State detection system, state detection device, and state detection method

Abstract

To suppress the influence of voltage changes due to loads and detect electrical discharges by an appropriate current value when detecting an internal resistance of a rechargeable battery.SOLUTION: A state detection system comprises: a discharge circuit for discharging a battery; an internal resistance estimation unit for estimating the internal resistance of the battery on the basis of the temperature, state, and reference resistance value of the battery; a setting unit for setting the discharge current value of a current flowing from the battery on the basis of at least one of a current change and a voltage change due to an internal resistance value and a load change; a discharge control unit for controlling the discharge circuit to discharge the battery so that a discharge is carried out by a prescribed current and the current of the discharge current value flows from the battery; an acquisition unit for acquiring the current and voltage values of a current flowing from the battery when a discharge from the battery is being carried out with a prescribed current; and a detection unit for detecting the internal resistance value of the battery on the basis of the current and voltage values acquired by the acquisition unit when the discharge from the battery is being carried out with the prescribed current.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a state detection system, a state detection device, and a state detection method.

Background Art

[0002] As inventions related to technologies for estimating the state of a rechargeable battery, there are, for example, the inventions disclosed in Patent Documents 1 and 2. The system disclosed in Patent Document 1 is a system for determining the degree of deterioration or discharge capacity of a battery using the impedance of the battery estimated from the current value and the response voltage when the battery is discharged in a predetermined discharge pattern, and forms a discharge pattern such that the response voltage at each discharge when the discharge is performed two or more times becomes substantially constant. The method disclosed in Patent Document 2 determines whether the battery is in a state of receiving either a charging polarization or a discharging polarization. When it is determined that the battery is receiving a charging polarization, a discharge current pulse with a variable period is applied to the battery, while when it is determined that the battery is receiving a discharging polarization, a charging current pulse with a variable period is applied to the battery. Then, the input current and the response voltage of the battery after a predetermined number of cycles have elapsed from the application start timing of the charging current pulse or the discharge current pulse are measured, and the internal impedance of the battery is calculated using the measured input current and response voltage.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, rechargeable batteries installed in actual vehicles come in various sizes and storage capacities. Such various batteries also have different internal resistances, and the voltage drop amounts when the same discharge current flows are also different. Further, when obtaining the internal resistance (impedance) of a battery from the current value and the response voltage when discharging at a predetermined discharge current, the voltage fluctuation due to load fluctuation in the predetermined discharge current for obtaining the internal resistance becomes a factor that greatly reduces the accuracy of the internal resistance. Regarding this load fluctuation, the equipment contents of the electrical components on the vehicle side also vary, and the degree of voltage fluctuation due to load fluctuation also varies. In order to ensure the accuracy of the internal resistance in such a situation, the current value of the predetermined discharge current may be set so that a sufficient voltage drop amount can be obtained even with the battery with the smallest assumed internal resistance and the vehicle with the largest assumed load fluctuation. However, this discharge consumes the power of the battery, and an excessive discharge current causes excessive power consumption, accelerating the battery degradation and battery deterioration. The inventions disclosed in Patent Documents 1 and 2 only estimate the internal impedance of the battery from the response when the battery is discharged and do not solve such problems.

[0005] The present invention has been made in view of the above, and an object thereof is to provide a technique for suppressing the influence of voltage fluctuation due to load and detecting with discharge at an appropriate current value when detecting the internal resistance of a rechargeable battery.

Means for Solving the Problems

[0006] In order to solve the above-described problems and achieve the object, a state detection system according to an aspect of the present invention is a state detection system that discharges the battery and detects the state of a rechargeable battery, and includes an internal resistance estimation unit that estimates an internal resistance value of the battery based on a temperature of the battery, a state of charge (SOC) of the battery, and a reference resistance value of the battery; a setting unit that sets a discharge current value of a current flowing from the battery based on the internal resistance value estimated by the internal resistance estimation unit and at least one of a current fluctuation and a voltage fluctuation due to a load fluctuation; a discharge control unit that controls the discharge circuit so that the battery is discharged at a predetermined current and a current having the discharge current value set by the setting unit flows from the battery; an acquisition unit that acquires a current value of a current flowing from the battery and a voltage value of the battery when the discharge from the battery is performed at the predetermined current; and a detection unit that detects the reference resistance value of the battery and the internal resistance value of the battery based on the current value and the voltage value acquired by the acquisition unit when the discharge from the battery is performed at the predetermined current.

[0007] In the state detection system according to an aspect of the present invention, the setting unit may set the discharge current value so that a voltage drop in the discharge circuit is within a predetermined range when the discharge from the battery is performed at the predetermined current.

[0008] In the state detection system according to an aspect of the present invention, the setting unit may set the discharge current value so that a voltage drop in the discharge circuit becomes greater than or equal to a predetermined threshold with respect to a voltage fluctuation due to a load current fluctuation when the discharge from the battery is performed at the predetermined current.

[0009] In the state detection system according to an aspect of the present invention, the setting unit may set a preset initial current value as the discharge current value at the time of the first discharge from the battery, and may set a current value at which a voltage drop in the discharge circuit is within a predetermined range as the discharge current value at the time of the second and subsequent discharges of the current from the battery.

[0010] In the state detection system according to one aspect of the present invention, when the voltage drop in the discharge circuit is excessive in the first discharge from the battery, the setting unit sets the discharge current value so that the voltage drop in the discharge circuit does not become excessive in the second and subsequent discharges of the current from the battery. When the voltage drop in the discharge circuit is too small in the first discharge from the battery, the discharge current value may be set so that the voltage drop in the discharge circuit does not become too small in the second and subsequent discharges from the battery.

[0011] In the state detection system according to one aspect of the present invention, when the voltage drop in the discharge circuit is too small in the first discharge from the battery, the detection unit may prevent the current value and voltage value acquired by the acquisition unit in the first discharge from being used for detecting the internal resistance value.

[0012] In the state detection system according to one aspect of the present invention, the discharge from the battery may be performed at a predetermined current and in a predetermined pattern.

[0013] In the state detection system according to one aspect of the present invention, the predetermined pattern may be a rectangular wave pattern.

[0014] The state detection apparatus according to the present invention is a state detection system that detects the state of a rechargeable battery, and includes an internal resistance estimation unit that estimates the internal resistance value of the battery based on the temperature of the battery, the state of charge (SOC) of the battery, and the reference resistance value of the battery; a setting unit that sets a discharge current value of the current flowing from the battery based on the internal resistance value estimated by the internal resistance estimation unit and at least one of current fluctuation and voltage fluctuation due to load fluctuation; a discharge control unit that controls a discharge circuit that discharges the battery so that the battery discharges at a predetermined current and the current having the discharge current value set by the setting unit flows from the battery; an acquisition unit that acquires the current value of the current flowing from the battery and the voltage value of the battery when the discharge from the battery is performed at a predetermined current; and a detection unit that detects the reference resistance value and the internal resistance value of the battery based on the current value and the voltage value acquired by the acquisition unit when the discharge from the battery is performed at a predetermined current.

[0015] The state detection method according to one aspect of the present invention is a state detection method for detecting the state of a rechargeable battery, and includes an internal resistance estimation step of estimating the internal resistance value of the battery based on the temperature of the battery, the state of charge (SOC) of the battery, and the reference resistance value of the battery; a setting step of setting the current value of the current flowing from the battery based on the internal resistance value estimated in the internal resistance estimation step and at least one of current fluctuation and voltage fluctuation due to load fluctuation; a discharge control step of controlling a discharge circuit that discharges the battery so that the battery discharges at a predetermined current and the current having the current value set in the setting step flows from the battery; an acquisition step of acquiring the current value of the current flowing from the battery and the voltage value of the battery when the discharge from the battery is performed at a predetermined current; and a detection step of detecting the reference resistance value and the internal resistance value of the battery based on the current value and the voltage value acquired in the acquisition step when the discharge from the battery is performed at a predetermined current.

Advantages of the Invention

[0016] According to the present invention, when detecting the internal resistance of a rechargeable battery, it is possible to suppress the influence of voltage fluctuations due to a load and perform detection by discharging with an appropriate current value.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

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Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Modes for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited by the embodiments described below. Also, in the description of the drawings, the same or corresponding elements are appropriately denoted by the same reference numerals.

[0019] [Embodiment] (Configuration of Embodiment) FIG. 1 is a diagram showing a power supply system of a vehicle V according to an embodiment of the present invention. The battery 20 is a rechargeable battery having an electrolytic solution, and is composed of, for example, a lead storage battery, a lithium ion battery, a nickel cadmium battery, or a nickel metal hydride battery. The battery 20 is charged by the alternator 25, drives the starter motor 27, and supplies power to the load 28. The starter motor 27 is composed of, for example, a DC motor, generates a rotational force by the power supplied from the battery 20, and starts the engine 26. The engine 26 is composed of, for example, a reciprocating engine such as a gasoline engine and a diesel engine, or a rotary engine. The engine 26 is started by the starter motor 27, drives the drive wheels via the transmission, gives a propulsive force to the vehicle VA, and drives the alternator 25. The alternator 25 is driven by the engine 26 to generate AC power, and the generated AC power is converted into DC power by a rectifier circuit to charge the battery 20. The load 28 is composed of, for example, an electric steering motor, a defroster, a seat heater, an ignition coil, a car audio, and a car navigation, and operates by the power supplied from the battery 20.

[0020] Also, the vehicle V includes an ECU (Electronic Control Unit) 3 which is a higher-level device that controls the main control of the drive system of the vehicle V, a state detection device 1 as a state detection system that detects the state of the battery 20, a voltage sensor 21, a current sensor 22, a temperature sensor 23, and a discharge circuit 24.

[0021] The voltage sensor 21, current sensor 22, and temperature sensor 23 are sensors used to detect the state of the battery 20. The voltage sensor 21 measures the terminal voltage of the battery 20 and outputs a signal indicating the measured voltage to the state detection device 1. The current sensor 22 measures the charging current and discharging current of the battery 20 and outputs a signal indicating the measured current to the state detection device 1. The temperature sensor 23 measures the temperature of the electrolyte of the battery 20 or the temperature around the battery 20 and outputs a signal indicating the measured temperature to the control unit 10.

[0022] The discharge circuit 24 is a circuit used to detect the state of the battery 20. Here, the discharge circuit 24 is a circuit different from the load 28 and is controlled independently of the load 28. The discharge circuit 24 is, for example, a circuit configured by connecting a semiconductor element and a resistor element, and discharges the battery 20 at a predetermined current value in response to control from the state detection device 1. Preferably, the battery 20 is discharged in a predetermined (e.g., rectangular wave) pattern. The predetermined pattern includes, for example, a pattern in which discharge is performed a predetermined number of times.

[0023] FIG. 2 is a diagram showing the circuit configuration of the discharge circuit 24. The discharge circuit 24 has a transistor TR1 and a resistor R11. The resistor R11 is a fixed resistor, one end of which is connected to the positive electrode of the battery 20 and the other end is connected to the collector of the transistor TR1. The transistor TR1 is an NPN-type transistor, the base of which is connected to the control unit 10, and the emitter of which is connected to one end of the shunt resistor SR. The shunt resistor SR is an example of the current sensor 22. One end of the shunt resistor SR is connected to the control unit 10 and the emitter of the transistor TR1, and the other end is connected to the negative electrode of the battery 20. In the discharge circuit 24, by changing the current value of the signal supplied by the control unit 10 to the base of the transistor TR1, the current value when discharging the battery 20 in a predetermined pattern can be changed.

[0024] The state detection device 1 acquires signals output from the voltage sensor 21, the current sensor 22, and the temperature sensor 23 when the battery 20 discharges in a predetermined pattern by the discharge circuit 24, and detects the state of the battery 20 based on the acquired signals. Note that the state detection device 1, the voltage sensor 21, the current sensor 22, the temperature sensor 23, and the discharge circuit 24 are not configured separately, and a configuration in which some or all of these are combined may be used as the state detection device.

[0025] FIG. 3 is a block diagram showing an example of the configuration of the state detection device 1. The state detection device 1 includes a control unit 10 including a CPU (Central Processing Unit) 10a, a ROM (Read Only Memory) 10b, and a RAM (Random Access Memory) 10c, a storage unit 11, a communication unit 12, an interface 13, and a bus 14. Note that the control unit 10 may be configured by a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), or a GPU (Graphics Processing Unit) instead of the CPU 10a. Here, all elements (control unit 10, storage unit 11, communication unit 12, interface 13) of the state detection device 1 do not have to be integrated, and for example, each element may be distributed inside the vehicle V as a state detection system.

[0026] The bus 14 is a group of signal lines that mutually connect the CPU 10a, the ROM 10b, the RAM 10c, the storage unit 11, the communication unit 12, and the interface 13 and enables the exchange of information between them. The communication unit 12 communicates with the ECU 3 and exchanges various information. The interface 13 converts and acquires signals supplied from the voltage sensor 21, the current sensor 22, and the temperature sensor 23 into digital signals, and outputs a control signal for controlling the discharge circuit 24.

[0027] The storage unit 11 is composed of a non-volatile memory and stores, for example, battery information. The battery information is, for example, the model number, part number, or size of the battery 20 mounted on the vehicle V. Note that the battery information may be any information that can uniquely identify the battery 20 mounted on the vehicle V. Further, the storage unit 11 stores a resistance value table TB1 and a current value table TB2. FIG. 4 is a diagram showing an example of the resistance value table TB1. The resistance value table TB1 stores the battery information in association with the reference resistance value of the battery 20 uniquely identified by the battery information. The reference resistance value is the internal resistance value of the battery 20 uniquely identified by the battery information, and is, for example, the internal resistance value in a reference state where the temperature is 25° C. and the SOC (State Of Charge) is 100%. FIG. 5 is a diagram showing an example of the current value table TB2. The current value table TB2 stores the internal resistance value of the battery 20 in association with the current value flowing from the battery 20 by a control signal. In the current value table TB2, the current value associated therewith decreases as the internal resistance value increases. Note that the relationship between the internal resistance value and the current value in the current value table TB2 is not limited to being linear and may be an inverse proportional relationship.

[0028] The ROM 10b is composed of a non-volatile semiconductor memory or the like and stores a program 10ba or the like. The RAM 10c is composed of a semiconductor memory or the like and stores data generated when the CPU 10a executes the program 10ba, the measurement results of the voltage sensor 21, the current sensor 22, and the temperature sensor 23, and various values calculated by the CPU 10a using these measurement results.

[0029] The CPU 10a controls each unit based on the program 10ba stored in the ROM 10b. The functions of the control unit 10 are realized as functional units by the CPU 10a reading and executing the program 10ba from the ROM 10b.

[0030] FIG. 6 is a functional block diagram showing the configuration of functions realized by the control unit 10 when the CPU 10a executes the program 10ba. In the control unit 10, an acquisition unit 101, an internal resistance estimation unit 102, a setting unit 103, a discharge control unit 104, and a state detection unit 105 are realized.

[0031] The acquisition unit 101 acquires the voltage value of the battery 20, the current value of the current flowing from the battery 20, and the temperature of the battery 20 indicated by the signals output from the voltage sensor 21, the current sensor 22, and the temperature sensor 23 and acquired by the interface 13. Further, the acquisition unit 101 acquires the battery information stored in the storage unit 11.

[0032] The internal resistance estimation unit 102 estimates the internal resistance value of the battery 20. Specifically, the internal resistance estimation unit 102 acquires a reference resistance value associated with the battery information acquired by the acquisition unit 101 from the resistance value table TB1. Next, the internal resistance estimation unit 102 estimates the internal resistance value (R_real) of the battery 20 using the following equations (1), (2), and (3).

[0033] First coefficient = a × exp(−T) + b ··· (1) Second coefficient = c × exp(−SOC) + d ··· (2) R_real = First coefficient × Second coefficient × R_STD ··· (3)

[0034] T in Equation (1) is the temperature represented by the signal acquired by the acquisition unit 101 from the temperature sensor 23. SOC in Equation (2) is the state of the battery 20, and is estimated, for example, by estimating the open circuit voltage of the battery 20 and estimating from the estimated open circuit voltage. R_STD in Equation (3) is the reference resistance value acquired from the resistance value table TB1 based on the battery information acquired by the acquisition unit 101.

[0035] Regarding the open-circuit voltage, for example, it can be estimated by using the approximate formula disclosed in Japanese Patent No. 4785056. Also, regarding the open-circuit voltage, the voltage between the terminals of the battery 20 measured by the voltage sensor 21 when the engine 26 is started, or the latest voltage between the terminals of the battery 20 measured periodically by the voltage sensor 21 and stored in the RAM 10c may be estimated as the open-circuit voltage. Further, the open-circuit voltage may be estimated based on the voltage between the terminals measured at the timing closest to the start of the engine 26, that is, the voltage between the terminals of the battery 20 measured immediately before the start of the engine 26. Regarding the SOC, it can be estimated by a well-known or publicly known method using the estimated open-circuit voltage.

[0036] The setting unit 103 sets the current value of the current flowing from the battery 20 when the discharge circuit 24 performs discharge in a predetermined pattern, using the internal resistance value R_real estimated by the internal resistance estimation unit 102 and the current value table TB2. Specifically, the setting unit 103 sets, as the current value of the current flowing from the battery 20 when the discharge circuit 24 performs discharge in a predetermined pattern, the current value associated with R_real estimated by the internal resistance estimation unit 102 in the current value table TB2. When the R_real estimated by the internal resistance estimation unit 102 is not stored in the current value table TB2, the setting unit 103 sets the current value associated with the internal resistance value closest to R_real in the current value table TB2.

[0037] The discharge control unit 104 controls the discharge circuit 24 by controlling the current value of the current flowing to the base of the transistor TR1 so that discharge is performed in a predetermined pattern in the battery 20 and the current of the current value set by the setting unit 103 flows from the battery 20.

[0038] The state detection unit 105 as an example of the detection unit calculates the internal resistance value of the battery 20 using the voltage value and current value of the battery 20 acquired by the acquisition unit 101 when the battery 20 is discharging in a predetermined pattern by the discharge circuit 24, and detects the state of the battery 20 based on the calculated internal resistance value. The internal resistance value of the battery 20 is obtained, for example, by the control unit 10 controlling the discharge circuit 24 to perform discharge on the battery 20 in a predetermined pattern, detecting the changes in the voltage and current of the battery 20 when the discharge is being performed in the predetermined pattern by the voltage sensor 21 and the current sensor 22, and calculating the internal resistance from the detection results. As a method of performing discharge in a predetermined pattern to calculate the internal resistance value, for example, there are methods disclosed in Japanese Patent No. 3960998 and Japanese Patent No. 4494904, but it may also be calculated by other known methods.

[0039] (Operation example of the embodiment) Next, an operation example of this embodiment will be described. FIG. 7 is a flowchart showing the flow of the process in which the control unit 10 detects the state of the battery 20. The control unit 10 executes the process shown in FIG. 7, for example, at a predetermined period or at a predetermined timing.

[0040] First, the control unit 10 determines whether the battery 20 is in the standby state (step S101). Here, when the engine 26 is stopped, the control unit 10 determines that it is in the standby state (YES in step S101). When the engine 26 is not stopped, the control unit 10 determines that it is not in the standby state (NO in step S101). Regarding the determination of whether the engine 26 is stopped, for example, the control unit 10 inquires the state of the engine 26 to the ECU3 via the communication unit 12. When a response of ignition off is obtained from the ECU3, it is determined that the engine 26 is in the stopped standby state and proceeds to step S102. When a response of ignition on is obtained from the ECU3, it is determined that the engine 26 is not in the stopped non-standby state and the process of FIG. 7 is terminated. Note that when the vehicle V is a hybrid vehicle, the ECU3 may set the state where the engine 26 and the electric motor are not operating as the standby state. When the vehicle V is an electric vehicle, the ECU3 may set the state where the electric motor is not operating as the standby state.

[0041] When the control unit 10 determines that it is in the standby state in step S101, it sets a discharge current value, which is the current value of the current flowing from the battery 20 when discharging is performed in a predetermined pattern (step S102). FIG. 8 is a flowchart showing the flow of the process of setting the discharge current value.

[0042] First, the control unit 10 acquires battery information (step S201). Next, the control unit 10 acquires the reference resistance value of the battery 20 using the acquired battery information and the resistance value table TB1 (step S202). Here, the control unit 10 acquires the reference resistance value associated with the acquired battery information from the resistance value table TB1, and sets the acquired resistance value as R_STD.

[0043] Next, the control unit 10 acquires the temperature and SOC of the battery 20 (step S203). Regarding the temperature of the battery 20, the control unit 10 acquires the temperature represented by the signal acquired by the acquisition unit 101 from the temperature sensor 23. Regarding the SOC, the control unit 10 acquires the open circuit voltage measured or estimated in advance by the aforementioned method, and estimates it by a well-known or publicly known method using the acquired open circuit voltage.

[0044] Next, the control unit 10 estimates the internal resistance value of the battery 20 using the reference resistance value acquired in step S202 and the temperature and SOC acquired in step S203 (step S204). Step S204 is an example of an internal resistance estimation step. Specifically, the control unit 10 substitutes the reference resistance value (R_STD) acquired in step S202 and the temperature acquired in step S203 into Equation (1) to calculate coefficient 1. Also, the control unit 10 substitutes the reference resistance value (R_STD) acquired in step S202 and the SOC acquired in step S203 into Equation (2) to calculate coefficient 2. Next, the control unit 10 substitutes the reference resistance value acquired in step S202, the calculated coefficient 1, and the calculated coefficient 2 into Equation (3) to calculate R_real, which is the internal resistance value of the battery 20.

[0045] Next, the control unit 10 sets the discharge current value using the internal resistance value estimated in step S204 (step S205). Step S205 is an example of a setting step. Specifically, the control unit 10 sets, as the discharge current value, the current value associated with the internal resistance value (R_real) estimated in step S204 in the current value table TB2. Note that when the R_real estimated in step S204 is not stored in the current value table TB2, the control unit 10 sets, as the discharge current value, the current value associated with the internal resistance value closest to the estimated R_real in the current value table TB2. Here, when the internal resistance value estimated in step S204 is small, the discharge current value becomes large, and when the internal resistance value is large, the discharge current value becomes small.

[0046] Returning to FIG. 7, the control unit 10 controls the discharge circuit 24 so that the battery 20 discharges in a predetermined pattern and the current of the discharge current value set in step S205 flows from the battery 20, and estimates the state of the battery 20 (step S103). Here, the control unit 10 controls the current value of the current flowing to the base of the transistor TR1 so that the current of the discharge current value set in step S205 flows from the battery 20, and discharges the battery 20 in a predetermined pattern. Further, here, the control unit 10 calculates the internal resistance value of the battery 20 using the voltage value and current value of the battery 20 acquired by the acquisition unit 101 when the battery 20 is discharging in a predetermined pattern by the discharge circuit 24, and detects the state of the battery 20 based on the calculated internal resistance value. The step of controlling the discharge circuit 24 in step S103 is an example of a discharge control step, and the step of the acquisition unit 101 acquiring the voltage value and current value of the battery 20 when the battery 20 is discharging in a predetermined pattern is an example of an acquisition step, and the step of calculating the internal resistance value of the battery 20 is an example of a detection step.

[0047] Here, as the internal resistance value estimated in step S204 becomes smaller, the discharge current value is set larger, and since the voltage change when the discharge is performed in a predetermined pattern becomes larger, even if the fluctuation of the output voltage to the load 28 is superimposed on the voltage of the predetermined pattern of discharge, the influence of the fluctuation on the voltage change of the discharge becomes smaller, and when calculating the internal resistance value of the battery 20 using the voltage value and current value of the battery 20, the influence of the fluctuation can be suppressed.

[0048] Next, the control unit 10 notifies the detection result of step S103 to the ECU 3 (step S104). The ECU 3 that has acquired the detection result of the state of the battery 20 notifies, for example, the state of the battery 20 on the instrument panel. Note that the notification of the state of the battery 20 is not limited to the notification on the instrument panel, and may be, for example, an alarm sound or voice. Further, these notifications may be performed at the timing when the accessory power supply is turned on in the vehicle V or at the timing of ignition on.

[0049] As described above, according to the present embodiment, by changing the discharge current value according to the internal resistance value of the battery 20, the voltage change during discharge is increased with respect to the fluctuation of the output voltage to the load 28. Therefore, the influence of the fluctuation on the voltage change during discharge is reduced, and when calculating the internal resistance value of the battery 20 using the voltage value and current value of the battery 20, the influence of the fluctuation can be suppressed. Further, when increasing the current value when discharging the battery in a predetermined discharge pattern, the influence of voltage fluctuation due to the load can be suppressed and the state can be detected accurately. However, when increasing the discharge current value, power is consumed, and there is a risk that the voltage of the battery will decrease and power cannot be supplied to the load. However, in the present embodiment, in a state where the charge rate is low and the internal resistance value is large, since the discharge current value is set small, power consumption of the battery 20 can be suppressed when calculating the internal resistance value.

[0050] Note that the process of step S202 for acquiring the reference resistance value may be acquired by the process of the flowchart shown in FIG. 9. Specifically, first, the control unit 10 acquires battery information (step S301). Next, the control unit 10 acquires the reference resistance value of the battery 20 using the acquired battery information and the resistance value table TB1 (step S302). Here, the control unit 10 acquires, as Rm, the reference resistance value associated with the acquired battery information from the resistance value table TB1 (step S302). Further, the control unit 10 acquires the internal resistance value calculated in the previous step S103 as Rpre (step S303).

[0051] When Rm - Rpre > C (YES in step S304), the control unit 10 sets R_STD = Rm (step S305). When Rm - Rpre > C is not satisfied (NO in step S304), the control unit 10 sets R_STD = Rm (step S306). Note that C is a predetermined constant. The control unit 10 estimates the internal resistance value of the battery 20 in step S204 using R_STD set in step S305 or step S306.

[0052] [Other Embodiments] In the above-described embodiment, the state detection device 1 provided in the vehicle V sets the current value of the current flowing from the battery 20 when the battery 20 discharges in a predetermined pattern and detects the state of the battery 20. However, these processes may be performed by the ECU 3. FIG. 10 is a block diagram showing the configuration of another embodiment of the state detection system.

[0053] The ECU 3 as an example of the state detection device has a control unit 30, a storage unit 31, an interface 33, and a bus (not shown). The control unit 30 has a CPU, a ROM, and a RAM, similar to the control unit 10. Note that the control unit 30 may be configured by a DSP, an FPGA, an ASIC, or the like instead of the CPU. The CPU, the ROM, the RAM, the storage unit 31, and the interface 33 are interconnected by a bus and exchange information therebetween. The storage unit 31 is composed of a non-volatile memory and stores, for example, a resistance value table TB1, a current value table TB2, and battery information.

[0054] The functions of the control unit 30 are realized as functional units by the CPU reading a program from the ROM and executing it. By executing the program stored in the ROM by the CPU, an acquisition unit 301, an internal resistance estimation unit 302, a setting unit 303, a discharge control unit 304, and a state detection unit 305 are realized in the control unit 30.

[0055] The acquisition unit 301 acquires the voltage value of the battery 20, the current value of the current flowing from the battery 20, and the temperature of the battery 20 indicated by the signals output from the voltage sensor 21, the current sensor 22, and the temperature sensor 23 and acquired by the interface 33. The acquisition unit 301 also acquires the battery information stored in the storage unit 31.

[0056] The internal resistance estimation unit 302 estimates the internal resistance value of the battery 20. Specifically, the internal resistance estimation unit 302 acquires a reference resistance value associated with the battery information acquired by the acquisition unit 301 from the resistance value table TB1. Next, the internal resistance estimation unit 302 estimates the internal resistance value (R_real) of the battery 20 in the same manner as the internal resistance estimation unit 102 using the above-described expressions (1), (2), and (3). Note that the open circuit voltage used for the estimation of SOC in Expression (2) may be acquired from the state detection device 1, or may be estimated using the voltage value transmitted from the state detection device 1.

[0057] The setting unit 303 sets the current value of the current flowing from the battery 20 when the discharge circuit 24 performs discharge in a predetermined pattern, using the R_real which is the internal resistance value estimated by the internal resistance estimation unit 302 and the current value table TB2. Specifically, the setting unit 303 sets, as the current value of the current flowing from the battery 20 when the discharge circuit 24 performs discharge in a predetermined pattern, the current value associated with the R_real estimated by the internal resistance estimation unit 302 in the current value table TB2. Note that when the R_real estimated by the internal resistance estimation unit 302 is not stored in the current value table TB2, the setting unit 303 sets the current value associated with the internal resistance value closest to R_real in the current value table TB2.

[0058] The discharge control unit 304 controls the current value of the current flowing to the base of the transistor TR1 so that the battery 20 discharges in a predetermined pattern and the current having the current value set by the setting unit 103 flows from the battery 20, thereby controlling the discharge circuit 24.

[0059] The state detection unit 305, in the same manner as the state detection unit 105, calculates the internal resistance value of the battery 20 using the voltage value and the current value of the battery 20 acquired by the acquisition unit 301 when the battery 20 discharges in a predetermined pattern by the discharge circuit 24, and detects the state of the battery 20 based on the calculated internal resistance value.

[0060] Even in this configuration, by changing the discharge current value according to the internal resistance value of the battery 20, the voltage change during discharge is made larger with respect to the variation in the output voltage to the load 28. Therefore, the influence of the variation on the voltage change during discharge is reduced, and when calculating the internal resistance value of the battery 20 using the voltage value and current value of the battery 20, the influence of the variation can be suppressed.

[0061] Also, in the present invention, when discharging is performed in a predetermined pattern by the battery 20, the server device connected to the communication network may be configured to set the current value of the current flowing from the battery 20 and detect the state of the battery 20. FIG. 11 is a block diagram showing the configuration of another embodiment of the state detection system.

[0062] The communication interface 5 is an interface that performs wireless communication via the communication network 1000 and is connected to the state detection device 1. The state detection device 1 is connected to the communication network 1000 via the communication interface 5 and exchanges information with the server device 4.

[0063] The server device 4 includes a control unit 40, a storage unit 41, a communication unit 42, a user interface 43, and a bus (not shown). The control unit 40 has a CPU, a ROM, and a RAM, similar to the control unit 10. The CPU, ROM, RAM, storage unit 41, communication unit 42, and user interface 43 are interconnected by a bus and exchange information therebetween. The communication unit 42 communicates with the state detection device 1 via the communication network 1000 and exchanges information with the state detection device 1. The storage unit 41 stores the resistance value table TB1 and the current value table TB2 described above. The user interface 43 has a mouse, a keyboard for inputting information, and a display device for displaying information. Note that the server device 4 may be configured not to have the user interface 43.

[0064] The functions of the control unit 40 are realized as functional units by the CPU reading and executing programs from the ROM. By executing the programs stored in the ROM, in the control unit 40, an acquisition unit 401, an internal resistance estimation unit 402, a setting unit 403, a discharge control unit 404, and a state detection unit 405 are realized.

[0065] The acquisition unit 401 acquires the voltage value, current value, and temperature that the acquisition unit 101 has acquired and transmitted from the state detection device 1 via the communication unit 42. Further, the acquisition unit 401 acquires the battery information that the acquisition unit 101 has acquired and transmitted from the state detection device 1 via the communication unit 42.

[0066] The internal resistance estimation unit 402 estimates the internal resistance value of the battery 20. Specifically, the internal resistance estimation unit 402 acquires the reference resistance value associated with the battery information acquired by the acquisition unit 401 from the resistance value table TB1 stored in the storage unit 41. Further, the internal resistance estimation unit 402 estimates the internal resistance value (R_real) of the battery 20 in the same manner as the internal resistance estimation unit 102 using the above-described equations (1), (2), and (3). Note that the open circuit voltage used for the estimation of the SOC in equation (2) may be acquired from the state detection device 1 or may be estimated using the voltage value transmitted from the state detection device 1.

[0067] The setting unit 403 sets the current value of the current flowing from the battery 20 when the discharge circuit 24 performs discharge in a predetermined pattern in the same manner as the setting unit 103 using the internal resistance value R_real estimated by the internal resistance estimation unit 402 and the current value table TB2 stored in the storage unit 41. Specifically, the setting unit 403 sets, as the current value of the current flowing from the battery 20 when the discharge circuit 24 performs discharge in a predetermined pattern, the current value associated with R_real estimated by the internal resistance estimation unit 402 in the current value table TB2. Note that when R_real estimated by the internal resistance estimation unit 402 is not stored in the current value table TB2, the setting unit 403 sets the current value associated with the internal resistance value closest to R_real in the current value table TB2.

[0068] The discharge control unit 404 transmits the current value set by the setting unit 403 to the state detection device 1 via the communication unit 42. The discharge control unit 104 of the state detection device 1 controls the current value of the current flowing to the base of the transistor TR1 so that the battery 20 discharges in a predetermined pattern and the current value of the current flowing from the battery 20 becomes the current value set by the setting unit 403, thereby controlling the discharge circuit 24.

[0069] The state detection unit 405 acquires the voltage value and current value of the battery 20 acquired by the acquisition unit 101 when the battery 20 is discharging in a predetermined pattern by the discharge circuit 24 from the state detection device 1 via the communication unit 42, calculates the internal resistance value of the battery 20 using the acquired voltage value and current value, and detects the state of the battery 20 based on the calculated internal resistance value.

[0070] FIG. 12 is a sequence diagram for explaining the operation of the state detection system having the configuration shown in FIG. 11. When the battery 20 is in the standby state, the state detection device 1 transmits battery information, the temperature measured by the temperature sensor 23, and the open circuit voltage of the battery 20 to the server device 4 via the communication interface 5 (step S11).

[0071] The server device 4 acquires the battery information, temperature, and open circuit voltage transmitted from the state detection device 1. The server device 4 acquires the reference resistance value associated with the acquired battery information from the resistance value table TB1 stored in the storage unit 41 (step S12). Next, the server device 4 estimates the internal resistance value of the battery 20 in the same manner as the internal resistance estimation unit 102 using the reference resistance value acquired in step S12, the temperature acquired in step S11, and the SOC estimated from the open circuit voltage acquired in step S11 (step S13). Next, the server device 4 sets the discharge current value using the internal resistance value estimated in step S13 and the current value table TB2 stored in the storage unit 41 (step S14). The server device 4 transmits the set discharge current value to the state detection device 1 (step S15).

[0072] The state detection device 1 acquires the discharge current value transmitted from the server device 4, and controls the discharge circuit 24 such that the battery 20 discharges in a predetermined pattern and the current of the discharge current value set in step S14 flows from the battery 20. Specifically, a signal of a current value corresponding to the acquired discharge current value is output to the base of the transistor TR1 (step S16). When the battery 20 discharges in a predetermined pattern by the discharge circuit 24, the state detection device 1 acquires the voltage value measured by the voltage sensor 21 and the current value measured by the current sensor 22 (step S17), and transmits the acquired voltage value and current value to the server device 4 (step S18).

[0073] The server device 4 acquires the voltage value and the current value transmitted from the server device 4, calculates the internal resistance value of the battery 20 using the acquired voltage value and current value, and detects the state of the battery 20 based on the calculated internal resistance value (step S19). The server device 4 transmits the detection result of the battery 20 to the ECU 3 (step S20).

[0074] Also in this configuration, by changing the discharge current value according to the internal resistance value of the battery 20, the voltage change of the discharge is made larger with respect to the fluctuation of the output voltage to the load 28, so that the influence of the fluctuation on the voltage change of the discharge becomes smaller. When calculating the internal resistance value of the battery 20 using the voltage value and the current value of the battery 20, the influence of the fluctuation can be suppressed. Note that the processing performed by the server device 4 may be executed by a terminal device such as a personal computer connected to the communication network 1000.

[0075] [Modification Example] The embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments and can be implemented in various other forms. For example, the present invention may be implemented by modifying the above-described embodiments as follows. Note that the above-described embodiments and the following modification examples may be combined with each other. The present invention also includes those configured by appropriately combining the constituent elements of the above-described embodiments and each modification example. Further, additional effects and modification examples can be easily derived by those skilled in the art. Therefore, a broader aspect of the present invention is not limited to the above-described embodiments and modification examples, and various changes are possible.

[0076] In the above-described embodiment, only the engine 26 outputs driving force in the vehicle V. However, the vehicle V may be, for example, a hybrid vehicle equipped with an electric motor that assists the engine 26 or an electric vehicle driven by an electric motor. In the case of an electric vehicle such as a hybrid vehicle or an electric vehicle, the battery 20 starts a high-voltage system (a system for driving the electric motor) configured by a lithium-ion battery or the like, and the high-voltage system starts the engine 26.

[0077] In the above-described embodiment, the state detection device 1 and the discharge circuit 24 are configured to be included in the vehicle V. However, a moving body such as a ship such as a motorboat, an aircraft such as a drone, an agricultural machine, or a construction machine may have the state detection device 1 and the discharge circuit 24. Further, those having the state detection device 1 and the discharge circuit 24 are not limited to moving bodies, and a device using the battery 20 in a gas, water supply, railway, communication, power facility, etc. may have the state detection device 1 and the discharge circuit 24.

[0078] In the above-described embodiment, the internal resistance estimation unit 102 may store a function representing the relationship between the internal resistance value and the current value stored in the current value table TB2, and estimate the internal resistance value using the stored function.

[0079] In the above-described embodiment, battery information is stored in the resistance value table TB1, but SOH (State of Health) may be stored instead of the battery information. When storing the SOH in the resistance value table TB1, the control unit 10 estimates the SOH and acquires the reference resistance value associated with the estimated SOH.

[0080] In the present invention, the control unit 10 may set the discharge current value stored in the current value table TB2 so that the voltage drop in the discharge circuit 24 when the discharge from the battery 20 is performed in a predetermined pattern is within a predetermined range. The upper limit of this predetermined range is a value at which the accuracy of calculating the internal resistance value saturates with respect to the change in current in the discharge in a predetermined pattern, and the lower limit is a value at which the accuracy required for calculating the internal resistance value can be obtained. For example, the lower limit of the predetermined range at which the accuracy required for calculating the internal resistance value can be obtained may be switched according to how much calculation accuracy is desired. For example, when it is desired to suppress the calculation accuracy of the resistance to ±10%, the current fluctuation of the vehicle load and the accompanying voltage fluctuation are observed and stored, and ΔV = R×I calculated from the internal resistance is set to be 10 times or more the voltage fluctuation due to the load fluctuation.

[0081] In the present invention, when the control unit 10 is to make the voltage drop in the discharge circuit 24 when the discharge from the battery 20 is performed in a predetermined pattern be within a predetermined range, for example, when discharging in a rectangular wave pattern, the discharge current value flowing from the battery 20 in the first discharge is set as a preset initial current value, and in the second and subsequent discharges, the discharge current value may be set so that the voltage drop in the discharge circuit 24 is within the predetermined range. The initial current value may be, for example, the median value or the average value of the current values stored in the current value table TB2. Also, the initial current value may be the lower limit value of the above-described predetermined range.

[0082] In the present invention, when the control unit 10 discharges from the battery 20 in a predetermined pattern of a rectangular wave, if the voltage drop in the discharge circuit 24 is excessive in the first discharge, the discharge current value is set so that the voltage drop in the discharge circuit 24 does not become excessive in the second and subsequent discharges. If the voltage drop in the discharge circuit 24 is too small in the first discharge, the discharge current value may be set so that the voltage drop in the discharge circuit 24 does not become too small in the second and subsequent discharges. Specifically, when the control unit 10 discharges from the battery 20 in a predetermined pattern of a rectangular wave, if the voltage drop in the discharge circuit 24 is excessive and equal to or greater than a predetermined first threshold value in the first discharge, the discharge current value is set so that the voltage drop in the discharge circuit 24 is less than the first threshold value in the second and subsequent discharges. If the voltage drop in the discharge circuit 24 is too small and less than a predetermined second threshold value smaller than the first threshold value in the first discharge, the discharge current value may be set so that the voltage drop in the discharge circuit 24 is equal to or greater than the second threshold value in the second and subsequent discharges.

[0083] In the present invention, when the control unit 10 discharges from the battery 20 in a predetermined pattern of a rectangular wave, if the voltage drop in the discharge circuit 24 is excessively large as predetermined in the first discharge, the voltage value acquired from the voltage sensor 21 and the current value acquired from the current sensor 22 during this discharge may not be used for calculating the internal resistance value of the battery 20. Specifically, when the voltage drop in the discharge circuit 24 is excessively large and equal to or greater than a predetermined first threshold value in the first discharge, the voltage value acquired from the voltage sensor 21 and the current value acquired from the current sensor 22 during this discharge may not be used for calculating the internal resistance value of the battery 20.

[0084] In the present invention, the circuit configuration of the discharge circuit for discharging the battery 20 in a predetermined pattern is not limited to the configuration shown in FIG. 2. FIG. 13 is a diagram showing the circuit configuration of a discharge circuit 24A which is a modified example of the discharge circuit 24.

[0085] The discharge circuit 24A includes resistors R11 to R14, which are an example of a resistive element, and FETs (Field Effect Transistors) 51 to 54, which are an example of a switching element. Resistors R11 to R14 are fixed resistors. The resistance values of resistors R11 to R14 are different from each other, and the resistance value of resistor R11 < the resistance value of resistor R12 < the resistance value of resistor R13 < the resistance value of resistor R14. Due to the different resistance values of resistors R11 to R14, for example, the current value of the current flowing through resistor R12 is less than or equal to twice the current value of the current flowing through resistor R11, the current value of the current flowing through resistor R13 is less than or equal to twice the current value of the current flowing through resistor R12, and the current value of the current flowing through resistor R14 is less than or equal to twice the current value of the current flowing through resistor R13. One end of resistors R11 to R14 is connected to the positive electrode of the battery 20. The other end of resistor R11 is connected to the drain of FET51, the other end of resistor R12 is connected to the drain of FET52, the other end of resistor R13 is connected to the drain of FET53, and the other end of resistor R14 is connected to the drain of FET54.

[0086] FETs 51 to 54 are N-channel MOS (Metal Oxide Semiconductor) type field effect transistors. The gates of FETs 51 to 54 are connected to the control unit 10, and the sources are connected to the shunt resistor SR. FETs 51 to 54 turn on or off according to the voltage applied to the gate from the control unit 10 described later. In the discharge circuit 24, current flows through the FET that is turned on by the control unit 10 and the resistor connected to the turned-on FET.

[0087] The shunt resistor SR is an example of a current sensor 22. One end of the shunt resistor SR is connected to the control unit 10 and the sources of FETs 51 to 54, and the other end is connected to the control unit 10 and the negative electrode of the battery 20.

[0088] When the vehicle V is equipped with the discharge circuit 24A, the control unit 10 selects, based on the discharge current value set in step S205, an FET to be used to discharge the battery 20 at the set discharge current value from among the FETs 51 to 54, and discharges the battery 20 in a predetermined pattern by turning the selected FET on and off. For example, when the control unit 10 selects any one of the FETs 51 to 54 to discharge the battery 20 in a predetermined pattern, the battery 20 discharges through the resistor connected to the selected FET, the selected FET, and the shunt resistor SR. Also, when the control unit 10 selects a plurality of FETs from among the FETs 51 to 54 to discharge the battery 20 in a predetermined pattern, the battery 20 discharges through a plurality of paths including the selected FETs. In this case, since the resistors R11 to R14 are in parallel, the discharge current becomes a discharge current corresponding to the combined resistance of the paths including the turned-on FETs. In the discharge circuit 24A, the number of sets of series resistors and FETs may be two, three, or five or more. However, since having a large number of sets of series resistors and FETs increases the cost and complicates the control, the number of sets of series resistors and FETs is preferably 2 to 4.

[0089] When the path for flowing the set discharge current value is not in the discharge circuit 24A, the control unit 10 selects one or more FETs capable of discharging the battery 20 at a current value closest to the set discharge current value, and discharges the battery 20 in a predetermined pattern by turning the selected FET on and off.

[0090] In the above-described embodiment, when the control unit 10 outputs a PWM signal to the base of the transistor TR1 and changes the duty ratio of the PWM signal, the current value when discharging the battery 20 in a predetermined pattern may be controlled.

Explanation of Reference Numerals

[0091] 1 State detection device 3 ECU 10 Control unit 11 Storage unit 12 Communication unit 13 Interface 14 Bus 20 Battery 21 Voltage Sensor 22 Current Sensor 23 Temperature Sensor 24 Discharge Circuit 28 Load 101, 301, 401 Acquisition Unit 102, 302, 402 Internal Resistance Estimation Unit 103, 303, 403 Setting Unit 104, 304, 404 Discharge Control Unit 105, 305, 405 State Detection Unit V Vehicle

Claims

1. A state detection system for detecting the state of a rechargeable battery, comprising: a discharge circuit for discharging the battery; an internal resistance estimation unit for estimating an internal resistance value of the battery based on a temperature of the battery, a state of charge (SOC) of the battery, and a reference resistance value of the battery; a setting unit for setting a discharge current value of a current flowing from the battery based on the internal resistance value estimated by the internal resistance estimation unit and at least one of a current fluctuation and a voltage fluctuation due to a load fluctuation; a discharge control unit for controlling the discharge circuit so that the battery is discharged at a predetermined current and a current having the discharge current value set by the setting unit flows from the battery; an acquisition unit for acquiring a current value of a current flowing from the battery and a voltage value of the battery when the discharge from the battery is performed at a predetermined current; a detection unit for detecting the reference resistance value and the internal resistance value of the battery based on the current value and the voltage value acquired by the acquisition unit when the discharge from the battery is performed at a predetermined current; A state detection system comprising the above.

2. The setting unit sets the discharge current value so that a voltage drop in the discharge circuit is within a predetermined range when the discharge from the battery is performed at the predetermined current. The state detection system according to Claim 1.

3. The setting unit sets the discharge current value so that the voltage drop in the discharge circuit becomes greater than or equal to a predetermined threshold with respect to a voltage fluctuation due to a load current fluctuation when the discharge from the battery is performed at the predetermined current. The state detection system according to Claim 2.

4. When performing the first discharge from the battery, the setting unit sets a preset initial current value as the discharge current value, and when performing the second and subsequent discharges from the battery, the setting unit sets a current value at which the voltage drop in the discharge circuit is within a predetermined range as the discharge current value. The state detection system according to Claim 2.

5. When the voltage drop in the discharge circuit is excessive during the first discharge from the battery, the setting unit sets the discharge current value so that the voltage drop in the discharge circuit does not become excessive during the second and subsequent discharges from the battery. When the voltage drop in the discharge circuit is too small during the first discharge from the battery, the setting unit sets the discharge current value so that the voltage drop in the discharge circuit does not become too small during the second and subsequent discharges from the battery. The state detection system according to claim 4.

6. When the voltage drop in the discharge circuit is too small during the first discharge from the battery, the detection unit does not use the current value and voltage value acquired by the acquisition unit during the first discharge for detecting the internal resistance value. The state detection system according to claim 4.

7. The discharge from the battery is performed at a predetermined current and in a predetermined pattern. The state detection system according to claim 1.

8. The predetermined pattern is a rectangular wave pattern. The state detection system according to claim 7.

9. A state detection device for detecting the state of a rechargeable battery, comprising: An internal resistance estimation unit that estimates the internal resistance value of the battery based on the temperature of the battery, the state of charge (SOC) of the battery, and the reference resistance value of the battery; A setting unit that sets the current value of the current flowing from the battery based on the internal resistance value estimated by the internal resistance estimation unit and at least one of the current fluctuation and voltage fluctuation due to load fluctuation; A discharge control unit that controls a discharge circuit that discharges the battery so that the discharge from the battery is performed at a predetermined current and the current of the current value set by the setting unit flows from the battery; An acquisition unit that acquires the current value of the current flowing from the battery and the voltage value of the battery when the discharge from the battery is performed at a predetermined current; A detection unit that detects the reference resistance value and the internal resistance value of the battery based on the current value and voltage value acquired by the acquisition unit when the discharge from the battery is performed at a predetermined current; A state detection device comprising the above.

10. A state detection method for detecting the state of a rechargeable battery, comprising an internal resistance estimation step of estimating an internal resistance value of the battery based on the temperature of the battery, the state of charge (SOC) of the battery, and a reference resistance value of the battery; a setting step of setting a current value of a current flowing from the battery based on the internal resistance value estimated in the internal resistance estimation step and at least one of a current fluctuation and a voltage fluctuation due to a load fluctuation; a discharge control step of discharging the battery by controlling a discharge circuit that discharges the battery so that the battery discharges at a predetermined current and the current having the current value set in the setting step flows from the battery; an acquisition step of acquiring a current value of a current flowing from the battery and a voltage value of the battery when the discharge from the battery is performed at a predetermined current; a detection step of detecting a reference resistance value and an internal resistance value of the battery based on the current value and the voltage value acquired in the acquisition step when the discharge from the battery is performed at a predetermined current; A state detection method comprising the above steps.

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