Charge / discharge control device

Abstract

To equalize the energy of each battery without adding any special circuitry. [Solution] The BEVECU of the battery module is a device that controls the charging and discharging of batteries in a plurality of battery packs connected in parallel, and comprises a battery ECU that identifies the State of Charge (SOC) of each of the plurality of batteries, and a BEVECU processor that identifies an index value indicating the variation in the SOC of the plurality of batteries identified by the battery ECU. When the index value exceeds a predetermined value, the processor performs equalization control to reduce the variation in the SOC of each of the plurality of batteries by exchanging power among the batteries when there is no system output request from an external system to the plurality of batteries, or when there is a margin for charge / discharge requests from an external system to the plurality of batteries (steps S111 to S114).

Description

Technical Field

[0001] This disclosure relates to a charge-discharge control device, and more particularly to a charge-discharge control device for a plurality of batteries connected in parallel.

Background Art

[0002] Conventionally, there has been a battery pack in which single batteries are connected in series (see, for example, Patent Document 1). In the battery pack of Patent Document 1, when the variation in the state of charge (SOC) of each single battery is within a predetermined range, charge-discharge is controlled so that the charging capacity of the battery pack becomes a first charging capacity. On the other hand, when the variation in the SOC of each single battery is not within the predetermined range, charge-discharge is controlled so that the charging capacity of the battery pack becomes a second charging capacity that is different from the first charging capacity and moves in a direction in which the variation converges.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the battery pack of Patent Document 1, in order to further equalize the SOC of each single battery, it is conceivable to add a special power supply circuit for performing charge-discharge for each single battery.

[0005] This disclosure has been made to solve the above-described problems, and an object thereof is to provide a charge-discharge control device capable of equalizing each battery without adding a special circuit.

Means for Solving the Problems

[0006] The charge / discharge control device described herein is a device for controlling the charging and discharging of a plurality of batteries connected in parallel, and comprises a specification unit that specifies the charge amount of each of the plurality of batteries, and a processor that specifies an index value indicating the variation in the charge amounts of the plurality of batteries specified by the specification unit. When the index value exceeds a predetermined value, the processor performs equalization control to reduce the variation in the charge amounts of each of the plurality of batteries by exchanging power between the batteries, when there are no charge / discharge requests for the plurality of batteries from an external system, or when there is sufficient capacity to handle charge / discharge requests for the plurality of batteries from an external system.

[0007] With this configuration, if an indicator value showing the variation in the charge levels of multiple batteries exceeds a predetermined value, the variation can be reduced by exchanging power between batteries if there are no charge / discharge requests or if there is sufficient capacity for charge / discharge requests. As a result, a charge / discharge control device can be provided that can equalize the charge levels of each battery without adding any special circuits.

[0008] The index value is the SOC difference between each combination of batteries included in a group of batteries, and the processor may perform equalization control to cause power to be exchanged between battery combinations that satisfy predetermined conditions indicating a large SOC difference.

[0009] With this configuration, if the SOC difference between each combination of batteries included in the multiple batteries exceeds a predetermined value, and there is no charge / discharge request, the variation can be reduced by executing control that causes power to be exchanged between battery combinations that satisfy predetermined conditions indicating a large SOC difference.

[0010] The system may further include multiple relays for switching between connected and disconnected states for each of the multiple batteries, and the processor may perform control to exchange power by switching the relay corresponding to each battery combination that satisfies predetermined conditions to the connected state.

[0011] With this configuration, if the SOC difference between each combination of batteries included in the multiple batteries exceeds a predetermined value, and there is no charge / discharge request, the control is executed to exchange power by switching the relays corresponding to each battery combination that satisfies predetermined conditions indicating a large SOC difference to a connected state, thereby reducing variability.

[0012] The processor may terminate the equalization control when it meets a condition indicating that an index value showing the variation in the charge levels of the batteries under equalization control has decreased.

[0013] With this configuration, the equalization control can be terminated when the variation in the charge levels of multiple batteries becomes small.

[0014] The processor may interrupt the equalization control if a charge / discharge request is received while equalization control is being performed.

[0015] With this configuration, charge and discharge requests can be met even when equalization control is being performed. [Effects of the Invention]

[0016] According to this disclosure, it is possible to provide a charge / discharge control device that can equalize the charge of each battery without adding any special circuitry. [Brief explanation of the drawing]

[0017] [Figure 1] This figure shows a schematic configuration of the electrical system 1 according to an embodiment of this disclosure. [Figure 2] This diagram shows a schematic configuration of the battery module 10 in this embodiment. [Figure 3] This flowchart shows the flow of the SOC equalization process performed by the BEVECU of the battery module in this embodiment. [Modes for carrying out the invention]

[0018] Embodiments and modifications according to this disclosure will be described below with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions of them will not be repeated. The embodiments and modifications described below may be combined selectively as appropriate.

[0019] Figure 1 is a schematic diagram of the configuration of the electrical system 1 according to an embodiment of this disclosure. Referring to Figure 1, thick solid lines indicate high-voltage power lines, thin solid lines indicate low-voltage (12V) power lines, and thin dashed lines indicate signal lines for digital or analog signals. The electrical system 1 is a system that repurposes a high-voltage battery and peripheral equipment that was installed in a vehicle as a stationary battery. The electrical system 1 includes a power generator 22, a power conditioner (hereinafter referred to as "PCS (Power Conditioning System)") 23, a distribution board 30, an electrical load 33, an uninterruptible power supply (hereinafter referred to as "UPS (Uninterruptible Power Supply)") 34, a step-down transformer 35, a 12V battery 36, battery modules 10AA~10CD, relays 11AA~11CD, 12A~12C, 31, 32, an energy management system (hereinafter referred to as "EMS (Energy Management System)") 100, an IF (Interface)-ECU (Electronic Control Unit) 200, and a BEV (Battery Electric Vehicle)-ECU 300.

[0020] The power generation device 22 is a device capable of generating electricity and that can be installed at the customer's location, such as a solar power generation device, a wind power generation device, an emergency backup power generation device, a fuel cell, and a cogeneration system. A cogeneration system is a system that generates electricity using a diesel engine, gas engine, gas turbine, or fuel cell, and also utilizes the waste heat for hot water supply or heating and cooling. The power generation device 22 outputs the generated DC power to the PCS 23.

[0021] The power system 21 is a system that integrates power generation equipment, transformer equipment, power transmission equipment, and power distribution equipment for supplying power to consumers. The power system 21 supplies AC power to the PCS 23.

[0022] The battery modules 10AA to 10CD (hereinafter also typically referred to as "battery module 10") are modules capable of charging and discharging power, as will be described in FIG. 2 below. In this embodiment, the battery modules 10AA to 10CD divert the high-voltage battery mounted on the electric vehicle.

[0023] The relays 11AA to 11CD, 12A to 12C, 31, and 32 switch between on (connected state) and off (disconnected state) of the circuit according to a control signal from the control device.

[0024] The switchboard 30 charges the battery modules 10AA to 10CD with the DC power received from the PCS 23 via the relays 12A to 12C, 11AA to 11CD. In addition, the switchboard 30 supplies the DC power discharged from the battery modules 10AA to 10CD to the PCS 23.

[0025] The PCS 23 converts the DC power supplied from the battery modules 10AA to 10CD via the switchboard 30 into AC power of a predetermined voltage, and supplies the converted AC power and the AC power from the power system 21 to electrical equipment installed at the consumer, such as the electrical load 33 and the UPS 34, via the relays 31 and 32. The PCS 23 converts the AC power from the power system 21 into DC power of a predetermined voltage, and also converts the DC power from the power generation device 22 into DC power of a predetermined voltage, and supplies the converted DC power to the battery modules 10AA to 10CD via the switchboard 30.

[0026] The electrical load 33 is an electrical device that consumes power installed at the consumer, such as an air conditioner and lighting equipment.

[0027] The UPS34 is a device that continues to supply power even when the power supply is interrupted due to a power outage or other reasons. The UPS34 converts the AC power supplied from the distribution panel 30 into DC power and stores it. When the power supply from the power system 21 supplied from the distribution panel 30 is cut off, it converts the stored DC power back into AC power and supplies it to other electrical equipment via the distribution panel 30. The UPS34 also outputs the stored DC power to the step-down transformer 35.

[0028] EMS100, also known as xEMS, is a system that appropriately monitors and manages energy usage at the consumer's site. EMS100 includes HEMS (Home EMS), BEMS (Building EMS), and FEMS (Factory EMS). EMS100 is equipped with a processor and memory.

[0029] The IF-ECU200 is a device that controls communication between ECUs and external communications, and is equipped with a processor and memory.

[0030] The BEV-ECU300 is a device that controls the drivetrain and battery module 10 of the electric vehicle, and includes a processor and memory. The BEV-ECU300 is a repurposed unit that was installed in the electric vehicle.

[0031] The step-down transformer 35 reduces the voltage of the DC power supplied from the UPS 34 to 12V and charges the 12V battery 36. The 12V battery 36 stores the 12V DC power from the step-down transformer 35 and outputs the stored 12V DC power to electrical equipment that operates at 12V (for example, IF-ECU200, BEV-ECU300, BEVECU110 which is an internal control device of the battery module 10 described later, battery ECU121A~121C, MGECU131A~131C).

[0032] Figure 2 is a schematic diagram of the configuration of the battery module 10 in this embodiment. Referring to Figure 2, the two bundles of thick solid lines indicate high-voltage DC power lines, and the thin dashed lines indicate signal lines for digital or analog signals. The battery module 10 comprises battery packs 120A to 120C (hereinafter also typically referred to as "battery pack 120"), PCUs (Power Control Units) 130A to 130C, a terminal block 140, a sub-relay 150, and a BEVECU 110.

[0033] Battery packs 120A to 120C each include battery ECUs 121A to 121C, batteries 122A to 122C, and SMR (System Main Relay) 123A to 123C (hereinafter also typically referred to as "SMR123"). In this embodiment, battery packs 120A to 120C are repurposed high-voltage batteries that were installed in electric vehicles. Because battery packs 120A to 120C that were installed in electric vehicles are used in this way, the degree of degradation of battery packs 120A to 120C tends to vary. As a result, even when battery packs 120A to 120C are used in the same way, differences tend to occur in how the State of Charge (SOC) of battery packs 120A to 120C changes, and variations in SOC tend to occur.

[0034] Batteries 122A to 122C include a battery pack consisting of multiple battery cells connected in series, and sensors. The sensors include a voltage sensor to detect the voltage of each battery cell, a current sensor to detect the current flowing through the battery pack, and a temperature sensor to detect the temperature of various parts of the battery pack. Note that batteries 122A to 122C may also include a single battery cell instead of a battery pack.

[0035] SMR123A~123C, respectively, control the circuits that exchange power between batteries 122A~122C and external devices, either by connecting them to an ON state or disconnecting them to an OFF state, in response to control signals from battery ECUs 121A~121C.

[0036] Each battery ECU 121A to 121C is equipped with a processor and memory, and controls the entire battery pack 120A to 120C. Each battery ECU 121A to 121C processes detection signals from the sensors of batteries 122A to 122C, controls the charging and discharging of batteries 122A to 122C by controlling SMR 123A to 123C, and calculates the charge level or state of charge (SOC) of batteries 122A to 122C using known methods.

[0037] PCU130A~130C each include MG (Motor Generator) ECU131A~131C, converter132A~132C, and inverter133A~133C, respectively. In this embodiment, PCU130A~130C are repurposed PCUs that were mounted on electric vehicles and controlled the traction and regeneration of the electric vehicle's motor generator.

[0038] Converters 132A to 132C each perform voltage conversion between the voltage of batteries 122A to 122C in battery packs 120A to 120C and the voltage of electrical equipment connected to the distribution board 30.

[0039] When inverters 133A to 133C were installed in electric vehicles, they converted power between DC power from converters 132A to 132C and external AC power, respectively. However, in this electrical system 1, they do not perform power conversion.

[0040] Each MGECU131A to 131C is equipped with a processor and memory. The MGECU131A to 131C controls the converters 132A to 132C to convert DC power from battery packs 120A to 120C into DC power of a predetermined voltage and output it to terminal block 140, or to convert DC power from terminal block 140 into DC power of the voltage of battery packs 120A to 120C and output it to battery packs 120A to 120C.

[0041] Terminal block 140 has terminals for connecting PCUs 130A to 130C and sub-relays 150, and electrically connects PCUs 130A to 130C and sub-relays 150.

[0042] The sub-relay 150, in response to a control signal from the BEVECU 110, switches the circuit that exchanges power between the terminal block 140 of the battery module 10 and an external electrical device to an ON state (connected) or an OFF state (disconnected).

[0043] The BEVECU110 has a processor and memory and controls the entire battery module 10 in response to instructions from an external ECU. The BEVECU110 controls the exchange of power between the battery pack 120A~120C and external electrical equipment via the PCU 130A~130C.

[0044] Conventionally, in battery packs such as the battery packs 122A to 122C of the battery module 10 of the aforementioned electrical system 1, when the variation in the state of charge (SOC) of each individual battery cell is within a predetermined range, the charging and discharging of the battery pack is controlled so that the charging capacity becomes a first charging capacity. On the other hand, in such a battery pack, when the variation in the SOC of each individual battery cell is not within the predetermined range, the charging and discharging of the battery pack is controlled so that the charging capacity becomes a second charging capacity, which is different from the first charging capacity and shifts in the direction of convergence of the variation.

[0045] However, in such a battery pack, in order to further equalize the state of charge (SOC) of each individual cell, it is conceivable to add a special power supply circuit for charging and discharging each individual cell.

[0046] Therefore, the electrical system 1 includes a identification unit that identifies the charge amount of each of the multiple batteries 122A to 122C, and a processor that identifies an index value indicating the variation in the charge amounts of the multiple batteries 122A to 122C identified by the identification unit. When the index value exceeds a predetermined value, the processor performs equalization control to reduce the variation in the charge amounts of the multiple batteries 122A to 122C by exchanging power among the multiple batteries 122A to 122C, either when there are no charge / discharge requests for the multiple batteries 122A to 122C from an external system, or when there is sufficient capacity to handle charge / discharge requests for the multiple batteries 122A to 122C from an external system.

[0047] As a result, if an indicator value showing the variation in the charge levels of multiple batteries 122A to 122C exceeds a predetermined value, and there is no charge / discharge request, the variation can be reduced by allowing power to be exchanged between batteries 122A to 122C. Consequently, the charge levels of each battery 122A to 122C can be equalized without adding any special circuits.

[0048] Figure 3 is a flowchart showing the flow of the SOC equalization process performed by the BEVECU 110 of the battery module 10 in this embodiment. Referring to Figure 3, this SOC equalization process is called and executed by the BEVECU 110 at predetermined intervals from higher-level processes.

[0049] The BEVECU110 processor determines whether the system output request is 0kW or not (step S111). The system output request is the output power from the battery module 10 requested by an external processor (for example, the processor of the BEV-ECU300 of electrical system 1). If it is determined that the system output request is 0kW (YES in step S111), the BEVECU110 processor calculates the SOC difference between adjacent battery packs 120 (step S112). Here, the SOC difference between battery pack 120A and battery pack 120B, the SOC difference between battery pack 120B and battery pack 120C, and the SOC difference between battery pack 120C and battery pack 120A are calculated.

[0050] Furthermore, when the system output request is 0kW, the sub-relay 150 in the battery module 10 is controlled to a shut-off state by the BEVECU 110. In other words, the battery module 10 is in a state where it cannot exchange power with the outside.

[0051] The BEVECU110 processor determines in step S112 whether there is an adjacent battery pack 120 whose SOC difference is A% or greater (step S113). A% is, for example, 10%, but is not limited to this and may be any other value. If it is determined that there is an adjacent battery pack 120 whose SOC difference is A% or greater (YES in step S113), the BEVECU110 processor controls only the SMR123 of the corresponding battery pack 120 to the ON state, which means it is connected to the outside (step S114), and switches the equalization flag corresponding to that battery pack 120 to the ON state (step S115). The equalization flag is a flag that indicates whether or not equalization control of the SOC between adjacent battery packs 120 is being performed. When the equalization flag is ON, it indicates that equalization control is being performed, while when the flag is OFF, it indicates that equalization control is not being performed. As a result, among the battery packs 120 with the SMR123 turned ON, current flows from the battery pack 120 with a high SOC (=high voltage) to the battery pack 120 with a low SOC (=low voltage), thereby supplying power and equalizing the SOC.

[0052] If it is determined that the system output request is not 0kW (NO in step S111), if it is determined that there are no adjacent battery packs 120 with a SOC difference of A% or more (NO in step S113), or after step S115, the processor of BEVECU 110 determines whether the equalization flag is in the ON state (step S121).

[0053] When it is determined that the flag is in the ON state during equalization (YES in step S121), the processor of the BEVECU 110 calculates the SOC difference between adjacent battery packs 120 (step S122). The processor of the BEVECU 110 determines whether the SOC difference is B% or less (B < A) (step S123). B% is, for example, 1%, but is not limited thereto, and may be other values as long as they are less than A%.

[0054] When it is determined that the SOC difference is B% or less (YES in step S123), the processor of the BEVECU 110 controls the SMR 123 of the corresponding battery pack 120 to the OFF state in which it is blocked from the outside (step S124), and switches the equalization-in progress flag corresponding to the battery pack 120 to the OFF state (step S125).

[0055] When it is determined that the SOC difference is not B% or less (NO in step S123), or after step S125, the processor of the BEVECU 110 determines whether the system output request has exceeded 0 kW (step S126).

[0056] When it is determined that the system output request has exceeded 0 kW (YES in step S126), the processor of the BEVECU 110 controls the SMRs 123A to 123C of all the battery packs 120A to 120C to the ON state (step S127). Then, the processor of the BEVECU 110 sets the equalization-in progress flags of all the battery packs 120A to 120C to the OFF state (step S128), and controls the battery packs 120A to 120C, the PCUs 130A to 130C, and the sub-relay 150 so as to start outputting power according to the system output request (step S129).

[0057] When it is determined that the equalization-in progress flag is not in the ON state (NO in step S121), when it is determined that the system output request has not exceeded 0 kW (NO in step S126), or after step S129, the processor of the BEVECU 110 returns the process to be executed to the higher-level process that called this SOC equalization process.

[0058] [Differentiation] (1) In the embodiment described above, the SOC equalization process shown in Figure 3 is performed by the battery ECUs 121A to 121C of the battery packs 120A to 120C. However, the SOC equalization process is not limited to this, and may be performed by other processors, for example, the BEVECU 110 of the battery module 10, the MGECU 131A to 131C of the PCUs 130A to 130C, or the processor of the BEV-ECU 300 or EMS 100 of the electrical system 1.

[0059] (2) In the embodiment described above, as explained in step S113 of Figure 3, when the SOC difference between adjacent battery packs 120 is A% or more, SOC equalization control between battery packs 120 is performed. However, the equalization control is not limited to this, and is performed when it can be determined that the charge amounts of multiple batteries (for example, battery packs 120) are varied, specifically when an index value indicating the variation in the charge amounts of multiple batteries exceeds a predetermined value. For example, this index value may be the difference between the maximum and minimum values ​​of the SOC or charge amounts of multiple batteries, the deviation from a reference value such as the average or median of the SOC or charge amounts of multiple batteries, or the variance or standard deviation of the SOC or charge amounts of multiple batteries.

[0060] (3) In the embodiment described above, as shown in Figure 2, the processors of the battery ECUs 121A to 121C were used to determine the SOC or charge amount of batteries 122A to 122C, respectively. However, the processors that determine the SOC or charge amount of batteries 122A to 122C are not limited to these, and other processors may be used, such as the processors of BEVECU 110 or MGECU 131A to 131C.

[0061] (4) In the embodiment described above, as shown in step S114 of Figure 3, only the SMR123 of the corresponding battery pack 120 is turned on. However, the embodiment is not limited to this, and the SMR123A to 123C of all battery packs 120A to 120C may be turned on.

[0062] (5) In the embodiments described above, as shown in Figures 2 and 3, equalization control is performed among the battery packs 120 included in the battery module 10. However, the invention is not limited to this, and equalization control may be performed among the battery modules 10.

[0063] (6) In the embodiment described above, as shown in steps S114 and S124 of Figure 3, equalization control is performed by supplying power from the battery pack 120 with a high SOC to the battery pack 120 with a low SOC, and the equalization control is terminated when the SOC difference becomes small. However, the invention is not limited to this, and for the battery pack 120 with a low SOC, after the equalization control is terminated, the SOC may be further increased by external power to compare it with the SOC of the other battery packs 120. This makes it possible to keep the SOC of the battery pack 120 whose SOC is decreasing rapidly due to a decrease in SOH (State of Health) higher.

[0064] (7) If the system output requirement is greater than 0kW, and the power can be supplied by only the battery pack 120 whose SOH has not decreased, then power may be not output from the battery pack 120 whose SOH has decreased.

[0065] (8) In the embodiment described above, as shown in step S111 of Figure 3, equalization control is performed when the system output request is 0kW. However, the invention is not limited to this, and even when the system output request is greater than 0kW, if the charge and discharge power of the system output request can be covered by a portion of the battery pack 120 and there is surplus charge and discharge power in the battery pack 120, equalization control may be performed in parallel with the exchange of charge and discharge power corresponding to the system output request.

[0066] For example, if there is a difference in State of Charge (SOC) among the battery modules 10 under relay 12A, and the battery modules 10BA~BD,CA~CD under relays 12B and 12C can meet the system's charging and discharging power requirements, relay 12A is controlled to the OFF state, and the relays between the battery modules 10, including the battery pack 120 that exchanges power (for example, relays 11AA and 11AB), are controlled to the ON state, and the SMR 123 of the battery pack 120 included in the battery module is also controlled to the ON state. As a result, power is supplied by current flowing from the battery pack 120 of the battery module 10 with a high SOC (=high voltage) to the battery pack 120 of the battery module 10 with a low SOC (=low voltage), thereby equalizing the SOC. If, during equalization control, the battery modules 10BA~BD,CA~CD under relays 12B and 12C can no longer meet the charging and discharging power requirements, the equalization control is immediately stopped, and relay 12A is controlled to the ON state.

[0067] Furthermore, for example, if there is a difference of A% or more in State of Charge (SOC) between battery packs 120A and 120B of battery module 10AA under relay 12A (battery pack 120A has a higher SOC than battery pack 120B), and if the battery modules 10AB~10AD other than battery module 10AA under relay 12A, and the battery modules 10BA~BD, CA~CD under relays 12B and 12C can meet the system's required charge and discharge power, then relay 11AA of battery module 10AA is controlled to the OFF state, and SMRs 123A and 123B of battery packs 120A and 120B of battery module 10AA are controlled to the ON state (specifically, the SOC equalization process shown in Figure 3 is performed for battery packs 120A and 120B of battery module 10AA). As a result, in battery module 10AA, power is supplied by current flowing from battery pack 120A, which has a high SOC (=high voltage), to battery pack 120B, which has a low SOC (=low voltage), thereby equalizing the SOC. If, during equalization control, battery modules AB~AD other than battery module AA under relay 12A, and battery modules 10BA~BD,CA~CD under relays 12B and 12C can no longer supply charge and discharge power, the equalization control is immediately stopped and relay 11AA is controlled to the ON state.

[0068] (9) The embodiments described above can be interpreted as disclosures of a charge / discharge system such as the electrical system 1 or a battery module 10, or as disclosures of charge / discharge control devices for the electrical system 1 or battery module 10, such as battery ECUs 121A to 121C, BEVECU 110, MGECU 131A to 131C, BEV-ECU 300, or EMS 100, or as disclosures of charge / discharge control methods or charge / discharge control programs executed by the charge / discharge control devices.

[0069] [summary] (1) As shown in Figures 1 and 2, the BEVECU110 of the battery module 10 is a device that controls the charging and discharging of multiple batteries connected in parallel (for example, batteries 122A to 122C of battery pack 120A to 120C), and comprises a identification unit (for example, battery ECUs 121A to 121C, BEVECU110) that identifies the charge amount (for example, SOC) of each of the multiple batteries, and a processor (for example, the processor of BEVECU110) that identifies an index value indicating the variation in the charge amounts of the multiple batteries identified by the identification unit. As shown in Figure 3, when the index value exceeds a predetermined value, the processor performs equalization control to reduce the variation in the charge amounts of each of the multiple batteries by exchanging power among the batteries when there are no charge / discharge requests (for example, system output requests) from an external system to the multiple batteries, or when there is sufficient capacity to handle charge / discharge requests from an external system to the multiple batteries (for example, steps S111 to S114).

[0070] As a result, if an indicator value showing the variation in the charge levels of multiple batteries exceeds a predetermined value, the variation can be reduced by exchanging power between batteries, provided there are no charge / discharge requests or there is sufficient capacity for charge / discharge requests. Consequently, equalization control for each battery can be performed without adding any special circuits. Furthermore, equalization control can be performed without purchasing power from the power grid 21 or using power from the power generator 22.

[0071] (2) As shown in Figure 3, the index value is the SOC difference between each combination of batteries included in the multiple batteries, and the processor may perform equalization control to cause power to be exchanged between battery combinations that satisfy a predetermined condition indicating a large SOC difference (for example, the condition that the SOC difference is A% or more) (for example, step S114).

[0072] This allows for reduced variability when the State of Charge (SOC) difference between different battery combinations exceeds a predetermined value, provided there are no charge / discharge requests. The system then controls the exchange of power between battery combinations that meet predetermined conditions indicating a large SOC difference. Furthermore, since power is exchanged between adjacent batteries, losses due to wiring resistance are also reduced.

[0073] (3) As shown in Figure 2, the system further includes multiple relays (e.g., SMR123A~123C) that switch between connected and disconnected states for each of the multiple batteries. As shown in Figure 3, the processor may perform control to exchange power by switching the relay corresponding to each battery combination that satisfies predetermined conditions to the connected state (e.g., step S114).

[0074] As a result, if the SOC difference between each combination of batteries included in a group of batteries exceeds a predetermined value, and there is no charge / discharge request, the system can reduce variability by switching the relays corresponding to each battery combination that meets predetermined conditions indicating a large SOC difference to a connected state, thereby exchanging power.

[0075] (4) As shown in Figure 3, the processor may terminate the equalization control when it satisfies a condition that indicates that the index value showing the variation in the charge amount of the battery under equalization control has decreased (for example, the condition that the SOC difference is B% or less) (for example, steps S121 to S124).

[0076] This allows the equalization control to be terminated when the variation in the charge levels of multiple batteries becomes small.

[0077] (5) As shown in Figure 3, the processor may interrupt the equalization control if a charge / discharge request is received while equalization control is being performed (for example, steps S121, S126, and S127).

[0078] This allows the system to respond to charge / discharge requests even when equalization control is being performed.

[0079] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0080] 1 Electrical systems, 10, 10AA~10CD battery modules, 11AA~11CD, 12A~12C, 31, 32 relays, 21 power grids, 22 power generators, 23 PCS, 30 distribution boards, 33 electrical loads, 34 UPS, 35 step-down transformers, 36 12V batteries, 100 EMS, 110 BEVECU, 120, 120A~120C battery packs, 121A~121C battery ECUs, 122A~122C batteries, 123, 123A~123C SMRs, 130A~130C PCUs, 131A~131C MGECUs, 132A~132C converters, 133A~133C inverters, 140 terminal blocks, 150 sub-relays, 200 IF-ECUs, 300 BEV-ECU.

Claims

1. A charge / discharge control device for multiple batteries connected in parallel, A unit for identifying the charge levels of each of the aforementioned multiple batteries, The system includes a processor that identifies an index value indicating the variation in the charge amounts of the plurality of batteries identified by the identification unit, The processor is a charge / discharge control device that, when the index value exceeds a predetermined value, when there are no charge / discharge requests for the multiple batteries from an external system, or when there is sufficient capacity to handle charge / discharge requests for the multiple batteries from an external system, performs equalization control to reduce variations in the charge levels of each of the multiple batteries by causing power to be exchanged between the batteries.

2. The aforementioned index value is the SOC difference between each combination of batteries included in the plurality of batteries. The charge / discharge control device according to claim 1, wherein the processor performs control to exchange power between combinations of batteries that satisfy predetermined conditions indicating a large SOC difference, as the equalization control.

3. The system further includes multiple relays for switching between a connected state and a disconnected state for each of the multiple batteries, The charge / discharge control device according to claim 2, wherein the processor performs control to exchange power by switching the relay corresponding to each of the battery combinations that satisfy the predetermined conditions to a connected state.

4. The charge / discharge control device according to claim 1, wherein the processor terminates the equalization control when it satisfies the condition that the index value indicating the variation in the charge amount of the battery on which the equalization control is being performed has decreased.

5. The charge / discharge control device according to claim 1, wherein the processor interrupts the equalization control when a charge / discharge request is made while the equalization control is being performed.

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