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

Abstract

When detecting the internal resistance of a rechargeable battery, the system minimizes the effects of voltage fluctuations caused by the load and detects the resistance by discharging at an appropriate current value. [Solution] A state detection system for detecting the state of a battery, comprising: a discharge circuit for discharging the battery; a setting unit for setting a discharge current value for the current to flow from the battery; a discharge control unit for discharging the battery by controlling the discharge circuit so that a current of the discharge current value set by the setting unit flows from the battery; an acquisition unit for acquiring the current value of the current flowing from the battery and the voltage value of the battery when the battery is being discharged by the discharge circuit; and an internal resistance estimation unit for estimating the internal resistance value of the battery based on the acquired current value and voltage value. The setting unit determines whether the discharge of the battery by the discharge control unit is appropriate based on the voltage value acquired by the acquisition unit, or the current value acquired by the acquisition unit and the internal resistance value estimated by the internal resistance estimation unit, and resets the discharge current value if it is not appropriate.

Description

Technical Field

[0004] , ,

[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 with a predetermined discharge waveform, and forms a discharge waveform so 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 charging polarization or discharging polarization, and when it is determined that the battery is receiving charging polarization, applies a discharge current pulse with a variable period to the battery, while when it is determined that the battery is receiving discharging polarization, applies a charging current pulse with a variable period 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

[0005] The present invention has been made in view of the above, and aims to provide a technology for detecting the internal resistance of a rechargeable battery by suppressing the influence of voltage fluctuations due to load and detecting it by discharging with an appropriate current value. [Means for solving the problem]

[0006] To solve the above-mentioned problems and achieve the objective, a state detection system according to one aspect of the present invention is a state detection system for detecting the state of a rechargeable battery, comprising: a discharge circuit for discharging the battery; a setting unit for setting a discharge current value of the current to flow from the battery; a discharge control unit for discharging the battery by controlling the discharge circuit so that a current of the discharge current value set by the setting unit flows from the battery; an acquisition unit for acquiring the current value of the current flowing from the battery and the voltage value of the battery when the battery is being discharged by the discharge circuit; and an internal resistance estimation unit for estimating the internal resistance value of the battery based on the current value and voltage value acquired by the acquisition unit, wherein the setting unit determines whether the discharge of the battery by the discharge control unit is appropriate based on the voltage value acquired by the acquisition unit, or the current value acquired by the acquisition unit and the internal resistance value estimated by the internal resistance estimation unit, and resets the discharge current value if it is not appropriate.

[0007] In a state detection system according to one aspect of the present invention, the setting unit may set the discharge current value such that, if the amount of voltage change when the battery is being discharged at the discharge current value is greater than or equal to a predetermined threshold, the amount of voltage change becomes less than the predetermined threshold.

[0008] In a state detection system according to one aspect of the present invention, the setting unit may set the discharge current value to a larger value if the voltage change when the battery is being discharged at the discharge current value is insufficient for the voltage change due to discharge to a load powered by the battery.

[0009] The state detection device according to the present invention is a state detection device for detecting the state of a rechargeable battery, and comprises: a discharge circuit for discharging the battery; a setting unit for setting a discharge current value of the current to flow from the battery; a discharge control unit for discharging the battery by controlling the discharge circuit so that a current of the discharge current value set by the setting unit flows from the battery; an acquisition unit for acquiring the current value of the current flowing from the battery and the voltage value of the battery when the battery is being discharged by the discharge circuit; and an internal resistance estimation unit for estimating the internal resistance value of the battery based on the current value and voltage value acquired by the acquisition unit, wherein the setting unit determines whether the discharge of the battery by the discharge control unit is appropriate based on the voltage value acquired by the acquisition unit, or the current value acquired by the acquisition unit and the internal resistance value estimated by the internal resistance estimation unit, and resets the discharge current value if it is not appropriate.

[0010] A state detection method according to one aspect of the present invention is a state detection method for detecting the state of a rechargeable battery, comprising: a setting step of setting a discharge current value of the current to flow from the battery; a discharge control step of discharging the battery by controlling a discharge circuit that discharges the battery so that a current of the discharge 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 battery is being discharged by the discharge control step; and an internal resistance estimation step of estimating the internal resistance value of the battery based on the current value and voltage value acquired in the acquisition step, wherein the setting step determines whether the discharge of the battery by the discharge control step is appropriate based on the voltage value acquired in the acquisition step, or the current value acquired in the acquisition step and the internal resistance value estimated in the internal resistance estimation step, and resets the discharge current value if it is not appropriate. [Effects of the Invention]

[0011] According to the present invention, when detecting the internal resistance of a rechargeable battery, the influence of voltage fluctuations due to the load can be suppressed, and detection can be performed by discharging with an appropriate current value. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 shows the power supply system of a vehicle according to an embodiment. [Figure 2] Figure 2 shows the circuit configuration of the discharge circuit. [Figure 3] Figure 3 is a block diagram showing an example of the configuration of a state detection device. [Figure 4] Figure 4 is a functional block diagram showing the configuration of the functions implemented in the control unit. [Figure 5] Figure 5 is a flowchart showing the processing flow performed by the control unit. [Figure 6] Figure 6 is a flowchart showing the processing flow performed by the control unit. [Figure 7A] Figure 7A shows an example of the change in current value due to discharge to a load. [Figure 7B] Figure 7B shows an example of the change in current value when a battery is discharged by a discharge circuit. [Figure 7C] Figure 7C shows an example of the change in the current value acquired by the acquisition unit. [Figure 8A] Figure 8A shows an example of the change in voltage value due to discharge to a load. [Figure 8B] Figure 8B shows an example of the change in voltage value when a battery is discharged by a discharge circuit. [Figure 8C] Figure 8C shows an example of the change in voltage value acquired by the acquisition unit. [Figure 9A] Figure 9A shows an example of the change in current value due to discharge to a load. [Figure 9B] Figure 9B shows an example of the change in current value when a battery is discharged by a discharge circuit. [Figure 9C] Figure 9C shows an example of the change in current value acquired by the acquisition unit. [Figure 10] Figure 10 is a flowchart showing the processing flow performed by the control unit. [Figure 11] FIG. 11 is a block diagram showing the configuration of another embodiment of the state detection system. [Figure 12] FIG. 12 is a block diagram showing the configuration of another embodiment of the state detection system. [Figure 13] FIG. 13 is a sequence diagram for explaining the operation of the state detection system. **[Embodiments for Carrying Out the Invention]**

[0013] Hereinafter, embodiments of the present invention will be described in detail based on the drawings. Note that the present invention is not limited to the embodiments described below. Also, in the description of the drawings, the same or corresponding elements are appropriately denoted by the same reference numerals.

[0014] [Embodiment] (Configuration of the Embodiment) FIG. 1 is a diagram showing the power supply system of a vehicle V according to an embodiment of the present invention. The battery 20 is a rechargeable battery having an electrolyte, and is constituted by, for example, a lead-acid 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 constituted by, 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 constituted by, 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 driving force to the vehicle V, and drives the alternator 25. The alternator 25 is driven by the engine 26 to generate AC power, converts the generated AC power into DC power by a rectifier circuit, and charges the battery 20. The load 28 is constituted by, for example, an electric steering motor, a defogger, a seat heater, an ignition coil, a car audio, and a car navigation, and operates by the power supplied from the battery 20.

[0015] Furthermore, vehicle V includes an ECU (Electronic Control Unit) 3, which is a higher-level device that controls the main aspects of the vehicle V's drive system; a state detection device 1, which is 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.

[0016] 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 electrolyte temperature of the battery 20 or the temperature of the surrounding area of ​​the battery 20 and outputs a signal indicating the measured temperature to the control unit 10.

[0017] The discharge circuit 24 is a circuit used to detect the state of the battery 20. Here, the discharge circuit 24 is a separate circuit 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 resistive 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 with a predetermined waveform (for example, a rectangular wave). The predetermined waveform includes, for example, a waveform that performs discharge a predetermined number of times.

[0018] Figure 2 shows the circuit configuration of the discharge circuit 24. The discharge circuit 24 includes a transistor TR1 and a resistor R11. The resistor R11 is a fixed resistor, with one end connected to the positive terminal of the battery 20 and the other end connected to the collector of transistor TR1. Transistor TR1 is an NPN type transistor, with its base connected to the control unit 10 and its emitter connected to one end of a shunt resistor SR. 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 emitter of transistor TR1, and the other end is connected to the negative terminal of the battery 20. In the discharge circuit 24, the current value when discharging the battery 20 with a predetermined waveform can be changed by changing the current value of the signal supplied by the control unit 10 to the base of transistor TR1.

[0019] The state detection device 1 acquires signals output from the voltage sensor 21, current sensor 22, and temperature sensor 23 when the battery 20 is discharged by the discharge circuit 24 in a predetermined waveform, and detects the state of the battery 20 based on the acquired signals. Note that the state detection device may be a combination of some or all of the following components, rather than being configured separately: the state detection device 1, voltage sensor 21, current sensor 22, temperature sensor 23, and discharge circuit 24.

[0020] Figure 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 containing 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. The control unit 10 may be configured with a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), or a GPU (Graphics Processing Unit) instead of the CPU 10a. Here, each element of the state detection device 1 (control unit 10, storage unit 11, communication unit 12, interface 13) does not need to be grouped together; for example, each element may be distributed inside the vehicle V as a state detection system.

[0021] Bus 14 is a group of signal lines that interconnect the CPU 10a, ROM 10b, RAM 10c, storage unit 11, communication unit 12, and interface 13, enabling the exchange of information between them. The communication unit 12 communicates with the ECU 3 and exchanges various types of information. Interface 13 converts signals supplied from the voltage sensor 21, current sensor 22, and temperature sensor 23 into digital signals and acquires them, and also outputs control signals to control the discharge circuit 24.

[0022] The memory unit 11 is composed of non-volatile memory and stores, for example, the current value (discharge current value) of the current flowing from the battery 20 when the battery 20 is discharged by the discharge circuit 24 in a predetermined waveform. The discharge current value initially stored in the memory unit 11 is a preset value. The memory unit 11 also stores the internal resistance value of the battery 20. The internal resistance value initially stored in the memory unit 11 is the internal resistance value of the battery 20 that has been measured in advance. If the control unit 10 resets the discharge current value through a process described later, the discharge current value stored in the memory unit 11 is updated to the reset discharge current value. Also, if the control unit 10 estimates the internal resistance value through a process described later, the internal resistance value stored in the memory unit 11 is updated to the estimated internal resistance value.

[0023] ROM 10b is composed of non-volatile semiconductor memory and stores the program 10ba, etc. RAM 10c is composed of semiconductor memory and stores data generated when the CPU 10a executes the program 10ba, measurement results from the voltage sensor 21, current sensor 22, and temperature sensor 23, and various values ​​calculated by the CPU 10a using these measurement results.

[0024] The CPU 10a controls each part based on the program 10ba stored in the ROM 10b. The functions of the control unit 10 are realized as a functional unit when the CPU 10a reads and executes the program 10ba from the ROM 10b.

[0025] Figure 4 is a functional block diagram showing the configuration of the functions realized in the control unit 10 when the CPU 10a executes the program 10ba. The control unit 10 realizes the acquisition unit 101, the internal resistance estimation unit 102, the setting unit 103, the discharge control unit 104, and the state detection unit 105.

[0026] 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, as indicated by the signals output from the voltage sensor 21, current sensor 22, and temperature sensor 23 and acquired by the interface 13. The acquisition unit 101 also acquires the discharge current value and internal resistance value stored in the storage unit 11.

[0027] The internal resistance estimation unit 102 estimates the internal resistance of the battery 20 based on the voltage and current values ​​acquired by the acquisition unit 101. The internal resistance of the battery 20 is obtained, for example, by the control unit 10 controlling the discharge circuit 24 to discharge the battery 20 in a predetermined waveform (e.g., a rectangular wave), detecting the changes in voltage and current at that time using the voltage sensor 21 and the current sensor 22, and calculating the internal resistance from the detection results. The predetermined waveform includes, for example, a waveform used when discharging a predetermined number of times. Methods for calculating such an internal resistance include, for example, the method disclosed in Japanese Patent Publication No. 3960998 and the method disclosed in Japanese Patent Publication No. 4494904, but it may also be calculated using other known methods. The internal resistance may also be an estimated value calculated from the voltage and current values ​​when the engine 26 is started. The open-circuit voltage can be estimated using, for example, the approximation formula disclosed in Japanese Patent Publication No. 4785056. Furthermore, the open-circuit voltage may be estimated as the terminal voltage of the battery 20 measured by the voltage sensor 21 when the engine 26 or electric motor is started, or the most recent terminal voltage of the battery 20 measured periodically by the voltage sensor 21 and stored in the RAM 10c. Alternatively, the open-circuit voltage may be estimated based on the terminal voltage measured at the timing closest to when the engine 26 or electric motor is started, that is, the terminal voltage of the battery 20 measured immediately before the engine 26 or electric motor is started.

[0028] The setting unit 103 sets the discharge current value, which is the current value that flows from the battery 20 when the battery 20 is discharged by the discharge circuit 24 in a predetermined waveform. Specifically, the setting unit 103 determines whether the discharge of the battery 20 by the discharge control unit 104 is appropriate based on the voltage value acquired by the acquisition unit 101, or the current value acquired by the acquisition unit 101 and the internal resistance value stored in the storage unit 11, and resets the discharge current value if it is not appropriate.

[0029] The discharge control unit 104 controls the discharge circuit 24 by controlling the current value of the current flowing to the base of transistor TR1 so that the battery 20 discharges with a predetermined waveform and a current of the discharge current value set by the setting unit 103 flows from the battery 20. By controlling the discharge circuit 24, the battery 20 is discharged at a predetermined current value for measuring the internal resistance value of the battery 20.

[0030] As an example of a detection unit, the state detection unit 105 detects the state of the battery 20 based on the internal resistance value estimated by the internal resistance estimation unit 102.

[0031] (Example of operation of the embodiment) Next, an example of operation of this embodiment will be described. Figure 5 is a flowchart showing the process flow for the control unit 10 to detect the state of the battery 20. First, the control unit 10 determines whether the vehicle V is in a standby state (step S101). Here, the control unit 10 determines that the vehicle is in a standby state if the engine 26 is stopped (step S101: YES), and determines that the vehicle is not in a standby state if the engine 26 is not stopped (step S101: NO). Regarding the determination of whether the engine 26 is stopped or not, for example, the control unit 10 queries the ECU 3 for the state of the engine 26 via the communication unit 12. If it receives a response of "ignition off" from the ECU 3, it determines that the vehicle is in a standby state with the engine 26 stopped and proceeds to step S102. If it receives a response of "ignition on" from the ECU 3, it determines that the vehicle is in a non-standby state with the engine 26 not stopped and terminates the process in Figure 5. Furthermore, if vehicle V is a hybrid vehicle, ECU3 may set the state where the engine 26 and electric motor are not operating to standby mode, and if vehicle V is an electric vehicle, ECU3 may set the state where the electric motor is not operating to standby mode.

[0032] If the control unit 10 determines in step S101 that it is in a standby state, it determines whether it is time for the discharge control unit 104 to control the discharge circuit 24 to measure the internal resistance of the battery 20 and discharge the battery 20 with a predetermined waveform at a predetermined period (step S102). If it is not time for the battery 20 to discharge with the predetermined waveform (step S102: NO), the control unit 10 returns the process to step S101.

[0033] If it is time to discharge the battery 20 with a predetermined waveform (step S102: YES), the control unit 10 acquires the discharge current value stored in the storage unit 11 (step S103). Next, the control unit 10 discharges the battery 20 with a predetermined current value using a predetermined waveform and acquires the voltage and current values ​​while the battery 20 is being discharged (step S104). Step S104 is an example of a discharge control step. Step S104 is also an example of an acquisition step. Here, the control unit 10 controls the current value of the current flowing to the base of transistor TR1 so that the current of the discharge current value acquired in step S103 flows from the battery 20, and controls the discharge circuit 24 so that the discharge from the battery 20 is performed with a predetermined waveform. Also, here, the control unit 10 samples and stores the voltage value and current value of the battery 20 acquired by the acquisition unit 101 while the battery 20 is being discharged by the discharge circuit 24 with a predetermined waveform.

[0034] Figure 7A is a graph showing an example of the change in current value due to discharge to load 28, where the current value changes at time t11 when discharge to load 28 occurs. Figure 7B is a graph showing an example of the change in current value when battery 20 is discharged by discharge circuit 24, where discharge by discharge circuit 24 occurs at time t21 and discharge by discharge circuit 24 stops at time t22. Figure 7C is a graph showing the change in current value acquired by acquisition unit 101 when discharge to load 28 occurs at the timing shown in Figure 7A and discharge by discharge circuit 24 occurs at the timing shown in Figure 7B. In Figures 7A, 7B, and 7C, the vertical axis is current value and the horizontal axis is time. Note that in Figures 7A, 7B, and 7C, the case when battery 20 is charged is defined as positive and the case when battery 20 is discharged is defined as negative. Therefore, when battery 20 is discharged, the current changes in the negative direction, and when the discharge of battery 20 is stopped at the discharge current value or when the discharge to load 28 is stopped, the current changes in the positive direction.

[0035] Figure 8A is a graph showing an example of voltage change due to discharge to load 28, where the voltage changes at time t11 when discharge to load 28 occurs. Figure 8B is a graph showing an example of voltage change when battery 20 is discharged by discharge circuit 24, where discharge by discharge circuit 24 occurs at time t21 and discharge by discharge circuit 24 stops at time t22. Figure 8C is a graph showing the change in voltage acquired by acquisition unit 101 when discharge to load 28 occurs at the timing shown in Figure 8A and discharge by discharge circuit 24 occurs at the timing shown in Figure 8B. In Figures 8A, 8B, and 8C, the vertical axis is current value and the horizontal axis is time. In Figures 8A, 8B, and 8C, the case when battery 20 is charged is defined as positive and the case when battery 20 is discharged is defined as negative. Therefore, when battery 20 is discharged, the voltage changes in the negative direction, and when the discharge of battery 20 at the discharge current value is stopped or when discharge to load 28 is stopped, the voltage changes in the positive direction.

[0036] Next, the control unit 10 determines whether the discharge current value obtained in step S104 is appropriate (step S105). Step S105 is an example of a step in determining whether the discharge by the discharge control unit 104 and the discharge circuit 24 is appropriate. Figure 6 is a flowchart showing the flow of the process for determining whether the discharge current value is appropriate. The control unit 10 obtains the internal resistance value from the storage unit 11 and uses the change in current value at time t21 and the obtained internal resistance value to calculate the change in voltage at time t21, that is, the first change in voltage due to discharge using the discharge circuit 24 (step S201). For example, as shown in Figure 7C, if the change in current value at time t21 is Δi1, the result of multiplying the internal resistance value by Δi1 is taken as the first change in voltage.

[0037] Furthermore, the control unit 10 obtains the internal resistance value from the storage unit 11 and uses the change in current value at time t11 and the obtained internal resistance value to calculate the change in voltage at time t11, i.e., the second voltage change due to discharge to the load 28 (step S202). For example, as shown in Figure 7C, if the change in current value at time t11 is Δi2, the result of multiplying the internal resistance value by Δi2 is taken as the second voltage change.

[0038] Figure 9A is a graph showing an example of the change in current value due to discharge to load 28, where the current value changes at time t12 when discharge to load 28 occurs. Figure 9B is a graph showing an example of the change in current value when battery 20 is discharged by discharge circuit 24, where discharge by discharge circuit 24 occurs at time t23 and discharge by discharge circuit 24 stops at time t24. Figure 9C is a graph showing the change in current value acquired by acquisition unit 101 when discharge to load 28 occurs at the timing shown in Figure 9A and discharge by discharge circuit 24 occurs at the timing shown in Figure 9B. For example, as shown in Figure 9C, if the change in current value at time t23 is Δi3, the result of multiplying the internal resistance value by Δi3 is taken as the first voltage change, and if the change in current value at time t12 is Δi4, the result of multiplying the internal resistance value by Δi4 is taken as the second voltage change. The control unit 10 may calculate the first voltage change and the second voltage change based on the voltage value acquired by acquisition unit 101.

[0039] Next, the control unit 10 determines whether the first voltage change is sufficient (step S203). Here, for example, if the control unit 10 wants to keep the estimation accuracy of the internal resistance of the battery 20 within ±n%, it determines that the first voltage change is sufficient if the first voltage change is n times or more the second voltage change (step S203: YES), and if the first voltage change is less than n times the second voltage change, it determines that the first voltage change is insufficient (step S203: NO). For example, if the control unit 10 wants to keep the estimation accuracy of the internal resistance of the battery 20 within ±10%, it sets n=10, and determines that the first voltage change is sufficient if the first voltage change is 10 times or more the second voltage change, and determines that the first voltage change is insufficient if the first voltage change is less than 10 times the second voltage change. In other words, if the control unit 10 wants to keep the estimation accuracy of the internal resistance value of the battery 20 within ±n%, it determines that the voltage change when the battery 20 is discharged at the discharge current value is insufficient compared to the voltage change when it is discharged to the load 28, if the first voltage change when the battery 20 is discharged at the discharge current value is less than n times the second voltage change due to discharge to the load 28 which is powered by the battery 20. If the control unit 10 determines that the first voltage change is insufficient, it determines that the discharge current value is too low (step S207).

[0040] If the control unit 10 determines that the first voltage change is sufficient, it determines whether the first voltage change is appropriate (step S204). Here, for example, if the first voltage change is greater than or equal to a predetermined threshold, the control unit 10 determines that the first voltage change is excessive and inappropriate (step S204: NO), and if the first voltage change is less than a predetermined threshold, it determines that the first voltage change is appropriate (step S204: YES). If the control unit 10 determines that the first voltage change is excessive and inappropriate, it determines that the discharge current value is excessive (step S206), and if it determines that the first voltage change is appropriate, it determines that the discharge current value is appropriate (step S205).

[0041] Returning to Figure 5, if the discharge current value is not appropriate (step S105: NO), that is, if the process shown in Figure 6 determines that the discharge current value is too low (the first voltage change is less than n times the second voltage change) or too high (the first voltage change is greater than or equal to a predetermined threshold), the control unit 104 and the discharge circuit 24 determine that the discharge is not appropriate and reset the discharge current value (step S107). Steps S105 and S107 are examples of setting steps. Figure 10 is a flowchart showing the flow of the process for resetting the discharge current value. If the discharge current value is too low, the control unit 10 increases the discharge current value so that the first voltage change is 10 times or more the second voltage change and the discharge current value is less than a predetermined threshold (step S302). If the discharge current value is too high, the control unit 10 decreases the discharge current value so that the first voltage change is 10 times or more the second voltage change and the discharge current value is less than a predetermined threshold (step S303). Returning to Figure 5, the control unit 10 resets the discharge current value and returns the processing flow to step S101.

[0042] If the discharge current value is appropriate (step S105: YES), the control unit 10 estimates the internal resistance value (step S106). Step S106 is an example of the internal resistance estimation step. 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 being discharged by the discharge circuit 24 in a predetermined waveform.

[0043] Next, the control unit 10 notifies the ECU 3 of the internal resistance value estimated in step S106 (step S108). The ECU 3, having obtained the internal resistance value of the battery 20, estimates the state of the battery 20 based on the obtained internal resistance value and, for example, notifies the estimated state of the battery 20 on the instrument panel. Note that notification of the state of the battery 20 is not limited to notification on the instrument panel, but may also be done by an alarm sound or voice. Furthermore, these notifications may be made when the accessory power is turned on in the vehicle V or when the ignition is turned on.

[0044] As described above, according to this embodiment, by changing the discharge current value according to the relationship between the first voltage change and the second voltage change, the voltage change due to discharge at a predetermined waveform for determining the internal resistance is made larger than the voltage change due to discharge to the load 28. As a result, the influence of the voltage change due to discharge to the load 28 on the voltage change due to discharge at a predetermined waveform is reduced, and the influence of the voltage change due to discharge to the load 28 can be suppressed when calculating the internal resistance of the battery 20 using the voltage and current values ​​of the battery 20. Furthermore, increasing the discharge current value when discharging the battery 20 at a predetermined waveform allows for accurate detection of the state by suppressing the influence of voltage fluctuations due to discharge to the load 28. However, if the discharge current value is made too large, power will be consumed, and there is a risk that the voltage of the battery 20 will drop and power will not be supplied to the load. However, in this embodiment, if the discharge current value is too large, the discharge current value is reset to a smaller value, so that the power consumption of the battery 20 can be suppressed when calculating the internal resistance.

[0045] [Other embodiments] In the above-described embodiment, the state detection device 1 provided in the vehicle V sets the discharge current value to be supplied from the battery 20 when the battery 20 is discharging with a predetermined waveform, and estimates the internal resistance value of the battery 20. However, these processes may be performed by the ECU 3. Figure 11 is a block diagram showing the configuration of another embodiment of the state detection system.

[0046] ECU3, as an example of a state detection device, has a control unit 30, a memory unit 31, an interface 33, and a bus (not shown). The control unit 30 has a CPU, ROM, and RAM, similar to the control unit 10. The control unit 30 may be configured with a DSP, FPGA, or ASIC instead of a CPU. The CPU, ROM, RAM, memory unit 31, and interface 33 are interconnected by a bus, and information is exchanged between them. The memory unit 31 is composed of non-volatile memory and stores discharge current values ​​and preliminary internal resistance values, similar to the memory unit 11.

[0047] The functions of the control unit 30 are realized as a functional unit when the CPU reads and executes a program from ROM. By the CPU executing the program stored in ROM, the control unit 30 realizes the acquisition unit 301, the internal resistance estimation unit 302, the setting unit 303, the discharge control unit 304, and the state detection unit 305.

[0048] 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, as indicated by the signals output from the voltage sensor 21, current sensor 22, and temperature sensor 23 and acquired by the interface 33. The acquisition unit 301 also acquires the discharge current value and internal resistance value stored in the storage unit 31.

[0049] The internal resistance estimation unit 302 estimates the internal resistance of the battery 20 based on the voltage and current values ​​acquired by the acquisition unit 301, similar to the acquisition unit 101.

[0050] Similar to the setting unit 103, the setting unit 303 determines whether the discharge of the battery 20 by the discharge control unit 304 is appropriate based on the voltage value acquired by the acquisition unit 301, or the current value acquired by the acquisition unit 301 and the internal resistance value stored in the storage unit 31. If it is not appropriate, it resets the discharge current value.

[0051] The discharge control unit 304 controls the discharge circuit 24 by controlling the current value of the current flowing to the base of transistor TR1 so that the battery 20 discharges with a predetermined waveform and a current value set by the setting unit 303 flows from the battery 20.

[0052] The state detection unit 305, like the state detection unit 105, detects the state of the battery 20 based on the internal resistance value estimated by the internal resistance estimation unit 302.

[0053] In this configuration as well, the voltage change due to discharge at a predetermined waveform for determining the internal resistance is made larger than the voltage change due to discharge to the load 28. This reduces the influence of the voltage change due to discharge to the load 28 on the voltage change due to discharge at the predetermined waveform, and thus suppresses the influence of the voltage change due to discharge to the load 28 when calculating the internal resistance of the battery 20 using the voltage and current values ​​of the battery 20. Furthermore, in this embodiment, if the discharge current value is too large, the discharge current value is reset to a smaller value, thereby reducing the power consumption of the battery 20 when calculating the internal resistance.

[0054] Furthermore, in the present invention, a server device connected to a communication network may be configured to set the discharge current value to be supplied from the battery 20 when the battery 20 is discharged with a predetermined waveform, and to estimate the internal resistance value of the battery 20. Figure 12 is a block diagram showing the configuration of another embodiment of the state detection system.

[0055] Communication interface 5 is an interface that performs wireless communication via the communication network 1000 and is connected to the status detection device 1. The status detection device 1 connects to the communication network 1000 via communication interface 5 and exchanges information with the server device 4.

[0056] 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, ROM, and 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 between them. 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 is composed of non-volatile memory and stores discharge current values ​​and internal resistance values, similar to the storage unit 11. The user interface 43 includes a mouse or keyboard for inputting information and a display device for displaying information. Note that the server device 4 may also be configured without the user interface 43.

[0057] The functions of the control unit 40 are realized as a functional unit when the CPU reads and executes a program from ROM. By the CPU executing the program stored in ROM, the control unit 40 realizes the acquisition unit 401, the internal resistance estimation unit 402, the setting unit 403, the discharge control unit 404, and the state detection unit 405.

[0058] The acquisition unit 401 acquires the voltage value, current value, and temperature acquired by the acquisition unit 101 and transmitted from the state detection device 1 via the communication unit 42. The acquisition unit 401 also acquires the discharge current value and internal resistance value stored in the storage unit 31.

[0059] The internal resistance estimation unit 402 estimates the internal resistance of the battery 20 based on the voltage and current values ​​acquired by the acquisition unit 401, similar to the acquisition unit 101.

[0060] Similar to the setting unit 103, the setting unit 403 determines whether the discharge of the battery 20 by the discharge circuit 24 is appropriate based on the voltage value acquired by the acquisition unit 401, or the current value acquired by the acquisition unit 401 and the internal resistance value stored in the storage unit 41. If it is not appropriate, it resets the discharge current value.

[0061] The discharge control unit 404 transmits the discharge current value set in 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 discharge circuit 24 by controlling the current value flowing to the base of the transistor TR1 so that the battery 20 discharges with a predetermined waveform and the current value flowing from the battery 20 is equal to the discharge current value set in the setting unit 403.

[0062] The state detection unit 405 detects the state of the battery 20 based on the internal resistance value estimated by the internal resistance estimation unit 402.

[0063] Figure 13 is a sequence diagram illustrating the operation of the state detection system configured as shown in Figure 12. The state detection device 1 acquires the discharge current value from the storage unit 11 and controls the discharge circuit 24 so that the discharge from the battery 20 is performed with a predetermined waveform and the acquired discharge current value flows from the battery 20 (step S11). When the state detection device 1 discharges the battery 20 with a predetermined current value using a predetermined waveform, it acquires the voltage value measured by the voltage sensor 21 and the current value measured by the current sensor 22 during the discharge with the predetermined waveform (step S12), and transmits the acquired voltage value and current value to the server device 4 (step S13).

[0064] The server device 4 acquires the voltage value and current value transmitted from the state detection device 1 (step S14). Next, the server device 4 determines whether the discharge current value is appropriate based on the acquired current value and the internal resistance value stored in the storage unit 41, in the same manner as the state detection device 1 (step S15). If the discharge current value is not appropriate, the server device 4 sets the discharge current value in the same manner as in step S107 (step S16) and transmits the set discharge current value to the state detection device 1 (step S17).

[0065] The state detection device 1 acquires the discharge current value transmitted from the server device 4 and controls the discharge circuit 24 so that the battery 20 discharges with a predetermined waveform and the acquired discharge current value flows from the battery 20 (step S18). When the state detection device 1 discharges the battery 20 with a predetermined current value using a predetermined waveform, it acquires the voltage value measured by the voltage sensor 21 and the current value measured by the current sensor 22 during the discharge with the predetermined waveform (step S19), and transmits the acquired voltage value and current value to the server device 4 (step S20).

[0066] The server device 4 acquires the voltage and current values ​​transmitted from the state detection device 1 (step S21). Next, the server device 4 determines whether the discharge current value is appropriate based on the acquired current value and the stored internal resistance value, in the same manner as the state detection device 1 (step S22). If the acquired discharge current value is appropriate, the server device 4 estimates the internal resistance value of the battery 20 using the acquired voltage and current values ​​(step S23), and transmits the estimated internal resistance value to the ECU 3 (step S24).

[0067] In this configuration as well, the voltage change due to discharge at a predetermined waveform for determining the internal resistance is made larger than the voltage change due to discharge to the load 28. This reduces the influence of the voltage change due to discharge to the load 28 on the voltage change due to discharge at the predetermined waveform, and thus suppresses the influence of the voltage change due to discharge to the load 28 when calculating the internal resistance of the battery 20 using the voltage and current values ​​of the battery 20. Furthermore, in this embodiment, if the discharge current value is too large, the discharge current value is reset to a smaller value, thereby reducing the power consumption of the battery 20 when calculating the internal resistance. 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.

[0068] [Differentiation] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above and can be implemented in various other forms. For example, the present invention may be implemented by modifying the embodiments described above as follows. The embodiments described above and the following modifications may be combined with each other. The present invention is also included in configurations that appropriately combine the components of each embodiment and each modification described above. Furthermore, further effects and modifications can be easily derived by those skilled in the art. Therefore, broader embodiments of the present invention are not limited to the embodiments and modifications described above, and various modifications are possible.

[0069] In the embodiment described above, the vehicle V is configured so that only the engine 26 outputs driving force. However, the vehicle V may be an electric vehicle such as 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 that drives the electric motor) which is composed of a lithium-ion battery or the like, and the high-voltage system starts the engine 26.

[0070] In the above-described embodiment, the vehicle V has the state detection device 1 and the discharge circuit 24, but a mobile body such as a motorboat or other vessel, a drone or other aircraft, agricultural machinery, or construction machinery may also have the state detection device 1 and the discharge circuit 24. Furthermore, the state detection device 1 and the discharge circuit 24 are not limited to mobile bodies; devices using batteries 20 in gas, water, railway, communication, power facilities, etc., may also have the state detection device 1 and the discharge circuit 24.

[0071] In the embodiment described above, the control unit 10 may output a PWM signal to the base of the transistor TR1 and control the current value when discharging the battery 20 with a predetermined waveform by changing the duty cycle of the PWM signal. [Explanation of symbols]

[0072] 1. State detection device 3 ECU 10 Control Unit 11 Storage section 12 Communications Department 13 Interfaces 14 bus 20 batteries 21 Voltage Sensor 22 Current Sensor 23 Temperature Sensor 24 Discharge circuit 28 load 101, 301, 401 Acquisition Department 102, 302, 402 Internal resistance estimation section 103, 303, 403 Setting section 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, A discharge circuit for discharging the aforementioned battery, A setting unit for setting the discharge current value of the current flowing from the aforementioned battery, A discharge control unit controls the discharge circuit to discharge the battery so that a current of the discharge current value set in the setting unit flows from the battery, and An acquisition unit that acquires the current value of the current flowing from the battery and the voltage value of the battery when the battery is being discharged by the discharge circuit, An internal resistance estimation unit estimates the internal resistance value of the battery based on the current value and voltage value acquired by the acquisition unit, It has, The setting unit determines whether the discharge of the battery by the discharge control unit is appropriate based on the voltage value acquired by the acquisition unit, or the current value acquired by the acquisition unit and the internal resistance value estimated by the internal resistance estimation unit, and resets the discharge current value if it is not appropriate. State detection system.

2. The setting unit sets the discharge current value so that if the amount of voltage change when the battery is being discharged at the discharge current value is greater than or equal to a predetermined threshold, the amount of voltage change becomes less than the predetermined threshold. The state detection system according to claim 1.

3. The setting unit sets the discharge current value to a larger value if the voltage change when the battery is being discharged at the discharge current value is insufficient to compensate for the voltage change caused by discharging to a load powered by the battery. A state detection system according to claim 1 or claim 2.

4. A status detection device for detecting the status of a rechargeable battery, A discharge circuit for discharging the aforementioned battery, A setting unit for setting the discharge current value of the current flowing from the aforementioned battery, A discharge control unit controls the discharge circuit to discharge the battery so that a current of the discharge current value set in the setting unit flows from the battery, and An acquisition unit that acquires the current value of the current flowing from the battery and the voltage value of the battery when the battery is being discharged by the discharge circuit, An internal resistance estimation unit estimates the internal resistance value of the battery based on the current value and voltage value acquired by the acquisition unit, It has, The setting unit determines whether the discharge of the battery by the discharge control unit is appropriate based on the voltage value acquired by the acquisition unit, or the current value acquired by the acquisition unit and the internal resistance value estimated by the internal resistance estimation unit, and resets the discharge current value if it is not appropriate. State detection device.

5. A state detection method for detecting the state of a rechargeable battery, A setting step to set the discharge current value of the current flowing from the aforementioned battery, A discharge control step involves controlling a discharge circuit to discharge the battery so that a current of the discharge current value set in the setting step flows from the battery, thereby discharging the battery. The acquisition step involves acquiring the current value of the current flowing from the battery and the voltage value of the battery when the battery is being discharged by the discharge control step, An internal resistance estimation step in which the internal resistance value of the battery is estimated based on the current value and voltage value obtained in the acquisition step, It has, The setting step determines whether the discharge of the battery by the discharge control step is appropriate based on the voltage value obtained in the acquisition step, or the current value obtained in the acquisition step and the internal resistance value estimated in the internal resistance estimation step, and if it is not appropriate, resets the discharge current value. A state detection method comprising the following features.

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