Management device and power supply system

Abstract

A management device (30) manages a plurality of power storage modules (M1) connected in parallel to power sources (60, 2) via respective switches (RY1). In a state where switches (RY1) connected to some of the plurality of power storage modules (M1) are on and switches (RY1) connected to the remaining power storage modules (M1) are off, if the turning on of at least one of the switches (RY1) in the off state will result in the upper limit of the current or power that is permitted to be supplied to all of the plurality of power storage modules (M1) when that switch (RY1) is turned on being lower than a threshold based on the upper limit before that switch (RY1) is turned on, a determination unit (313) of the management device (30) does not permit the turning on of that 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 power source, and a power supply system. [Background technology]

[0002] In recent years, relatively low-power (e.g., 48V) electric vehicles such as electric motorcycles, electric golf carts, electric land cars, and forklifts have become popular. Some of these electric vehicles employ power supply systems in which multiple detachable, 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, control has been proposed to prevent cross currents from flowing through the battery packs or relays in excess of their rated voltage (see, for example, Patent Document 1). Also proposed is control 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] Japanese Patent Application Laid-Open No. 2009-33936 [Patent Document 2] International Publication No. 2012 / 164630 Summary of the Invention [Problem to be solved by the invention]

[0005] When disconnected battery packs are 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 the cross current 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 lower upper limit may have adverse effects such as increased charging time and reduced regenerative braking power.

[0006] The present disclosure has been made in view of the above circumstances, and its purpose is to provide a technique for preventing a decrease in charging efficiency when charging a parallel system. [Means for solving the problem]

[0007] 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 connected in parallel to a power source, each connected via a switch, and when the switches connected to some of the plurality of storage modules are on and the 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 the current or power that is allowed to be charged to all of the plurality of storage modules when the switch is turned on is lower than a threshold value based on the upper limit value before the switch is turned on, the management device includes a determination unit that does not allow the switch to be turned on. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to prevent a decrease in charging efficiency when charging a parallel system. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating an electric vehicle equipped with a power supply system according to an embodiment. [Figure 2] 2 is a diagram showing an example of the internal configuration of the battery pack of FIG. 1. [Figure 3]2 is a diagram illustrating an example of the internal configuration of a management unit in FIG. 1; [Figure 4] FIG. 1 is a diagram showing an example of SOC-charge upper limit current characteristics at 0° C. of a certain battery pack. [Figure 5] FIG. 10 is a diagram for explaining a cross current between battery packs. [Figure 6] 10 is a flowchart illustrating a process of determining parallel connection according to the first embodiment. [Figure 7] FIG. 1 is a diagram for explaining cross current between battery packs and convergence of OCV. [Figure 8] 10A and 10B are diagrams 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. [Figure 9] 10 is a flowchart illustrating a process of determining whether a parallel connection is performed according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] FIG. 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 an exchangeable battery pack 20 as a power source, and corresponds to, for example, an electric motorcycle, an electric golf cart, an electric land cart, a forklift, etc. The battery pack 20 is a detachable, portable, and exchangeable battery pack that is attached by the user to an attachment slot of the electric vehicle 1.

[0011] The power supply system 10 is connected to the motor 60 via the main relay RYc and the inverter 50. During power running, the inverter 50 converts the 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 the 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 in response to the AC power supplied from the inverter 50. During regeneration, the rotational energy generated by deceleration is converted into AC power and supplied to the inverter 50.

[0012] 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.

[0013] 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 grid (hereinafter simply referred to as grid 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 standard charger, it generally charges the battery pack 20 with single-phase 100 / 200V AC power. In this case, conduction between the charger 2 and the battery pack 20 is established via the charging cable 5, the external charging relay RYo, and the AC / DC converter 70.

[0014] During charging from the charger 2, the vehicle ECU 40 controls the external charging relay RYo to the on state. Note that other types of switches, such as semiconductor switches, 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.

[0015] When the charger 2 is a rapid charger, the charger 2 generates direct current power by rectifying the alternating current power supplied from the grid 3. As the rapid charging standard, for example, CHAdeMO (registered trademark), GB / T, Combo (Combined Charging System), etc. can be used.

[0016] The charging cable 5 that supports rapid 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 electrically powered vehicle 1 is bypassed. Note that it is also possible to bypass only the rectifier circuit of the AC / DC converter 70 and control the current or voltage of the DC power by the DC / DC converter in the AC / DC converter 70 rather than controlling it on the charger 2 side.

[0017] 1 is an example in which the battery pack 20 is charged while attached to the electric vehicle 1. However, it is also possible to charge the battery pack 20 while it is separated from the electric vehicle 1. In this case, the battery pack 20 can be charged by attaching it to a charging stand outside the electric vehicle 1.

[0018] 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 the load (mainly the motor 60) of the electric vehicle 1. Note that the motor 60 serves as the 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 output of the electric vehicle 1. While FIG. 1 shows an example in which three battery packs 20a-20c are connected in parallel, this is not limited to three battery packs connected in parallel. To extend the cruising range, more battery packs 20 may be connected in parallel. Furthermore, in the case of a small electric vehicle 1, two battery packs may be connected in parallel.

[0019] Fig. 2 is a diagram showing an example of the internal configuration of the battery pack 20 of 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.

[0020] The battery module M1 includes a plurality of cells E1-En connected in series. The battery module M1 may be configured by connecting in series a plurality of cell blocks, each of which is made up of a plurality of cells connected in parallel. The cells may be lithium-ion battery cells, nickel-metal hydride battery cells, lead battery cells, etc. In the following description, an example using lithium-ion battery cells (nominal voltage: 3.6-3.7V) is assumed.

[0021] 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. In addition, multiple temperature sensors T1, T2 are installed to detect the temperatures of the multiple cells E1-En. One or more temperature sensors may be installed in the battery module M1. The temperature sensors T1, T2 can be, for example, thermistors.

[0022] 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 between each two adjacent voltage lines to measure the voltage of each cell E1-En. The voltage measurement unit 21 transmits the measured voltage of each cell E1-En to the control unit 24 via a communication line.

[0023] Because 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 using 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 top to bottom. The A / D converter converts the analog voltage input from the multiplexer into a digital value.

[0024] The temperature measurement unit 22 includes a voltage dividing resistor and an A / D converter. The A / D converter sequentially converts multiple analog voltages, which are respectively divided by the multiple temperature sensors T1, T2 and the multiple voltage dividing resistors, into digital values ​​and outputs them to the control unit 24. The control unit 24 estimates the temperatures of the multiple cells E1-En based on the digital values.

[0025] 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.

[0026] In addition, if an A / D converter is installed in the control unit 24 and an analog input port is installed 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.

[0027] 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, temperature measurement unit 22, and current measurement unit 23. The control unit 24 can be configured with a microcomputer and non-volatile memory (for example, an EEPROM (Electrically Erasable Programmable Read-Only Memory), flash memory).

[0028] A SOC (State Of Charge)-OCV (Open Circuit Voltage) map 241 is stored in the microcomputer's internal memory. The SOC-OCV map 241 describes characteristic data of the SOC-OCV curve of cells E1-En. The SOC-OCV curve of cells E1-En is created in advance based on characteristic tests conducted by the battery manufacturer and registered in the microcomputer's internal memory at the time of shipment. The SOC-OCV map 241 may also be registered in non-volatile memory. To estimate the SOC or OCV of cells E1-En with higher accuracy, the battery manufacturer may derive and map the SOC-OCV characteristics of cells E1-En for each combination of temperature category and state of health (SOH) category. Instead of a map, a function may be used in which the SOC is the target variable and the OCV, temperature, and state of health are explanatory variables.

[0029] The control unit 24 can estimate the SOC and SOH of each of the multiple cells E1-En. The control unit 24 can estimate the SOC using 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 characteristic data of the SOC-OCV curve described in the SOC-OCV map 241. The future OCV 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 charge / discharge and the integrated value of the current measured by the current measurement unit 23. With the current integration method, measurement errors by the current measurement unit 23 accumulate as charge / discharge time increases. Therefore, it is preferable to correct the SOC estimated by the current integration method using the SOC estimated by the OCV method.

[0030] SOH is defined as the ratio of the current full charge capacity to the initial full charge capacity, and the lower the value (closer to 0%), the more advanced the deterioration. SOH can be determined by measuring the capacity after full charge and discharge, 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 through experiments or simulations. The SOC, temperature, SOC range, and current rate can be determined by measurement.

[0031] SOH can also be estimated based on its correlation with the cell's internal resistance. Internal resistance can be estimated by dividing the voltage drop that occurs when a specified current flows through the cell for a specified time by the current value. Internal resistance decreases as temperature increases, and increases as SOH decreases.

[0032] 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 via power line communication.

[0033] 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.

[0034] 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. As hardware resources, a CPU, ROM, RAM, DSP, ASIC, FPGA, and other LSIs can be used. As software resources, programs such as firmware can be used.

[0035] The storage unit 32 includes a non-volatile recording medium such as a flash memory. The storage unit 32 stores an SOC-charging upper limit current map 322. The SOC-charging upper limit current map 322 describes characteristic data of the SOC-charging upper limit current curve of cells E1-En. The SOC-charging upper limit current curve of cells E1-En is created based on characteristic tests conducted by the battery manufacturer. The SOC-charging upper limit current curve is characteristic data that specifies, for each SOC, the upper limit of the charging current allowed for charging a cell, from the standpoint of cell protection and safety. For a typical cell, the higher the SOC, the lower the upper limit of the current allowed for charging. Note that in this specification, the charging current is considered as an absolute value.

[0036] When discharging from a cell, the greater 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 a cell, the greater the charging current, the higher the CCV. The CCV of a cell when charging is defined by the following (Equation 2).

[0037] 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.

[0038] As shown in Equation 2 above, as the charging current Ic increases, the CCV rises. When the CCV enters the overcharge region, the burden on the battery increases, causing deterioration. As shown in Equation 2 above, the higher the OCV, the higher the CCV. Since the higher the SOC, the higher the OCV, the lower the upper limit of the charging current Ic must be set.

[0039] The SOC-maximum charging current characteristic of cells E1-En depends on the temperature and the state of health (SOH). Battery manufacturers derive and map the SOC-maximum charging current characteristic of cells E1-En for each combination of temperature category and state of health category. The SOC-maximum charging current characteristic is registered in the control unit 24 of the battery pack 20 (e.g., in the internal memory of a microcomputer) at the time of shipment. The management unit 30 of the electric vehicle 1 acquires the SOC-maximum charging current characteristic from the control unit 24 of the battery pack 20 when the battery pack 20 is first installed in the electric vehicle 1. Note that the SOC-maximum charging power characteristic may be used instead of the SOC-maximum charging current characteristic, or both may be used. For example, the upper limit of the charging current from the charger 2 may be controlled with reference to the SOC-maximum charging current characteristic, and the upper limit of the regenerative power from the motor 60 may be controlled with reference to the SOC-maximum charging power characteristic. Alternatively, instead of the map, a function may be used with the upper limit charging current or upper limit charging power as the objective variable and the SOC, temperature, and state of health as explanatory variables.

[0040] Fig. 4 is a diagram showing an example of the SOC-charge upper limit current characteristics of a certain battery pack at 0° C. As shown in Fig. 4, the higher the SOC, the lower the charge upper limit current.

[0041] Returning to FIG. 3, the acquisition unit 311 acquires monitoring data including at least the voltage and SOC of 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. Typically, the SOC of the pack is determined to be the SOC of the lowest cell when the SOC is low, and the SOC of the highest cell when the SOC is high. Note that the calculation unit 312 may convert the SOC of the multiple cells E-En included in the battery pack 20 into capacity, calculate the combined capacity of the multiple cells E-En, and use the SOC corresponding to this combined capacity as the SOC of the pack.

[0042] 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. When one of the off-state pack relays RY1 (hereinafter referred to as the target pack relay RY1) should be turned on, the calculation unit 312 estimates the upper limit of the current or power that is permitted to be charged to all of the multiple battery packs 20 (hereinafter referred to as the parallel system) when the target pack relay RY1 is turned on.

[0043] 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 threshold value based on the upper limit value of the current or power allowed to be charged into the parallel system before turning on the target pack relay RY1 (hereinafter referred to as the current upper limit value). The threshold value may be the same as the current upper limit value (adjustment value α = 0), may be the current upper limit value plus the adjustment value α, or may be the current upper limit value minus the adjustment value α. The designer can set the adjustment value α taking into consideration the number of parallel battery packs 20, the application, etc. The determination unit 313 permits the target pack relay RY1 to be turned on if the predicted upper limit value is equal to or greater than the threshold value, and does not permit the target pack relay RY1 to be turned on if the predicted upper limit value is lower than the threshold value. The relay driver 25 turns on the target pack relay RY1 if the determination unit 313 permits the target pack relay RY1 to be turned on.

[0044] The notification unit 314 notifies the vehicle ECU 40 of the upper limit of the current or power allowed to be charged from the parallel system (hereinafter referred to as the upper limit charging current value or upper limit charging power value of the entire parallel system (collectively referred to as the upper limit charging 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 controls the regenerative current or regenerative power of the motor 60 within the upper limit charging current value or 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 regenerative braking to mechanical braking. The mechanical brake converts regenerative energy into thermal energy. Furthermore, when rapid charging is performed using DC from the charger 2, the notification unit 314 notifies the charger 2 of the upper limit charging current value or upper limit charging power value of the entire parallel system.

[0045] Basically, the more parallel-connected the battery packs 20 are, the higher the upper limit of charging for the entire parallel system becomes. However, even if a battery pack 20 is added to the parallel system, there are cases where the upper limit of charging for the entire parallel system does not increase. This is the case when a cross current occurs between the multiple battery packs 20 due to the connection of the new battery pack 20.

[0046] FIG. 5 is a diagram illustrating cross currents between battery packs 20. For ease of understanding, FIG. 5 shows two battery packs 20 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 from a power source (e.g., charger 2) only to the first battery pack 20a. In this case, the upper limit charging current value of the entire parallel system matches the upper limit charging current value of the first battery pack 20a.

[0047] The state on the right side of Figure 5 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 charging the first battery pack 20a at the upper limit charging current, a cross current will occur from the second battery pack 20b to the first battery pack 20a. As a result, the upper limit charging current 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 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.

[0048] The CCV when charging the first battery pack 20a at the upper limit charging current value is an estimated value. The current charged to the first battery pack 20a fluctuates due to fluctuations in the power supply voltage, and the CCV of the first battery pack 20a also fluctuates due to these fluctuations. The CCV when charging the first battery pack 20a at the upper limit charging current value is a value that indicates the maximum voltage of the first battery pack 20a during charging.

[0049] 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 decreases. Not at all.

[0050] If the current actually charging the first battery pack 20a from the power source is lower than the upper limit charging current of the first battery pack 20a, the actual CCV of the first battery pack 20a will be lower than the CCV when charging at the upper limit charging current. In this case, a cross current will occur from the second battery pack 20b to the first battery pack 20a. However, if the output current from the power source increases to the upper limit charging current of the first battery pack 20a, the cross current will stop, and the upper limit charging current of the entire parallel system will not decrease.

[0051] Next, consider the case where the OCV of the second battery pack 20b is lower than the CCV when charging the first battery pack 20a with the upper limit charging current, and the second pack relay RY1 is turned on. Because the upper limit charging current of the second battery pack 20b is greater than the upper limit charging current of the first battery pack 20a, the upper limit charging current of the entire parallel system does not decrease when the second pack relay RY1 is turned on.

[0052] In the above description, an example has been described in which the calculation unit 312 of the management unit 30 calculates both the upper limit charging current value of each battery pack 20 and the upper limit charging current value of the entire parallel system. In this regard, the upper limit charging current value of a 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 upper limit charging current value of the battery pack 20 to the management unit 30. The calculation unit 312 of the management unit 30 calculates the upper limit charging current value of the entire parallel system based on the upper limit charging current values ​​received from the multiple battery packs 20.

[0053] Two examples of the determination process for determining whether or not to permit parallel connection of the target pack relay RY1 will be described below. Example 1 is a dynamic determination process, and Example 2 is a static determination process.

[0054] 6 is a flowchart for explaining the parallel connection determination process according to Example 1. When the power supply of the electric vehicle 1 is turned on (corresponding to turning on the ignition 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). If 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 simultaneously turned on.

[0055] 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 whose pack relay RY1 is in the off state as the connection candidate for which the pack relay RY1 should be turned on next (S33).

[0056] 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.

[0057] The determination unit 313 compares the estimated CCV 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 (S36) and causes the relay driver 25 to turn on the pack relay RY1 connected to the connection candidate battery pack 20. If the estimated CCV is lower than the OCV of the connection candidate battery pack 20 (N in S35), the determination unit 313 does not permit connection of the connection candidate battery pack 20 (S37). The process proceeds to step S32.

[0058] When there are multiple battery packs 20 with the pack relay RY1 in the ON state, the same CCV is available for the upper limit charging current values ​​of the multiple battery packs 20. With the same CCV available, the calculation unit 312 estimates the CCVs for the upper limit charging current values ​​of the multiple battery packs 20 in the ON state.

[0059] If the estimated CCV is lower than the OCV of the battery pack 20 that is a candidate for connection in the determination of step S35, the battery pack 20 that is a candidate for connection cannot be connected. However, if the battery pack 20 in the ON state continues to be charged, the SOC of the battery pack 20 in the ON state increases. As the SOC increases, the OCV increases, and the CCV corresponding to the upper limit charging current value also increases. When the CCV corresponding to the upper limit charging current value increases to the OCV of the battery pack 20 that is a candidate for connection, the battery pack 20 that is a candidate for connection can be connected. Note that the CCV corresponding to the upper limit charging current value may also increase due to temperature changes.

[0060] Next, a second embodiment of the parallel connection determination process will be described. As described above, when the OCVs of multiple battery packs 20 connected in parallel are not the same, 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 equalized.

[0061] Figure 7 is a diagram for explaining cross currents and OCV convergence between battery packs 20. For ease of understanding, Figure 7 shows two battery packs 20 connected in parallel. 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.

[0062] The state on the right side of Figure 7 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, causing the OCV of the second battery pack 20b to decrease and the OCV of the first battery pack 20a to increase. 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.

[0063] Under ideal conditions where the pack capacities and other factors are the same, the OCVs of the first battery pack 20a and the second battery pack 20b when the cross current has stopped will be 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 occurred, and the OCVs when the cross current has stopped will be the OCV corresponding to this average SOC. Even when three or more battery packs 20 with mismatched OCVs are connected in parallel, under ideal conditions, the OCVs of the three or more battery packs 20 will be matched due to the cross current. In this case, the OCVs of the three or more battery packs 20 after the OCVs have matched will be the average value of the OCVs of the three or more battery packs 20 before the cross current occurred.

[0064] In the second embodiment, the calculation unit 312 estimates the upper limit charging 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 connection of the new battery pack 20 when the estimated upper limit charging current value is equal to or greater than the upper limit charging current value of the entire parallel system before the new battery pack 20 was connected to the parallel system. The determination unit 313 does not allow connection of the new battery pack 20 when the estimated upper limit charging current value is lower than the upper limit charging current value of the entire parallel system before the new battery pack 20 was connected.

[0065] FIG. 8 is a diagram illustrating an example of how the upper limit charging current value of the entire parallel system changes before and after connecting a new battery pack 20. 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, as shown on the left side of FIG. 7. The following explanation assumes that battery packs using the same type of cells are used and that the conditions regarding pack capacity, SOH, and temperature are the same. Assume that 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-upper limit charging current characteristic shown in FIG. 8, the upper limit charging current value when the SOC is 80% is 15 A. The upper limit charging current value of the entire parallel system when only the first battery pack 20a is connected is also 15 A.

[0066] Next, consider the state after the second battery pack 20b is connected to the parallel system, as shown on the right side of Figure 7. 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. This cross current reduces the SOC of the second battery pack 20b and increases the SOC of the first battery pack 20a. When the SOC of both battery packs reaches 85%, the cross current stops. Referring to the SOC-maximum charging current characteristics shown in Figure 8, the maximum charging current is 6A when the SOC is 85%. Therefore, the maximum charging current of the entire parallel system when the first battery pack 20a and the second battery pack 20b are connected is 12A (=6A x 2).

[0067] In this example, when the second battery pack 20b is connected, the upper limit charging current value of the entire parallel system drops from 15 A to 12 A. As shown in Fig. 8, when the upper limit charging current value when the SOCs are equal (SOC = 85%) is below the imaginary line connecting the upper limit charging current value (15 A) of the first battery pack 20a before the second battery pack 20b is connected 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 second battery pack 20b is connected is estimated without reference to the SOC-upper limit charging current characteristics, the upper limit charging current value may be overestimated, resulting in a situation where the actual upper limit charging current value is lower than the charging current value from the charger 2.

[0068] 9 is a flowchart for explaining the parallel connection determination process according to Example 2. 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). If 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 simultaneously turned on.

[0069] 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 connection candidate for which the pack relay RY1 should be turned on next (S43).

[0070] The calculation unit 312 estimates converged values ​​of the OCVs of the multiple battery packs 20 connected to the parallel system when a battery pack 20 that is a candidate for connection 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 a battery pack 20, the calculation unit 312 takes into account at least the temperature and SOH of the battery pack 20 as parameters.

[0071] The determination unit 313 determines whether the charging upper limit current value of the entire parallel system will decrease due to the connection of the battery pack 20 that is a candidate for connection (S46). If the charging upper limit current value of the entire parallel system will not decrease (N in S46), the determination unit 313 permits the connection of the battery pack 20 that is a candidate for connection (S47) 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 charging upper limit current value of the entire parallel system will decrease (Y in S46), the determination unit 313 does not permit the connection of the battery pack 20 that is a candidate for connection (S48). The process proceeds to step S42.

[0072] In the determination of step S46, if the charging upper limit current value of the entire parallel system will decrease due to the connection of the battery pack 20 that is a candidate for connection, the battery pack 20 that is a candidate for connection cannot be connected. However, if the state in which the battery pack 20 in the ON state is charged continues, the SOC of the battery pack 20 in the ON state will increase. As the SOC increases, the charging upper limit current value of the entire parallel system will also increase. Eventually, a state will occur in which the charging upper limit current value of the entire parallel system will not decrease even if the battery pack 20 that is a candidate for connection is connected. Furthermore, the charging upper limit current value of the entire parallel system may decrease due to temperature changes.

[0073] As described above, according to this embodiment, when the connection of a new battery pack 20 would lower the upper charge limit of the entire parallel system, 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.

[0074] 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 the respective components and processing steps, and that such modifications are also within the scope of the present disclosure.

[0075] The parallel connection determination process according to the first embodiment and the parallel connection determination process according to the second embodiment may be used together. In this case, if connection is permitted in both determination processes, the connection candidate battery pack 20 is connected, and if 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 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.

[0076] 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 charge limit value of the entire parallel system at a certain point in the future. The upper charge limit value in the process leading up to that point in time 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 charge limit value, which changes from moment to moment. Therefore, there may be cases where the results of the two determinations 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 together, it is possible to further prevent a decrease in charging efficiency.

[0077] In the above embodiment, an example has been described in which the management unit 30 is provided outside the plurality of battery packs 20. In this regard, the management unit 30 may be provided inside any one of the plurality of battery packs 20. In this case, the battery pack 20 that realizes the function of the management unit 30 becomes the master device, and the remaining battery packs 20 become slave devices.

[0078] 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 fixed battery packs 20 are used, 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.

[0079] In the above-described embodiment, an example has been described in which a battery pack 20 incorporating a battery module M1 including lithium-ion battery cells, nickel-metal hydride battery cells, lead-acid battery cells, etc. has been 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 capacitor module are collectively referred to as a power storage module, and the battery pack and capacitor pack are collectively referred to as a power storage pack.

[0080] In the above-described embodiment, an example has been described in which detachable and replaceable electricity storage packs are connected in parallel. In this regard, the present disclosure can also be applied to the process of determining whether multiple electricity storage modules are connected in parallel within one electricity storage pack. Note that, since the above-described embodiment is based on an example in which one electricity storage module is provided within one electricity storage pack, the process of determining whether multiple electricity storage packs are connected in parallel is synonymous with performing the process of determining whether multiple electricity storage modules are connected in parallel.

[0081] 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 also 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 body. An electric flying body includes a multicopters (drones). The multicopters also include so-called flying cars.

[0082] The embodiment may be specified by the following items.

[0083] [Item 1] A management device (30) that manages a plurality of storage modules (M1) that are connected in parallel to a power source (60, 2) via 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 the switch (RY1) to be turned on if an upper limit value of 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 threshold value based on the upper limit value before the switch (RY1) is turned on; A management device (30) comprising: This can 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 2] an acquisition unit (311) that acquires at least a SOC (State Of Charge) 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 charged to all of the plurality of power storage modules (M1) based on an SOC-charge upper limit characteristic that defines the relationship between the SOC of the power storage module (M1) and an upper limit of current or power that is permitted to be charged to the power storage module (M1), The SOC-charge upper limit characteristic is a characteristic in which the higher the SOC of the power storage module (M1), the lower the upper limit of the current or power that is allowed to be charged to 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 charged into the plurality of power storage modules (M1). [Item 3] The acquisition unit (311) acquires an OCV (Open Circuit Voltage) of a connection candidate storage module (M1) among the remaining storage modules (M1), the calculation unit (312) derives an upper limit value of current or power that is permitted to be charged to the storage module (M1) based on the SOC-charge upper limit characteristic and a SOC (State Of Charge) of the storage module (M1) connected to the power source (60, 2), and estimates a CCV (Closed Circuit Voltage) of the storage module (M1) when the storage module (M1) is charged at the upper limit value; When the OCV of the storage module (M1) as a candidate for connection is higher than the estimated CCV of the storage module (M1), the determination unit (313) does not permit the switch (RY1) connected to the storage module (M1) as a candidate for connection to be turned on. 3. The management device (30) according to item 2. This makes it possible to dynamically determine whether or not the charging efficiency from the power source (60, 2) to the plurality of power storage modules (M1) as a whole is reduced. [Item 4] the calculation unit (312) estimates an upper limit value of current or power that is 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 the switch (RY1) connected to the storage module (M1) as a connection candidate is turned on, based on the SOC-charge upper limit characteristic and the correspondence between the SOC corresponding to 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; The determination unit (313) does not permit the switch (RY1) to be turned on when the estimated upper limit value is lower than 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 charging efficiency from the power source (60, 2) to the plurality of power storage modules (M1) as a whole will decrease. [Item 5] When the power supply (60,2) starts to supply power to the plurality of storage modules (M1), 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. 5. The management device (30) according to any one of items 1 to 4. This makes it possible to connect the plurality of power storage modules (M1) in parallel while preventing a decrease in the efficiency of charging the entire plurality of power storage modules (M1) from the power source (60, 2). [Item 6] a plurality of storage modules (M1) connected in parallel to a power source (60, 2) via switches (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 decrease in the charging efficiency of the power source (60, 2) to all of the plurality of power storage modules (M1) due to the new connection of the power storage module (M1). [Item 7] 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 current or power that is permitted to be regenerated from the motor (60) to 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 the regenerative energy generated by the motor (60) from being wasted. [Explanation of symbols]

[0084] 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 Determination unit, 314 Notification unit, 32 Memory unit, 322 SOC-charging 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 sensors.

Claims

1. 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 switch to be turned on if an upper limit value of current or power allowed to be charged to all of the plurality of power storage modules when the switch is turned on is lower than a threshold value based on the upper limit value before the switch is turned on; A management device comprising:

2. an acquisition unit that acquires at least an SOC (State Of Charge) for each of the plurality of power storage modules; a calculation unit that estimates an upper limit value of current or power that is allowed to be charged to all of the plurality of power storage modules, based on an SOC-charge upper limit characteristic that defines the relationship between the SOC of the power storage module and an upper limit value of current or power that is allowed to be charged to the power storage module, The SOC-charge 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 that is allowed to be charged to the power storage module. The management device according to claim 1 .

3. the acquisition unit acquires an OCV (Open Circuit Voltage) of a connection candidate power storage module from among the remaining power storage modules; the calculation unit derives an upper limit value of current or power that is permitted to be charged to the power storage module based on the SOC-charge upper limit characteristic and the SOC of the power storage module connected to the power source, and estimates a CCV (Closed Circuit Voltage) of the power storage module when charging the power storage module at the upper limit value; the determination unit does not permit turning on of a switch connected to the connection candidate power storage module when the OCV of the connection candidate power storage module is higher than the estimated CCV of the power storage module.

3. The management device according to claim 2.

4. the calculation unit estimates an upper limit value of current or power that is 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 that is a connection candidate correspond to each other after a switch connected to the power storage module that is a connection candidate is turned on, based on the SOC-charge upper limit characteristic, an SOC that corresponds to the OCV of the power storage module connected to the power source, and an SOC that corresponds to the OCV of the power storage module that is a connection candidate; the determination unit does not permit the switch to be turned on when the estimated upper limit value is lower than the upper limit value before the switch is turned on; 4. The management device according to claim 2 or 3.

5. 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 is the next candidate for connection whose switch should be turned on.

5. The management device according to claim 1, wherein the management device is a device for managing a plurality of data.

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

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

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