Charger including balancing charging control between serial battery packs and charging control method

Abstract

The present invention relates to a charger and a charging control method including a balancing charging control function between series battery packs, and provides a charger and a charging control method capable of charging by balancing the SOC state between series-connected battery packs by having a single power supply.

Description

Technology Field

[0001] The present invention relates to a charger and a charging control method thereof that charges by balancing the SOC between battery packs through the adjustment of the charge amount when charging series-connected battery packs. Background Technology

[0002] Batteries are used in various fields, including portable electronic devices such as smartphones, laptop computers, and tablet PCs, as well as electric scooters, electric vehicles, and energy storage capacitors. Fields such as electric vehicles or smart grid systems often require large capacities, so multiple battery packs are connected in series to increase output.

[0003] In order to charge multiple series-connected battery packs (10) in this manner, a charger (20) is required that has a power supply (22) corresponding to each of the battery packs as shown in FIG. 1, in order to prevent SOC deviation between battery packs that occurs according to the characteristics and capacity of each battery pack during charging.

[0004] However, in such cases, there is a problem where the cost of the charger increases because the number of power supplies required in the charger also increases as the number of series-connected battery packs increases.

[0005] (Patent Document 1) KR10-2110043 B1 The problem to be solved

[0006] The present invention aims to solve the aforementioned problem and provides a charger and a charging control method that can balance the SOC between multiple series battery packs and charge them even with only one power supply. means of solving the problem

[0007] A charger for charging by balancing the State of Charge (SOC) between two or more battery packs connected in series according to the present invention comprises: a power supply connected in parallel with the battery packs to supply a charging current; a charging current control unit configured at each connection terminal with each battery pack located between the battery packs and the power supply, which controls the amount of charging current supplied from the power supply to the corresponding battery pack according to the occurrence of an SOC deviation between the battery packs; a second communication unit that establishes mutual communication with each of the battery packs; and a control unit that detects whether an abnormal SOC deviation has occurred between the battery packs based on the SOC of each battery pack obtained through the second communication unit, and balances the SOC state between the battery packs through the control of the charging current control unit corresponding to the battery pack in which the abnormal SOC deviation has occurred.

[0008] Specifically, the charging current control unit is characterized by comprising: a distribution switch connected in parallel to the battery pack and power supply, which connects a current control path that controls the amount of charging current of the battery pack as it is switched on by the control of the control unit; and a resistor connected in series to the distribution switch to form the current control path.

[0009] Meanwhile, the control unit comprises: an SOC receiving unit that receives an SOC from each of the battery packs through the second communication unit; an SOC deviation calculation unit that calculates an SOC deviation between the battery packs using the SOC values ​​received from the SOC receiving unit; an SOC deviation detection unit that detects an SOC deviation that has a value greater than or equal to a predetermined reference deviation by comparing each SOC deviation calculated by the SOC deviation calculation unit with a predetermined reference deviation; a charge control pack determination unit that determines a battery pack corresponding to the higher SOC value among the SOCs corresponding to the detected SOC deviation as a charge control pack when an SOC deviation is detected by the SOC deviation detection unit; and a distribution switch control unit that turns on the distribution switch corresponding to the battery pack determined to be a charge control pack by the charge control pack determination unit.

[0010] When the distribution switch is turned on by the distribution switch control unit, the charging current from the power supply is distributed and flows through the current control path formed by the distribution switch and the resistor.

[0011] Accordingly, the battery pack corresponding to the charge control pack is characterized by being charged with a current amount reduced by the current flowing through the current control path from the charging current from the power supply.

[0012] Meanwhile, the amount of current flowing through the above current control path is characterized by varying according to the voltage of the battery pack and the value of the resistance.

[0013] Meanwhile, each of the above battery packs is characterized by being configured to include: a first communication unit that communicates with a second communication unit of the charger; a SOC measuring unit that measures the SOC of the battery pack; and an SOC transmitting unit that transmits the SOC measured by the SOC measuring unit to the charger through the first communication unit.

[0014] A method for charging by balancing the State of Charge (SOC) between two or more battery packs connected in series in a charger having a single power supply according to the present invention comprises: a communication connection step of establishing mutual communication with each of the battery packs; a SOC acquisition step of acquiring a corresponding SOC value from each of the battery packs connected through communication in the communication connection step; a SOC deviation calculation step of calculating a SOC deviation between the battery packs using the SOC values ​​acquired in the SOC value acquisition step; a SOC deviation detection step of detecting an SOC deviation that has a value greater than or equal to a predetermined reference deviation by comparing each SOC deviation calculated in the SOC deviation calculation step with a predetermined reference deviation; a charging control pack determination step of determining a battery pack corresponding to the higher SOC value among the SOCs corresponding to the SOC deviation when an SOC deviation is detected in the SOC deviation detection step as a charging control pack; and a distribution switch ON step of turning on a distribution switch corresponding to the battery pack determined as a charging control pack in the charging control pack determination step to distribute the charging current from the power supply to another battery pack.

[0015] When the distribution switch is turned on by the above switch-on switching step, a current control path is formed to the distribution switch and the resistor connected in series therewith.

[0016] Accordingly, when the current control path is formed, the charging current from the power supply is distributed and flows through the current control path, and the battery pack corresponding to the charging control pack is charged with a current amount that is reduced by the amount of the current flowing through the current control path from the charging current of the power supply.

[0017] Meanwhile, the amount of current flowing through the above current control path is characterized by varying according to the voltage of the battery pack and the value of the resistance. Effects of the invention

[0018] The present invention has the effect of lowering the manufacturing cost of the charger because it is possible to charge multiple battery packs connected in series by balancing the SOC even with only one power supply in the charger. Brief explanation of the drawing

[0019] Figure 1 is a drawing showing a charger for charging a conventional series-connected battery pack. FIG. 2 is a diagram showing the connection state between a charger and a series-connected battery pack according to the present invention. Figure 3 is a block diagram schematically showing the detailed configuration of each battery pack and charger. Figure 4 is a diagram showing the charging current flow in a normal state where no abnormal deviation in SOC occurs between batteries. Figure 5 is a diagram showing the charging current flow when the charge amount of the first battery pack is controlled. Figure 6 is a diagram showing the charging current flow when the charge amount of the second battery pack is controlled. FIG. 7 is a flowchart illustrating a charging control method for balancing SOC between series-connected battery packs according to the present invention. Specific details for implementing the invention

[0020] Embodiments of the present invention are described in detail below with reference to the attached drawings so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. Furthermore, in order to clearly explain the present invention in the drawings, parts unrelated to the explanation have been omitted, and similar parts throughout the specification have been given similar reference numerals.

[0021] The present invention will be described in detail below with reference to the drawings.

[0022] 1. Charger according to the present invention

[0023] Before describing the charger according to the present invention, a battery pack connected to the charger is described.

[0024] 1.1. Battery pack (100)

[0025] The charger (200) of the present invention is connected to two or more battery packs (100a to 100n) connected in series and charges the battery packs (100a to 100n). For convenience of explanation, the battery packs from the topmost battery pack (100a) to the bottommost battery pack (100n) may be sequentially referred to as the first, second, ..., n battery packs.

[0026] Meanwhile, each of the interconnected battery packs (100a to 100n) is configured to include the following configuration.

[0027] a. First communication unit (110)

[0028] The first communication unit is configured to communicate with the charger (200), specifically being mutually connected to the second communication unit (230) of the charger (200) described later. Through this, the battery pack (100) can transmit its measured SOC (State Of Charge, hereinafter referred to as 'SOC') value to the charger (200).

[0029] b. SOC measurement unit (120)

[0030] The SOC measuring unit can measure its own SOC at predetermined periodic intervals. The method for measuring SOC may use conventional methods such as the current integration method or voltage modeling techniques.

[0031] c. SOC transmission unit (130)

[0032] The SOC transmission unit is configured to transmit the SOC measured by the SOC measurement unit (120) to the charger (200) via the first communication unit (110). At this time, the pack identification number can be transmitted together with the SOC transmission. Through this SOC transmission unit, the charger (200) can check the SOC status of each of the battery packs (100a to 100n). In addition, the switch identification number of the charging current control unit (220), which will be described later and corresponds to the battery pack, can also be transmitted along with the pack identification number.

[0033] 1.2. Charger (200)

[0034] Hereinafter, a charger (200) according to the present invention will be described.

[0035] a. Power supply (210)

[0036] The charger (200) of the present invention is equipped with a single power supply connected in parallel with series-connected battery packs (100a to 100n). The power supply is configured to convert current from an external power source (not shown) into direct current and supply it as charging current to the battery packs (100a to 100n). Conventional chargers (20) had the problem of increasing the cost of the charger by individually equipping a power supply (22) for each series-connected battery pack (10) as shown in FIG. 1, but the charger (200) of the present invention is equipped with only one power supply as shown in FIG. 2, so the cost of the charger can be lowered.

[0037] b. Charging current control unit (220)

[0038] The charging current control unit is configured to correspond to each of the battery packs (100a to 100n) between the series-connected battery packs (100a to 100n) and the power supply (210), and is configured to control the amount of charging current supplied from the power supply (210) to the corresponding battery pack (100). More specifically, the charging current control unit may be provided at each connection terminal with each battery pack (100a to 100n). Such a charging current control unit is configured to include the following detailed configurations.

[0039] 1) Distribution switch (222)

[0040] A distribution switch is connected in parallel to the corresponding battery pack (100) and power supply (210) and is turned on according to the control of the control unit (240) described later, thereby forming a current control path that regulates the amount of charging current from the power supply (210). The distribution switch is initially in an off state, and when it is switched to an on state according to the control of the control unit (240) described later, a current control path is formed to a resistor (224) connected in series thereto.

[0041] In the initial state where the series-connected battery packs (100a~100n) and the charger (200) are connected, and in the normal state where no SOC deviation occurs between the battery packs (100a~100n), all distribution switches (222a~222n) are in the off state, so the charging current from the charger (200) flows along the path indicated by the arrow in FIG. 4 to charge the battery packs (100a~100n).

[0042] In this state, if an abnormal deviation in SOC occurs between battery packs, turning on the distribution switch corresponding to the battery pack with the higher SOC state causes the charging current from the power supply to flow through the current control path formed by the distribution switch (222) - resistor (224), thereby reducing the amount of charge supplied to the corresponding battery pack.

[0043] Meanwhile, a switch identification number may be assigned to each distribution switch. Accordingly, the corresponding pack identification number and switch identification number can be stored in conjunction for each battery pack, or the pack identification number and switch identification number can be stored in conjunction within the charger itself, thereby enabling the identification of the distribution switch corresponding to the battery pack requiring charge level adjustment.

[0044] 2) Resistance (224)

[0045] A resistor can be connected in series with the distribution switch (222) to form a current control path to reduce the amount of charge supplied from the power supply (210) to the corresponding battery pack (100) when the distribution switch (222) is switched to the ON state. As previously described, when the distribution switch (222) is turned ON, a portion of the charging current from the power supply (210) flows through the current control path formed by the distribution switch-resistor, thereby reducing the amount of charge supplied to the corresponding battery pack. At this time, the magnitude of the current flowing through the current control path depends on the battery pack voltage and the value of the resistor.

[0046] A detailed description of the current flow formed according to such a distribution switch (222) and resistor (224) will be provided in the configuration of the distribution switch control unit (245) below.

[0047] Meanwhile, although the present specification describes the charging current control unit (220) as being configured inside the charger (200), it is not limited thereto and may be configured in the battery pack (100). However, if configured in the battery pack, it may affect the miniaturization / lightweighting of the battery when considering the space occupied, so it may be preferable to configure it inside the charger.

[0048] c. Second communication unit (230)

[0049] The second communication unit is configured to communicate with the serially connected battery packs (100a to 100n) and is mutually connected to the first communication unit (110) configured in each of the previously described battery packs (100a to 100n). Through this, SOC status information for each of the battery packs (100a to 100n) can be obtained.

[0050] D. Control unit (240)

[0051] The control unit determines whether an abnormal deviation in SOC has occurred between battery packs based on the SOC of each of the series-connected battery packs (100a to 110n), and controls the charging current control unit (220) corresponding to the battery pack where an abnormal deviation in SOC has occurred to balance the SOC state between battery packs. Such a control unit may be configured to include the following detailed configurations.

[0052] 1) SOC receiver (241)

[0053] The SOC receiving unit can receive the SOC from the SOC transmitting unit (130) of each of the battery packs (100a~100n) through the second communication unit (230).

[0054] 2) SOC deviation calculation unit (242)

[0055] The SOC deviation calculation unit can calculate the SOC deviation between battery packs (100a to 100n) using the SOC of the battery packs (100a to 100n) received from the SOC receiving unit (241).

[0056] 3) SOC abnormal deviation detection unit (243)

[0057] The SOC abnormal deviation detection unit can detect an SOC abnormal deviation having a value greater than or equal to a predetermined reference deviation by comparing each SOC deviation calculated by the SOC deviation calculation unit (243) with a predetermined reference deviation. When detected, it can output an SOC abnormal deviation detection signal indicating this.

[0058] 4) Charging control pack judgment unit (244)

[0059] When the charge control pack extraction unit detects an SOC deviation that is greater than or equal to a predetermined reference deviation by the SOC deviation detection unit (243), it can determine that the battery pack having the higher SOC value among the detected SOC deviation values ​​that are greater than or equal to the predetermined reference deviation is a battery pack requiring charge amount control. Upon determination, it can output a charge control pack signal including the corresponding battery pack identification number.

[0060] For example, if the SOC corresponding to the SOC deviation value above the SOC is the SOC of the first and second battery packs (100a, 100b), and the battery pack having the higher SOC value among them is the first battery pack (100a), then the first battery pack (100a) is determined to be a charge control pack that requires charge amount control.

[0061] 5) Distribution switch control unit (245)

[0062] The distribution switch control unit can switch the distribution switch (222) corresponding to the battery pack determined to be a charge control pack by the charge control pack determination unit (244) to an ON state. Accordingly, as described above, a current control path from the ON-controlled distribution switch to the resistor is formed, and the charging current from the power supply (210) is distributed and flows through the current control path, thereby reducing the amount of charge supplied to the corresponding battery pack.

[0063] To explain the principle, assuming the charger (200) current is 10A, the battery pack voltage is 50V, and the resistance is 10 ohms, the current flowing through the current control path formed by the distribution switch-resistor becomes 5A according to I = V / R.

[0064] For example, if the battery pack determined to be the charge control pack is the first battery pack (100a), the distribution switch control unit (245) switches the corresponding distribution switch (222a) to the ON state. Then, as shown in FIG. 5, the charging current of 10A from the power supply (210) corresponding to path ① is divided and flows into paths ② and ③. At this time, since the current flowing into path ③, which is the current control path, is 5A, the current flowing into path ② becomes 5A (10A-5A), and the first battery pack (100a) is charged only with the current of 5A flowing into path ②. Accordingly, the second battery pack (100b) is charged to 10A, which corresponds to the original charger current, by the current of 5A from path ③ and the current of 5A from path ④. In this way, as the first battery pack (100a) is charged at 5A and the second battery pack (100b) is charged at 10A, the SOC difference between the first and second battery packs (100a, 100b) corresponding to the SOC difference is reduced.

[0065] As another example, if the battery pack determined to be the charging control pack is the second battery pack (100b), the distribution switch control unit (245) switches the corresponding distribution switch (222b) to the ON state. Then, as shown in FIG. 6, the charging current of 10A from the power supply (210) that charged the first battery pack (100a) through path ① is divided and flows into paths ② and ③. At this time, since the current flowing through path ③, which is the current control path, is 5A, the current flowing through path ② becomes 5A (10A minus 5A), and the second battery pack (100b) is charged only with the 5A coming in through path ②. Accordingly, the third battery pack (100c) is charged with the current of 5A from path ③ and the current of 5A from path ④, i.e., 5A + 5A = 10A. Therefore, the second battery pack (100b) is charged with a lower current than the other battery packs (100a, 100c, … , 100n), and the SOC difference between the battery packs is reduced.

[0066] In this way, when an abnormal deviation in SOC occurs between battery packs, a discharge path is formed through a distribution switch and a resistor, causing the charging current from the power supply to be distributed and flow. Consequently, the amount of charging current supplied to the corresponding battery pack is reduced, thereby resolving the abnormal deviation in SOC between the battery packs. Therefore, unlike conventional methods that require power supplies corresponding to the number of battery packs in the charger to prevent SOC deviation between series-connected battery packs, it is possible to charge by balancing the SOC status between series-connected battery packs using only a single power supply, thereby providing improved charging efficiency while lowering charger costs.

[0067] 2. Charging control method according to the present invention (see FIG. 7)

[0068] A charging control method for balancing the SOC between series-connected battery packs (100a to 100n) in a charger (200) according to the present invention may be configured to include the following steps.

[0069] 2.1. Communication connection step (S100)

[0070] The communication connection step is a step of connecting communication with two or more serially connected battery packs (100a to 100n), and as previously described, the first communication unit (110) of each of the battery packs (100a to 100n) and the second communication unit (230) of the charger (200) may be connected to each other for communication.

[0071] 2.2. SOC Value Acquisition Step (S200)

[0072] The step of obtaining the SOC value is a step of obtaining the corresponding SOC value from each of the battery packs (100a to 100n) that are connected via communication through the communication connection step (S100). This can be achieved by each of the battery packs (100a to 100n) measuring its own SOC (SOC measuring unit, 120) and transmitting it to the charger (200) side (SOC transmitting unit, 130), and then the charger (200) obtaining the SOC value transmitted from each of the battery packs (100a to 100n) through the communication connection by the communication connection step (S100).

[0073] 2.3. SOC Deviation Calculation Step (S300)

[0074] The SOC deviation calculation step is a step of calculating the SOC deviation between battery packs using the SOC values ​​of each of the battery packs (100a~100n) obtained in the SOC value acquisition step (S200). This step is performed by the SOC deviation calculation unit (244) described above.

[0075] 2.4. SOC Abnormal Deviation Detection Step (S400)

[0076] The SOC abnormal deviation detection step is a step of detecting an SOC abnormal deviation having a value greater than or equal to a predetermined reference deviation by comparing each SOC deviation calculated in the SOC deviation calculation step (S300) with a predetermined reference deviation, and is performed by the SOC abnormal deviation detection unit (245) described above.

[0077] 2.5. Charge control pack determination step (S500)

[0078] The charge control pack determination step can determine that when an SOC deviation that is greater than or equal to a predetermined reference deviation is detected by the SOC deviation detection step (S400), the battery pack having the higher SOC value among the detected SOC deviation values ​​that are greater than or equal to the predetermined reference deviation is a charge control pack that requires charge amount adjustment (charge control pack determination unit, 244).

[0079] For example, if the SOC corresponding to the SOC deviation is the SOC of the first and second battery packs (100a, 100b), and the battery pack having the higher SOC value among them is the first battery pack (100a), then the first battery pack (100a) is determined to be a charge control pack that requires charge amount control.

[0080] 2.6. Distribution switch ON step (S600)

[0081] The distribution switch ON switching step may switch the distribution switch corresponding to the charging control pack to the ON state in order to reduce the amount of charging current supplied to the battery pack determined as the charging control pack in the charging control pack determination step (S500). When the distribution switch is turned ON, a current control path from the distribution switch to the resistor is formed to distribute the charging current from the power supply to the battery pack connected to the bottom of the charging control pack by a predetermined amount of current, and the amount of current reduced by the amount of current flowing through the current control path from the charging current from the power supply (210) is supplied to the corresponding battery pack so that the amount of charging can be controlled.

[0082] For example, when the charging control pack is the first battery pack (100a) and the corresponding distribution switch (222a) is turned on, as shown in FIG. 5, the charging current from the power supply in path ① is distributed and flows into path ②, which is the charging current path to the battery pack (100a), and path ③, which is the current control path formed by the distribution switch (222a) and the resistor (224a). At this time, the magnitude of the current flowing into path ③ depends on the voltage of the battery pack (100a) and the value of the resistor (224a). Then, the amount of current reduced by the amount of current flowing into path ③ from the charging current from the power supply flows into path ② to charge the battery pack (100a), thereby charging the first battery pack (100a) to a low charge amount. And, the current flowing through path ③ is supplied to the second battery pack (100b), which is the battery pack at the bottom, so that the second battery pack (100b) is eventually charged with a current amount equal to the amount of the charging current that is the sum of the charging current that charges the first battery pack (100b) flowing into path ④ and the charging current flowing in from path ③, that is, the amount of the charging current of the original power supply. Therefore, the first battery pack (100a) with a high SOC is charged with a low amount of charge, and the second battery pack (100b) with a lower SOC than the first battery pack is charged with the existing amount of charge, so that the SOC difference between the first and second battery packs (100b) can be eliminated.

[0083] Meanwhile, although the technical concept of the present invention has been specifically described according to the above embodiments, it should be noted that the above embodiments are for illustrative purposes only and are not intended to be limiting. Furthermore, those skilled in the art will understand that various embodiments are possible within the scope of the technical concept of the present invention. Explanation of the symbols

[0084] 100: Battery pack 110: 1st Communications Unit 120: SOC measurement section 130: SOC Transmission Section 200: Charger 210: Power supply 220: Charging current regulator 222: Distribution switch 224: Resistance 230: 2nd Communications Division 240: Control unit 241: SOC receiver 242: SOC Deviation Calculation Unit 243: SOC Abnormal Deviation Detector 244: Charge control pack judgment unit 245: Distribution switch control unit

Claims

Claim 1 A charger for charging by balancing the State of Charge (SOC) between two or more battery packs connected in series, comprising: a power supply connected in parallel with the battery packs to supply a charging current; a charging current control unit configured at each connection terminal with each battery pack located between the battery packs and the power supply, forming a current control path including a distribution switch and a resistor connected in parallel with the battery pack, and controlling the amount of charging current supplied to the corresponding battery pack by turning on the distribution switch according to the occurrence of an SOC deviation between the battery packs to divert a portion of the charging current from the power supply to the current control path; a second communication unit connecting to each of the battery packs for mutual communication; and a control unit that detects whether an abnormal SOC deviation has occurred between the battery packs based on the SOC of each battery pack obtained through the second communication unit, and controls the distribution switch of the charging current control unit corresponding to the battery pack where the abnormal SOC deviation has occurred to balance the SOC state between the battery packs. Claim 2 delete Claim 3 The charger according to claim 1, wherein the control unit comprises: an SOC receiving unit that receives an SOC from each of the battery packs through the second communication unit; an SOC deviation calculation unit that calculates an SOC deviation between the battery packs using the SOC values ​​received from the SOC receiving unit; an SOC deviation detection unit that detects an SOC deviation that has a value greater than or equal to the predetermined reference deviation by comparing each SOC deviation calculated by the SOC deviation calculation unit with a predetermined reference deviation; a charge control pack determination unit that determines a battery pack corresponding to the higher SOC value among the SOCs corresponding to the detected SOC deviation as a charge control pack when an SOC deviation is detected by the SOC deviation detection unit; and a distribution switch control unit that turns on the distribution switch corresponding to the battery pack determined as a charge control pack by the charge control pack determination unit. Claim 4 delete Claim 5 A charger according to paragraph 3, wherein the battery pack corresponding to the charge control pack is charged with a current amount reduced by the current flowing through the current control path from the charging current from the power supply. Claim 6 A charger according to claim 5, characterized in that the amount of current flowing through the current control path varies depending on the voltage of the battery pack and the value of the resistance. Claim 7 A charger according to claim 1, wherein each of the battery packs comprises: a first communication unit that communicates with a second communication unit of the charger; a SOC measuring unit that measures the SOC of the battery pack; and a SOC transmitting unit that transmits the SOC measured by the SOC measuring unit to the charger through the first communication unit. Claim 8 A method for charging by balancing the State of Charge (SOC) between two or more battery packs connected in series in a charger equipped with a single power supply, comprising: a communication connection step for establishing mutual communication with each of the battery packs; a SOC acquisition step for acquiring a corresponding SOC value from each of the battery packs connected through communication in the communication connection step; a SOC deviation calculation step for calculating a SOC deviation between the battery packs using the SOC values ​​acquired in the SOC value acquisition step; and a SOC deviation detection step for detecting an SOC deviation having a value greater than or equal to the predetermined reference deviation by comparing each SOC deviation calculated in the SOC deviation calculation step with a predetermined reference deviation. A charging control method comprising: a charging control pack determination step in which, when an abnormal deviation in SOC is detected in the above SOC abnormal deviation detection step, a battery pack corresponding to the higher SOC value among the SOCs corresponding to the abnormal deviation in SOC is determined as a charging control pack; and a step of balancing by adjusting the amount of charging current of the battery pack by turning on a distribution switch of a current control path connected in parallel to the battery pack determined as a charging control pack in the above charging control pack determination step, thereby branching a portion of the charging current from the power supply to the current control path. Claim 9 A charging control method according to claim 8, characterized in that when a distribution switch is turned on by the above-mentioned switch-on switching step, a current control path is formed to the distribution switch and a resistor connected in series thereto. Claim 10 A charging control method according to claim 9, wherein when the current control path is formed, the charging current from the power supply is distributed and flows through the current control path, and the battery pack corresponding to the charging control pack is charged with a current amount reduced by the amount of the current flowing through the current control path from the charging current of the power supply. Claim 11 A charging control method according to claim 10, characterized in that the amount of current flowing through the current control path varies depending on the voltage of the battery pack and the value of the resistance.

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