowing through each of the first transistor and the second transistor is adjusted, thereby equally controlling the first current supplied to the first battery and the second current supplied to the second battery.

2. The charging device according to claim 1, wherein, The controller is configured to: The charging current supplied to each of the first and second batteries is varied and adjusted so that the charge of the first battery is equal to the charge of the second battery.

3. The charging device according to claim 1, wherein: The first switching element further includes a first relay configured to control the charging current; and The second switching element also includes a second relay configured to control the charging current.

4. The charging device according to claim 1, wherein, The controller is configured to: By switching on the third switching element and disconnecting the first and second switching elements, the first and second batteries can be controlled to charge as a single battery.

5. The charging device according to claim 1, wherein, The controller is configured to: By disconnecting the third switching element and connecting the first and second switching elements, the first and second batteries can be controlled to be charged independently.

6. The charging device according to claim 1, wherein, The controller is configured to: Only one of the first and second batteries is charged independently, controlled by the following method: Disconnect the third switching element; Connect one of the first switching element and the second switching element; as well as When one of the first switching element and the second switching element is turned on, the other of the first switching element and the second switching element is turned off.

7. The charging device according to claim 1, wherein, The controller is configured to: The charging capacity of the external charger supplying the charging current controls the first switching element, the second switching element, and the third switching element so that at least one of the first battery and the second battery is selectively charged.

8. A method for controlling a charging device for a vehicle, the method comprising: The controller identifies the charging capacity of the external charger supplying the charging current; as well as The controller controls a first switching element, a second switching element, and a third switching element in response to the charging capacity of the external charger, such that at least one of the first battery and the second battery is selectively charged. The first switching element is configured to supply or cut off the charging current supplied from the external source to the first battery, and the second switching element is configured to supply or cut off the charging current supplied from the external source to the second battery. The method further includes: The supply of charging current is regulated by a first transistor included in the first switching element; and The supply of charging current is regulated by a second transistor included in the second switching element; and By adjusting the gate voltage of each of the first transistor and the second transistor, the magnitude of the current flowing through each of the first transistor and the second transistor is adjusted, thereby equally controlling the first current supplied to the first battery and the second current supplied to the second battery.

9. The method according to claim 8, wherein, The method further includes: The controller variably adjusts the magnitude of the charging current supplied to the first battery and the second battery so that the charge amount of the first battery is equal to the charge amount of the second battery.

10. The method according to claim 8, wherein, The method includes: The charging current is controlled by a first relay included in the first switching element; and The charging current is controlled by a second relay included in the second switching element.

11. The method according to claim 8, wherein, The method further includes: The controller controls the first battery and the second battery to be charged as a single battery by turning on the third switching element and turning off the first switching element and the second switching element.

12. The method according to claim 8, wherein, The method further includes: The controller controls the independent charging of the first battery and the second battery by disconnecting the third switching element and connecting the first switching element and the second switching element.

13. The method according to claim 8, wherein, The method further includes: The controller controls only one of the first and second batteries to be charged independently in the following manner: Disconnect the third switching element; Connect one of the first switching element and the second switching element; and When one of the first switching element and the second switching element is turned on, the other of the first switching element and the second switching element is turned off.

14. A vehicle comprising: First battery and second battery; A third switching element is disposed between the first battery and the second battery, and the third switching element is configured to electrically connect or disconnect the first battery and the second battery. A first switching element is configured to supply or cut off charging current supplied from the outside to the first battery; The second switching element is configured to supply or cut off the charging current supplied from the outside to the second battery; as well as The controller is configured to control the first switching element, the second switching element, and the third switching element to selectively charge at least one of the first battery and the second battery. The first switching element includes a first transistor configured to regulate the supply of charging current; as well as The second switching element includes a second transistor configured to regulate the supply of charging current. By adjusting the gate voltage of each of the first transistor and the second transistor, the magnitude of the current flowing through each of the first transistor and the second transistor is adjusted, thereby equally controlling the first current supplied to the first battery and the second current supplied to the second battery.

15. A method for controlling a vehicle, the method comprising: The controller identifies the charging capacity of the external charger supplying the charging current; as well as The controller controls a first switching element, a second switching element, and a third switching element in response to the charging capacity of the external charger, such that at least one of the first battery and the second battery is selectively charged. The first switching element is configured to supply or cut off the charging current supplied from the external source to the first battery, and the second switching element is configured to supply or cut off the charging current supplied from the external source to the second battery. The method further includes: The supply of charging current is regulated by a first transistor included in the first switching element; and The supply of charging current is regulated by a second transistor included in the second switching element; and By adjusting the gate voltage of each of the first transistor and the second transistor, the magnitude of the current flowing through each of the first transistor and the second transistor is adjusted, thereby equally controlling the first current supplied to the first battery and the second current supplied to the second battery.

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