Management device and power supply system

Abstract

This management device (30) manages a plurality of power storage modules (M1) connected in parallel to a load (60) via switches (RY1), respectively. In a state where among the plurality of power storage modules (M1), switches (RY1) connected to some of the power storage modules (M1) are on and switches (RY1) connected to the remaining power storage modules (M1) are off, when at least one of the switches (RY1) in the off state is turned on, and the upper limit of current or power that is permitted to be electrically discharged from all of the plurality of power storage modules (M1) when the switch (RY1) is turned on is less than a first threshold value based on the maximum value of current or power required by the load (60), a determination unit (313) of the management device (30) does not permit turn-on of the switch (RY1).

Description

[Technical field]

[0001] The present disclosure relates to a management device that manages a plurality of power storage modules connected in parallel to a load, and a power supply system. [Background technology]

[0002] In recent years, relatively low-power (e.g., 48V drive) electric vehicles such as electric motorcycles, electric golf carts, electric land cars, and forklifts have become widespread. Some of these electric vehicles employ power supply systems in which multiple removable, replaceable battery packs are connected in parallel. When multiple battery packs are connected in parallel, cross currents may occur.

[0003] When disconnected battery packs are connected in parallel, a control has been proposed to prevent a current exceeding the rated value from flowing through the battery packs or relays due to cross current (see, for example, Patent Document 1). Also, a control has been proposed that estimates the transient voltage at the time of disconnection between parallel-connected batteries, and turns off the relay if it is likely to exceed the rated voltage of the relay (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-33936 A [Patent Document 2] International Publication No. 2012 / 164630 Summary of the Invention [Problem to be solved by the invention]

[0005] When discharging, if a disconnected battery pack is connected in parallel, the upper limit of the current or power allowed to be discharged from the entire parallel system usually increases. However, due to a cross current generated by the parallel connection, the upper limit of the current or power allowed to be discharged from the entire parallel system may be lower than before the parallel connection. This reduction in the upper limit may cause adverse effects such as a decrease in the acceleration performance of the electric vehicle.

[0006] When a disconnected battery pack is connected in parallel during charging, the upper limit of the current or power allowed to be charged to the entire parallel system usually increases. However, due to cross currents generated by the parallel connection, the upper limit of the current or power allowed to be charged to the entire parallel system may be lower than before the parallel connection. This reduction in the upper limit may cause adverse effects such as an increase in charging time and a decrease in regenerative braking force.

[0007] The present disclosure has been made in view of the above circumstances, and has an object to provide a technology for preventing a current shortage state from occurring in a parallel system supplied to a load, and a technology for preventing a decrease in charging efficiency when charging the parallel system. [Means for solving the problem]

[0008] In order to solve the above problems, a management device of one embodiment of the present disclosure is a management device that manages a plurality of storage modules that are each connected in parallel to a load via a switch, and when switches connected to some of the plurality of storage modules are on and switches connected to the remaining storage modules are off, and at least one of the off switches is turned on, if the upper limit value of current or power allowed to be discharged from all of the plurality of storage modules when the switch is turned on is lower than a first threshold value based on the maximum value of the current or power required by the load, the management device is equipped with a determination unit that does not allow the switch to be turned on.

[0009] Another aspect of the present disclosure is a management device that manages a plurality of power storage modules that are connected in parallel to a power source via respective switches, and includes a determination unit that, when at least one of the off-state switches is turned on while the switches connected to some of the plurality of power storage modules are on and the switches connected to the remaining power storage modules are off, does not permit the switch to be turned on if an upper limit value of a current or power permitted to be charged to all of the plurality of power storage modules when the switch is turned on is lower than a third threshold value based on a maximum value of a current or power that the power source can output. Effect of the Invention

[0010] According to the present disclosure, it is possible to prevent a current shortage state from occurring when supplying a current from a parallel system to a load, and also to prevent a decrease in charging efficiency when charging the parallel system. [Brief description of the drawings]

[0011] [Figure 1] 1 is a diagram for explaining an electric vehicle equipped with a power supply system according to an embodiment. [Diagram 2] 2 is a diagram showing an example of the internal configuration of the battery pack shown in FIG. 1; [Diagram 3] 2 is a diagram illustrating an example of an internal configuration of a management unit in FIG. 1; [Figure 4] FIG. 1 is a diagram showing an example of SOC-upper discharge power limit characteristics at 0° C. of a certain battery pack. [Diagram 5] FIG. 1 is a diagram showing an example of SOC-charge upper limit current characteristics at 0° C. of a certain battery pack. [Figure 6] FIG. 2 is a diagram for explaining a cross current between battery packs during discharging. [Figure 7] 1 is a flowchart for explaining a parallel connection determination process according to the first embodiment. [Figure 8] 11 is a flowchart illustrating a process of determining whether a parallel connection is performed according to an application example of the first embodiment. [Figure 9] FIG. 2 is a diagram for explaining cross current between battery packs and convergence of OCV during discharge. [Figure 10] 11 is a diagram for explaining an example of a change in the discharge upper limit power value of the entire parallel system before and after connecting a new battery pack during discharging. FIG. [Figure 11] 13 is a flowchart illustrating a process of determining whether a parallel connection is performed according to the second embodiment. [Figure 12] 13 is a flowchart illustrating a process of determining whether a parallel connection is established according to a modified example of the second embodiment. [Figure 13] FIG. 2 is a diagram for explaining a cross current between battery packs during charging. [Figure 14] 13 is a flowchart illustrating a process of determining whether a parallel connection is performed according to a third embodiment. [Figure 15] 13 is a flowchart illustrating a process of determining whether a parallel connection is performed according to an application example of the third embodiment. [Figure 16] FIG. 2 is a diagram for explaining cross current between battery packs and convergence of OCV during charging. [Figure 17] 11 is a diagram for explaining an example of a change in the discharge upper limit power value of the entire parallel system before and after connecting a new battery pack during charging. FIG. [Figure 18] 13 is a flowchart illustrating a process of determining whether a parallel connection is performed according to a fourth embodiment. [Figure 19] 13 is a flowchart illustrating a process of determining whether a parallel connection is performed according to a modification of the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] 1 is a diagram illustrating an electric vehicle 1 equipped with a power supply system 10 according to an embodiment. The electric vehicle 1 is an electric vehicle that uses a replaceable battery pack 20 as a power source, and examples of such vehicles include electric motorcycles, electric golf carts, electric land cars, and forklifts. The battery pack 20 is a detachable, portable, and replaceable battery pack that is attached to an attachment slot of the electric vehicle 1 by a user.

[0013] The power supply system 10 is connected to the motor 60 via a main relay RYc and an inverter 50. During power running, the inverter 50 converts DC power supplied from the power supply system 10 into AC power and supplies it to the motor 60. During regeneration, the inverter 50 converts AC power supplied from the motor 60 into DC power and supplies it to the power supply system 10. The motor 60 is a three-phase AC motor, and during power running, it rotates according to the AC power supplied from the inverter 50. During regeneration, the inverter 50 converts rotational energy generated by deceleration into AC power and supplies it to the inverter 50.

[0014] The vehicle ECU (Electronic Control Unit) 40 is a control device that controls the entire electric vehicle 1. The main relay RYc is a contactor that is inserted between the wiring that connects the power supply system 10 and the inverter 50. When the electric vehicle 1 is running, the vehicle ECU 40 controls the main relay RYc to an on state (closed state) to electrically connect the power supply system 10 and the power system of the electric vehicle 1. When the electric vehicle 1 is not running, the vehicle ECU 40 controls the main relay RYc to an off state (open state) to electrically disconnect the power supply system 10 and the power system of the electric vehicle 1. Note that instead of a relay, another type of switch, such as a semiconductor switch, may be used.

[0015] The electric vehicle 1 can be connected to the charger 2 via a charging cable 5. The charger 2 is connected to a commercial power system (hereinafter simply referred to as system 3) and can charge the battery pack 20 in the power supply system 10 from outside the electric vehicle 1. When the charger 2 is a normal charger, it generally charges the battery pack 20 with single-phase 100 / 200V AC power. In this case, electrical continuity is established between the charger 2 and the battery pack 20 via the charging cable 5, the external charging relay RYo, and the AC / DC converter 70.

[0016] During charging from the charger 2, the vehicle ECU 40 controls the external charging relay RYo to an on state. Note that other types of switches, such as a semiconductor switch, may be used instead of the relay. The AC / DC converter 70 includes a rectifier circuit and a DC / DC converter. The rectifier circuit rectifies the AC power supplied from the charger 2 to generate DC power. The DC / DC converter controls the current or voltage of the DC power generated by the rectifier circuit according to a current command value or voltage command value specified by the vehicle ECU 40. This enables constant current (CC) charging or constant voltage (CV) charging.

[0017] When the charger 2 is a rapid charger, the charger 2 generates direct current power by rectifying the alternating current power supplied from the system 3. For example, CHAdeMO (registered trademark), GB / T, Combo (Combined Charging System), etc. can be used as the rapid charging standard.

[0018] The charging cable 5 compatible with quick charging includes a communication line in addition to a power line. The vehicle ECU 40 can transmit a current command value or a voltage command value to the charger 2 via the communication line. The charger 2 controls the current or voltage of the DC power to be output according to the current command value or voltage command value received from the vehicle ECU 40. In this case, the AC / DC converter 70 in the electric vehicle 1 is bypassed. Note that only the rectifier circuit of the AC / DC converter 70 may be bypassed, and the current or voltage of the DC power may be controlled by the DC / DC converter in the AC / DC converter 70, rather than being controlled on the charger 2 side.

[0019] 1 is an example in which the battery pack 20 is charged in a state where it is attached to the electric vehicle 1. In this regard, it is also possible to charge the battery pack 20 in a state where it is separated from the electric vehicle 1. In that case, the battery pack 20 can be charged by attaching it to a charging stand outside the electric vehicle 1.

[0020] The power supply system 10 includes a plurality of battery packs 20a-20c and a management unit 30. The plurality of battery packs 20a-20c are connected in parallel to a load (mainly a motor 60) of the electric vehicle 1. The motor 60 serves as a power source for the plurality of battery packs 20a-20c during regeneration. The number of battery packs 20 connected in parallel is determined according to the required capacity or required output of the electric vehicle 1. Although FIG. 1 shows an example in which three battery packs 20a-20c are connected in parallel, the number of battery packs connected in parallel is not limited to three. To extend the cruising distance, more battery packs 20 may be connected in parallel. In the case of a small electric vehicle 1, two battery packs may be connected in parallel.

[0021] Fig. 2 is a diagram showing an example of the internal configuration of the battery pack 20 in Fig. 1. The battery pack 20 includes a pack relay RY1, a relay driving unit 25, a battery module M1, a shunt resistor Rs, temperature sensors T1 and T2, a voltage measurement unit 21, a temperature measurement unit 22, a current measurement unit 23, and a control unit 24. The relay driving unit 25 turns the pack relay RY1 on / off in response to a control signal received from the management unit 30 via the control unit 24.

[0022] The battery module M1 includes a number of cells E1-En connected in series. The battery module M1 may be configured by connecting in series a number of cell blocks, each of which is made up of a number of cells connected in parallel. The cells may be lithium-ion battery cells, nickel-metal hydride battery cells, lead battery cells, or the like. In the following description, an example in which lithium-ion battery cells (nominal voltage: 3.6-3.7V) are used is assumed.

[0023] A shunt resistor Rs is connected in series with the multiple cells E1-En that make up the battery module M1. The shunt resistor Rs functions as a current detection element. Note that a Hall element may be used instead of the shunt resistor Rs. Also, multiple temperature sensors T1, T2 are provided to detect the temperatures of the multiple cells E1-En. One or multiple temperature sensors may be provided in the battery module M1. The temperature sensors T1, T2 can be, for example, thermistors.

[0024] A plurality of voltage lines connect each node of the plurality of serially connected cells E1-En to the voltage measurement unit 21. The voltage measurement unit 21 measures the voltage of each cell E1-En by measuring the voltage between each of two adjacent voltage lines. The voltage measurement unit 21 transmits the measured voltage of each cell E1-En to the control unit 24 via a communication line.

[0025] Since the voltage measurement unit 21 has a high voltage relative to the control unit 24, the voltage measurement unit 21 and the control unit 24 are connected by a communication line, with the communication line being insulated as necessary. The voltage measurement unit 21 can be configured with an ASIC (Application Specific Integrated Circuit) or a general-purpose analog front-end IC. The voltage measurement unit 21 includes a multiplexer and an A / D converter. The multiplexer outputs the voltage between two adjacent voltage lines to the A / D converter in order from the top. The A / D converter converts the analog voltage input from the multiplexer into a digital value.

[0026] The temperature measurement unit 22 includes a voltage dividing resistor and an A / D converter. The A / D converter sequentially converts a plurality of analog voltages divided by the plurality of temperature sensors T1, T2 and the plurality of voltage dividing resistors into digital values ​​and outputs them to the control unit 24. The control unit 24 estimates the temperatures of the plurality of cells E1-En based on the digital values.

[0027] The current measurement unit 23 includes a differential amplifier and an A / D converter. The differential amplifier amplifies the voltage across the shunt resistor Rs and outputs it to the A / D converter. The A / D converter converts the analog voltage input from the differential amplifier into a digital value and outputs it to the control unit 24. The control unit 24 estimates the current flowing through the multiple cells E1-En based on the digital value.

[0028] In addition, if an A / D converter is installed in the control unit 24 and an analog input port is provided in the control unit 24, the temperature measurement unit 22 and the current measurement unit 23 may output analog voltages to the control unit 24, which may be converted into digital values ​​by the A / D converter in the control unit 24.

[0029] The control unit 24 manages the states of the cells E1-En based on the voltages, temperatures, and currents of the cells E1-En measured by the voltage measurement unit 21, the temperature measurement unit 22, and the current measurement unit 23. The control unit 24 can be configured with a microcomputer and non-volatile memory (e.g., an EEPROM (Electrically Erasable Programmable Read-Only Memory), a flash memory).

[0030] A SOC (State Of Charge)-OCV (Open Circuit Voltage) map 241 is held in the internal memory of the microcomputer. The SOC-OCV map 241 describes characteristic data of the SOC-OCV curve of the cell E1-En. The SOC-OCV curve of the cell E1-En is created in advance based on a characteristic test by the battery manufacturer, and is registered in the internal memory of the microcomputer at the time of shipment. The SOC-OCV map 241 may be registered in a non-volatile memory. In order to estimate the SOC or OCV of the cell E1-En with higher accuracy, the battery manufacturer may derive and map the SOC-OCV characteristics of the cell E1-En for each combination of temperature category and deterioration level (SOH: State Of Health) category. Instead of the map, a function may be used in which the SOC is the objective variable and the OCV, temperature, and deterioration level are explanatory variables.

[0031] The control unit 24 can estimate the SOC and SOH of each of the cells E1-En. The control unit 24 can estimate the SOC by the OCV method or the current integration method. The OCV method is a method of estimating the SOC based on the OCV of each cell E1-En measured by the voltage measurement unit 21 and the characteristic data of the SOC-OCV curve described in the SOC-OCV map 241. The OCV at a future time point is estimated based on the voltage of each cell E1-En measured by the voltage measurement unit 21, the current of the battery module M1 measured by the current measurement unit 23, and the temperature of the battery module M1 measured by the temperature measurement unit 22. The current integration method is a method of estimating the SOC based on the OCV of each cell E1-En at the start of charging / discharging and the integrated value of the current measured by the current measurement unit 23. In the current integration method, the measurement error of the current measurement unit 23 accumulates as the charging / discharging time becomes longer. Therefore, it is preferable to correct the SOC estimated by the current integration method using the SOC estimated by the OCV method.

[0032] SOH is defined as the ratio of the current fully charged capacity to the initial fully charged capacity, and the lower the value (closer to 0%), the more the deterioration has progressed. SOH may be determined by measuring the capacity after complete charging and discharging, or by adding up the storage deterioration and cycle deterioration. Storage deterioration can be estimated based on the SOC, temperature, and storage deterioration rate. Cycle deterioration can be estimated based on the SOC range, temperature, current rate, and cycle deterioration rate used. The storage deterioration rate and cycle deterioration rate can be derived in advance by experiment or simulation. SOC, temperature, SOC range, and current rate can be determined by measurement.

[0033] SOH can also be estimated based on its correlation with the cell's internal resistance. The internal resistance can be estimated by dividing the voltage drop that occurs when a certain current flows through the cell for a certain time by the current value. The internal resistance decreases as the temperature increases, and increases as the SOH decreases.

[0034] The control unit 24 periodically transmits monitoring data including at least one of the voltage, temperature, current, SOC, SOH, and internal resistance of the multiple cells E1-En included in the battery pack 20 to the management unit 30. For example, serial communication conforming to the RS-485 standard can be used for communication between the control unit 24 of the battery pack 20 and the management unit 30. The control unit 24 of the battery pack 20 and the management unit 30 may be connected by a dedicated communication line, wirelessly, or by power line communication.

[0035] Fig. 3 is a diagram showing an example of the internal configuration of the management unit 30 in Fig. 1. The management unit 30 includes a processing unit 31 and a storage unit 32, and manages a plurality of battery packs 20a-20c.

[0036] The processing unit 31 includes an acquisition unit 311, a calculation unit 312, a determination unit 313, and a notification unit 314. The functions of the processing unit 31 can be realized by a combination of hardware resources and software resources, or by hardware resources alone. A CPU, ROM, RAM, DSP, ASIC, FPGA, and other LSIs can be used as hardware resources. A program such as firmware can be used as software resources.

[0037] The storage unit 32 includes a non-volatile recording medium such as a flash memory. The storage unit 32 holds a SOC-discharge upper limit current map 321 and a SOC-charge upper limit current map 322. The SOC-discharge upper limit current map 321 describes characteristic data of the SOC-discharge upper limit current curve of the cell E1-En. The SOC-discharge upper limit current curve of the cell E1-En is created based on a characteristic test by the battery manufacturer. The SOC-discharge upper limit current curve is characteristic data that specifies, for each SOC, the upper limit of the discharge current at which discharge from the cell is permitted, from the viewpoint of cell protection and safety. In a typical cell, the lower the SOC, the lower the upper limit of the current at which discharge is permitted.

[0038] The SOC-charging upper limit current map 322 describes characteristic data of the SOC-charging upper limit current curve of the cell E1-En. The SOC-charging upper limit current curve of the cell E1-En is created based on characteristic tests by the battery manufacturer. The SOC-charging upper limit current curve is characteristic data that specifies the upper limit of the charging current allowed for charging the cell for each SOC from the viewpoint of cell protection and safety. In a typical cell, the higher the SOC, the lower the upper limit of the current allowed for charging. In this specification, both the discharge current and the charge current are considered in absolute values ​​for ease of understanding. In practice, it is common to define the discharge current as positive and the charge current as negative.

[0039] When discharging from a cell, the larger the discharge current, the lower the CCV (Closed Circuit Voltage). The CCV of a cell when discharging is defined by the following (Equation 1). When charging to a cell, the larger the charging current, the higher the CCV. The CCV of a cell when charging is defined by the following (Equation 2).

[0040] CCVd=OCV-Id×R (Formula 1) CCVc = OCV + Ic × R (Equation 2) Id is the discharge current, Ic is the charge current, and R is the internal resistance.

[0041] As shown in the above (Equation 1), as the discharge current Id increases, the CCV decreases. When the CCV enters the overdischarge region, the burden on the battery increases, which causes deterioration. As shown in the above (Equation 1), the CCV decreases as the OCV decreases. Since the OCV decreases as the SOC decreases, the lower the SOC, the lower the upper limit value of the discharge current Id must be set. As shown in the above (Equation 2), as the charging current Ic increases, the CCV increases. When the CCV enters the overcharge region, the burden on the battery increases, which causes deterioration. As shown in the above (Equation 2), the CCV increases as the OCV increases. Since the OCV increases as the SOC increases, the higher the SOC, the higher the upper limit value of the charging current Ic must be set.

[0042] The SOC-discharge upper limit current characteristic of the cell E1-En depends on the temperature and the deterioration level (SOH). The battery manufacturer derives and maps the SOC-discharge upper limit current characteristic of the cell E1-En for each combination of the temperature category and the deterioration level category. The SOC-discharge upper limit current characteristic is registered in the control unit 24 of the battery pack 20 (for example, in the internal memory of a microcomputer) at the time of shipment. The management unit 30 of the electric vehicle 1 acquires the SOC-discharge upper limit current characteristic from the control unit 24 of the battery pack 20 when the battery pack 20 is first mounted on the electric vehicle 1. Note that instead of the SOC-discharge upper limit current characteristic, the SOC-discharge upper limit power characteristic may be used, or both may be used. Also, instead of the map, a function may be used in which the discharge upper limit current or discharge upper limit power is the objective variable, and the SOC, temperature, and deterioration level are explanatory variables.

[0043] The SOC-charging upper limit current characteristic of the cell E1-En also depends on the temperature and the deterioration level (SOH). The battery manufacturer derives and maps the SOC-charging upper limit current characteristic of the cell E1-En for each combination of temperature category and deterioration level category. The SOC-charging upper limit current characteristic is registered in the control unit 24 of the battery pack 20 (for example, in the internal memory of a microcomputer) at the time of shipment. The management unit 30 of the electric vehicle 1 acquires the SOC-charging upper limit current characteristic from the control unit 24 of the battery pack 20 when the battery pack 20 is first mounted on the electric vehicle 1. Note that instead of the SOC-charging upper limit current characteristic, the SOC-charging upper limit power characteristic may be used, or both may be used. For example, the upper limit value of the charging current from the charger 2 may be controlled by referring to the SOC-charging upper limit current characteristic, and the upper limit value of the regenerative power from the motor 60 may be controlled by referring to the SOC-charging upper limit power characteristic. Also, instead of the map, a function may be used in which the charging upper limit current or the charging upper limit power is the objective variable, and the SOC, temperature, and deterioration level are explanatory variables.

[0044] Fig. 4 is a diagram showing an example of the SOC-upper limit discharge power characteristic at 0°C of a certain battery pack. As shown in Fig. 4, the lower the SOC, the lower the upper limit discharge power. Fig. 5 is a diagram showing an example of the SOC-upper limit charge current characteristic at 0°C of a certain battery pack. As shown in Fig. 5, the higher the SOC, the lower the upper limit charge current.

[0045] Returning to FIG. 3, the acquisition unit 311 acquires monitoring data including at least the voltage and SOC of the cells E-En from the control unit 24 of each battery pack 20. The calculation unit 312 estimates the SOC of each battery pack 20 based on the SOC of the multiple cells E-En included in each battery pack 20. Normally, the SOC of the lowest cell is taken as the SOC of the pack when the SOC is low, and the SOC of the highest cell is taken as the SOC of the pack when the SOC is high. The calculation unit 312 may convert the SOC of the multiple cells E-En included in the battery pack 20 into capacity, calculate a combined capacity of the multiple cells E-En, and take the SOC corresponding to the combined capacity as the SOC of the pack.

[0046] As described above, in this embodiment, a state occurs in which the pack relay RY1 connected to some of the battery packs 20a-20c is on and the pack relay RY1 connected to the remaining battery packs 20 is off.

[0047] During discharge, when one of the pack relays RY1 in the off state (hereinafter referred to as the target pack relay RY1) should be turned on, the calculation unit 312 estimates the upper limit value of current or power that is permitted to be discharged from all of the multiple battery packs 20 (hereinafter referred to as the parallel system) when the target pack relay RY1 is turned on.

[0048] The determination unit 313 compares the upper limit value estimated by the calculation unit 312 (hereinafter referred to as the predicted upper limit value) with a first threshold value based on the maximum value of the current or power required by the load (mainly the motor 60). The first threshold value may be set to the same value as the maximum value of the current or power required by the load, or may be set to a value lower (less stringent condition) than the maximum value of the current or power required by the load based on past running data of the electric vehicle 1. For example, if the past running data shows that 95% or more of the running time of the electric vehicle 1 was run at 80% or less of the maximum value of the power required by the load, the vehicle ECU 40 may set the first threshold value to a value that is 80% of the maximum value of the power required by the load. The vehicle ECU 40 sets the first threshold value in the management unit 30 of the power supply system 10.

[0049] If the predicted upper limit value is equal to or greater than the first threshold value, the determination unit 313 permits the target pack relay RY1 to be turned on, and if the predicted upper limit value is lower than the first threshold value, the determination unit 313 does not permit the target pack relay RY1 to be turned on. If the determination unit 313 permits the target pack relay RY1 to be turned on, the relay drive unit 25 turns on the target pack relay RY1.

[0050] The determination unit 313 also compares the upper limit value estimated by the calculation unit 312 (hereinafter referred to as the predicted upper limit value) with a second threshold value based on the upper limit value of the current or power permitted to be discharged from the parallel system before turning on the target pack relay RY1 (hereinafter referred to as the current upper limit value). The second threshold value may be the same value as the current upper limit value (adjustment value α=0), may be a value obtained by adding the adjustment value α to the current upper limit value, or may be a value obtained by subtracting the adjustment value α from the current upper limit value. The designer can set the adjustment value α in consideration of the number of parallel battery packs 20, the application, and the like. When the predicted upper limit value is equal to or greater than the second threshold value, the determination unit 313 permits the target pack relay RY1 to be turned on, and when the predicted upper limit value is lower than the second threshold value, does not permit the target pack relay RY1 to be turned on. When the determination unit 313 permits the target pack relay RY1 to be turned on, the relay drive unit 25 turns on the target pack relay RY1.

[0051] The notification unit 314 notifies the vehicle ECU 40 of the upper limit of current or power permitted to be discharged from the parallel system (hereinafter referred to as the upper limit discharge current value or upper limit discharge power value of the entire parallel system (when both are collectively referred to as the upper limit discharge value)). The management unit 30 and the vehicle ECU 40 are connected via an in-vehicle network. For example, a controller area network (CAN) or a local interconnect network (LIN) can be used as the in-vehicle network. The vehicle ECU 40 sets the upper limit discharge current value or upper limit discharge power value of the entire parallel system received from the management unit 30 in the inverter 50. The inverter 50 controls the output current or output power supplied to the motor 60 within the range of the set upper limit discharge current value or upper limit discharge power value.

[0052] When the target pack relay RY1 should be turned on during charging, the calculation unit 312 estimates the upper limit of the current or power that is permitted to be charged to the parallel system when the target pack relay RY1 is turned on.

[0053] The determination unit 313 compares a predicted upper limit value that is permitted to be charged to the parallel system when the target pack relay RY1 is turned on with a third threshold value based on the maximum value of the current or power that the power source can output. During running, the third threshold value may be set to the same value as the maximum value of the current or power that can be regenerated from the motor 60, or may be set to a value (with looser conditions) lower than the maximum value of the current or power that can be regenerated from the motor 60 based on past running data of the electric vehicle 1. For example, if 95% or more of the total regeneration time of the electric vehicle 1 is regenerated at 80% or less of the maximum value of the power that can be regenerated from the motor 60 according to the past running data, the vehicle ECU 40 may set the third threshold value to a value that is 80% of the maximum value of the power that can be regenerated from the motor 60. During charging from the charger 2, the third threshold value is set to the maximum value of the current or power that the charger 2 can output.

[0054] If the predicted upper limit value is equal to or greater than the third threshold value, the determination unit 313 permits the target pack relay RY1 to be turned on, and if the predicted upper limit value is lower than the third threshold value, the determination unit 313 does not permit the target pack relay RY1 to be turned on. If the determination unit 313 permits the target pack relay RY1 to be turned on, the relay drive unit 25 turns on the target pack relay RY1.

[0055] Furthermore, the determination unit 313 compares the predicted upper limit value with a fourth threshold value based on the current upper limit value before turning on the target pack relay RY1. The fourth threshold value may be the same value as the current upper limit value (adjustment value α=0), may be a value obtained by adding the adjustment value α to the current upper limit value, or may be a value obtained by subtracting the adjustment value α from the current upper limit value. The designer can set the adjustment value α in consideration of the number of parallel battery packs 20, the application, and the like. When the predicted upper limit value is equal to or greater than the fourth threshold value, the determination unit 313 permits the target pack relay RY1 to be turned on, and when the predicted upper limit value is lower than the fourth threshold value, does not permit the target pack relay RY1 to be turned on.

[0056] The notification unit 314 notifies the vehicle ECU 40 of the upper limit of the current or power permitted to be charged from the parallel system (hereinafter referred to as the upper limit charging current value or the upper limit charging power value of the entire parallel system (both are collectively referred to as the charging upper limit value)). The vehicle ECU 40 controls the regenerative current or regenerative power of the motor 60 within the range of the upper limit charging current value or the upper limit charging power value of the entire parallel system received from the management unit 30. For example, when the regenerative power value of the regenerative brake reaches the upper limit charging power value of the entire parallel system, the vehicle ECU 40 switches from the regenerative brake to the mechanical brake. The mechanical brake converts the regenerative energy into thermal energy. Furthermore, when rapid charging is performed from the charger 2 with DC, the notification unit 314 notifies the charger 2 of the upper limit charging current value or the upper limit charging power value of the entire parallel system.

[0057] Basically, the more the number of parallel battery packs 20 increases, the higher the upper discharge limit and the upper charge limit of the entire parallel system. However, even if a battery pack 20 is added to the parallel system, there are cases where the upper discharge limit and the upper charge limit of the entire parallel system do not increase. This is the case where a cross current occurs between the multiple battery packs 20 due to the connection of a new battery pack 20.

[0058] FIG. 6 is a diagram for explaining cross current between battery packs 20 during discharging. In FIG. 6, for ease of explanation, two battery packs 20 are shown connected in parallel. The state on the left is a state in which the first pack relay RY1 connected to the first battery pack 20a is on and the second pack relay RY1 connected to the second battery pack 20b is off, and current is supplied to the load only from the first battery pack 20a. In this case, the upper discharge current value of the entire parallel system is equal to the upper discharge current value of the first battery pack 20a.

[0059] The state on the right side of Fig. 6 shows the state after the second pack relay RY1 is turned on. When the OCV of the second battery pack 20b is lower than the CCV when discharging from the first battery pack 20a at the upper discharge current value, a cross current is generated from the first battery pack 20a to the second battery pack 20b. As a result, the current discharged from the first battery pack 20a is branched to the load and the second battery pack 20b, and the upper discharge current value of the entire parallel system is reduced. When the motor 60 of the electric vehicle 1 is rotating near the upper discharge current value, the reduction in the upper discharge current value may cause unintended deceleration.

[0060] The CCV when discharging from the first battery pack 20a at the upper limit discharge current value is an estimated value. The current discharged from the first battery pack 20a varies with load fluctuations, and the CCV of the first battery pack 20a varies according to the variation in the discharge current. The CCV when discharging from the first battery pack 20a at the upper limit discharge current value is a value indicating the minimum voltage during discharge of the first battery pack 20a.

[0061] Next, consider the case where the CCV when discharging from the first battery pack 20a at the upper limit discharge current value matches the OCV of the second battery pack 20b, and the second pack relay RY1 is turned on. When the current actually discharged from the first battery pack 20a to the load matches the upper limit discharge current value of the first battery pack 20a, the CCV of the first battery pack 20a and the OCV of the second battery pack 20b become equal. In this case, no cross current occurs between the first battery pack 20a and the second battery pack 20b, and the upper limit discharge current value of the entire parallel system does not decrease.

[0062] When the current actually discharged from the first battery pack 20a to the load is lower than the upper discharge current value of the first battery pack 20a, the actual CCV of the first battery pack 20a becomes higher than the CCV when discharging at the upper discharge current value. In this case, a cross current occurs from the first battery pack 20a to the second battery pack 20b. However, when the current consumption of the load increases to the upper discharge current value of the first battery pack 20a, the cross current stops, and the upper discharge current value of the entire parallel system does not decrease.

[0063] Next, consider the case where the OCV of the second battery pack 20b is higher than the CCV when discharging the first battery pack 20a at the upper limit discharge current value, and the second pack relay RY1 is turned on. Since the upper limit discharge current value of the second battery pack 20b is higher than the upper limit discharge current value of the first battery pack 20a, the upper limit discharge current value of the entire parallel system does not decrease when the second pack relay RY1 is turned on.

[0064] In the above description, an example has been described in which the calculation unit 312 of the management unit 30 calculates both the discharge upper limit current value of each battery pack 20 and the discharge upper limit current value of the entire parallel system. In this regard, the discharge upper limit current value of the battery pack 20 may be calculated by the control unit 24 in the battery pack 20. The control unit 24 in each battery pack 20 transmits the calculated discharge upper limit current value of the battery pack 20 to the management unit 30. The calculation unit 312 of the management unit 30 calculates the discharge upper limit current value of the entire parallel system based on the respective discharge upper limit current values ​​received from the multiple battery packs 20.

[0065] Hereinafter, two examples of the determination process for determining whether or not to permit parallel connection of the target pack relay RY1 during discharge will be described. Example 1 is a dynamic determination process, and Example 2 is a static determination process.

[0066] 7 is a flowchart for explaining the parallel connection determination process according to the first embodiment. When the power source of the electric vehicle 1 is turned on (corresponding to the ignition on of an engine vehicle) (Y in S10), the determination unit 313 causes the relay drive unit 25 to turn on the pack relay RY1 connected to the battery pack 20 with the highest OCV among the multiple battery packs 20 (S11). When there are multiple battery packs 20 with the highest OCV, the determination unit 313 causes the multiple pack relays RY1 connected to the multiple battery packs 20 to be turned on simultaneously.

[0067] During execution of the parallel connection control (N in S12), the following process is executed: The determination unit 313 identifies the battery pack 20 with the highest OCV among the battery packs 20 with the pack relay RY1 in the off state as the battery pack 20 for which the pack relay RY1 should be turned on next (S13).

[0068] The calculation unit 312 derives the upper discharge current value of the battery pack 20 with the pack relay RY1 in the on state by referring to the SOC-discharge upper current map 321 based on the SOC of the battery pack 20. The calculation unit 312 applies the OCV, internal resistance, and upper discharge current value of the battery pack 20 to the above (Equation 1) to estimate the CCV corresponding to the upper discharge current value of the battery pack 20 (S14). When deriving the SOC, internal resistance, and upper discharge current value of the battery pack 20, the calculation unit 312 takes into account at least the temperature and SOH of the battery pack 20 as parameters.

[0069] The calculation unit 312 estimates the current value flowing through the connection candidate battery pack 20 when the CCV of the connection candidate battery pack 20 corresponds to (is substantially equal to) the CCV when the already connected battery pack 20 discharges at the upper discharge current limit value (S16).

[0070] The current value used is the current value flowing through the load. Since the current value actually flowing through the load is usually lower than the upper limit discharge current value, the CCV of the connected battery pack 20 is higher than the CCV when discharging at the upper limit discharge current value by an amount corresponding to the difference between the two currents. The calculation unit 312 calculates the differential voltage between the actual CCV of the connected battery pack 20 and the CCV of the connection candidate battery pack 20 (= the CCV when the connected battery pack 20 discharges at the upper limit discharge current value), and estimates the current value flowing through the connection candidate battery pack 20 based on the differential voltage and the internal resistance of the connection candidate battery pack 20. This current value becomes the cross current value flowing from the connected battery pack 20 to the connection candidate battery pack 20.

[0071] The calculation unit 312 subtracts the estimated current value (cross current value) from the upper discharge current value of the entire parallel system before the connection of the candidate battery pack 20, and estimates the upper discharge current value of the entire parallel system after the connection of the candidate battery pack 20 (S17).

[0072] The determination unit 313 compares the estimated post-connection upper limit current value with a threshold value based on the maximum current required by the load (S18). If the post-connection upper limit current value is equal to or greater than the threshold value (Y in S18), the determination unit 313 permits connection of the connection candidate battery pack 20 (S19) and causes the relay driving unit 25 to turn on the pack relay RY1 connected to the connection candidate battery pack 20. The process proceeds to step S12. If the post-connection upper limit current value is lower than the threshold value (N in S18), the determination unit 313 does not permit connection of the connection candidate battery pack 20 (S110). The process proceeds to step S12.

[0073] When there are a plurality of battery packs 20 with the pack relay RY1 in the ON state, there are the same CCVs corresponding to the upper discharge current values ​​of the plurality of battery packs 20. In the state in which the CCVs are the same, the calculation unit 312 estimates the CCVs corresponding to the upper discharge current values ​​of the plurality of battery packs 20 in the ON state.

[0074] Fig. 8 is a flowchart for explaining a parallel connection determination process according to the application example of the embodiment 1. The flowchart according to the application example of the embodiment 1 shown in Fig. 8 is obtained by adding a process of step S15 to the flowchart according to the basic example of the embodiment 1 shown in Fig. 7.

[0075] In step S15, the determination unit 313 compares the estimated CCV when the connected battery pack 20 discharges at the upper discharge current value with the OCV of the connection candidate battery pack 20 (S15). If the estimated CCV is equal to or lower than the OCV of the connection candidate battery pack 20 (Y in S15), the determination unit 313 permits connection of the connection candidate battery pack 20 (S19) and causes the relay driving unit 25 to turn on the pack relay RY1 connected to the connection candidate battery pack 20. The process proceeds to step S12. If, in step S15, the estimated CCV is higher than the OCV of the connection candidate battery pack 20 (N in S15), the process proceeds to step S16.

[0076] In an application example, if the estimated CCV when the connected battery pack 20 discharges at the upper discharge current value is equal to or lower than the OCV of the battery pack 20 that is a candidate for connection, the calculation processes of steps S16 to S18 can be skipped, thereby reducing the amount of calculation.

[0077] Next, a second embodiment of the process for determining whether a parallel connection is in progress during discharge will be described. As described above, when the OCVs of the multiple battery packs 20 connected in parallel are not uniform, a cross current occurs from a battery pack 20 with a high OCV to a battery pack 20 with a low OCV. The cross current decreases the OCV of the battery pack 20 with a high OCV, and increases the OCV of the battery pack 20 with a low OCV. When the voltage difference between the two is eliminated, the cross current stops. When the cross current stops, the OCVs of the multiple battery packs 20 connected in parallel are uniform.

[0078] Fig. 9 is a diagram for explaining cross currents between battery packs 20 and convergence of OCV during discharge. For ease of explanation, Fig. 9 shows a parallel connection of two battery packs 20. The state on the left shows a state in which the first pack relay RY1 connected to the first battery pack 20a is on and the second pack relay RY1 connected to the second battery pack 20b is off, and the OCV of the first battery pack 20a is higher than the OCV of the second battery pack 20b.

[0079] The state on the right side of Fig. 9 shows the state after the second pack relay RY1 is turned on. When the first battery pack 20a and the second battery pack 20b are conductive, current flows from the first battery pack 20a to the second battery pack 20b, the OCV of the first battery pack 20a decreases, and the OCV of the second battery pack 20b increases. When the OCVs of both battery packs eventually become equal, the cross current from the first battery pack 20a to the second battery pack 20b stops.

[0080] Under ideal conditions where the pack capacities and the like are uniform, the OCV of the first battery pack 20a and the second battery pack 20b when the cross current is stopped is the average SOC of the SOC of the first battery pack 20a and the SOC of the second battery pack 20b before the cross current occurs, and the OCV when the cross current is stopped is the OCV corresponding to the average SOC. Even when three or more battery packs 20 with mismatched OCVs are connected in parallel, the OCVs of the three or more battery packs 20 will be uniform due to the cross current under ideal conditions. In that case, the OCV of the three or more battery packs 20 after the OCVs are uniform will be the average value of the OCVs of the three or more battery packs 20 before the cross current occurs.

[0081] In the second embodiment, the calculation unit 312 estimates a discharge upper limit current value of the entire parallel system at the time when the OCV converges after a new battery pack 20 is connected to the parallel system. The determination unit 313 permits connection of the new battery pack 20 when the estimated discharge upper limit current value is equal to or greater than a threshold based on the maximum value of the current required by the load. The determination unit 313 does not permit connection of the new battery pack 20 when the estimated discharge upper limit current value is lower than a threshold based on the maximum value of the current required by the load. In addition, the determination unit 313 permits connection of the new battery pack 20 when the estimated discharge upper limit current value is equal to or greater than the discharge upper limit current value of the entire parallel system before the new battery pack 20 is connected. The determination unit 313 does not permit connection of the new battery pack 20 when the estimated discharge upper limit current value is lower than the discharge upper limit current value of the entire parallel system before the new battery pack 20 is connected.

[0082] FIG. 10 is a diagram for explaining an example of change in the discharge upper limit power value of the entire parallel system before and after connecting a new battery pack 20 during discharging. For example, consider a state in which the first battery pack 20a is connected to a load and the second battery pack 20b is not connected to a load, as shown on the left side of FIG. 9. The following description is based on the assumption that battery packs using the same type of cells are used and that the conditions regarding the pack capacity, SOH, and temperature are the same. The SOC of the first battery pack 20a is 15%, and the SOC of the second battery pack 20b is 5%. Referring to the SOC-discharge upper limit power characteristic shown in FIG. 10, the discharge upper limit power value when the SOC is 15% is 5.8 kW. Similarly, the discharge upper limit power value of the entire parallel system in a state in which only the first battery pack 20a is connected is also 5.8 kW.

[0083] Next, consider the state after the second battery pack 20b is connected to the parallel system as shown on the right side of FIG. 9. When the second battery pack 20b is connected to the parallel system, a cross current occurs from the first battery pack 20a to the second battery pack 20b. Due to the cross current, the SOC of the first battery pack 20a decreases and the SOC of the second battery pack 20b increases. When the SOC of both battery packs reaches 15%, the cross current stops. Referring to the SOC-upper discharge power characteristic shown in FIG. 10, the upper discharge power value is 2.0 kW when the SOC is 10%. Therefore, the upper discharge power value of the entire parallel system in the state where the first battery pack 20a and the second battery pack 20b are connected is 4.0 kW (= 2.0 kW × 2).

[0084] In this example, when the second battery pack 20b is connected, the upper discharge power value of the entire parallel system is reduced from 5.8 kW to 4.0 kW. As shown in Fig. 10, when the upper discharge power value in the state where the SOCs are equal (SOC = 10%) is below the imaginary line that connects the upper discharge power value (5.8 kW) of the first battery pack 20a before the connection of the second battery pack 20b and the upper discharge power value (1.0 kW) of the second battery pack 20b, the upper discharge power value of the entire parallel system is lower than the power value obtained by simply averaging the upper discharge power value (5.8 kW) of the first battery pack 20a before the connection and the upper discharge power value (1.0 kW) of the second battery pack 20b. Therefore, if the upper discharge power value of the entire parallel system after the connection of the second battery pack 20b is estimated without referring to the SOC-upper discharge power characteristic, the upper discharge power value may be overestimated, and the actual upper discharge power value may be lower than the power required by the load.

[0085] 11 is a flowchart for explaining the parallel connection determination process according to the second embodiment. When the power supply of the electric vehicle 1 is turned on (Y in S20), the determination unit 313 causes the relay drive unit 25 to turn on the pack relay RY1 connected to the battery pack 20 with the highest OCV among the multiple battery packs 20 (S21). When there are multiple battery packs 20 with the highest OCV, the determination unit 313 causes the multiple pack relays RY1 connected to the multiple battery packs 20 to be turned on simultaneously.

[0086] During execution of the parallel connection control (N in S22), if there is a battery pack 20 whose pack relay RY1 is in the off state, the following process is executed: The determination unit 313 identifies the battery pack 20 with the highest OCV among the battery packs 20 whose pack relay RY1 is in the off state as the battery pack 20 whose pack relay RY1 should be turned on next (S23).

[0087] The calculation unit 312 estimates convergence values ​​of the OCVs of the multiple battery packs 20 connected to the parallel system when the battery pack 20 that is a candidate for connection is turned on (S24). The calculation unit 312 derives a discharge upper limit current value of one battery pack 20 by referring to the SOC-discharge upper limit current map 321 based on the SOC corresponding to the converged OCV. The calculation unit 312 multiplies the discharge upper limit current value of one battery pack 20 by the number of parallel connections to estimate a discharge upper limit current value of the entire parallel system (S25). When deriving the SOC and discharge upper limit current value of a battery pack 20, the calculation unit 312 takes into account at least the temperature and SOH of the battery pack 20 as parameters.

[0088] The determination unit 313 compares the estimated upper discharge current value of the entire parallel system with a threshold value based on the maximum current required by the load (S27). If the estimated upper discharge current value is equal to or greater than the threshold value (Y in S27), the determination unit 313 permits connection of the battery pack 20 that is a candidate for connection (S28) and causes the relay driver 25 to turn on the pack relay RY1 connected to the battery pack 20 that is a candidate for connection. If the estimated upper discharge current value is lower than the threshold value (N in S27), the determination unit 313 does not permit connection of the battery pack 20 that is a candidate for connection (S29). The process proceeds to step S22.

[0089] Fig. 12 is a flowchart for explaining a parallel connection determination process according to a modified example of the embodiment 2. The flowchart according to the modified example of the embodiment 2 shown in Fig. 12 is obtained by adding a process of step S26 to the flowchart according to the basic example of the embodiment 2 shown in Fig. 11.

[0090] In step S26, the determination unit 313 determines whether or not the estimated upper discharge current value of the entire parallel system will decrease due to the connection of the battery pack 20 that is a candidate for connection (S26). If the upper discharge current value of the entire parallel system will not decrease (N in S26), the determination unit 313 permits the connection of the battery pack 20 that is a candidate for connection (S28) and causes the relay driver 25 to turn on the pack relay RY1 connected to the battery pack 20 that is a candidate for connection. If the upper discharge current value of the entire parallel system will decrease (Y in S26), the process proceeds to step S27.

[0091] In the modified example, the basic criterion for judgment is whether or not the upper discharge power value of the entire parallel system decreases after the connection of a new battery pack 20. Even if the upper discharge power value decreases, if there is no problem in practical use, the connection of the new battery pack 20 is permitted, thereby reducing the standby time of the battery pack 20.

[0092] As described above, according to the first and second embodiments, when the connection of a new battery pack 20 causes the discharge upper limit current value or the discharge upper limit power value of the entire parallel system to be lower than a threshold value based on the maximum value of the current or power required by the load, the connection of the new battery pack 20 is prohibited. This makes it possible to prevent a shortage of current supplied from the parallel system to the load, and to prevent adverse effects such as a decrease in the acceleration performance of the electric vehicle 1 from occurring.

[0093] Fig. 13 is a diagram for explaining cross current between battery packs 20 during charging. For ease of explanation, Fig. 13 shows a parallel connection of two battery packs 20. The state on the left is a state in which the first pack relay RY1 connected to the first battery pack 20a is on and the second pack relay RY1 connected to the second battery pack 20b is off, and current is supplied from a power source (e.g., charger 2) only to the first battery pack 20a. In this case, the charging upper limit current value of the entire parallel system matches the charging upper limit current value of the first battery pack 20a.

[0094] The state on the right side of Fig. 13 shows the state after the second pack relay RY1 is turned on. If the OCV of the second battery pack 20b is higher than the CCV when the first battery pack 20a is charged at the upper limit charging current value, a cross current is generated from the second battery pack 20b to the first battery pack 20a. As a result, the upper limit charging current value of the first battery pack 20a does not change, but the current that can be charged from the power source to the first battery pack 20a decreases, and the upper limit charging current value of the entire parallel system as seen from the power source decreases. If charging is being performed at the maximum current from the charger 2, charging may be stopped by control within the charger 2.

[0095] The CCV when the first battery pack 20a is charged at the upper limit charging current value is an estimated value. The current charged to the first battery pack 20a varies due to fluctuations in the power supply voltage, etc., and the CCV of the first battery pack 20a varies according to fluctuations in the charging current. The CCV when the first battery pack 20a is charged at the upper limit charging current value is a value that indicates the maximum voltage during charging of the first battery pack 20a.

[0096] Next, consider the case where the CCV when charging the first battery pack 20a with the upper limit charging current value matches the OCV of the second battery pack 20b, and the second pack relay RY1 is turned on. When the current actually charging the first battery pack 20a from the power source matches the upper limit charging current value of the first battery pack 20a, the CCV of the first battery pack 20a and the OCV of the second battery pack 20b become equal. In this case, no cross current occurs between the first battery pack 20a and the second battery pack 20b, and the upper limit charging current value of the entire parallel system does not decrease.

[0097] When the current actually charged from the power source to the first battery pack 20a is lower than the upper limit charging current value of the first battery pack 20a, the actual CCV of the first battery pack 20a is lower than the CCV when the first battery pack 20a is charged at the upper limit charging current value. In this case, a cross current occurs from the second battery pack 20b to the first battery pack 20a. However, when the output current from the power source increases to the upper limit charging current value of the first battery pack 20a, the cross current stops, and the upper limit charging current value of the entire parallel system does not decrease.

[0098] Next, consider the case where the OCV of the second battery pack 20b is lower than the CCV when the first battery pack 20a is charged with the upper limit charging current value, and the second pack relay RY1 is turned on. Because the upper limit charging current value of the second battery pack 20b is greater than the upper limit charging current value of the first battery pack 20a, the upper limit charging current value of the entire parallel system does not decrease when the second pack relay RY1 is turned on.

[0099] In the above description, an example has been described in which the calculation unit 312 of the management unit 30 calculates both the charging upper limit current value of each battery pack 20 and the charging upper limit current value of the entire parallel system. In this regard, the charging upper limit current value of the battery pack 20 may be calculated by the control unit 24 in the battery pack 20. The control unit 24 in each battery pack 20 transmits the calculated charging upper limit current value of the battery pack 20 to the management unit 30. The calculation unit 312 of the management unit 30 calculates the charging upper limit current value of the entire parallel system based on the respective charging upper limit current values ​​received from the multiple battery packs 20.

[0100] Hereinafter, two examples of the determination process for determining whether or not to permit parallel connection of the target pack relay RY1 during charging will be described. Example 3 is a dynamic determination process, and Example 4 is a static determination process.

[0101] 14 is a flowchart for explaining the parallel connection determination process according to the third embodiment. When the power source of the electric vehicle 1 is turned on (corresponding to the ignition on of an engine vehicle) (Y in S30), the determination unit 313 causes the relay drive unit 25 to turn on the pack relay RY1 connected to the battery pack 20 with the lowest OCV among the plurality of battery packs 20 (S31). When there are multiple battery packs 20 with the lowest OCV, the determination unit 313 causes the multiple pack relays RY1 connected to the plurality of battery packs 20 to be turned on simultaneously.

[0102] During execution of the parallel connection control (N in S32), the following process is executed: The determination unit 313 identifies the battery pack 20 with the lowest OCV among the battery packs 20 with the pack relay RY1 in the off state as the battery pack 20 for which the pack relay RY1 should be turned on next (S33).

[0103] The calculation unit 312 derives the upper limit charging current value of the battery pack 20 based on the SOC of the battery pack 20 with the pack relay RY1 in the on state, by referring to the SOC-upper limit charging current map 322. The calculation unit 312 applies the OCV, internal resistance, and upper limit charging current value of the battery pack 20 to the above (Equation 2) to estimate the CCV corresponding to the upper limit charging current value of the battery pack 20 (S34). When deriving the SOC, internal resistance, and upper limit charging current value of the battery pack 20, the calculation unit 312 takes into account at least the temperature and SOH of the battery pack 20 as parameters.

[0104] The calculation unit 312 estimates the current value flowing through the connection candidate battery pack 20 when the CCV of the connection candidate battery pack 20 corresponds to (is substantially equal to) the CCV when the already connected battery pack 20 is charged at the upper limit charging current value (S36).

[0105] The current value used is the current value flowing from the power source. Since the current value actually flowing from the power source is usually lower than the upper limit charging current value, the CCV of the connected battery pack 20 is lower than the CCV when charging at the upper limit charging current value by an amount corresponding to the current difference between the two. The calculation unit 312 calculates the differential voltage between the actual CCV of the connected battery pack 20 and the CCV of the connection candidate battery pack 20 (= the CCV when the connected battery pack 20 is charged at the upper limit charging current value), and estimates the current value flowing to the connection candidate battery pack 20 based on the differential voltage and the internal resistance of the connection candidate battery pack 20. This current value becomes the cross current value flowing from the connection candidate battery pack 20 to the connected battery pack 20.

[0106] The calculation unit 312 subtracts the estimated current value (cross current value) from the upper limit charging current value of the entire parallel system before the connection of the candidate battery pack 20, and estimates the upper limit charging current value of the entire parallel system after the connection of the candidate battery pack 20 (S37).

[0107] The determination unit 313 compares the estimated post-connection charging upper limit current value with a threshold based on the maximum current that the power source can output (S38). If the post-connection charging upper limit current value is equal to or greater than the threshold (Y in S38), the determination unit 313 permits connection of the connection candidate battery pack 20 (S39) and causes the relay driving unit 25 to turn on the pack relay RY1 connected to the connection candidate battery pack 20. The process proceeds to step S32. If the post-connection charging upper limit current value is lower than the threshold (N in S38), the determination unit 313 does not permit connection of the connection candidate battery pack 20 (S310). The process proceeds to step S32.

[0108] When there are multiple battery packs 20 with the pack relay RY1 in the ON state, there are the same CCVs corresponding to the upper limit charging current values ​​of the multiple battery packs 20. In the state where the CCVs are all set, the calculation unit 312 estimates the CCVs corresponding to the upper limit charging current values ​​of the multiple battery packs 20 in the ON state.

[0109] Fig. 15 is a flowchart for explaining a parallel connection determination process according to an application example of the embodiment 3. The flowchart according to the application example of the embodiment 3 shown in Fig. 15 is obtained by adding a process of step S35 to the flowchart according to the basic example of the embodiment 3 shown in Fig. 12.

[0110] In step S35, the determination unit 313 compares the estimated CCV when the connected battery pack 20 is charged at the upper limit charging current value with the OCV of the connection candidate battery pack 20 (S35). If the estimated CCV is equal to or higher than the OCV of the connection candidate battery pack 20 (Y in S35), the determination unit 313 permits connection of the connection candidate battery pack 20 (319) and causes the relay drive unit 25 to turn on the pack relay RY1 connected to the connection candidate battery pack 20. The process proceeds to step S32. If, in step S35, the estimated CCV is higher than the OCV of the connection candidate battery pack 20 (N in S35), the process proceeds to step S36.

[0111] In the application example, if the estimated CCV when the connected battery pack 20 is being charged at the upper limit charging current value is equal to or greater than the OCV of the battery pack 20 that is a candidate for connection, the calculation processes of steps S36 to S38 can be skipped, thereby reducing the amount of calculation.

[0112] Next, a fourth embodiment of the process for determining whether a parallel connection is in progress during charging will be described. As described above, when the OCVs of the multiple battery packs 20 connected in parallel are not uniform, a cross current occurs from the battery pack 20 with a high OCV to the battery pack 20 with a low OCV. The cross current decreases the OCV of the battery pack 20 with a high OCV, and increases the OCV of the battery pack 20 with a low OCV. When the voltage difference between the two is eliminated, the cross current stops. When the cross current stops, the OCVs of the multiple battery packs 20 connected in parallel are uniform.

[0113] Fig. 16 is a diagram for explaining the cross current between the battery packs 20 and the convergence of the OCV during charging. For ease of explanation, Fig. 16 shows a parallel connection of two battery packs 20. The state on the left shows a state in which the first pack relay RY1 connected to the first battery pack 20a is on and the second pack relay RY1 connected to the second battery pack 20b is off, and the OCV of the first battery pack 20a is lower than the OCV of the second battery pack 20b.

[0114] The state on the right side of Fig. 16 shows the state after the second pack relay RY1 is turned on. When the first battery pack 20a and the second battery pack 20b are conductive, current flows from the second battery pack 20b to the first battery pack 20a, the OCV of the second battery pack 20b decreases, and the OCV of the first battery pack 20a increases. When the OCVs of both battery packs eventually become equal, the cross current from the second battery pack 20b to the first battery pack 20a stops.

[0115] Under ideal conditions where the pack capacities and the like are uniform, the OCV of the first battery pack 20a and the second battery pack 20b when the cross current is stopped is the average SOC of the SOC of the first battery pack 20a and the SOC of the second battery pack 20b before the cross current occurs, and the OCV when the cross current is stopped is the OCV corresponding to the average SOC. Even when three or more battery packs 20 with mismatched OCVs are connected in parallel, the OCVs of the three or more battery packs 20 will be uniform due to the cross current under ideal conditions. In that case, the OCV of the three or more battery packs 20 after the OCVs are uniform will be the average value of the OCVs of the three or more battery packs 20 before the cross current occurs.

[0116] In the fourth embodiment, the calculation unit 312 estimates the charging upper limit current value of the entire parallel system at the time when the OCV converges after a new battery pack 20 is connected to the parallel system. The determination unit 313 allows the connection of the new battery pack 20 when the estimated charging upper limit current value is equal to or greater than a threshold based on the maximum current that the power source can output. The determination unit 313 does not allow the connection of the new battery pack 20 when the estimated charging upper limit current value is lower than a threshold based on the maximum current that the power source can output. In addition, the determination unit 313 allows the connection of the new battery pack 20 when the estimated charging upper limit current value is equal to or greater than the charging upper limit current value of the entire parallel system before the new battery pack 20 is connected. The determination unit 313 does not allow the connection of the new battery pack 20 when the estimated charging upper limit current value is lower than the charging upper limit current value of the entire parallel system before the new battery pack 20 is connected.

[0117] FIG. 17 is a diagram for explaining an example of change in the charging upper limit current value of the entire parallel system before and after connecting a new battery pack 20 during charging. For example, consider a state in which the first battery pack 20a is connected to a power source and the second battery pack 20b is not connected to a power source, as shown on the left side of FIG. 16. The following description is based on the assumption that battery packs using the same type of cells are used and that the conditions regarding pack capacity, SOH, and temperature are the same. The SOC of the first battery pack 20a is 80%, and the SOC of the second battery pack 20b is 90%. Referring to the SOC-charging upper limit current characteristic shown in FIG. 17, the charging upper limit current value when the SOC is 80% is 15A. The charging upper limit current value of the entire parallel system in a state in which only the first battery pack 20a is connected is also 15A.

[0118] Next, consider the state after the second battery pack 20b is connected to the parallel system as shown on the right side of FIG. 16. When the second battery pack 20b is connected to the parallel system, a cross current is generated from the second battery pack 20b to the first battery pack 20a. Due to the cross current, the SOC of the second battery pack 20b decreases and the SOC of the first battery pack 20a increases. When the SOC of both battery packs reaches 85%, the cross current stops. Referring to the SOC-maximum charging current characteristic shown in FIG. 17, the maximum charging current value is 6A when the SOC is 85%. Therefore, the maximum charging current value of the entire parallel system when the first battery pack 20a and the second battery pack 20b are connected is 12A (=6A×2).

[0119] In this example, when the second battery pack 20b is connected, the upper limit charging current value of the entire parallel system is reduced from 15 A to 12 A. As shown in Fig. 16, when the upper limit charging current value in the state where the SOCs are equal (SOC = 85%) is below the imaginary line that connects the upper limit charging current value (15 A) of the first battery pack 20a before the connection of the second battery pack 20b and the upper limit charging current value (2 A) of the second battery pack 20b, the upper limit charging current value of the entire parallel system is lower than the current value obtained by simply averaging the upper limit charging current value (15 A) of the first battery pack 20a before the connection and the upper limit charging current value (2 A) of the second battery pack 20b. Therefore, if the upper limit charging current value of the entire parallel system after the connection of the second battery pack 20b is estimated without referring to the SOC-upper limit charging current characteristic, the upper limit charging current value may be overestimated, resulting in a state in which the actual upper limit charging current value is lower than the charging current value from the charger 2.

[0120] 18 is a flowchart for explaining the parallel connection determination process according to the fourth embodiment. When the power supply of the electric vehicle 1 is turned on (Y in S40), the determination unit 313 causes the relay drive unit 25 to turn on the pack relay RY1 connected to the battery pack 20 with the lowest OCV among the plurality of battery packs 20 (S41). When there are multiple battery packs 20 with the lowest OCV, the determination unit 313 causes the multiple pack relays RY1 connected to the plurality of battery packs 20 to be turned on simultaneously.

[0121] During execution of the parallel connection control (N in S42), if there is a battery pack 20 whose pack relay RY1 is in the off state, the following process is executed: The determination unit 313 identifies the battery pack 20 with the lowest OCV among the battery packs 20 whose pack relay RY1 is in the off state as the battery pack 20 whose pack relay RY1 should be turned on next (S43).

[0122] The calculation unit 312 estimates the convergence value of the OCV of the multiple battery packs 20 connected to the parallel system when the connection candidate battery pack 20 is turned on (S44). The calculation unit 312 derives the upper limit charging current value of one battery pack 20 by referring to the SOC-upper limit charging current map 322 based on the SOC corresponding to the converged OCV. The calculation unit 312 multiplies the upper limit charging current value of one battery pack 20 by the number of parallel connections to estimate the upper limit charging current value of the entire parallel system (S45). When deriving the SOC and upper limit charging current value of the battery pack 20, the calculation unit 312 takes into account at least the temperature and SOH of the battery pack 20 as parameters.

[0123] The determination unit 313 compares the estimated upper limit charging current value of the entire parallel system with a threshold value based on the maximum current that the power source can output (S47). If the estimated upper limit charging current value is equal to or greater than the threshold value (Y in S47), the determination unit 313 permits connection of the battery pack 20 that is a candidate for connection (S48) and causes the relay driver 25 to turn on the pack relay RY1 connected to the battery pack 20 that is a candidate for connection. If the estimated upper limit charging current value is lower than the threshold value (N in S47), the determination unit 313 does not permit connection of the battery pack 20 that is a candidate for connection (S49). The process proceeds to step S42.

[0124] Fig. 19 is a flowchart for explaining a parallel connection determination process according to a modification of the embodiment 4. The flowchart according to the modification of the embodiment 4 shown in Fig. 19 is obtained by adding a process of step S46 to the flowchart according to the basic example of the embodiment 4 shown in Fig. 18.

[0125] In step S46, the determination unit 313 determines whether or not the estimated upper limit charging current value of the entire parallel system will decrease due to the connection of the candidate battery pack 20 (S46). If the upper limit charging current value of the entire parallel system will not decrease (N in S46), the determination unit 313 permits the connection of the candidate battery pack 20 (S48) and causes the relay driver 25 to turn on the pack relay RY1 connected to the candidate battery pack 20. If the upper limit charging current value of the entire parallel system will decrease (Y in S46), the process proceeds to step S47.

[0126] In the modified example, when the basic criterion for judgment is whether or not the upper limit charging power value of the entire parallel system decreases after the connection of a new battery pack 20, if the upper limit charging power value decreases but there is no problem in practical use, the connection of the new battery pack 20 is permitted, thereby reducing the standby time of the battery pack 20.

[0127] As described above, according to the third and fourth embodiments, when the upper limit charging current value or the upper limit charging power value of the entire parallel system becomes lower than the threshold value based on the maximum current or power that the power source can output due to the connection of a new battery pack 20, the connection of the new battery pack 20 is prohibited. This makes it possible to prevent an increase in charging time and waste of regenerative energy, and to prevent a decrease in the charging efficiency of the battery pack 20.

[0128] The present disclosure has been described above based on the embodiments. The embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of each component and each processing step, and that such modifications are also within the scope of the present disclosure.

[0129] The parallel connection determination process according to the first embodiment and the parallel connection determination process according to the second embodiment may be used in combination. In this case, if the connection is permitted in both determination processes, the connection candidate battery pack 20 is connected, and if the connection is not permitted in at least one of the determination processes, the connection candidate battery pack 20 is not connected. For example, even if the connection of the connection candidate battery pack 20 is permitted in the determination process according to the second embodiment, the connection may not be permitted in the determination process according to the first embodiment.

[0130] The determination process according to the second embodiment determines whether or not the connection candidate battery pack 20 can be connected based on the upper discharge limit value of the entire parallel system at a certain point in the future. The upper discharge limit value in the process until that point in time is reached is not taken into consideration. On the other hand, the determination process according to the first embodiment determines whether or not the connection candidate battery pack 20 can be connected based on the current upper discharge limit value that changes from moment to moment. Therefore, there may be cases where the two determination results do not match. When the parallel connection determination process according to the first embodiment and the parallel connection determination process according to the second embodiment are used in combination, the stability of the current supplied from the parallel system to the load can be further improved.

[0131] The parallel connection determination process according to the third embodiment and the parallel connection determination process according to the fourth embodiment may be used in combination. In this case, if the connection is permitted in both determination processes, the connection candidate battery pack 20 is connected, and if the connection is not permitted in at least one of the determination processes, the connection candidate battery pack 20 is not connected. For example, even if the connection of the connection candidate battery pack 20 is permitted in the determination process according to the fourth embodiment, the connection may not be permitted in the determination process according to the third embodiment.

[0132] The determination process according to the fourth embodiment determines whether or not the connection candidate battery pack 20 can be connected based on the upper charge limit value of the entire parallel system at a certain point in the future. The upper charge limit value in the process until that point in time is reached is not taken into consideration. On the other hand, the determination process according to the third embodiment determines whether or not the connection candidate battery pack 20 can be connected based on the current upper charge limit value that changes from moment to moment. Therefore, there may be cases where the two determination results do not match. When the parallel connection determination process according to the third embodiment and the parallel connection determination process according to the fourth embodiment are used in combination, it is possible to further prevent the occurrence of a decrease in charging efficiency.

[0133] In the above embodiment, an example has been described in which the management unit 30 is provided outside the multiple battery packs 20. In this regard, the management unit 30 may be provided inside any one of the multiple battery packs 20. In this case, the battery pack 20 that realizes the function of the management unit 30 becomes a master device, and the remaining battery packs 20 become slave devices.

[0134] In the above embodiment, an example has been described in which detachable and replaceable battery packs 20 are connected in parallel. In this regard, fixed battery packs 20 may also be connected in parallel. When using fixed battery packs 20, the functions of the multiple control units 24 and management units 30 provided in the multiple battery packs 20 can be integrated. For example, the multiple control units 24 and management units 30 may be realized by a single microcomputer.

[0135] In the above-described embodiment, an example has been described in which the battery pack 20 incorporating the battery module M1 including lithium-ion battery cells, nickel-metal hydride battery cells, lead battery cells, etc. is used. In this regard, a capacitor pack incorporating a capacitor module including electric double layer capacitor cells, lithium-ion capacitor cells, etc. may also be used. In this specification, the battery module and the capacitor module are collectively referred to as the power storage module, and the battery pack and the capacitor pack are collectively referred to as the power storage pack.

[0136] In the above-described embodiment, an example in which detachable and replaceable electricity storage packs are connected in parallel has been described. In this regard, the present disclosure is also applicable to a process for determining whether a plurality of electricity storage modules are connected in parallel in one electricity storage pack. Note that, since the above-described embodiment assumes an example in which one electricity storage module is provided in one electricity storage pack, the process for determining whether a plurality of electricity storage packs are connected in parallel is synonymous with performing a process for determining whether a plurality of electricity storage modules are connected in parallel.

[0137] The mobile body powered by the replaceable battery pack 20 is not limited to the electric vehicle 1. For example, the mobile body also includes an electric ship. For example, the replaceable battery pack 20 may be used as the power source for a water bus or a water taxi. The battery pack 20 may supply power to an outboard motor. The mobile body also includes a train. For example, a train equipped with the replaceable battery pack 20 can be used instead of a diesel railcar used on a non-electrified line. The mobile body also includes an electric flying object. An electric flying object includes a multicopters (drones). The multicopters also include so-called flying cars.

[0138] The embodiment may be specified by the following items.

[0139] [Item 1] A management device (30) that manages a plurality of power storage modules (M1) that are connected in parallel to a load (60) via respective switches (RY1), a determination unit (313) that, when at least one of the switches (RY1) in the off state is turned on while the switches (RY1) connected to some of the plurality of storage modules (M1) are on and the switches (RY1) connected to the remaining storage modules (M1) are off, does not permit turning on of the switch (RY1) when an upper limit value of a current or power permitted to be discharged from all of the plurality of storage modules (M1) when the switch (RY1) is turned on is lower than a first threshold value based on a maximum value of a current or power required by the load (60); A management device (30) comprising: This makes it possible to prevent a shortage of current supplied to the load (60) from all of the multiple parallel-connected power storage modules (M1) due to the new connection of the power storage module (M1). [Item 2] An acquisition unit (311) that acquires at least a State Of Charge (SOC) for each of the plurality of power storage modules (M1); a calculation unit (312) that estimates an upper limit of current or power that is permitted to be supplied from the plurality of storage modules (M1) as a whole, based on an SOC-discharge upper limit characteristic that specifies the relationship between the SOC of the storage module (M1) and an upper limit of current or power that is permitted to be discharged from the storage module (M1), The SOC-discharge upper limit characteristic is a characteristic in which the lower the SOC of the power storage module (M1), the lower the upper limit value of the current or power permitted to be discharged from the power storage module (M1). 2. The management device (30) according to item 1, This makes it possible to specify with high accuracy the upper limit of the current or power that is permitted to be supplied to the load (60) from all of the multiple power storage modules (M1). [Item 3] The acquisition unit (311) acquires an OCV (Open Circuit Voltage) of a storage module (M1) that is a candidate for connection among the remaining storage modules (M1); the calculation unit (312) derives an upper limit value of a current or power permitted to be discharged from the power storage module (M1) based on the SOC-discharge upper limit characteristic and a State Of Charge (SOC) of the power storage module (M1) connected to the load (60), and estimates a Closed Circuit Voltage (CCV) of the power storage module (M1) when discharging from the power storage module (M1) at the upper limit value; When the OCV of the connection candidate power storage module (M1) is equal to or greater than the estimated CCV of the power storage module (M1), the determination unit (313) permits turn-on of a switch connected to the connection candidate power storage module, When the OCV of the storage module (M1) as a connection candidate is lower than the estimated CCV of the storage module (M1), the calculation unit (312) estimates a current value flowing through the storage module (M1) as a connection candidate when the CCV of the storage module (M1) as a connection candidate corresponds to a CCV of the storage module (M1) connected to the load (60) when discharging at the upper limit value, and determines a value obtained by subtracting the estimated current value from the upper limit value as an upper limit value of current or power permitted to be discharged from all of the multiple storage modules (M1), and the determination unit (313) permits the switch to be turned on when the upper limit value is equal to or greater than the first threshold value. 3. The management device (30) according to item 2. This makes it possible to dynamically determine whether or not the current supplied from the entire plurality of power storage modules (M1) to the load (60) becomes insufficient. [Item 4] the calculation unit (312) estimates an upper limit value of current or power permitted to be supplied from all of the plurality of storage modules (M1) when the OCV of the storage module (M1) connected to the load (60) and the OCV of the storage module (M1) as a connection candidate correspond to each other after a switch (RY1) connected to the storage module (M1) as a connection candidate is turned on, based on the SOC-discharge upper limit characteristic, an SOC corresponding to the OCV of the storage module (M1) connected to the load (60), and an SOC corresponding to the OCV of the storage module (M1) as a connection candidate; The determination unit (313) does not permit the switch (RY1) to be turned on when the estimated upper limit value is lower than the first threshold value or lower than a second threshold value based on the upper limit value before turning on the switch (RY1). 4. The management device (30) according to item 2 or 3. This makes it possible to statically predict whether or not the current supplied from the entire plurality of power storage modules (M1) to the load (60) will become insufficient. [Item 5] When starting to supply power from the plurality of storage modules (M1) to the load (60), a switch (RY1) connected to a storage module (M1) having the highest OCV among the plurality of storage modules (M1) is turned on; Among the storage modules (M1) whose switch (RY1) is in the off state, the storage module (M1) with the highest OCV is the connection candidate for turning on the switch (RY1) next. 5. The management device (30) according to any one of items 1 to 4. This makes it possible to prevent a shortage of current supplied to the load (60) and to connect the plurality of power storage modules (M1) in parallel. [Item 6] a plurality of power storage modules (M1) each connected in parallel to a load (60) via a switch (RY1); A management device (30) according to any one of items 1 to 5; A power supply system (10) comprising: This makes it possible to realize a power supply system (10) that can prevent a shortage of current supplied to the load (60) from all of the multiple parallel-connected energy storage modules (M1) due to the connection of a new energy storage module (M1). [Item 7] The load (60) is a motor (60) of a moving body (1), the management device (30) notifies a control unit (40) in the moving object (1) of an upper limit value of a current or power that is permitted to be supplied to the motor (60) from all of the plurality of power storage modules (M1); 7. The power supply system (10) according to item 6, This makes it possible to prevent adverse effects such as a decrease in the acceleration performance of the moving body (1) from occurring. [Item 8] A management device (30) that manages a plurality of power storage modules (M1) that are connected in parallel to a power source (60, 2) via respective switches (RY1), a determination unit (313) that, when at least one of the switches (RY1) in the off state is turned on while the switches (RY1) connected to some of the plurality of storage modules (M1) are on and the switches (RY1) connected to the remaining storage modules (M1) are off, does not permit turning on of the switch (RY1) when an upper limit value of a current or power permitted to be charged to all of the plurality of storage modules (M1) when the switch (RY1) is turned on is lower than a third threshold value based on a maximum value of a current or power that can be output by the power source (60, 2); A management device (30) comprising: This makes it possible to prevent a decrease in the efficiency of charging the plurality of power storage modules (M1) as a whole from the power source (60, 2) due to the new connection of the power storage module (M1). [Item 9] An acquisition unit (311) that acquires at least a State Of Charge (SOC) for each of the plurality of power storage modules (M1); a calculation unit (312) that estimates an upper limit value of current or power that is permitted to be charged to the entire plurality of storage modules (M1) based on an SOC-charge upper limit characteristic that specifies the relationship between the SOC of the storage module (M1) and an upper limit value of current or power that is permitted to be charged to the storage module (M1), The SOC-charging upper limit characteristic is a characteristic in which the higher the SOC of the power storage module (M1), the lower the upper limit value of the current or power allowed to be charged to the power storage module (M1). 9. The management device (30) according to item 8, This makes it possible to specify with high accuracy the upper limit of the current or power that is permitted to be charged to the multiple power storage modules (M1). [Item 10] The acquisition unit (311) acquires an OCV (Open Circuit Voltage) of a storage module (M1) that is a candidate for connection among the remaining storage modules (M1); the calculation unit (312) derives an upper limit value of a current or power permitted to be charged to the power storage module (M1) based on the SOC-charge upper limit characteristic and a State Of Charge (SOC) of the power storage module (M1) connected to the power source (60, 2), and estimates a Closed Circuit Voltage (CCV) of the power storage module (M1) when the power storage module (M1) is charged at the upper limit value; When the OCV of the connection candidate power storage module (M1) is equal to or lower than the estimated CCV of the power storage module (M1), the determination unit (313) permits turn-on of a switch (RY1) connected to the connection candidate power storage module (M1); When the OCV of the storage module (M1) as a connection candidate is higher than the estimated CCV of the storage module (M1), the calculation unit (312) estimates a current value flowing through the storage module (M1) as a connection candidate when the CCV of the storage module (M1) as a connection candidate corresponds to a CCV in the case of charging the storage module (M1) connected to the power source (60, 2) at the upper limit value, and sets a value obtained by subtracting the estimated current value from the upper limit value as an upper limit value of current or power permitted to be charged to all of the multiple storage modules (M1), and the determination unit (313) permits the switch to be turned on when the upper limit value is equal to or higher than the third threshold value. 10. The management device (30) according to item 9, This makes it possible to dynamically determine whether or not the efficiency of charging the entire plurality of power storage modules (M1) from the power source (60, 2) decreases. [Item 11] the calculation unit (312) estimates an upper limit value of current or power permitted to be charged to all of the plurality of storage modules (M1) when the OCV of the storage module (M1) connected to the power source (60, 2) and the OCV of the storage module (M1) as a connection candidate correspond to each other after a switch (RY1) connected to the storage module (M1) as a connection candidate is turned on, based on the SOC-charge upper limit characteristic, an SOC corresponding to the OCV of the storage module (M1) connected to the power source (60, 2), and an SOC corresponding to the OCV of the storage module (M1) as a connection candidate; The determination unit (313) does not permit the switch (RY1) to be turned on when the estimated upper limit value is lower than the third threshold value or lower than a fourth threshold value based on the upper limit value before turning on the switch (RY1). 11. The management device (30) according to item 9 or 10. This makes it possible to statically predict whether or not the charging efficiency from the power source (60, 2) to the entire plurality of power storage modules (M1) will decrease. [Item 12] When the power supply from the power source (60,2) to the plurality of storage modules (M1) is started, a switch (RY1) connected to the storage module (M1) having the lowest OCV among the plurality of storage modules (M1) is turned on; Among the storage modules (M1) whose switch (RY1) is in the off state, the storage module (M1) with the lowest OCV is the connection candidate for turning on the switch (RY1) next. 12. The management device (30) according to any one of items 8 to 11. This makes it possible to prevent a decrease in the efficiency of charging the plurality of power storage modules (M1) as a whole from the power source (60, 2) and to connect the plurality of power storage modules (M1) in parallel. [Item 13] a plurality of power storage modules (M1) connected in parallel to a power source (60,2) via respective switches (RY1); A management device (30) according to any one of items 8 to 12, A power supply system (10) comprising: This prevents a decrease in the efficiency of charging the plurality of power storage modules (M1) from the power source (60, 2) as a whole due to the new connection of the power storage module (M1). It is possible to realize a power supply system (10) capable of [Item 14] The power source (60, 2) is a motor (60) of the moving object (1) or an external charger (2); The management device (30) notifies a control unit (40) in the moving body (1) of an upper limit value of a current or power that is permitted to be regenerated from the motor (60) to the entire plurality of power storage modules (M1). Item 14. The power supply system (10) according to item 13. This makes it possible to prevent the regenerative energy generated by the motor (60) from being wasted. [Explanation of symbols]

[0140] 1 electric vehicle, 2 charger, 3 system, 5 charging cable, 10 power supply system, 20 battery pack, 30 management unit, M1 battery module, E1-En cell, 21 voltage measurement unit, 22 temperature measurement unit, 23 current measurement unit, 24 control unit, 241 SOC-OCV map, 25 relay drive unit, 31 processing unit, 311 acquisition unit, 312 calculation unit, 313 judgment unit, 314 notification unit, 32 memory unit, 321 SOC-discharge upper limit current map, 322 SOC-charge upper limit current map, 40 vehicle ECU, 50 inverter, 60 motor, 70 AC / DC converter, RYc main relay, RY1 pack relay, Rs shunt resistor, T1, T2 temperature sensor.

Claims

1. A management device that manages a plurality of power storage modules that are connected in parallel to a load via switches, a determination unit that, when at least one of the switches in the off state is turned on while switches connected to some of the plurality of power storage modules are on and switches connected to the remaining power storage modules are off, does not permit turning on of the switch when an upper limit value of a current or power permitted to be discharged from all of the plurality of power storage modules when the switch is turned on is lower than a first threshold value based on a maximum value of a current or power required by the load; A management device comprising:

2. An acquisition unit that acquires at least a state of charge (SOC) for each of the plurality of power storage modules; A calculation unit that estimates an upper limit value of a current or power that is permitted to be discharged from the entire plurality of power storage modules based on an SOC-discharge upper limit characteristic that defines a relationship between an SOC of the power storage module and an upper limit value of a current or power that is permitted to be discharged from the power storage module, The SOC-discharge upper limit characteristic is a characteristic in which the lower the SOC of the storage module, the lower the upper limit value of the current or power allowed to be discharged from the storage module.

2. The management device according to claim 1.

3. The acquisition unit acquires an OCV (Open Circuit Voltage) of a connection candidate power storage module among the remaining power storage modules, The calculation unit derives an upper limit value of a current or power permitted to be discharged from the storage module based on the SOC-discharge upper limit characteristic and an SOC of the storage module connected to the load, and estimates a CCV (Closed Circuit Voltage) of the storage module when discharging from the storage module at the upper limit value; When the OCV of the power storage module that is a candidate for connection is equal to or higher than the estimated CCV of the power storage module, the determination unit permits turning on of a switch that is connected to the power storage module that is a candidate for connection; When the OCV of the storage module of the connection candidate is lower than the estimated CCV of the storage module, the calculation unit estimates a current value flowing through the storage module of the connection candidate when the CCV of the storage module of the connection candidate corresponds to a CCV of the storage module connected to the load when discharging at the upper limit value, and sets a value obtained by subtracting the estimated current value from the upper limit value as an upper limit value of current or power permitted to be discharged from all of the multiple storage modules, and the determination unit permits turning on of the switch when the upper limit value is equal to or greater than the first threshold value.

3. The management device according to claim 2.

4. the calculation unit estimates an upper limit value of current or power permitted to be discharged from all of the multiple power storage modules when the OCV of the power storage module connected to the load and the OCV of the power storage module of the connection candidate correspond to each other after a switch connected to the power storage module of the connection candidate is turned on, based on the SOC-discharge upper limit characteristic, an SOC corresponding to an OCV of the power storage module connected to the load, and an SOC corresponding to an OCV of the power storage module of the connection candidate; the determination unit does not permit turning on of the switch when the estimated upper limit value is lower than the first threshold value or lower than a second threshold value based on the upper limit value before turning on the switch.

4. The management device according to claim 2 or 3.

5. When starting power supply from the plurality of power storage modules to the load, a switch connected to a power storage module having a highest OCV among the plurality of power storage modules is turned on; Among the storage modules whose switches are in an off state, the storage module with the highest OCV becomes a connection candidate whose switch should be turned on next.

5. The management device according to claim 1,

6. A plurality of power storage modules are connected in parallel to a load via respective switches; A management device according to any one of claims 1 to 5; A power supply system comprising:

7. the load is a motor of a moving body, the management device notifies a control unit in the moving object of an upper limit value of a current or power that is permitted to be supplied to the motor from all of the plurality of power storage modules; 7. The power supply system of claim 6.

8. A management device that manages a plurality of power storage modules that are connected in parallel to a power source via switches, a determination unit that, when at least one of the switches in the off state is turned on while the switches connected to some of the plurality of power storage modules are on and the switches connected to the remaining power storage modules are off, does not permit the turn-on of the switch when an upper limit value of a current or power permitted to be charged to all of the plurality of power storage modules when the switch is turned on is lower than a third threshold value based on a maximum value of a current or power that can be output by the power source; A management device comprising:

9. An acquisition unit that acquires at least a state of charge (SOC) for each of the plurality of power storage modules; A calculation unit that estimates an upper limit value of a current or power that is permitted to be charged to all of the plurality of power storage modules based on an SOC-charging upper limit characteristic that specifies a relationship between an SOC of the power storage module and an upper limit value of a current or power that is permitted to be charged to the power storage module, The SOC-charging upper limit characteristic is a characteristic in which the higher the SOC of the power storage module, the lower the upper limit value of the current or power allowed to be charged to the power storage module.

9. The management device according to claim 8.

10. The acquisition unit acquires an OCV (Open Circuit Voltage) of a connection candidate power storage module among the remaining power storage modules, the calculation unit derives an upper limit value of a current or power permitted to be charged to the power storage module based on the SOC-charge upper limit characteristic and an SOC of the power storage module connected to the power source, and estimates a CCV (Closed Circuit Voltage) of the power storage module when the power storage module is charged at the upper limit value; When the OCV of the power storage module that is a candidate for connection is equal to or lower than the estimated CCV of the power storage module, the determination unit permits turning on of a switch that is connected to the power storage module that is a candidate for connection; When the OCV of the storage module of the connection candidate is higher than the estimated CCV of the storage module, the calculation unit estimates a current value flowing through the storage module of the connection candidate when the CCV of the storage module of the connection candidate corresponds to a CCV of the storage module connected to the power source when charging at the upper limit value, and sets a value obtained by subtracting the estimated current value from the upper limit value as an upper limit value of current or power permitted to be charged to all of the multiple storage modules, and the determination unit permits turning on the switch when the upper limit value is equal to or greater than the third threshold value.

10. The management device according to claim 9.

11. the calculation unit estimates an upper limit value of current or power permitted to be charged to all of the plurality of power storage modules when the OCV of the power storage module connected to the power source and the OCV of the power storage module of the connection candidate correspond to each other after a switch connected to the power storage module of the connection candidate is turned on, based on the SOC-charge upper limit characteristic, an SOC corresponding to the OCV of the power storage module connected to the power source, and an SOC corresponding to the OCV of the power storage module of the connection candidate; the determination unit does not permit turning on of the switch when the estimated upper limit value is lower than the third threshold value or lower than a fourth threshold value based on the upper limit value before turning on the switch.

11. The management device according to claim 9 or 10.

12. When starting to supply power from the power source to the plurality of power storage modules, a switch connected to a power storage module having a lowest OCV among the plurality of power storage modules is turned on; Among the storage modules whose switches are in an off state, the storage module with the lowest OCV becomes a connection candidate whose switch should be turned on next.

12. The management device according to claim 8, wherein the management device is a device for managing a plurality of data.

13. A plurality of power storage modules each connected in parallel to a power source via a switch; A management device according to any one of claims 8 to 12; A power supply system comprising:

14. The power source is a motor of a moving object or an external charger; The management device notifies a control unit in the moving object of an upper limit value of a current or power that is permitted to be regenerated from the motor to the entire plurality of power storage modules.

14. The power system of claim 13.

Images