Charging system

Abstract

This charging system prevents the terminal voltage from exceeding the rated voltage of the contactor on the battery pack when disconnected, and also reduces the overall weight. [Solution] The charging system 10 does not have a lead-acid battery, but has a plurality of battery units 12, a plurality of AC / DC converters 14, a DC / DC converter 16, and a control unit 18. Each of the plurality of battery units 12 has a plurality of battery packs 30 connected in parallel to each other and connected in series to each other. Each of the plurality of AC / DC converters 14 is individually connected in parallel to each battery unit 12 and converts the AC current of the system 20 into DC current and outputs it to each battery unit 12. The DC / DC converter 16 is connected between the ends of the series connection of the plurality of battery units 12 and the charger 22 and converts the DC voltage of the plurality of battery units 12 and outputs it to the charger 22. Each battery pack 30 has a lithium-ion battery 32, a contactor 34 and a BMS 36.

Description

Technical Field

[0001] The present invention relates to a charging system that supplies DC power from a plurality of battery packs charged with power from a system.

Background Art

[0002] Conventionally, users of electric vehicles charge the built-in battery of the electric vehicle using a charger installed at home, charging stands installed at various places when going out, and the like. In order to improve the convenience of users, it is necessary to increase not only the charger at home but also the number of charging stands installed when going out. However, since charging stands are often expensive and have limited capacity, it is desired to increase their capacity and reduce their price. In response to these needs, a charging system using used battery packs has been proposed.

[0003] Patent Document 1 describes a charging system in which the built-in battery of a used electric vehicle is diverted to a device battery that stores the power of a charging stand. On the other hand, in order to charge, adjust the voltage, and replenish a plurality of battery packs, a configuration in which a lead-acid battery or a converter is individually connected in parallel to each battery pack is disclosed. Patent Document 2 describes a hybrid battery in which a plurality of virtual batteries formed by connecting an organic solution-based battery such as a lithium-ion battery and an aqueous solution-based battery such as a lead-acid battery in parallel are connected in series. Patent Document 3 describes a power supply device that supplies power to an external device using a battery pack having a terminal portion that can be electrically connected to a plurality of different types of devices.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

[0005] However, the charging system described in Patent Document 1 has a problem in that, when multiple used battery packs are connected in series to increase the output voltage, and each used battery pack has a built-in contactor, if one of the used battery packs is disconnected, the output voltage of the series-connected used battery packs is applied to the terminals of the contactor on the disconnected used battery pack, exceeding the rated voltage of the contactor. Furthermore, this problem is independent of whether the battery packs are new or used, and is an unavoidable problem when multiple battery packs equipped with contactors are connected in series. In addition, the hybrid battery described in Patent Document 2 has the problem of being heavy because it uses many lead-acid batteries. The power supply device described in Patent Document 3 has the problem that it does not take into account the series connection of battery packs. The charging system described in Patent Document 1, the hybrid battery described in Patent Document 2, and the power supply device described in Patent Document 3 have the problem that they do not take into account battery packs that have a contactor and BMS integrated into one unit, as well as secondary batteries.

[0006] This invention has been made in view of the problems of the conventional invention, and the object of this invention is to provide a charging system that prevents the terminal voltage at the time of disconnection from the rated voltage of the contactor provided in the battery pack from exceeding the rated voltage of the contactor provided in the battery pack, even when multiple battery packs are connected in series with each other in order to increase the output voltage, and that can reduce the total weight. Furthermore, other objectives of the present invention, in addition to the above objectives, include simplifying the control during battery pack connection and equalization, and providing a charging system that can achieve a capacity equal to or greater than conventional systems while remaining inexpensive. [Means for solving the problem]

[0007] To achieve the above objective, the inventors conducted extensive research and first discovered that by individually connecting an AC / DC converter in parallel to each of several battery packs connected in series, instead of a lead-acid battery, and outputting at predetermined voltage and current values, it is possible to prevent the terminal voltage from exceeding the rated voltage of the contactor provided in the battery pack when disconnected, and to reduce the overall weight.

[0008] Furthermore, the inventors have discovered that by using this configuration to connect and equalize multiple battery packs connected in series with each other, the control during battery pack connection and equalization can be simplified, leading to the present invention.

[0009] In other words, the present invention provides a charging system comprising: a plurality of battery packs each connected in parallel to one another, a plurality of battery sections connected in series to one another, a plurality of AC / DC converters each individually connected in parallel to each battery section and converting the alternating current of the system into a direct current and outputting it to each battery section, a DC / DC converter connected between the ends of the series connection of the plurality of battery sections and a charger and converting the DC voltage of the plurality of battery sections and outputting it to the charger, and a control unit, wherein the charging system does not include a lead-acid battery, each battery pack includes a lithium-ion battery, a contactor for electrically connecting and disconnecting the lithium-ion battery, and a BMS having the function of collecting battery data output by the lithium-ion battery and transmitting it to the control unit, and the control unit is connected to the BMS of each battery pack, the DC / DC converter and each AC / DC converter, and provides a charging system that controls the on / off state of each contactor via each BMS and controls the operation of the DC / DC converter and each AC / DC converter based on the battery data.

[0010] In this invention, it is preferable that the control unit specifies the output voltage and output current of each AC / DC converter connected in parallel to each battery section based on the voltage of the corresponding battery section, and controls each AC / DC converter to apply a voltage higher than that of the corresponding battery section to the corresponding battery section. It is preferable that the control unit activates multiple AC / DC converters before activating the DC / DC converter, and while raising and lowering the output voltage of each AC / DC converter, it controls the battery pack contactor to turn on when the difference between the output voltage of each AC / DC converter and the battery pack contactor falls within a preset voltage difference.

[0011] Furthermore, in the present invention, it is preferable that the control unit, when voltage variations occur among the multiple battery units and the voltage of the first battery unit becomes lower than the voltage of the second battery unit, controls the first AC / DC converter connected in parallel to the first battery unit to apply a voltage higher than the voltage of the second battery unit to the first battery unit and control the charging current to the first battery unit, thereby equalizing the voltage variations that have occurred among the multiple battery units. Each battery pack is preferably a used, undisassembled, second-hand item that has been previously used in an electric vehicle. [Effects of the Invention]

[0012] According to the present invention, it is possible to prevent the terminal voltage during disconnection from exceeding the rated voltage of the contactor provided in the battery pack, and to reduce the overall weight. Furthermore, in addition to the above effects, the present invention simplifies the control during battery pack connection and equalization, and enables a capacity equal to or greater than conventional methods while remaining at a low cost. [Brief explanation of the drawing]

[0013] [Figure 1] This is a block diagram of the charging system of the present invention. [Figure 2] This is a block diagram illustrating the voltage when the battery pack is disconnected. [Figure 3] Block diagram showing a modified example of the charging system of the present invention. [Modes for carrying out the invention]

[0014] The charging system of the present invention will be described in detail below based on preferred embodiments shown in the accompanying drawings. Figure 1 is a block diagram of the charging system of the present invention.

[0015] The charging system 10 of the present invention does not include a lead-acid battery, but has multiple battery units 12, multiple AC / DC converters 14, a DC / DC converter 16, and a control unit 18. Each of the multiple battery units 12 has multiple battery packs 30 connected in parallel to each other and connected in series to each other. Each of the multiple AC / DC converters 14 is individually connected in parallel to each battery unit 12 and converts the AC current of the system 20 into DC current and outputs it to each battery unit 12. The DC / DC converter 16 is connected between the ends of the series connection of the multiple battery units 12 and the charger 22 and converts the DC voltage of the multiple battery units 12 and outputs it to the charger 22. The charger 22 is not particularly limited as long as the input and output are DC power, and is compatible with the CHAdeMO fast charging standard for electric vehicles (EVs). (Registered trademark) , CCS (Combined Charging System) NACS (North American Charging Standard) Any charger compatible with your device, such as those from ChaoJi, will also work.

[0016] Each battery pack 30 comprises a lithium-ion battery 32, a contactor 34, and a BMS 36. The contactor 34 electrically connects and disconnects the lithium-ion battery 32. The BMS 36 has the function of collecting battery data output by the lithium-ion battery 32 and transmitting it to the control unit 18. The control unit 18 is connected to the BMS 36, DC / DC converter 16, and each AC / DC converter 14 of each battery pack 30, and controls the on / off state of each contactor 34 via each BMS 36, as well as the operation of the DC / DC converter 16 and each AC / DC converter 14, based on the battery data.

[0017] That is, a plurality of battery packs 30 each including a lithium-ion battery 32, a contactor 34, and a BMS 36 are connected in parallel to each other to form a battery unit 12. A plurality of battery units 12 connected in series to each other are connected to a system 20 via respective AC / DC converters 14 individually connected in parallel to each of them, and are connected to a charger 22 via a DC / DC converter 16 connected to both ends thereof. On the opposite side of each AC / DC converter 14 connected to the system 20, the battery units 12 are individually connected in parallel. On the opposite side of the DC / DC converter 16 connected to the charger 22, both ends of a plurality of battery units 12 connected in series to each other are connected. Since the charging system 10 uses the AC / DC converter 14 instead of a lead-acid battery to adjust the voltage and replenish each battery pack 30, there is no need to provide a lead-acid battery. A control unit 18 is connected to each AC / DC converter 14, DC / DC converter 16, and each BMS 36 to form the charging system 10. Battery data is output from a voltage sensor, current sensor, temperature sensor, etc. provided in the lithium-ion battery 32. When the BMS 36 detects an abnormality such as voltage, current, or temperature of the battery pack 30 based on the battery data collected from the lithium-ion battery 32, the BMS 36 turns off the contactor 34 instead of the control unit 18. Also, the AC / DC converter 14 is preferably an insulated type although not particularly limited.

[0018] Here, the voltage at the time of disconnecting the battery pack will be described. FIG. 2 is a block diagram for explaining the voltage at the time of disconnecting the battery pack. Disconnecting means disconnecting the battery pack 30 from the system 20. As an example, battery packs 30a and 30b corresponding to a plurality of battery packs 30 are connected in series to each other, and both ends are connected to a load 38. The battery pack 30a includes a lithium-ion battery 32a, a contactor 34a, and a BMS 36a, and the battery pack 30b includes a lithium-ion battery 32b, a contactor 34b, and a BMS 36b. When the voltages of the lithium-ion battery 32a and the lithium-ion battery 32b are both 400 V, 800 V is applied between the terminals of the turned-off contactor 34a.

[0019] Also, even when driving a plurality of contactors connected in series with each other using a single relay, the timing at which the contacts of the plurality of contactors move is not exactly the same, and it is known that all the load is instantaneously applied to one contact. Therefore, even when the contactors 34a and 34b are controlled to be turned on and off simultaneously, 800V is applied between one of the terminals, so there is a high possibility of exceeding the rated voltage of the contactors 34a and 34b. Here, the rated voltage is the reference voltage guaranteed by the manufacturer in order for the device or component to exhibit the performance as specified and ensure safety. Using a voltage exceeding the rated voltage increases the risk of dielectric breakdown, overheating, and fire.

[0020] Next, a modified example of the charging system of the present invention will be described. FIG. 3 is a block diagram showing a modified example of the charging system of the present invention. The charging system 40 is different from the charging system 10 in that the number of series connections of the battery unit 12 and the AC / DC converter 14 is three instead of two, and the output voltage is 1.5 times as a result. However, since the rest is the same, the same reference numerals are assigned to the same components and the description thereof is omitted. Note that the number of parallel connections of the battery pack 30 is three in FIGS. 1 and 3, but is not particularly limited and may be two or four or more. Also, the number of series connections of the battery unit 12 is two in FIG. 1 and three in FIG. 3, but is not particularly limited and may be four or more.

[0021] With such a configuration, the charging system of the present invention can prevent the terminal voltage from exceeding the rated voltage of the contactors provided in the battery pack during disconnection, reduce the total weight, and simplify the control during connection and equalization of the battery pack.

[0022] Next, the battery pack 30 constituting the charging system 10 of the present invention will be described in detail. Each battery pack 30 is preferably a used product that has been used once in an electric vehicle and has been recovered and remains undissembled.

[0023] In this case, each battery pack 30 is a used EV battery and contains a lithium-ion battery 32, a contactor 34, and a BMS 36. Furthermore, each battery pack 30 has been used without being repacked.

[0024] By adopting this configuration, the charging system of the present invention can achieve a capacity equal to or greater than that of conventional systems while remaining low-cost.

[0025] Next, the control methods for the AC / DC converter 14 and DC / DC converter 16 during normal use will be described in detail. Here, "normal use" means a state in which the contactor 34 of a predetermined battery pack 30 to be operated is turned on, and the lithium-ion battery 32 can be charged with power from the grid 20.

[0026] The control unit 18 preferably specifies the output voltage and output current for each AC / DC converter 14, which is individually connected in parallel to each battery unit 12, based on the voltage of the corresponding battery unit 12. Furthermore, the control unit 18 preferably controls each AC / DC converter 14 to apply a voltage higher than that of the corresponding battery unit 12 to the corresponding battery unit 12.

[0027] In that case, the control unit 18 commands the DC / DC converter 16 to start and stop discharging from the battery unit 12 to the charger 22. The control unit 18 works in conjunction with the DC / DC converter 16 to output power to the charger 22 in conjunction with the discharge and to stop the output in case of error detection. Since the voltage of the battery unit 12 changes due to the discharge, the control unit 18 changes the output voltage of the AC / DC converter 14 so that it does not deviate significantly from that voltage.

[0028] Next, the control method for the AC / DC converter 14 and DC / DC converter 16 during a power outage will be described in detail. Here, a power outage means a state in which the power supply from the grid 20 is stopped. At least one of the AC / DC converter 14 and DC / DC converter 16 detects the occurrence of a power outage and notifies the control unit 18.

[0029] During a power outage, the control unit 18 operates without interruption, receiving power from a control power supply DC / DC converter (not shown) connected in parallel to the DC / DC converter 16 to the DC / DC converter 16, contactors 34, and BMS 36. Power is supplied from the lithium-ion battery 32 to the charger 22 via the DC / DC converter 16, while, unlike during normal use, the application of voltage to each battery section 12 by the AC / DC converter 14 is stopped. To shut down the charging system 10, the main contactor (not shown) connected between the battery section 12 and the DC / DC converter 16 is turned off, followed by turning off all contactors 34. With both the main contactor and all contactors 34 turned off, no voltage exceeding the rated voltage of the contactors 34 will be applied to the contactors 34.

[0030] With this configuration, the charging system of the present invention connects an independent power supply to each battery section. As a result, only the output voltage of the battery section is applied to the contactor of each battery section, independently of the other battery sections. This prevents the terminal voltage from exceeding the rated voltage of the contactor when disconnected, and also reduces the overall weight.

[0031] Next, the control method for the AC / DC converter 14 and contactors 34 when the battery pack 30 is connected will be described in detail. Here, "when the battery pack 30 is connected" means sequentially turning on the contactors 34, which are all turned off when the charging system 10 is stopped, and turning on the contactors 34 of the other battery pack 30 after replacing a battery pack 30 that is in an abnormal state due to failure, deterioration, etc. with another battery pack 30. The control unit 18 determines whether the SOC, SOH, etc. of the lithium-ion battery 32 are in a normal or abnormal state based on battery data transmitted from the BMS 36 and a preset threshold. Also, when connecting the battery pack 30, power from the grid 20 is used during normal use, but in the event of a power outage, the power supply to the AC / DC converter 14 is stopped, so the connection of the battery pack 30 is also stopped.

[0032] It is preferable for the control unit 18 to start up multiple AC / DC converters 14 before starting up the DC / DC converter 16. Then, it is preferable for the control unit 18 to control the battery pack 30 to turn on the contactor 34 when the difference between the output voltage of the AC / DC converter 14 and the battery pack 30 falls within a preset voltage difference while the output voltage of the AC / DC converter 14 corresponding to the connected battery pack 30 is raised or lowered.

[0033] In this case, first, the control unit 18 starts up the AC / DC converter 14 and changes the output voltage of the AC / DC converter 14 corresponding to the connected battery pack 30 from low voltage to high voltage or from high voltage to low voltage. Next, the control unit 18 calculates the voltage difference between the output of the AC / DC converter 14 and the lithium-ion battery 32 of the connected battery pack 30, and when the voltage difference becomes smaller than or equal to a preset value, it turns on the contactor 34 corresponding to that lithium-ion battery 32. At this time, if there are multiple contactors 34 to turn on, they can be turned on in any order.

[0034] Next, the control unit 18 specifies a low current value to the AC / DC converter 14 corresponding to the turned-on contactor 34 and controls it to charge the lithium-ion battery 32 with that current. Then, as a result of turning on the contactor 34 once or multiple times, when both ends of the series connection of the multiple battery units 12 become conductive, it becomes possible to charge and discharge the lithium-ion battery 32 corresponding to the turned-on contactor 34 within its allowable current value, so the control unit 18 may start the DC / DC converter 16. Then, when the contactor 34 of the predetermined battery pack 30 to be operated is turned on, the system transitions to the normal operation described above. Note that the control unit 18 does not coordinate with the DC / DC converter 16 when the battery pack 30 is connected.

[0035] With this configuration, the charging system of the present invention allows each battery section to change its voltage and turn on the contactor simultaneously and independently of other battery sections, thus simplifying the control when connecting the battery pack.

[0036] Next, the control method of the AC / DC converter 14 during the equalization of the battery pack 30 will be explained in detail. Here, the equalization of the battery pack 30 refers to the case where voltage variations that have occurred among the multiple battery units 12 are eliminated. The control unit 18 determines whether or not voltage variations have occurred based on battery data transmitted from the BMS 36 and a preset threshold. In addition, when equalizing the battery pack 30, power from the grid 20 is used during normal use, but in the event of a power outage, the power supply to the AC / DC converter 14 is stopped, and therefore the equalization of the battery pack 30 is also stopped.

[0037] The control unit 18 preferably controls the first AC / DC converter connected in parallel to the first battery unit when voltage variations occur among the multiple battery units 12 and the voltage of the first battery unit becomes lower than the voltage of the second battery unit. The control unit 18 then preferably equalizes the voltage variations that have occurred among the multiple battery units 12 by applying a voltage higher than the voltage of the second battery unit to the first battery unit and controlling the charging current to the first battery unit.

[0038] In this case, among the multiple battery units 12 connected in series, the AC / DC converter 14 connected in parallel to the battery unit 12 with the lowest voltage is used to perform supplemental charging, thereby equalizing the voltage variations that have occurred among the multiple battery units 12. Note that the control unit 18 does not cooperate with the DC / DC converter 16 when equalizing the voltages of the battery pack 30.

[0039] With this configuration, the charging system of the present invention can supplementally charge a battery section with a low voltage independently of other battery sections, thus simplifying the control during battery pack equalization. The charging system of the present invention is basically configured as described above.

[0040] Although the charging system of the present invention has been described in detail above, the present invention is not limited to the above description, and various improvements and modifications may be made without departing from the spirit of the present invention. [Industrial applicability]

[0041] The charging system of the present invention has several advantages: it prevents the terminal voltage from exceeding the rated voltage of the contactor provided in the battery pack when disconnected, and it reduces the overall weight. In addition, it simplifies the control during battery pack connection and equalization, and it can achieve a capacity equal to or greater than conventional systems at a lower cost, making it industrially useful. [Explanation of symbols]

[0042] 10, 40 charging system 12 Battery section 14 AC / DC Converters 16 DC / DC Converters 18 Control Unit 20 lines 22 Charger 30, 30a, 30b battery packs 32, 32a, 32b Lithium-ion batteries 34, 34a, 34b Contactors 36, 36a, 36b BMS 38 load

Claims

1. Each unit is equipped with multiple battery packs connected in parallel to each other, and multiple battery units are connected in series to each other, Each of the AC / DC converters is individually connected in parallel to each battery unit, converting the AC current of the system into DC current and outputting it to each battery unit. A DC / DC converter is connected between the ends of the series connection of the multiple battery units and the charger, and converts the DC voltage of the multiple battery units and outputs it to the charger. A charging system having a control unit, The aforementioned charging system does not include a lead-acid battery. Each battery pack comprises a lithium-ion battery, a contactor for electrically connecting and disconnecting the lithium-ion battery, and a BMS having the function of collecting battery data output by the lithium-ion battery and transmitting it to the control unit. The control unit is connected to the BMS of each battery pack, the DC / DC converter, and each AC / DC converter, and is a charging system that controls the on / off state of each contactor via each BMS and the operation of the DC / DC converter and each AC / DC converter based on the battery data.

2. The charging system according to claim 1, wherein the control unit specifies an output voltage and output current to each AC / DC converter individually connected in parallel to each battery unit based on the voltage of the corresponding battery unit, and controls each AC / DC converter to apply a voltage higher than that of the corresponding battery unit to each corresponding battery unit.

3. The charging system according to claim 1, wherein the control unit activates the plurality of AC / DC converters before activating the DC / DC converter, and controls the battery pack contactor to turn on when the difference between the output voltage of each AC / DC converter and the output voltage of each AC / DC converter becomes within a preset voltage difference while the output voltage of each AC / DC converter is raised or lowered.

4. The charging system according to claim 1, wherein when a voltage variation occurs among the plurality of battery units and the voltage of the first battery unit becomes lower than the voltage of the second battery unit, the control unit controls the first AC / DC converter connected in parallel to the first battery unit, applies a voltage higher than the voltage of the second battery unit to the first battery unit, and controls the charging current to the first battery unit, thereby equalizing the voltage variation that occurred among the plurality of battery units.

5. The charging system according to any one of claims 1 to 4, wherein each battery pack is a used battery that has been first used in an electric vehicle and is a second-hand product that has been collected and not disassembled.

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