Charge control device, charge control method, and program

Abstract

To charge a battery that has deteriorated or is in a low-temperature state in a shorter time.SOLUTION: A charge control device includes a controller that, when charging a storage battery, performs constant-current charging at a constant current until a target voltage is reached and then performs constant-voltage charging at a constant voltage. The controller estimates the internal resistance of the storage battery and reduces the value of the constant current as the internal resistance is increased to perform the constant-current charging.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present invention relates to a charge control device, a charge control method, and a program. [Background technology]

[0002] When charging a battery, constant current charging (CC charging) is performed until the battery voltage reaches, for example, an upper limit voltage specified for the battery, and then constant voltage charging (CV charging) is performed at the upper limit voltage after the upper limit voltage is reached, in a method called CCCV charging in which the battery is charged to a target state of charge (see, for example, Patent Document 1 below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-97553 [Patent Document 2] JP 2018-166404 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, a deteriorated battery or a battery in a low temperature state has a high internal resistance. Therefore, when constant current charging is performed on a battery in such a state, the battery voltage reaches the upper limit voltage earlier than when constant current charging a battery in a normal state, and constant voltage charging at the upper limit voltage begins. Note that in constant voltage charging at the above upper limit voltage, the charging current value is smaller than in constant current charging.

[0005] Therefore, if constant voltage charging is started earlier in such a state than in a normal state, the charging time until the target charging state is reached will be longer than the charging time in a normal state. In other words, the total time from the start of charging by constant current charging to the end of charging by constant voltage charging will be longer. An aspect of the disclosed embodiment is to charge a deteriorated battery or a battery in a low temperature state in a shorter time. [Means for solving the problem]

[0006] One aspect of the disclosed embodiment is exemplified by a charge control device. The charge control device includes a controller that, when charging a storage battery, performs constant current charging at a constant current up to a target voltage, and then performs constant voltage charging at a constant voltage. The controller estimates the internal resistance of the storage battery, and performs constant current charging by decreasing the value of the constant current as the internal resistance increases. Effect of the Invention

[0007] The charging control device estimates the internal resistance of the storage battery, and performs constant current charging by lowering the value of the constant current as the internal resistance increases. Therefore, the charging control device can prevent the storage battery from reaching an upper limit voltage in constant current charging earlier than in a normal state due to the internal resistance of the storage battery being higher than in a normal state. As a result, the charging control device can prevent the period of constant current charging from being shortened even when the internal resistance of the storage battery is higher than in a normal state. Furthermore, the charging control device can delay the start of charging by constant voltage charging, and can shorten the period of constant voltage charging. And, as described above, the charging current is larger in constant current charging than in constant voltage charging. That is, the charging control device can lengthen the period of constant current charging with a large charging current. Furthermore, the charging control device can shorten the period of constant voltage charging with a small charging current.

[0008] As described above, the charge control device of the present invention can charge a deteriorated battery or a battery in a low temperature state in a shorter time. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating an example of the change over time in current and voltage input to a battery during CCCV charging. [Diagram 2] FIG. 2 is a diagram illustrating the time variations in the current and voltage input to the battery during CCCV charging at a low temperature or when the battery is degraded. [Diagram 3] FIG. 3 is a diagram illustrating a countermeasure against an increase in the internal resistance of a battery cell in this embodiment. [Figure 4] FIG. 4 is a diagram illustrating the relationship between the temperature, internal resistance, and current value of the battery during CC charging. [Diagram 5] FIG. 5 is a diagram illustrating the relationship between the degree of deterioration of a battery, the internal resistance, and the current value during CC charging. [Figure 6] FIG. 6 is a diagram illustrating a first application example of the charge control device of this embodiment and a charge control method. [Figure 7] FIG. 7 is a diagram illustrating a second application example of the charge control device of this embodiment and a charge control method. [Figure 8] FIG. 8 is a diagram illustrating an example of a hardware configuration of the charging control device. [Figure 9] FIG. 9 is a diagram illustrating an example of the configuration of the internal resistance table. [Figure 10] FIG. 10 is a diagram illustrating an example of control of CCCV charging by the charge control device of the present embodiment. [Figure 11] FIG. 11 is a diagram illustrating the details of the process of estimating the internal resistance value of the battery. [Figure 12] FIG. 12 is a diagram illustrating the details of the current value changing process. [Figure 13] FIG. 13 is a diagram illustrating a process for determining an appropriate current value for CC charging. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, a charge control device, a charge control method, and a program according to an embodiment will be described with reference to the drawings. The charge control device executes the charge control method in accordance with the program, and controls charging of a battery of an electric vehicle or the like. In addition, a storage battery is generally also called a battery or a secondary battery.

[0011] (How to charge the battery) In this embodiment, CCCV charging is performed to charge the battery of an electric vehicle or the like. CCCV charging is a charging method that combines constant current charging (CC charging), which charges at a constant current (CC), and constant voltage charging (CV charging), which charges at a constant voltage (CV). That is, in CCCV charging, CC charging is performed at a constant current during the initial period from the start of charging. Then, when the voltage at the battery terminals reaches a target voltage (predetermined value), control is switched to CV charging at a constant voltage, and CV charging is performed until the target state of charge is reached. The target state of charge is, for example, a full charge. This is because even if the voltage of the battery reaches the target voltage (predetermined value), the actual voltage of the battery is lower than the target voltage (predetermined value) because the battery cells are in a polarized state. For this reason, CV charging is performed thereafter so that the actual voltage of the battery becomes the target voltage (predetermined value).

[0012] FIG. 1 is a diagram illustrating the time change of the current and voltage input to a battery during CCCV charging. Here, the current is the current flowing in from the battery terminals, and the voltage is the voltage generated between the battery terminals. In FIG. 1, the horizontal axis indicates the time after charging starts, and the vertical axis indicates the current and voltage values ​​without units. As shown in FIG. 1, after charging starts, the horizontal axis indicates the CC charging period Tcc1, Then, when the voltage reaches a predetermined voltage, the CV charging period Tcv1 begins. Here, the predetermined voltage is, for example, a target voltage in CC charging. As shown in FIG. 1, during the CV charging period Tcv1, the current value gradually decreases, and when the battery reaches a target state of charge, charging control ends. When the battery reaches a target state of charge, this can also be expressed as, for example, when the amount of stored power reaches a target amount of charge. Whether or not the amount of stored power has reached the target amount of charge is determined, for example, from the current value during CV charging.

[0013] Fig. 2 is a diagram illustrating the time variation of the current and voltage input to the battery during CCCV charging at a low temperature or when the battery is degraded. A low temperature is, for example, a winter temperature. An example of a low-temperature battery is, for example, a battery that was mounted on an electric vehicle or the like when the battery was mounted and left in an outdoor temperature in winter for a long period of time. Battery degradation refers to, for example, a state in which the battery is used and repeatedly charged and discharged, resulting in the battery being unable to exhibit the power storage performance it had in the initial stage of use.

[0014] At low temperatures or when the battery is degraded, the internal resistance of the battery cell becomes high. When the internal resistance becomes high, the voltage fluctuation becomes large due to Ohm's law (V=IR). In other words, even if charging is performed with the same charging current, the higher the internal resistance, the larger the voltage drop in the battery. The voltage at the battery terminals is the voltage resulting from the accumulation of charge plus the voltage drop resulting from charging (or discharging). Therefore, when the internal resistance becomes high at low temperatures or when the battery is degraded, the voltage at the battery terminals reaches the target voltage for CC charging relatively soon after the start of CC charging, depending on the current value. However, at this time, the actual charging state is much lower than the target charging state (e.g., fully charged state) compared to when the internal resistance is low. Then, after the start of charging, CV charging starts earlier than usual, i.e., when the battery is not degraded at low temperatures, and the charging time to the target charging state (fully charged, etc.) becomes longer.

[0015] In FIG. 2, after the start of charging, the CC charging period is Tcc2, and then the CV charging period is Tcv2. Comparing FIG. 1 and FIG. 2, Tcc2<Tcc1であり、Tcv2> 2. In addition, the total charging period Tcc1+Tcv1 in FIG. 1 is smaller than the total charging period Tcc2+Tcv2 in FIG.

[0016] FIG. 3 is a diagram illustrating a countermeasure against an increase in the internal resistance of the battery cells in the present embodiment. The present charge control device estimates the internal resistance value of the battery from the temperature before charging and the degree of battery degradation in advance, and performs CC charging with an appropriate current value according to the internal resistance value. That is, the present charge control device freely sets the current value of CC charging to a value corresponding to the internal resistance value. As an example, the present charge control device performs CC charging with a smaller current value as the internal resistance value is higher. That is, the present charge control device sets the current value so that the voltage at the terminals of the battery does not reach the target voltage in CC charging prematurely due to an increase in the internal resistance value, and controls the power supply circuit to perform CC charging.

[0017] By such control, the present charge control device can avoid a situation where the voltage at the terminals of the battery reaches the target voltage in CC charging prematurely due to an increase in the internal resistance caused by low temperature or battery degradation. That is, in FIG. 3, the CC charging period Tcc3 can be set such that Tcc2 < Tcc3 with respect to the CC charging period Tcc2 in FIG. 2. And the present charge control device can make the total charging period Tcc3 + Tcv3 in FIG. 3 < the total charging period Tcc2 + Tcv2 in FIG. 2.

[0018] FIG. 4 illustrates the relationship between the temperature of the battery, the internal resistance, and the current value in CC charging. In FIG. 4, the horizontal axis of both the upper and lower graphs is the temperature of the battery cells. The upper graph in FIG. 4 illustrates the change in the internal resistance of the battery with respect to the temperature of the battery cells. The lower the cell temperature, the higher (larger) the internal resistance. The lower graph in FIG. 4 illustrates the current value in CC charging with respect to the cell temperature. The present charge control device decreases the current value in CC charging as the internal resistance is higher.

[0019] FIG. 5 illustrates the relationship between the degree of deterioration of a battery, its internal resistance, and the current value during CC charging. In FIG. 5, the horizontal axis of both the upper and lower graphs represents the degree of deterioration of the battery. The upper graph in FIG. 5 illustrates the change in the internal resistance of the battery relative to the degree of deterioration of the battery. The higher (larger) the degree of deterioration of the battery, the higher the internal resistance. The lower graph in FIG. 5 illustrates the current value during CC charging relative to the degree of deterioration of the battery. This charging control device reduces the current value during CC charging as the degree of deterioration of the battery increases. A method for estimating the degree of deterioration of the battery is illustrated together with an explanation of the charging control device 9 in FIG. 6.

[0020] (composition) FIG. 6 is a diagram illustrating a first application example of the charge control device 10 of the present embodiment and a charge control method. FIG. 6 illustrates the configuration of an electric vehicle 1A equipped with the charge control device 10. Note that FIG. 6 also illustrates a charging facility 1B. In this embodiment, the electric vehicle 1A and the charging facility 1B are called a charging system 1. The electric vehicle 1A has a battery 19, a power supply circuit 14 that supplies power to the battery 19, and a charging control device 10 that controls the power supply circuit 14. In addition, a voltage sensor 11 that measures the voltage between the terminals of the battery 19 and a current sensor 12 that measures the charging current supplied from the power supply circuit 14 to the battery 19 are provided. Furthermore, a temperature sensor 13 is provided on the battery 19. Meanwhile, in FIG. 6, the charging facility 1B is connected to the electric vehicle 1A. A power line of the charging facility 1B is connected to the power supply circuit 14. In addition, a communication line of the charging facility 1B is connected to the charging control device 10.

[0021] The electric vehicle 1A is connected to the charging equipment 1B via a power line and a communication line, for example, by attaching a plug of the charging equipment 1B to a connection part of the electric vehicle 1A. The electric vehicle 1A is connected to the charging equipment 1B when charging the battery 19, and can receive power supply to the power supply circuit 14. When the electric vehicle 1A is connected to the charging equipment 1B, the charging control device 10 performs a procedure such as PnC (Plug and Charge) and performs a charging contract with the charging equipment 1B. Performs authentication, billing, and other processes.

[0022] The voltage sensor 11 measures the voltage value between the terminals of the battery 19, and inputs a measurement signal to the charging control device 10. In Fig. 6, the voltage sensor 11 is connected in parallel to the terminals of the battery 19, and measures the voltage between the terminals. In this embodiment, there is no limitation on the type of the voltage sensor 11.

[0023] The current sensor 12 measures the value of a current supplied from the power supply circuit 14 to the terminals of the battery 19, and inputs a measurement signal to the charging control device 10. In this embodiment, there is no limitation on the type of the current sensor 12. For example, in FIG. 6, the current sensor 12 is provided in series with the power supply circuit 14 and the battery 19 on a circuit extending from the power supply circuit 14 to the battery 19. However, the current sensor 12 is not limited to one provided on the circuit (one that uses a voltage drop across a shunt resistor), and may be one that measures the current in a non-contact manner by using the magnetic field of the current. Although omitted in FIG. 6, the current sensor 12 may be one that can measure a discharge current from the battery 19 to a load (such as a motor) in addition to a charging current.

[0024] The temperature sensor 13 is installed inside the housing of the battery 19, measures the temperature of the cells of the battery 19, and inputs a measurement signal to the charge control device 10. There is no limitation on the type of the temperature sensor 13. The temperature sensor 13 may be, for example, one that uses a thermocouple or a resistance temperature detector.

[0025] In the charging control device 10, an input interface 108 (see FIG. 8) receives measurement signals from the voltage sensor 11, the current sensor 12, and the temperature sensor 13, and converts them into digital data. The charge control device 10 converts the charge current into data and transmits it to an internal controller. Therefore, the internal controller of the charge control device 10 constantly obtains the charge current to the battery 19, the voltage between the terminals of the battery 19, and the temperature of the cells of the battery 19. Note that even during discharging, the internal controller of the charge control device 10 may constantly obtain the discharge current from the battery 19, the voltage between the terminals of the battery 19, and the temperature of the cells of the battery 19.

[0026] Fig. 7 is a diagram illustrating a second application example of the charge control device 10 of this embodiment and a charge control method. Fig. 7 illustrates the configuration of a charging facility 1B incorporating the charge control device 10. Note that Fig. 7 also illustrates an electric vehicle 1A receiving power supply from the charging facility 1B. In Fig. 7 as well, the electric vehicle 1A and the charging facility 1B are referred to as a charging system 1.

[0027] The electric vehicle 1A has a battery 19, a temperature sensor 13, and an on-board circuit 18. Also in Fig. 7, a charging facility 1B is connected to the electric vehicle 1A. A power line of the charging facility 1B is connected to a terminal of the battery 19 of the electric vehicle 1A. Also, a communication line of the charging facility 1B is connected to the on-board circuit 18 of the electric vehicle 1A.

[0028] On the other hand, charging equipment 1B has a power supply circuit 14 that supplies power to electric vehicle 1A, and a charging control device 10 that controls power supply circuit 14. Charging equipment 1B is also provided with a voltage sensor 11 for measuring the voltage supplied from power supply circuit 14. Charging equipment 1B is also provided with a current sensor 12 that measures the current supplied from power supply circuit 14 to electric vehicle 1A. The power line of charging equipment 1B is connected to the terminals of the battery of electric vehicle 1A, so that voltage sensor 11 is connected in parallel to battery 19.

[0029] In the configuration of FIG. 7 , for example, by attaching a plug of the charging equipment 1B to a connection part of the electric vehicle 1A, the electric vehicle 1A is connected to the charging equipment 1B via a power line and a communication line. When the battery 19 is charged, the electric vehicle 1A is connected to the charging equipment 1B and can receive power supply to the battery 19. When the electric vehicle 1A is connected to the charging equipment 1B, the on-board circuit 18 performs authentication, billing, and other processes in accordance with the charging contract with the charging equipment 1B, following a procedure such as PnC. The on-board circuit 18 also receives a measurement signal from the temperature sensor 13 via an input interface, converts it into digital data, sets it as the temperature of the cell of the battery 19, and notifies the charging control device 10 of the charging equipment 1B.

[0030] 7, the charge control device 10 does not need to be notified of the temperature of the cells of the battery 19 from the on-board circuit 18 of the electric vehicle 1A. For example, the charge control device 10 may have a temperature sensor that measures the temperature of the surrounding environment. The charge control device 10 may perform charge control using the temperature of the surrounding environment as the temperature of the cells of the battery 19.

[0031] 7, voltage sensor 11 also measures the voltage value between the terminals of battery 19 and inputs a measurement signal to charging control device 10. Current sensor 12 measures the value of a current supplied from power supply circuit 14 to the terminals of battery 19 and inputs a measurement signal to charging control device 10. Voltage sensor 11, current sensor 12 and temperature sensor 13 in FIG. 7 are the same as those in FIG. 6, so their description will be omitted. An application example of the charge control device 10 of the present embodiment is not limited to the charging system between a charging facility and a vehicle shown in Fig. 7 or 8. In other words, the present invention is applicable to any charge control device that has a first power source and a second power source and charges the second power source from the first power source via a DC-DC converter.

[0032] Fig. 8 is a diagram illustrating an example of the hardware configuration of the charge control device 10. Fig. 8 illustrates an example of the configuration when the charge control device 10 is mounted on an electric vehicle 1A (see Fig. 6). For this reason, in Fig. 8, a temperature sensor 13 is connected to the charge control device 10 via an interface 108.

[0033] The charging control device 10 includes a CPU 101, a main memory unit 102, an external memory unit 103, a display unit 104, an operation unit 105, a general-purpose communication unit 106, a PLC communication unit 107, and an interface 108. The CPU 101 and the main memory unit 102 can be collectively referred to as a control unit or a controller. The control unit is also called an Electronic Control Unit (ECU). do.

[0034] The CPU 101 executes a computer program that has been loaded in an executable manner into the main memory unit 102, and provides the functions of the charging control device 10. The main memory unit 102 is also simply called a memory, and stores the computer program executed by the CPU 101, data processed by the CPU 101, and the like. The CPU 101 is also called a processor. The main memory unit 102 is a dynamic random access memory (DRAM), a static random access memory (SRAM), a read only memory (ROM), and the like. Furthermore, the external memory unit 103 is, for example, a memory that supports the main memory unit 102. The external storage unit 103 is used as a storage area for storing computer programs executed by the CPU 101, data processed by the CPU 101, etc. The external storage unit 103 is a hard disk drive, a solid state drive (SSD), or the like.

[0035] The display unit 104 is, for example, a liquid crystal display, an electroluminescence panel, an organic light emitting diode (OLED), etc. The operation unit 105 is, for example, a keyboard, a pointing device, etc. In this embodiment, a touch panel is exemplified as the pointing device.

[0036] The general-purpose communication unit 106 transmits and receives data to and from other devices on the public network. For example, the CPU 101 communicates with a computer of a charging service provider or the like on the public network through the general-purpose communication unit 106. The general-purpose communication unit 106 may be a wireless communication device that accesses a mobile phone network. That is, the general-purpose communication unit 106 may be a wireless communication device that accesses a wireless access network such as Long Term Evolution (LTE), 4th Generation Mobile Communication System (4G), or 5th Generation Mobile Communication System (5G). The general-purpose communication unit 106 may be a communication device that accesses a wireless LAN (Local Area Network). The general-purpose communication unit 106 may be, for example, a device called a TCU (Telematics Control Unit). The general-purpose communication unit 106 may include an internal CPU, a memory, an input / output interface, a communication interface, and the like.

[0037] The PLC communication unit 107 transmits and receives signals to and from the charging facility 2. Here, the PLC communication unit 107 may execute Power Line Communications (PLC) with the charging facility 2. In this embodiment, the PLC is not limited to communication via a power line through which power is supplied from the charging facility 2. That is, the PLC communication unit 107 may execute a PLC-like communication procedure with the charging facility 2 via a communication line other than a power line. The PLC communication unit 107 may execute a procedure called HD-PLC (registered trademark) (High Definition - Power Line Communication). The PLC communication unit 107 may be an interface that communicates using a wireless LAN or Ethernet. The PLC communication unit 107 may have a CPU, a memory, an input / output interface, a communication interface, and the like. Thus, in this embodiment, the charging control device 10 communicates with the charging facility 2 via the general-purpose communication unit 106 or the PLC communication unit 107, and executes a charging request and billing process.

[0038] An interface (I / F) 108 receives analog detection signals from the voltage sensor 11, the current sensor 12, the temperature sensor 13, etc., converts them into digital data, and inputs them to the CPU 101. However, the interface 108 may also receive digital detection signals from the voltage sensor 11, the current sensor 12, the temperature sensor 13, etc. In this case, an AD (Analog Digital) converter may be provided on the output side of each of the voltage sensor 11, the current sensor 12, the temperature sensor 13, etc., and the AD converter may convert the analog detection signal into digital data and input it to the interface .

[0039] When the charging control device 10 is provided in the charging equipment 1B (see FIG. 7), the data of the temperature sensor 13 is transmitted from the on-board circuit 18 of the electric vehicle 1A to the CPU 101 of the charging equipment 1B via the PLC communication unit 107. However, in this case, the data of the temperature sensor 13 may be transmitted from the on-board circuit 18 of the electric vehicle 1A to the CPU 101 of the charging equipment 1B via the general-purpose communication unit 106.

[0040] (Method of estimating internal resistance and method of controlling charging) As described above, the charge control device 10 constantly acquires the charging current or discharging current to the battery 19, the voltage between the terminals of the battery 19, and the temperature of the cells of the battery 19.

[0041] The charge control device 10 estimates the deterioration level of the battery from, for example, the relationship between the charging current and the terminal voltage of the battery 19. For example, the charge control device 10 may estimate the internal resistance of the battery 19 from the relationship between the charging current at room temperature and the terminal voltage of the battery 19, and specify the deterioration level from the internal resistance value at room temperature. The room temperature is, for example, a temperature in the range of 15 degrees Celsius to 25 degrees Celsius.

[0042] Also, for example, the charge control device 10 may estimate the internal resistance of the battery 19 from the relationship between the discharge current and the terminal voltage of the battery 19 at room temperature, and identify the degree of deterioration from the internal resistance value at room temperature.

[0043] For example, the deterioration level D is defined by the following (Equation 1). D=ΔR / R0; (Formula 1) Here, R0 is the internal resistance value of the battery 19 at the start of use at room temperature. The start of use is, for example, an early stage of use when the battery 19 has been charged and discharged several times to several tens of times. Also, ΔR is the increase in the internal resistance R at the current time point at room temperature, and ΔR=R-R0. Therefore, the charge control device 10 can estimate the deterioration degree D of the battery 19 by measuring the internal resistance R of the battery 19 when it is charged or discharged at room temperature.

[0044] Also, for example, the charge control device 10 may estimate the deterioration level of the battery 19 from the relationship between the integral value of the discharge current during discharge (amount of discharged charge) and the amount of change in the terminal voltage of the battery 19 before and after discharge. Also, the charge control device 10 may estimate the deterioration level from the open circuit voltage (no-load voltage) of the battery 19 in a target state of charge (for example, fully charged).

[0045] Further, for example, the deterioration level D is defined by the following (Equation 2). D=ΔV / V0; (Formula 2) Here, V0 is the open circuit voltage of the battery 19 in a target state of charge (fully charged) at the start of use (initial stage of use). Also, ΔV is the difference value of the open circuit voltage V of the battery 19 in the target state of charge (fully charged) at the current point in time from V0, ΔV=V0-V. Therefore, the charge control device 10 can estimate the deterioration level D of the battery 19 by measuring the current open circuit voltage V of the battery 19 when the target state of charge (fully charged) is reached. However, the method of calculating the deterioration level is not limited to the above (Equation 1) and (Equation 2).

[0046] Furthermore, the charge control device 10 estimates the internal resistance of the battery 19 from the deterioration of the battery 19 and the current temperature of the cells of the battery 19. As shown in Fig. 4 or 5, the charge control device 10 sets a smaller current value for CC charging as the internal resistance value of the battery 19 increases. Then, the charge control device 10 sets a charging current value determined when charging the battery 19. CC charging is performed by controlling the voltage of the power supply circuit 14 to maintain a current value (constant value). Furthermore, when the voltage at the terminals of the battery 19 reaches a target value, the charge control device 10 reduces the charging current while maintaining the voltage at the terminals of the battery 19 at the target value, and performs CV charging until the battery 19 reaches a target charging state, such as a fully charged state.

[0047] FIG. 9 is a diagram illustrating the configuration of the internal resistance table stored in the main storage unit 102. The internal resistance table has three-dimensional elements. The first dimension is the deterioration degree, the second dimension is the temperature of the cell of the battery 19, and the third dimension is the internal resistance value of the battery 19. Therefore, each row of the internal resistance table corresponds to a point in a three-dimensional space. In the example of FIG. 9, a plurality of temperatures T1 to TM (M is an integer equal to or greater than 1) are combined with one deterioration degree D1. Furthermore, a plurality of points are set for the deterioration degree, such as D1, D2, D3, . . . The internal resistance table is sorted with the deterioration degree as a first key and the temperature as a second key. Here, it is assumed that the pair of the deterioration degree and the temperature in each row of the internal resistance table of FIG. 9 is (deterioration degree Di, temperature Tj). Therefore, the internal resistance table covers a two-dimensional plane with the deterioration degree and the temperature as two axes (two independent variables) at mesh-like intersections.

[0048] The charge control device 10 may obtain a pair (d, t) of the current deterioration level d and temperature t of the battery 19, and search the internal resistance table for four rows having a pair (deterioration level Di, temperature Tj) that is closest to the pair (d, t).The charge control device 10 may then estimate, by interpolation, an internal resistance value that corresponds to the pair (d, t) of the current deterioration level and temperature from the internal resistance values ​​of the four rows having a pair (deterioration level Di, temperature Tj) that is closest to the pair (d, t).

[0049] The method of calculating the deterioration degree has already been exemplified by (Equation 1), (Equation 2), etc. Furthermore, the charging control device 10 can acquire the current temperature of the cells of the battery 19 from the temperature sensor 13. However, as illustrated in FIG. 7, when the charging control device 10 is provided in the charging equipment 1B, the charging control device 10 does not need to acquire the temperature at the temperature sensor 13 from the in-vehicle circuit 18. For example, the charging control device 10 may regard the temperature of the surrounding environment measured by a temperature sensor provided in the charging equipment 1B as the temperature of the cells of the battery 19. Therefore, the charging control device 10 can uniquely estimate the current internal resistance value of the battery by referring to the internal resistance table.

[0050] Instead of storing the internal resistance table in the main storage unit 102, the charge control device 10 may store a regression equation by multiple regression analysis with deterioration x and temperature y as independent variables, as exemplified by the following (Equation 3), in the main storage unit 102. Then, the charge control device 10 may use the regression equation to obtain the internal resistance R of the battery 19. R(x,y)=a+b*x+c*y; (Equation 3) Here, * indicates multiplication. a, b, and c are coefficients calculated by, for example, the least squares method. However, the form of the regression equation is not limited to (Equation 3). For example, the regression equation may include higher-order terms of second order or higher.

[0051] (Processing example) 10 to 12 illustrate the processing of the charging control device 10 according to the present embodiment. The CPU 101 executes the processing of Fig. 10 to 12 according to a computer program on the main storage unit 102. However, in the present embodiment, the processing will be described as being performed by the charging control device 10.

[0052] FIG. 10 is a diagram illustrating the control of CCCV charging by the charge control device 10 of this embodiment. The charge control device 10 first estimates the internal resistance value of the battery 19 (S1). Next, the charge control device 10 determines the current value of CC charging according to the internal resistance value of the battery 19 ( S2).

[0053] In the process of S2, basically, the charge control device 10 reduces the current value of CC charging as the internal resistance value increases. The charge control device 10 may store in the main storage unit 102 a value indicating to what extent the current value is to be reduced according to the internal resistance value. For example, the current value of CC charging according to the internal resistance value is determined by a prior experiment, simulation, or the like. Then, the charge control device 10 may store in the main storage unit 102 a relationship between the internal resistance value and the current value of CC charging as a current value table. The charge control device 10 may also store in the main storage unit 102 a function expression that represents the relationship between the internal resistance value and the current value of CC charging, and determine the current value of CC charging from the value of the internal resistance value. Here, the relationship between the internal resistance value and the current value of CC charging may be, for example, the current value of CC charging itself corresponding to the internal resistance value, or may be the relationship between the internal resistance value and the amount of change that reduces the current value of CC charging corresponding to the internal resistance value.

[0054] Next, the charge control device 10 executes CC charging (S3). During CC charging, the charge control device 10 determines whether or not the voltage at the terminals of the battery 19 has reached a target voltage (S4). If the voltage has not reached the target voltage, the charge control device 10 executes a current value change process (S7). The process of S7 is a process in which the charge control device 10 detects the temperature of the cells of the battery 19 again and resets the current value for CC charging. Details of the process of S7 will be described separately with reference to FIG. 12. The process of S7 may be omitted. That is, the charge control device 10 may execute the process of FIG. 10 without executing the process of S7. Then, the charge control device 10 continues the CC charging of S3. On the other hand, when the voltage reaches the target voltage, the charge control device 10 executes CV charging (S5).

[0055] The charge control device 10 judges whether the battery 19 has reached the target state of charge during CV charging (S6). The target state of charge is, for example, fully charged. However, the target state of charge may be a state of charge that is less than the fully charged state by a specified charge amount. The specified charge amount is, for example, a value experimentally determined by the manufacturer of the battery 19. The charge control device 10 may judge whether the battery 19 has reached the target state of charge from, for example, the current value during CV charging. The charge control device 10 may judge that the battery 19 has reached the target state of charge when the current value during CV charging is equal to or less than an allowable limit. The allowable limit is, for example, determined from performance information, specifications, or performance test results of the battery 19. If the battery 19 has not reached the target state of charge, the charge control device 10 continues the CV charging in S5. On the other hand, if the voltage reaches the target state of charge, the charge control device 10 ends the process.

[0056] Fig. 11 is a diagram illustrating the details of the process (S1 in Fig. 10) for estimating the internal resistance value of the battery 19. In this process, the charge control device 10 estimates the deterioration level of the battery 19 (S11). The method for estimating the deterioration level has already been explained above (method for estimating internal resistance and method for controlling charging) using (Equation 1), (Equation 2), etc. The charge control device 10 may execute the procedure explained using (Equation 1), (Equation 2), etc.

[0057] Next, the charging control device 10 detects the temperature of the cells of the battery 19 by the temperature sensor 13 (S12). When the charging control device 10 is provided in the charging equipment 1B (see FIG. 7), the on-board circuit 18 acquires the temperature of the cells of the battery 19 measured by the temperature sensor 13 and notifies the charging control device 10. However, the charging control device 10 may execute the following process by regarding the temperature of the surrounding environment as the temperature of the cells of the battery 19 without acquiring the temperature of the cells of the battery 19 from the on-board circuit 18.

[0058] Then, the charge control device 10 estimates the internal resistance value of the battery 19 from the deterioration degree of the battery 19 and the temperature of the cells of the battery 19 (S13). 9. The charge control device 10 may estimate the internal resistance value of the battery 19 based on, for example, an internal resistance table in the main storage unit 102. The charge control device 10 may also estimate the internal resistance value of the battery 19 from, for example, a regression equation exemplified in (Equation 3).

[0059] FIG. 12 is a diagram illustrating the details of the current value change process (S7 in FIG. 10). In this process, the charge control device 10 detects the temperature of the cells of the battery 19 again by the temperature sensor 13 (S71). In S71, the procedure in which the charge control device 10 acquires the temperature of the cells of the battery 19 is similar to that in S12 in FIG. 11. Then, the charge control device 10 determines whether the cell temperature has increased by a change equal to or greater than a threshold (S72). The threshold is used to determine whether to change the current value of CC charging, and is determined, for example, experimentally or empirically.

[0060] If the cell temperature has not increased by a change equal to or greater than the threshold (NO in S72), the charge control device 10 determines whether the cell temperature has decreased by a change equal to or greater than the threshold (S74). If the cell temperature has not decreased by a change equal to or greater than the threshold (NO in S74), the charge control device 10 ends the process.

[0061] On the other hand, if the cell temperature is rising with a change of more than the threshold value (YES in S72), the charge control device 10 increases the current value of CC charging according to the cell temperature of the battery 19 (S73). If the cell temperature is falling with a change of more than the threshold value (YES in S74), the charge control device 10 reduces the current value of CC charging according to the cell temperature of the battery 19 (S75). The processes of S73 and S75 are similar to S2 in FIG.

[0062] For example, the charge control device 10 acquires the internal resistance value based on an internal resistance table or a regression equation according to the battery temperature. Then, the charge control device 10 may determine the increased or decreased CC charging current value from the relationship between the internal resistance value and the CC charging current value stored in the main storage unit 102. The charge control device 10 may also determine the CC charging current value by the process of Fig. 13 in the following modified example 1.

[0063] Then, the charge control device 10 sets the changed current value as a new current value for CC charging (S76). After that, the charge control device 10 ends the process and returns the process to CC charging in S3 of FIG.

[0064] The charging control device 10 may execute the above-described process of changing the current value of CC charging as a parallel process (independent process) executed in parallel with the process of Fig. 10. For example, the charging control device 10 may execute the process of Fig. 12 independently of Fig. 10 at a period required for monitoring the temperature of the cells of the battery 19. That is, in the process of Fig. 12, it may be desirable that the detection interval (S71) when the temperature of the cells of the battery 19 is detected again by the temperature sensor 13 is shorter than the determination interval of S4 in Fig. 10 for determining whether the battery voltage has reached the target voltage. If it is desirable that the detection interval of S71 is shorter than the determination interval of S4, the charging control device 10 may execute the process of Fig. 12 as a parallel process (independent process).

[0065] In this case, the process of executing the process of Fig. 12 in the charging control device 10 may transfer the new current value for CC charging to the process of executing the process of Fig. 10 in a shared memory or the like. The process of executing the process of Fig. 10 may read the determined current value from the shared memory in the process of S7 and set it as the current value for CC charging.

[0066] (Effects of the embodiment) As described above, the charging control device 10 performs CC charging at a constant current up to the target voltage, and then Then, CV charging is performed at a constant voltage. In such CCCV charging, the charge control device 10 estimates the internal resistance value of the battery 19 (S1 above). Then, the higher the internal resistance value is, the lower the value of the constant current is reduced to perform constant current charging (CC charging) (S2 above). Therefore, when the internal resistance value of the battery 19 is higher than the normal internal resistance value, the charge control device 10 can prevent the voltage at the terminals of the battery 19 from reaching the target voltage earlier in CC charging than in the normal state (when the internal resistance value is lower than the current value). As a result, the charge control device 10 can extend the period of CC charging compared to when the value of the constant current is not reduced. Furthermore, the charge control device 10 can prevent the time of CCCV charging, including the period of CC charging and the period of CV charging, from becoming longer.

[0067] Furthermore, the charge control device 10 estimates the internal resistance value of the battery 19 based on the cell temperature of the battery 19 and the deterioration level of the battery 19. Therefore, the charge control device 10 can accurately estimate the internal resistance value according to the deterioration level that depends on the number of times the battery 19 is charged and discharged, and the cell temperature that depends on the environment in which the battery 19 is used and the current, voltage, and other factors of the battery 19.

[0068] Furthermore, the charge control device 10 determines that the internal resistance value is higher as the temperature of the battery 19 is lower. Furthermore, the charge control device 10 determines that the internal resistance value is higher as the deterioration level of the battery 19 is higher. Therefore, the charge control device 10 can accurately determine the internal resistance value according to the physical characteristics of the battery 19.

[0069] Furthermore, according to this embodiment, as in S7 of Fig. 10, the charge control device 10 increases the value of the constant current in CC charging in response to an increase in the temperature of the battery 19 during charging. Also, the charge control device 10 decreases the value of the constant current in CC charging in response to a decrease in the temperature of the battery 19 during charging. That is, the charge control device 10 can flexibly reset the current value of CC charging in response to changes in the temperature of the cells of the battery 19. Note that, as already described, the process of S7 does not necessarily have to be executed. That is, the charge control device 10 may omit the process of S7 and execute the process of Fig. 10.

[0070] (Variation 1) In the above embodiment, the charge control device 10 performs CC charging by decreasing the current value of CC charging as the internal resistance value increases, as shown in Fig. 10. However, the charge control device 10 may calculate and estimate an appropriate current value of CC charging in the process of S2.

[0071] 13 is a diagram illustrating a process in which the charge control device 10 determines an appropriate current value for CC charging. In this process, the charge control device 10 calculates changes in current and voltage of the battery 19 by simulating the execution of CC charging and CV charging at multiple current values ​​for the current internal resistance R of the battery 19. Then, the charge control device 10 determines, from among the multiple current values, the current value that provides the shortest period for CCCV charging.

[0072] As a premise of the process of FIG. 13, the charge control device 10 is assumed to have current-voltage characteristics in CC charging and CV charging when the battery 19 has an internal resistance R0 in the initial stage of use. More specifically, the charge control device 10 is assumed to store the current value of the CC current at the internal resistance R0 of the battery 19 and the target voltage in the main storage unit 102. Such current-voltage characteristics can be determined, for example, for the actual battery 19. Such current-voltage characteristics may be obtained, for example, from performance information, specification information, etc. of the battery 19. Then, when the internal resistance value of the battery 19 changes from R0 to R, the charge control device 10 determines the current value by the following process.

[0073] First, the charge control device 10 stores the initial current value I0 and the current increment value ΔI in the main memory unit 102. (S21). Then, the charging control device 10 executes the following process in a loop within the range of variable K=0 to N-1 (S22). The initial current value I0, the current increment value ΔI, and the integer N are parameters that are given to the charging control device 10 before it executes the process of FIG.

[0074] That is, the charge control device 10 calculates the current value of CC charging as Icc=I0+k*ΔI (S23). Then, the charge control device 10 calculates the change in terminal voltage of the battery 19 when CC charging is performed at a current value Icc when the internal resistance value is changed from R0 to R. As described above, the charge control device 10 has current-voltage characteristics in CC charging and CV charging at an internal resistance R0. Therefore, the charge control device 10 may calculate that when the internal resistance becomes R, the terminal voltage in CC charging will reach the target voltage earlier by the increase in terminal voltage due to the increase in internal resistance=Icc*(R-R0).

[0075] Furthermore, when the voltage at the terminals of the battery 19 reaches the target voltage, the charge control device 10 simulates CV charging. Then, the charge control device 10 calculates the charging time Tk of CCCV charging and stores it in the main storage unit 102.

[0076] For CV charging, the charge control device 10 may first obtain the charge of the battery 19 at the end of CC charging by "Icc*CC charging time". Here, * is multiplication. After that, the charge control device 10 may further execute a simulation of CV charging until the charge of the battery 19 reaches the target charging state. After CC charging is completed, the terminal voltage of the battery 19 when the charging current is cut off is reduced by the terminal voltage increase due to the increase in internal resistance = Icc * (R-R0). Therefore, for CV charging, the charge control device 10 may calculate a charging time in which the terminal voltage decrease due to the increase in internal resistance = Icc * (R-R0) is added by the increase in charge during CV charging. Through such processing, the charge control device 10 may simulate CC charging and CV charging and calculate the charging time Tk of CCCV charging. Then, the charging control device 10 judges whether the variable k has become N-1 (S25). That is, the charging control device 10 judges whether the process has been looped for all current values ​​Icc=I0+k*ΔI. If the process has not been looped for all current values ​​Icc, the charging control device 10 returns the process to S22, increments k, and executes the process in the next loop.

[0077] When the process is completed for all the current values ​​Icc in the determination of S25, the charge control device 10 determines the shortest Tk and Icc among Tk (k=1 to N-1) (S26). Through the above process, the charge control device 10 can determine an appropriate current value Icc for CC charging when the internal resistance value of the battery 19 changes from R0 to R. As a result, even if the internal resistance value of the battery 19 changes, the charge control device 10 can perform CCCV charging in a shorter time or the shortest time. The total charging time of CCCV charging is the sum of a first time until the voltage of the storage battery reaches a target voltage by performing CC charging at a constant current, and a second time until the battery 19 reaches a target charge state by performing CV charging at a constant voltage. The charge control device 10 can set an appropriate current value Icc for CC charging so that this total time is within the target time.

[0078] The process of FIG. 13 can also be incorporated into S2 of FIG. 10 as a process for determining a CC current value according to the internal resistance value of the battery 19. In the above description, the process of FIG. 13 is executed by the charging control device 10. However, for example, a computer on a network may execute the process of FIG. 13. The charging control device 10 may pass the current deterioration level, cell temperature, or internal resistance value of the battery 19 to the computer on the network and request it to determine an appropriate CC charging current value. Here, the network may be, for example, , which is a network that the charging control device 10 can access via the general-purpose communication unit 106 or the PLC communication unit 107.

[0079] (Computer-readable recording medium) A program for causing a computer or other machine or device (hereinafter, referred to as a computer, etc.) to realize any of the above functions can be recorded on a recording medium readable by the computer, etc. Then, the computer, etc. can provide the function by reading and executing the program from the recording medium.

[0080] Here, a computer-readable recording medium refers to a recording medium that stores information such as data and programs through electrical, magnetic, optical, mechanical, or chemical action and can be read by a computer. Among such recording media, those that can be removed from a computer include, for example, flexible disks, magneto-optical disks, CDs (Compact Discs), DVDs (Digital Versatile Discs), Blu-ray discs, and memory cards such as flash memory. In addition, examples of recording media that are fixed to a computer include hard disks and ROMs (Read Only Memory). Furthermore, SSDs (Solid State Drives) ) can be used as a recording medium that can be removed from a computer or the like, or as a recording medium that is fixed to a computer or the like.

[0081] (Other) This embodiment can be said to include the following aspects (called supplementary notes). The following supplementary notes can be freely combined. (Appendix 1) A charge control device including a controller that controls a storage battery to be charged at a constant current up to a target voltage and then to be charged at a constant voltage, The controller estimates an internal resistance of the storage battery, and performs the constant current charging by decreasing a value of the constant current as the internal resistance increases. (Appendix 2) 2. The charge control device according to claim 1, wherein the controller estimates the internal resistance of the storage battery based on a temperature of the storage battery and a deterioration level of the storage battery. (Appendix 3) 3. The charge control device according to claim 1, wherein the controller estimates that the internal resistance is higher as the temperature of the storage battery is lower, and that the internal resistance is higher as the degree of degradation of the storage battery is higher. (Appendix 4) 4. The charge control device according to claim 1, wherein the controller increases a value of the constant current in response to an increase in temperature of the storage battery during charging. (Appendix 5) 5. The charge control device according to claim 1, wherein the controller reduces a value of the constant current in response to a decrease in temperature of the storage battery during charging. (Appendix 6) 6. The charging control device according to any one of appendixes 1 to 5, wherein the controller sets a value of the constant current so as to minimize a total time of a first time until the voltage of the storage battery reaches the target voltage by performing the constant current charging at the constant current, and a second time until the storage battery reaches a target charge state by performing the constant voltage charging at the constant voltage. (Appendix 7) A charging control method for controlling a storage battery to be charged at a constant current up to a target voltage and then to be charged at a constant voltage, comprising the steps of: A charging control method comprising: estimating an internal resistance of the storage battery; and performing the constant current charging by decreasing a value of the constant current as the internal resistance becomes higher. (Appendix 8) When charging a storage battery, a computer controls the charging so that the battery is charged at a constant current up to a target voltage, and then at a constant voltage. A program for estimating an internal resistance of the storage battery, and for performing the constant current charging by decreasing a value of the constant current as the internal resistance is higher. [Explanation of symbols]

[0082] 1 Charging System 1A electric vehicle 1B Charging equipment 11 Voltage Sensor 12 Current Sensor 13 Temperature Sensor 14 Power circuit 19 Battery 20 Commercial power supply 101 CPU 102 Main memory 103 External memory unit 104 Display section 105 Operation section 106 General Communication Department 107 PLC communication section

Claims

1. A charge control device including a controller that controls a storage battery to be charged at a constant current up to a target voltage and then to be charged at a constant voltage, The controller estimates an internal resistance of the storage battery, and performs the constant current charging by decreasing a value of the constant current as the internal resistance increases.

2. The charge control device according to claim 1 , wherein the controller estimates the internal resistance of the storage battery based on a temperature of the storage battery and a deterioration level of the storage battery.

3. The charge control device according to claim 1 , wherein the controller estimates that the internal resistance is higher as the temperature of the storage battery is lower, and that the internal resistance is higher as the deterioration level of the storage battery is higher.

4. The charge control device according to claim 1 , wherein the controller increases the value of the constant current in response to an increase in temperature of the storage battery during charging.

5. The charge control device according to claim 1 , wherein the controller reduces the value of the constant current in response to a decrease in temperature of the storage battery during charging.

6. 2. The charging control device according to claim 1, wherein the controller sets a value of the constant current so as to minimize a total time of a first time until the voltage of the storage battery reaches the target voltage by performing the constant current charging at the constant current and a second time until the storage battery reaches a target charging state by performing the constant voltage charging at the constant voltage.

7. A charging control method for controlling a storage battery to be charged at a constant current up to a target voltage and then to be charged at a constant voltage, comprising the steps of: A charging control method comprising: estimating an internal resistance of the storage battery; and performing the constant current charging by decreasing a value of the constant current as the internal resistance becomes higher.

8. When charging a storage battery, a computer controls the charging so that the battery is charged at a constant current up to a target voltage, and then at a constant voltage. A program for estimating an internal resistance of the storage battery, and performing the constant current charging by decreasing a value of the constant current as the internal resistance is higher.

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