Battery Control Method

Abstract

To provide a storage battery control method, with which even if a battery cell whose OCV curve, charge curve, or discharge curve is flat is used, it is possible to grasp a charge amount of the battery cell and perform sufficient balance adjustment.SOLUTION: A storage battery control method for controlling a charge state of each battery cell of a storage battery obtained by connecting a plurality of battery cells in series, comprises: a charge step for, when a predetermined condition is satisfied, charging the storage battery to a predetermined charge rate or higher; a detection step for, when the storage battery is charged to the predetermined charge rate or higher, detecting a cell voltage of each battery cell of the storage battery; and a determination step for determining a charge rate of each battery cell of the storage battery with reference to a measurement value of the cell voltage of each battery cell of the storage battery.SELECTED DRAWING: Figure 11

Description

[Technical field]

[0001] The present invention relates to a storage battery control method. [Background technology]

[0002] Power supply systems in which solar panels are installed on the roofs of houses and the electricity generated by the solar panels is used as household electricity are becoming widespread. As a storage battery unit for use in such a power supply system, a configuration has been proposed in which a plurality of battery cells are connected in series to form a battery stack so that a desired voltage can be obtained (for example, Patent Document 1). For example, the voltage of a lithium-ion battery cell is about 2V to 4V. In contrast, the voltage of a household power supply is several hundred volts. In this case, several dozen battery cells are connected in series to ensure a voltage of several hundred volts for household use.

[0003] Balancing is essential for the battery cells that make up the battery stack. For this reason, such storage battery units are equipped with an AFE (Analog Front End) that detects the voltage of each battery cell and a balancing circuit. The AFE detects the voltage of each battery cell and controls it so that the charge level of each battery cell is uniform. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-156200 A Summary of the Invention [Problem to be solved by the invention]

[0005] In general, home storage batteries were fully charged within the range of use, but as usage diversifies, there are cases where the battery does not necessarily reach full charge. For example, when an EV (Electric Vehicle) stand is installed, the battery may not reach full charge for several days because the battery is used to charge the electric vehicle.

[0006] In the balance adjustment, the cell voltage of the battery cell is usually detected, the charging rate (SOC: State Of Charge) is determined from the cell voltage, and the charge amount of the battery cell is controlled to be uniform depending on the usage environment, the connected circuit components, and the passage of time. In the control of the charge amount, the balance adjustment is performed using a balance adjustment function provided in a balance adjustment circuit or AFE that equalizes the voltage of each battery cell. The cell voltage of the battery cell can be detected, for example, from the voltage in a state where no current flows (OCV (Open Circuit Voltage)), the charge curve, or the discharge curve. However, depending on the type of battery cell, the OCV curve, the charge curve, or the discharge curve may be almost flat, making it difficult to detect the relationship between the cell voltage of the battery cell and the SOC. Therefore, it may be difficult to detect the cell voltage from the OCV curve, the charge curve, or the discharge curve to determine the SOC and perform the balance adjustment of the charge amount of the battery cell.

[0007] In view of the above-mentioned problems, the present invention aims to provide a storage battery control method that is capable of grasping the charge amount of a battery cell and performing sufficient balance adjustment, even when a battery cell with a flat OCV curve, charge curve, or discharge curve is used. [Means for solving the problem]

[0008] A storage battery control method according to one aspect of the present invention is a storage battery control method for controlling a charging state of each battery cell of a storage battery in which a plurality of battery cells are connected in series, the method including: a charging step for charging the storage battery to a predetermined charging rate or higher when a predetermined condition is satisfied; a detection step for detecting a cell voltage of each battery cell of the storage battery when the storage battery is charged to the predetermined charging rate or higher; and a determination step for determining the charging rate of each battery cell of the storage battery from a measured value of the cell voltage of each battery cell of the storage battery. The charging step includes determining whether a period during which the storage battery has not been detected as being fully charged continues for a predetermined period or longer, and if the determination result is affirmative, charging the storage battery to a charging rate equal to or higher than the predetermined charging rate. Effect of the Invention

[0009] According to the present invention, even when a battery cell having a flat OCV curve, charge curve, or discharge curve is used, it is possible to grasp the charge amount of the battery cell and perform sufficient balance adjustment. This makes it possible to easily perform balance adjustment of the charge amount of the battery cell. Furthermore, by performing balance adjustment of the charge amount of the battery cell, it is possible to prevent deterioration of the performance of the storage battery and shortening of the lifespan. [Brief description of the drawings]

[0010] [Figure 1] 1 is a block diagram showing an overview of a power supply system according to the present invention; [Diagram 2] FIG. 1 is an explanatory diagram illustrating an overview of a storage battery unit used in a power supply system according to the present invention. [Diagram 3] 1 is an explanatory diagram illustrating an overview of a relay cable that connects a connector of a battery module and a connector of a control management module. [Figure 4] 1 is an explanatory diagram illustrating an overview of a relay cable that connects a connector of a battery module and a connector of a control management module. [Diagram 5] FIG. 2 is an explanatory diagram of an example of a battery module. [Figure 6] FIG. 2 is a block diagram showing a configuration of a control management module. [Figure 7] FIG. 2 is a block diagram showing an overview of an AFE circuit element disposed on a BMS substrate. [Figure 8]FIG. 1 is an explanatory diagram when an AFE circuit element is arranged corresponding to a battery module. [Figure 9] 1 is a graph showing the relationship between voltage and SOC of a lithium iron phosphate battery. [Figure 10] 1 is a graph showing an enlarged portion of the relationship between voltage and SOC of a lithium iron phosphate battery. [Figure 11] FIG. 2 is a sequence diagram showing an outline of a storage battery control method according to the present invention. [Figure 12] 5 is a flowchart showing a full charge request process on the storage battery unit side in the storage battery control method according to the present invention. [Figure 13] 4 is a flowchart showing an operation process of a balancing circuit in the storage battery control method according to the present invention. [Figure 14] FIG. 13 is a block diagram showing an outline of another configuration example of a power supply system according to the present invention. [Figure 15] FIG. 13 is a block diagram showing an outline of another configuration example of a power supply system according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention relates to a storage battery control method for controlling the state of charge of each battery cell of a storage battery in which a plurality of battery cells are connected in series. Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] <Overall system> First, an overview of a power supply system according to the present invention will be described with reference to Fig. 1. Fig. 1 is a block diagram showing an overview of a power supply system 10 according to the present invention. As shown in FIG. 1, a power supply system 10 according to an embodiment of the present invention includes a power conditioner 1, a solar panel 2, and a storage battery unit 3.

[0013] The power conditioner 1 performs processes such as conversion between DC and AC power, control of power supply voltage, and buying and selling electricity. That is, while the commercial power supply 5 uses AC power, solar power generation and electricity storage use DC power. Also, the voltage of the commercial power supply 5 and the voltage of the batteries used in the solar panel 2 and the storage battery unit 3 are different. The power conditioner 1 performs conversion between DC and AC power and controls the power supply voltage between the commercial power supply 5, the solar panel 2, and the storage battery unit 3. The power conditioner 1 then supplies power to the distribution board 6, which distributes the power to the outlets in each room.

[0014] The solar panel 2 can generate electricity during the daytime when the sun is out, but cannot generate electricity at night when the sun sets, and the amount of electricity generated is unstable. The storage battery unit 3 can be charged from the grid via the commercial power source 5 and power conditioner 1 during the day, and can also be charged via the solar panel 2 and power conditioner 1, and can also supplement the power supply via the power conditioner 1. The storage battery unit 3 can be charged from the grid via the commercial power source 5 and power conditioner 1 at night, and can also supplement the power supply via the power conditioner 1.

[0015] In addition, the power conditioner 1 performs processes such as purchasing and selling power, such as purchasing power from a commercial power source 5 when there is a power shortage, and selling power to the commercial power source 5 when there is surplus power from the solar panel 2.

[0016] An EV (Electric Vehicle) stand 4 can also be incorporated into the power supply system 10. The EV stand 4 can be used to charge an electric vehicle, as well as to store power using a battery installed in the electric vehicle. The EV stand 4 can also supplement the power supply via the power conditioner 1.

[0017] Here, an overview of the storage battery unit 3 used in the power supply system 10 according to the present invention will be described with reference to Fig. 2. Fig. 2 is an explanatory diagram illustrating the overview of the storage battery unit 3 used in the power supply system 10 according to the present invention. 2, the storage battery unit 3 includes, for example, seven battery modules 11-1 to 11-7 and a control management module 12. The battery modules 11-1 to 11-7 include a battery stack including a plurality of battery cells. The battery modules 11-1 to 11-7 also include connectors 13-1 to 13-7 and connectors 14-1 to 14-7, respectively.

[0018] The control management module 12 manages the charge / discharge states of the battery modules 11-1 to 11-7. The control management module 12 is provided with connectors 45-1 to 45-7 and connectors 56-1 to 56-7.

[0019] The connectors 13-1 to 13-7 of the battery modules 11-1 to 11-7 and the connectors 45-1 to 45-7 of the control management module 12 are connected by relay cables 60-1 to 60-7 as shown in Fig. 3. The connectors 14-1 to 14-7 of the battery modules 11-1 to 11-7 and the connectors 56-1 to 56-7 of the control management module 12 are connected by relay cables 70-1 to 70-7 as shown in Fig. 4.

[0020] Here, an overview of the relay cable that connects the connector of the battery module and the connector of the control management module will be described with reference to Figs. 3 and 4.

[0021] FIG. 3 is an explanatory diagram illustrating an outline of relay cables 60 (60-1 to 60-7) that connect the connectors 13-1 to 13-7 of the battery modules 11-1 to 11-7 and the connectors 45-1 to 45-7 of the control management module 12. As shown in FIG.

[0022] 3, the relay cable 60 is made up of connectors 61 (61-1 to 61-n) on the battery modules 11-1 to 11-7 side, connectors 62 (62-1 to 62-n) on the control management module 12 side, and cables 63 (63-1 to 63-n) therebetween. The cables 63 (63-1 to 63-n) are two wires, one for a positive electrode and one for a negative electrode.

[0023] FIG. 4 is an explanatory diagram illustrating an outline of relay cables 70 (70-1 to 70-7) that connect the connectors 14-1 to 14-7 of the battery modules 11-1 to 11-7 and the connectors 56-1 to 56-7 of the control management module 12. As shown in FIG.

[0024] 4, the relay cables 70 (70-1 to 70-7) are made up of connectors 71 (71-1 to 71-7) on the battery modules 11-1 to 11-7 side, connectors 72 (72-1 to 72-7) on the control management module 12 side, and cables 73 (73-1 to 73-7) therebetween. The cables 73 (73-1 to 73-7) are made up of wiring whose number corresponds to the number of battery cells that make up the battery stack.

[0025] Here, an example of a battery module will be described with reference to Fig. 5. Fig. 5 is an explanatory diagram of an example of a battery module 11 (11-1 to 11-7). Note that the battery modules 11-1 to 11-7 are all configured in the same way.

[0026] As shown in FIG. 5, the battery module 11 (11-1 to 11-7) is provided with a battery stack consisting of battery cells 20-1, 20-2, ..., 20-n connected in series. For example, lithium iron phosphate ion batteries are used as the battery cells 20-1, 20-2, ..., 20-n. The lithium iron phosphate ion battery uses lithium iron phosphate in the positive electrode, and is characterized by its high safety as its crystal structure is not easily destroyed even if heat is generated inside the battery. The cell voltage of each battery cell 20-1, 20-2, ..., 20-n varies depending on the cell structure. In the case of a lithium ion battery, the cell voltage is 2V to 4V. In the case of a lithium iron phosphate ion battery, the cell voltage is, for example, about 3.3V.

[0027] The battery modules 11 (11-1 to 11-7) are provided with connectors 13 (13-1 to 13-7) and connectors 14 (14-1 to 14-7). The connectors 13 (13-1 to 13-7) are connectors for charging and discharging the battery modules 11. The connectors 14 (14-1 to 14-7) are connectors for monitoring the cell voltages of the battery cells 20-1, 20-2, ..., 20-n.

[0028] The configuration of the control management module will now be described with reference to Fig. 6. Fig. 6 is a block diagram showing the configuration of the control management module 12. As shown in FIG. 6, the control management module 12 has a terminal block 31, a breaker 33, an HV (High-Voltage) board 40, and a BMS (Battery Management System) board 50 mounted thereon.

[0029] The terminal block 31 is a connector for connecting wiring from the power conditioner 1. The terminal block 31 is provided with a positive terminal 31a, a negative terminal 31b, and a ground terminal 31c. In this example, the ground terminal 31c is connected to the housing as a zero potential. Wires extending from the positive terminal 31a and the negative terminal 31b of the terminal block 31 form charge / discharge lines 35a and 35b. The breaker 33 is for protection when a large current flows.

[0030] The communication connector 32 is a connector for connecting a shielded wire for communication from the power conditioner 1. The communication connector 32 is connected to a communication connector 51 on the BMS board 50. Data from the power conditioner 1 is received via the communication connector 32 and sent to the microprocessor 54. In addition, data from the microprocessor 54 is sent to the power conditioner 1 via the communication connector 32.

[0031] The HV board 40 is a board for charging and discharging the battery modules 11-1 to 11-7. On the HV board 40, a relay 41, a current sensor 42, a communication connector 43, and connectors 45-1 to 45-7 are mounted.

[0032] The relay 41 serves as a switch for starting / stopping the operation of the storage battery unit 3. The current sensor 42 detects charging / discharging current to / from the battery modules 11-1 to 11-7. The communication connector 43 is connected to a communication connector 52 on the BMS board 50. The communication connector 43 transmits the detected current of the current sensor 42 to a microprocessor 54, for example.

[0033] The connectors 45-1 to 45-7 are terminals that connect to the connectors 13-1 to 13-7 on the battery modules 11-1 to 11-7 side, respectively. The connectors 13-1 to 13-7 on the battery modules 11-1 to 11-7 side are connectors for charging and discharging, and wiring from both ends of the battery cells 20-1, 20-2, ..., 20-n that constitute the battery stack is led out from the connectors 13-1 to 13-7. The connectors 45-1 to 45-7 are connected in series to obtain a desired charging and discharging voltage. The positive electrode of the connector 45-1 with the highest potential is connected to the charging and discharging line 35a, and the negative electrode of the connector 45-7 with the lowest potential is connected to the charging and discharging line 35b.

[0034] The BMS board 50 is a board for monitoring and controlling the states of the battery modules 11-1 to 11-7. The BMS board 50 is mounted with communication connectors 51 and 52, an AFE (Analog Front End) 53, a microprocessor 54, an optical isolation element 55, and connectors 56-1 to 56-7.

[0035] The communication connector 51 is connected to the communication connector 32, and transmits and receives data to and from the power conditioner 1. The communication connector 52 is connected to the communication connector 43, and transmits and receives data to and from the HV board 40.

[0036] AFE 53 detects the cell voltage of each of battery modules 11-1 to 11-7 and converts it into digital data.

[0037] The microprocessor 54 performs various controls based on data from the power conditioner 1, data from the HV board 40, data from the AFE 53, and the like.

[0038] The optical isolation element 55 is an element such as a photocoupler or a digital isolator, and connects the AFE 53 and the microprocessor 54. Since a high voltage is applied to the AFE 53, the optical isolation element 55 provides isolation between the AFE 53 and the microprocessor 54.

[0039] The connectors 56-1 to 56-7 are terminals that connect to the connectors 14-1 to 14-7 on the battery modules 11-1 to 11-7 side, respectively. The connectors 14 (14-1 to 14-7) are connectors for monitoring the cell voltages of the battery cells 20-1, 20-2, ..., 20-n. The connectors 56-1 to 56-7 transmit the cell voltages of the battery modules 11-1 to 11-7 to the BMS board 50 side, respectively.

[0040] Here, an overview of the AFE circuit element arranged on the BMS substrate will be described with reference to Fig. 7. Fig. 7 is a block diagram showing an overview of an AFE circuit element 530 arranged on the BMS substrate 50. In this embodiment, the function of the AFE 53 is realized by arranging AFE circuit elements 530 as shown in Fig. 7 in the number corresponding to the battery modules 11-1 to 11-7. Note that, here, only a part of the function of the AFE circuit element 530 that is necessary for explaining the present invention will be described. Note that the number of AFE circuit elements 530 is not limited to the number corresponding to the battery modules 11-1 to 11-7. For example, one AFE circuit element 530 may be connected to two battery modules.

[0041] 7, terminals A1, A2, ..., Am (m is any integer) are measurement terminals for detecting the cell voltage of the battery stack. When detecting the cell voltage of the battery stack, the battery cells are connected in the order from terminal A1 to terminal Am, from the electrode with the highest potential to the electrode with the lowest potential.

[0042] The resistor Ra and the switch circuit Sa between the terminals A1, A2, ..., Am are for balancing the battery cells. That is, when the switch circuit Sa is turned on, both poles of the battery cells are connected via the resistor Ra, and the energy in the battery cells is consumed by Joule heat. This causes the energy of the battery cells with a large charge to be consumed, and the charge amount of each battery cell can be equalized.

[0043] The terminals D1 and D2 are terminals for inputting and outputting data. Data is input and output between the AFE 53 and the microprocessor 54 via the terminals D1 and D2.

[0044] Here, the arrangement of AFE circuit elements corresponding to the battery modules will be described with reference to Fig. 8. Fig. 8 is an explanatory diagram of AFE circuit elements 530-1 to 530-7 arranged corresponding to battery modules 11-1 to 11-7.

[0045] 5, battery modules 11-1 to 11-7 are provided with a battery stack consisting of battery cells 20-1, 20-2, ..., 20-n. Both ends and inter-stages of each battery cell 20-1, 20-2, ..., 20-n are connected to terminals A1, A2, ..., Am of AFE circuit elements 530-1 to 530-7, respectively. Furthermore, each AFE circuit element 530-1 to 530-7 is connected in series.

[0046] 8, the cell voltages of the battery cells constituting the battery stack of each of the battery modules 11-1 to 11-7 are detected by the AFE circuit elements 530-1 to 530-7. The cell voltages of the battery cells constituting the battery stack of each of the battery modules 11-1 to 11-7 are then converted into digital values ​​by the AFE circuit elements 530-1 to 530-7 and sent to the microprocessor 54 via the optical isolation element 55.

[0047] <Embodiment> The storage battery control method according to the present invention is applied to charge control of battery modules 11-1 to 11-7 in storage battery unit 3 configured as described above.

[0048] As described above, the battery modules 11-1 to 11-7 are provided with a battery stack in which a plurality of battery cells 20-1 to 20-n are connected in series. In a configuration in which the battery cells 20-1 to 20-n are connected in series, a balance adjustment is required so that the charge amounts of the battery cells are constant.

[0049] 7, a balance circuit is configured by a resistor Ra and a switch circuit Sa. When the switch circuit Sa is turned on, both electrodes of the battery cell are connected via the resistor Ra, and the stored energy in the battery cell is consumed by Joule heat. This makes it possible to equalize the charge amount of each battery cell.

[0050] The example shown in Fig. 7 is called a passive system, and there is another type of balancing circuit called an active system. In the passive system, as described above, the battery cells are balanced by discharging the cells with a high charge level and matching them with the cells with a low charge level. In contrast, the active system regenerates the discharged power of the cells with a high charge level to the cells with a low charge level.

[0051] The state of charge (SOC) of a battery cell can usually be detected by the cell voltage. Therefore, by detecting the cell voltage of the battery cell and determining the SOC from this cell voltage, it is possible to perform balance adjustment so that the charge amounts of the battery cells are uniform. However, in the case of a type of battery cell such as a lithium iron phosphate battery, the cell voltage is almost constant up to a certain change point, so it is difficult to determine the SOC from the cell voltage and perform balance adjustment so that the charge amounts of the battery cells are uniform.

[0052] Here, the relationship between the voltage and SOC of a lithium iron phosphate ion battery will be described with reference to Figures 9 and 10. Figure 9 is a graph showing the relationship between the voltage and SOC of a lithium iron phosphate ion battery. Figure 10 is a graph showing an enlarged portion of the relationship between the voltage and SOC of a lithium iron phosphate ion battery. In Figures 9 and 10, the horizontal axis represents SOC, and the vertical axis represents cell voltage.

[0053] As shown in Fig. 9, in the case of a lithium iron phosphate battery, the cell voltage is constant at approximately 3.2V to 3.3V, except when the SOC is 10% or less, or when the SOC is 95% or more. When the cell voltage is in a substantially constant range, it is difficult to detect the cell voltage and determine the SOC. As shown in Fig. 10, when the SOC is 95% or more, which is the change point of the cell voltage, the cell voltage fluctuates greatly with respect to the SOC, and the SOC can be determined by detecting the cell voltage. For this reason, by fully charging the battery modules 11-1 to 11-7, balance adjustment is possible.

[0054] However, with the diversification of usage, cases are expected in which battery modules 11-1 to 11-7 will not be fully charged. In other words, while a home storage battery was generally used to be fully charged within the range of use, as shown in Fig. 1, when an EV stand 4 is installed, it is expected that battery modules 11-1 to 11-7 will not be fully charged in order to charge an electric vehicle.

[0055] Therefore, in this embodiment, when a predetermined condition is satisfied, the state of charge of the battery modules 11-1 to 11-7 is controlled. For example, when a predetermined condition is satisfied, the battery modules 11-1 to 11-7 are charged to a predetermined SOC or higher. The predetermined SOC is the SOC at which the voltage changes (for example, 95%). In other words, the state of charge is controlled to be fully charged or close to being fully charged.

[0056] When the charging state of battery modules 11-1 to 11-7 becomes fully charged or close to being fully charged, the cell voltages of battery modules 11-1 to 11-7 are detected. This makes it possible to determine the SOC of each battery cell of battery modules 11-1 to 11-7 from the measured values ​​of the detected cell voltages.

[0057] By operating the balancing circuit in accordance with the SOC of each battery cell of the battery modules 11-1 to 11-7, it is possible to perform a balancing adjustment of the charge amounts.

[0058] The predetermined condition is, for example, that the storage battery has not been in a fully charged state for a predetermined period of time. The predetermined period of time is, for example, 10 days or more. When the predetermined condition is met, that is, when the battery modules 11-1 to 11-7 have not been in a fully charged state for 10 days or more, a process of fully charging the battery modules 11-1 to 11-7 is performed. Then, after the battery modules 11-1 to 11-7 are set to a fully charged or nearly fully charged state, the balancing circuit is operated. Note that the predetermined period of time is not limited to 10 days or more.

[0059] The predetermined condition is not limited to this example. For example, the predetermined condition may be that the balancing circuit has not operated for a predetermined period of time. When the predetermined condition is satisfied, that is, when the balancing circuit has not operated for a predetermined period of time, a process of fully charging the battery modules 11-1 to 11-7 may be performed.

[0060] Here, the flow of processing in the storage battery control method according to the present invention will be described with reference to Figs.

[0061] First, an overview of the storage battery control method according to the present invention will be described with reference to Fig. 11. Fig. 11 is a sequence diagram showing an overview of the storage battery control method according to the present invention.

[0062] As shown in FIG. 11, first, the microprocessor 54 of the storage battery unit 3 determines whether or not full charge has not been detected for 10 days or more (step S101). If full charge has not been detected for 10 days or more (step S101 / YES), the microprocessor 54 transmits a full charge request to the power conditioner 1 (step S102). On the other hand, if full charge has not been detected for 10 days or more (step S101 / NO), the microprocessor 54 may, for example, repeat step S101.

[0063] When the power conditioner 1 receives a full charge request from the microprocessor 54, it performs charging (step S103). That is, the power conditioner 1 supplies a charging current from the solar panel 2 or the commercial power source 5 to the storage battery unit 3.

[0064] When the microprocessor 54 detects full charge (step S104), it transmits a cancellation of the charge request to the power conditioner 1 (step S105). Note that the microprocessor 54 may transmit a cancellation of the charge request to the power conditioner 1 when it detects a state close to full charge. When the power conditioner 1 receives the cancellation of the charging request from the microprocessor 54, it stops charging (step S106).

[0065] Next, a full charge request process on the storage battery unit 3 side in the storage battery control method according to the present invention will be described with reference to Fig. 12. Fig. 12 is a flowchart showing a full charge request process on the storage battery unit 3 side in the storage battery control method according to the present invention.

[0066] As shown in FIG. 12, first, the microprocessor 54 of the storage battery unit 3 determines whether or not full charge has not been detected for 10 days or more (step S201). If the full charge has not been detected for 10 days or more (step S201 / Yes), the microprocessor 54 advances the process to step S202. On the other hand, if the full charge has not been detected for 10 days or more (step S201 / No), the microprocessor 54 ends the process.

[0067] In step S202, the microprocessor 54 transmits a full charge request to the power conditioner 1, and ends the process.

[0068] 11 and 12, each of the battery modules 11-1 to 11-7 is set to a fully charged or nearly fully charged state. When each of the battery modules 11-1 to 11-7 is set to a fully charged or nearly fully charged state, the balancing circuit is operated as described below, and the charge amounts of the battery cells 20-1 to 20-n of the battery modules 11-1 to 11-7 are equalized.

[0069] Next, the operation process of the balancing circuit in the storage battery control method according to the present invention will be described with reference to Fig. 13. Fig. 13 is a flowchart showing the operation process of the balancing circuit in the storage battery control method according to the present invention.

[0070] As shown in FIG. 13, first, when the microprocessor 54 detects full charge, the microprocessor 54 advances the process to step S302 (step S301).

[0071] The microprocessor 54 determines whether or not to operate the balance circuit (step S302). If it is determined that the balance circuit needs to operate (step S302 / YES), the microprocessor 54 advances the process to step S303. On the other hand, if it is determined that the balance circuit does not need to operate (step S303 / No), the microprocessor 54 ends the process.

[0072] In step S303, the microprocessor 54 determines the difference in the charge amount of each battery cell. For example, the microprocessor 54 first acquires the measured value of the cell voltage of each battery cell 20-1 to 20-n from the AFE 53. Next, the microprocessor 54 determines the SOC of each battery cell 20-1 to 20-n from the acquired measured value of the cell voltage. That is, when the microprocessor 54 acquires the measured value of the cell voltage from the AFE 53, it determines the SOC corresponding to the cell voltage using the curve showing the relationship between the voltage and the SOC shown in FIG. 9 and FIG. 10. Then, the microprocessor 54 determines the difference in the charge amount of each battery cell 20-1 to 20-n from the SOC of each battery cell 20-1 to 20-n.

[0073] After determining the difference in the charge amount, the microprocessor 54 operates the balancing circuit of the AFE circuit element 530 according to the difference in the charge amount of each of the battery cells 20-1 to 20-n (step S304), and ends the process.

[0074] The above-mentioned SOC is the ratio of the remaining capacity to the maximum capacity of the cell. For example, if the remaining capacity of a battery cell is 5 Ah with a maximum capacity of 10 Ah, the SOC is 50%. Therefore, if the SOC is found, the remaining capacity is determined, and the charge amount of the battery cell to reach a specified capacity is also determined. For example, if the SOC of a battery cell with a maximum capacity of 10 Ah is 50%, the charge amount of the battery cell is 5 Ah, and to charge to the maximum capacity, it is sufficient to charge at a current of 5 A for one hour. The discharge amount to reach a specified capacity can also be found in the same way.

[0075] The AFE circuit element 530 shown in FIG. 7 is a passive type, and is configured to equalize the charge amount by discharging the stored energy in the battery cells. In this case, the charge amount of each battery cell 20-1 to 20-n is discharged so as to match the charge amount of the cell with the lowest charge amount. That is, the difference between the charge amount of each battery cell 20-1 to 20-n and the charge amount of the battery cell 20-1 to 20-n with the lowest charge amount is obtained, and the discharge amount of each battery cell 20-1 to 20-n for equalizing the charge amount is calculated according to the difference. Then, the switch circuit Sa shown in FIG. 7 is turned on for a time according to the difference from the charge amount of the battery cell 20-1 to 20-n with the lowest charge amount, thereby discharging each battery cell 20-1 to 20-n, and the charge amount of each battery cell 20-1 to 20-n is equalized.

[0076] The discharge amount is determined by the discharge current from the battery cells 20-1 to 20-n and the discharge time. When the AFE circuit element 530 having the configuration shown in Fig. 7 is used, the discharge current is determined by the resistance Ra and the on-resistance value of the MOS transistor that constitutes the switch circuit Sa, and the discharge time is determined by the on-time of the switch circuit Sa. Therefore, the discharge amount can be managed by the resistance value of the resistor Ra and the on-time of the switch circuit Sa.

[0077] In the above description, a passive type balance circuit is used, but the present invention can be similarly applied to an active type balance circuit.

[0078] In the above explanation, the SOC with respect to the cell voltage is obtained from the curves showing the relationship between the voltage and SOC shown in Figures 9 and 10, but the SOC with respect to the cell voltage may be obtained from the OVC, the charge curve, or the discharge curve. Also, the SOC with respect to the cell voltage may be obtained from a curve formed from both the discharge curve and the charge curve.

[0079] The balancing of the charge amounts of the battery cells is not necessarily limited to the above-mentioned configuration. Each battery module may be provided with a microprocessor and an AFE. The balancing circuit may be realized by a balance adjustment circuit configuration other than the AFE.

[0080] As described above, the storage battery control method according to the embodiment of the present invention is a method for controlling the state of charge of each battery cell of a storage battery in which a plurality of battery cells are connected in series. The storage battery control method includes a charging step, a detection step, and a determination step. In the charging step, when a predetermined condition is satisfied, the storage battery is charged to a predetermined charging rate or higher. In the detection step, when the storage battery is charged to a predetermined charging rate or higher, the cell voltage of each battery cell of the storage battery is detected. In the determination step, the charging rate of each battery cell of the storage battery is determined from the measured cell voltage value of each battery cell of the storage battery.

[0081] For example, in the charging process, if full charge detection of the storage batteries has not been performed for a predetermined period of time, full charge processing is performed to set the charge states of battery modules 11-1 to 11-7 to full charge or close to full charge. In the detection step, the cell voltages of the battery modules 11-1 to 11-7 are detected after the full charge process. In the determination step, the charging rates of battery modules 11-1 to 11-7 are determined from the measured values ​​of the cell voltages of battery modules 11-1 to 11-7 detected in the detection step.

[0082] With this configuration, the storage battery control method according to this embodiment can detect the cell voltage from the OCV curve, charge curve, or discharge curve when the storage battery is close to full charge (e.g., 95% or more). In the OCV curve, charge curve, or discharge curve, a large change in cell voltage is observed when the storage battery is close to full charge (e.g., 95% or more). Therefore, in the storage battery control method according to the present embodiment, the cell voltage can be easily detected from the OCV curve, the charge curve, or the discharge curve, and the charge amount of the battery cell can be grasped according to the detected cell voltage, and the charge amount of the battery cell can be sufficiently balanced.

[0083] Therefore, in the storage battery control method according to the present embodiment, even when a battery cell with a flat OCV curve, charge curve, or discharge curve is used, it is possible to grasp the charge amount of the battery cell and perform sufficient balance adjustment. By performing balance adjustment of the charge amount of the battery cell, it is also possible to prevent deterioration of the performance of the storage battery and shortening of its lifespan.

[0084] In the above-described embodiment, the power supply system may be configured as shown in Fig. 14. Fig. 14 is a block diagram showing an outline of another configuration example of the power supply system according to the present invention. In a power supply system 10A in Fig. 14, a solar panel 2, a storage battery unit 3, and an EV stand 4 are each independently connected to power conditioners 1A, 1B, and 1C, respectively. In FIG. 14, each of power conditioners 1A, 1B, and 1C supplies or demands power (electrical energy) between a solar panel 2, a storage battery unit 3, and an EV stand 4, respectively, via a distribution board 6. The configuration and operation of the storage battery unit 3 in FIG. 14 are similar to those of the storage battery unit 3 in the present embodiment already described.

[0085] In the above-described embodiment, the power supply system may be configured as shown in Fig. 15. Fig. 15 is a block diagram showing an outline of another configuration example of the power supply system according to the present invention. In a power supply system 10B in Fig. 15, each of the solar panel 2 and the storage battery unit 3 is connected to a power conditioner 1D, and the EV stand 4 is connected to a power conditioner 1C. In FIG. 15, each of power conditioners 1C and 1D supplies or demands power (electrical energy) between a solar panel 2, a storage battery unit 3, and an EV stand 4, via a distribution board 6, respectively. The configuration and operation of the storage battery unit 3 in FIG. 15 are similar to those of the storage battery unit 3 in the present embodiment already described.

[0086] The power supply system 10 in the above-described embodiment may be realized in whole or in part by a computer. In this case, a program for realizing this function may be recorded in a computer-readable recording medium, and the program recorded in the recording medium may be read into a computer system and executed to realize the function. The term "computer system" as used herein includes hardware such as an OS and peripheral devices. The term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, and storage devices such as hard disks built into a computer system. The term "computer-readable recording medium" may also include a medium that dynamically holds a program for a short period of time, such as a communication line when a program is transmitted via a network such as the Internet or a communication line such as a telephone line, and a medium that holds a program for a certain period of time, such as a volatile memory inside a computer system that is a server or client in such a case. The above-described program may be a program for realizing a part of the above-described function, or may be a program that can realize the above-described function in combination with a program already recorded in the computer system, or may be a program that is realized using a programmable logic device such as an FPGA.

[0087] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and designs that do not deviate from the gist of the present invention are also included. [Explanation of symbols]

[0088] 3... storage battery unit, 11 (11-1 to 11-7)... battery module, 12... control management module, 13 (13-1 to 13-7)... connector, 14 (14-1 to 17-7)... connector, 53... AFE, 54... microprocessor, 530-1 to 530-7... AFE circuit element

Claims

1. A battery control method for controlling a state of charge of each battery cell of a storage battery in which a plurality of battery cells are connected in series, comprising: a charging step of charging the storage battery to a predetermined charging rate or higher when a predetermined condition is satisfied; a detection step of detecting a cell voltage of each battery cell of the storage battery when the storage battery is charged to the predetermined charging rate or higher; a determination step of determining a charging rate of each battery cell of the storage battery from a measured value of a cell voltage of each battery cell of the storage battery; Including, The charging step is a step of determining whether a period during which the full charge of the storage battery has not been detected continues for a predetermined period or more, and, when the determination result is affirmative, charging the storage battery to a charging rate equal to or higher than the predetermined charging rate. Battery control method.

2. A battery control method for controlling a state of charge of each battery cell of a storage battery in which a plurality of battery cells are connected in series, comprising: a charging step of charging the storage battery to a predetermined charging rate or higher when a predetermined condition is satisfied; a detection step of detecting a cell voltage of each battery cell of the storage battery when the storage battery is charged to the predetermined charging rate or higher; a determination step of determining a charging rate of each battery cell of the storage battery from a measured value of a cell voltage of each battery cell of the storage battery; Including, the charging step is a step of determining whether a non-operating period of a balancing circuit of the storage battery continues for a predetermined period or more, and charging the storage battery to a charging rate equal to or higher than the predetermined charging rate when the determination result is affirmative; Battery control method.

3. The predetermined charging rate is set based on a change point at which the cell voltage changes significantly with respect to the charging rate in a charging curve, a discharging curve, a voltage (OCV (Open circuit voltage)) curve in a state where no current flows, or a curve obtained from both the charging curve and the discharging curve, which show the relationship between the charging rate and the cell voltage of the battery cell of the storage battery. The battery control method according to claim 1 or 2.

4. In the determination step, the charging rate of each battery cell of the storage battery is calculated from a measured value of the cell voltage of each battery cell of the storage battery based on a charge curve, a discharge curve, a voltage (OCV (Open circuit voltage)) curve in a state where no current flows, which indicates a relationship between the charging rate and the cell voltage of the battery cell, or a curve obtained from both the charge curve and the discharge curve. The battery control method according to any one of claims 1 to 3.

5. a balancing step of balancing each battery cell of the storage battery based on a charging rate of each battery cell of the storage battery so that the charging rate of each battery cell of the storage battery is uniform; The battery control method according to claim 1 , further comprising:

6. In the balancing process, a passive control is performed so that the charging rate of each battery cell is uniform. The battery control method according to claim 5 .

7. In the balancing process, active control is performed so that the charging rate of each battery cell is uniform. The battery control method according to claim 5 .

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