JP2021069163A - Rechargeable battery status detection device and rechargeable battery status detection method - Google Patents

Abstract

To perform accurate charge control regardless of the capacity of a rechargeable battery.SOLUTION: In a rechargeable battery status detection device that detects the status of a rechargeable battery includes first estimation means (control unit 10) that acquires an estimated value of the capacity of the rechargeable battery and estimates the charge rate of the rechargeable battery on the basis of the estimated value of the capacity, second estimation means (control unit 10) that detects a current flowing through the rechargeable battery by a current detection value output from a current sensor, and estimates the charge rate of the rechargeable battery on the basis of the current detection value, and correction means (control unit 10) that corrects the estimated value of the capacity of the rechargeable battery on the basis of the charge rate estimated by the first estimation means and the second estimation means.SELECTED DRAWING: Figure 1

Description

The present invention relates to a rechargeable battery state detecting device and a rechargeable battery state detecting method.

In Patent Document 1, the remaining capacity of electric power when a rechargeable battery is used is obtained by adding the integrated value of charge / discharge current to the initial capacity of the rechargeable battery, and the integrated value of charge / discharge current can be charged. A technique is disclosed in which the remaining capacity is accurately obtained by correcting with the charging efficiency of the battery, and the charging control is accurately executed based on the remaining capacity.

Japanese Unexamined Patent Publication No. 03-231175

By the way, in the technique disclosed in Patent Document 1, when the capacity of the rechargeable battery is different from the actual capacity, the remaining capacity cannot be accurately obtained, and as a result, the charge control cannot be performed accurately. There is a problem.

The present invention has been made in view of the above situations, and provides a rechargeable battery state detection device and a rechargeable battery state detection method capable of accurately performing charge control regardless of the capacity of the rechargeable battery. The purpose is to provide.

In order to solve the above problems, the present invention obtains an estimated value of the capacity of the rechargeable battery in a rechargeable battery state detecting device that detects the state of the rechargeable battery, and based on the estimated value of the capacity, The first estimation means for estimating the charge rate of the rechargeable battery and the current flowing through the rechargeable battery are detected by the current detection value output from the current sensor, and the rechargeable battery is based on the current detection value. A second estimation means for estimating the charge rate of the battery, and a correction means for correcting the estimated value of the capacity of the rechargeable battery based on the charge rate estimated by the first estimation means and the second estimation means. And, characterized by having.
With such a configuration, it is possible to accurately perform charge control regardless of the capacity of the rechargeable battery.

Further, the present invention is characterized in that the first estimation means obtains the estimated value of the capacity from the outside or calculates the estimated value of the capacity based on the resistance of the rechargeable battery. ..
According to such a configuration, the estimated value of the capacity can be obtained depending on the case.

Further, in the present invention, the first estimation means measures the voltage and current during discharge of the rechargeable battery, calculates a resistance value based on these, and obtains the capacity based on the calculated resistance value. It is characterized by that.
With such a configuration, it is possible to accurately determine the capacity regardless of the type of rechargeable battery.

Further, in the present invention, the first estimation means measures the voltage and current during discharge of the rechargeable battery, calculates a resistance value that changes in time series based on these, and linearly calculates the calculated resistance value. It is characterized in that the capacitance is obtained from the slope of the obtained linear function by fitting to the function.
With such a configuration, the capacity can be obtained more accurately regardless of the type of rechargeable battery.

Further, the present invention is characterized in that the second estimation means determines that the charge rate of the rechargeable battery is fully charged when the charge resistance of the rechargeable battery exceeds a predetermined threshold value. To do.
According to such a configuration, the charging rate can be accurately obtained based on the charging resistance.

Further, the present invention is characterized in that the threshold value uses a different threshold value depending on the charging voltage when charging the rechargeable battery.
According to such a configuration, even if the charging voltage is different, the full charge can be accurately determined.

Further, the present invention is characterized in that the same threshold value is used and the charging rate is corrected to a different value according to the charging voltage when charging the rechargeable battery.
According to such a configuration, the charge rate at the time of full charge can be accurately obtained.

Further, in the present invention, the correction means corrects the estimated value of the capacity when the charge rate estimated by the first estimation means and the second estimation means is different by a predetermined threshold value or more. , The capacity is recalculated from the slope of the linear function.
According to such a configuration, the capacity can be accurately determined by a simple process.

Further, the present invention is characterized in that the correction value of the capacity corrected by the correction means is supplied to a higher-level device, and the rechargeable battery is charge-controlled based on the correction value of the supplied capacity. And.
According to such a configuration, the capacity of the rechargeable battery can be accurately determined, and the charge control can be efficiently executed based on the accurate capacity.

Further, the present invention obtains an estimated value of the capacity of the rechargeable battery in the rechargeable battery state detecting method for detecting the state of the rechargeable battery, and charges the rechargeable battery based on the estimated value of the capacity. The first estimation step for estimating the rate and the current flowing through the rechargeable battery are detected by the current detection value output from the current sensor, and the charge rate of the rechargeable battery is estimated based on the current detection value. It has a second estimation step to be performed, and a correction step for correcting the estimated value of the capacity of the rechargeable battery based on the charge rate estimated in the first estimation step and the second estimation step. It is a feature.
With such a configuration, it is possible to accurately perform charge control regardless of the capacity of the rechargeable battery.

According to the present invention, it is possible to provide a rechargeable battery state detection device and a rechargeable battery state detection method capable of accurately performing charge control regardless of the capacity of the rechargeable battery.

It is a figure which shows the structural example of the rechargeable battery state detection apparatus which concerns on embodiment of this invention. It is a block diagram which shows the detailed configuration example of the control part of FIG. It is a figure which shows the state of sampling of voltage and current at the time of pulse discharge. It is a figure which shows the time change of the resistance value obtained by the pulse discharge shown in FIG. It is a figure which shows the relationship between the slope value obtained by fitting a linear function to the result shown in FIG. 4, and SOH. It is a figure which shows the relationship between SOC and charge resistance when the charge voltage is different. It is a figure which shows the relationship between SOC and charge resistance when the charge voltage is different. It is a figure for demonstrating an example of the process executed in Embodiment of this invention. It is a figure for demonstrating the detail of the initial capacity detection process shown in FIG. It is a figure for demonstrating the detail of the full charge detection process shown in FIG. It is a figure for demonstrating the detail of the initial capacity change process shown in FIG. It is a figure which shows the modification embodiment of the process shown in FIG. It is a figure which shows the embodiment when SOC is corrected by a charge voltage. This is an example of the process for executing the correction shown in FIG.

Next, an embodiment of the present invention will be described.

(A) Explanation of Configuration of Embodiment of the Present Invention FIG. 1 is a diagram showing a power supply system of a vehicle having a rechargeable battery state detection device according to the embodiment of the present invention. In this figure, the rechargeable battery state detection device 1 has a control unit 10, a voltage sensor 11, a current sensor 12, a temperature sensor 13, and a discharge circuit 15 as main components, and determines the charge state of the rechargeable battery 14. Control. Here, the control unit 10 refers to the outputs from the voltage sensor 11, the current sensor 12, and the temperature sensor 13, detects the state of the rechargeable battery 14, and controls the generated voltage of the alternator 16 to charge the battery. The charge state of the possible battery 14 is controlled. The voltage sensor 11 detects the terminal voltage of the rechargeable battery 14 and notifies the control unit 10. The current sensor 12 detects the current flowing through the rechargeable battery 14 and notifies the control unit 10. The temperature sensor 13 detects the electrolytic solution of the rechargeable battery 14 or the ambient temperature, and notifies the control unit 10. The discharge circuit 15 is composed of, for example, a semiconductor switch connected in series and a resistance element, a constant current element, or the like, and the rechargeable battery 14 is rechargeable by controlling the semiconductor switch on / off by the control unit 10. Discharge according to the instruction of the device 1.

The rechargeable battery 14 is composed of a rechargeable battery having an electrolytic solution, for example, a lead storage battery, a nickel cadmium battery, a nickel hydrogen battery, or the like, and is charged by an alternator 16 to drive a starter motor 18 to start an engine. At the same time, power is supplied to the load 19. The alternator 16 is driven by the engine 17, generates AC power, converts it into DC power by a rectifier circuit, and charges the rechargeable battery 14. The alternator 16 is controlled by the control unit 10 so that the generated voltage can be adjusted.

The engine 17 is composed of, for example, a reciprocating engine such as a gasoline engine and a diesel engine, a rotary engine, or the like, is started by a starter motor 18, drives drive wheels via a transmission, gives propulsion to a vehicle, and is an alternator 16. To generate power. The starter motor 18 is composed of, for example, a DC motor, and generates a rotational force by the electric power supplied from the rechargeable battery 14 to start the engine 17. The load 19 is composed of, for example, an electric steering motor, a defogger, a seat heater, an ignition coil, a car audio, a car navigation system, and the like, and is operated by electric power from the rechargeable battery 14.

FIG. 2 is a diagram showing a detailed configuration example of the control unit 10 shown in FIG. As shown in this figure, the control unit 10 includes a CPU (Central Processing Unit) 10a, a ROM (Read Only Memory) 10b, a RAM (Random Access Memory) 10c, a communication unit 10d, and an I / F (Interface) 10e. ing. Here, the CPU 10a controls each unit based on the program 10ba stored in the ROM 10b. The ROM 10b is composed of a semiconductor memory or the like and stores the program 10ba or the like. The RAM 10c is composed of a semiconductor memory or the like, and stores data generated when the program 10ba is executed and data 10ca such as a mathematical formula or a table described later. The communication unit 10d communicates with an ECU (Electronic Control Unit) or the like, which is a higher-level device, and notifies the higher-level device of the detected information or control information. The I / F 10e converts the signals supplied from the voltage sensor 11, the current sensor 12, and the temperature sensor 13 into digital signals and captures them, and transfers the drive current to the discharge circuit 15, the alternator 16, the starter motor 18, and the like. Supply and control these. The control of the alternator 16, the starter motor 18, and the like may be executed by the ECU. The configuration is not limited to that shown in FIG.

In the example of FIG. 2, one CPU 10a is provided, but the distributed processing may be executed by a plurality of CPUs. Further, instead of the CPU 10a, it may be configured by a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), or the like. Alternatively, the processing may be performed on the computer on the server by a general-purpose processor or cloud computing that executes a function by loading a software program. Further, although the ROM 10b and the RAM 10c are provided in FIG. 2, for example, a storage device other than these (for example, an HDD (Hard Disk Drive) which is a magnetic storage device) may be used.

(B) Description of Operation of Embodiment of the Present Invention Next, the operation of the embodiment of the present invention will be described. In the following, the outline of the operation of the embodiment of the present invention will be described, and then the detailed operation will be described.

First, the outline of the operation of the embodiment will be described. In the present embodiment, when the rechargeable battery 14 mounted on the vehicle is replaced with a new rechargeable battery 14 due to deterioration or the like, the rechargeable battery 14 after the replacement is assumed. When the rechargeable battery 14 has an initial capacity different from the nominal capacity due to being left unattended or when it has an initial capacity different from the nominal capacity, it is possible to detect and correct this. The capacity of the rechargeable battery 14 indicates the amount of electricity that can be taken out from the battery, and is represented by, for example, Ah (amp-hour). Further, the amount of electricity that can be taken out from the rechargeable battery 14 decreases as it deteriorates. Therefore, the capacity in the initial state in which deterioration has not occurred is defined as the initial capacity. The nominal capacity means, for example, the capacity described in the catalog.

As an example, it is assumed that the rechargeable battery 14 of the vehicle is replaced due to deterioration over time due to use or the like. In that case, when the rechargeable battery 14 is removed, the power supply to the control unit 10 is cut off, and then the power supply is restarted by installing a new rechargeable battery 14. The control unit 10 executes the operation described later due to the cutoff and restart of the power supply power.

That is, the control unit 10 acquires information on the recommended initial capacity (hereinafter referred to as "recommended initial capacity") of the rechargeable battery 14 from an ECU (not shown) of the vehicle. For example, 50Ah is acquired as information on the recommended initial capacity. The CPU 10a of the control unit 10 uses the recommended initial capacity as the initial capacity IC.

If the ECU does not have information on the recommended initial capacity, the control unit 10 executes the following process for estimating the initial capacity of the rechargeable battery 14 after replacement.

In the initial capacity estimation process, the control unit 10 controls the discharge circuit 15 to pulse discharge the rechargeable battery 14, and measures the temporal changes in voltage and current at that time. FIG. 3 is a diagram showing temporal changes in voltage and current during pulse discharge. In FIG. 3, the horizontal axis represents time and the vertical axis represents current or voltage. First, the CPU 10a measures the voltage Vb before the start of discharge and the current Ib before the start of discharge. Next, the CPU 10a controls the discharge circuit 15 to pulse discharge the rechargeable battery 14. At this time, the CPU 10a samples the outputs of the voltage sensor 11 and the current sensor 12 at a predetermined cycle. In the example of FIG. 3, sampling is executed at timings t1, t2, t3, ..., TN, and the voltage value and the current value of the rechargeable battery 14 are acquired.

Next, the CPU 10a sets the time-series voltage value V (tun) sampled at the timings t1, t2, t3, ..., TN according to the time-series current value I (tn) sampled at the same timing, respectively. Divide to obtain the time-series resistance value R (tun). Instead of using the voltage value as it is, the drop voltage ΔV (tun) from the voltage Vb before the start of discharge is obtained, and this drop voltage ΔV (tun) is divided by the current value I (tun). The resistance value R (tn) of the series may be obtained.

Next, the CPU 10a fits the time-series resistance value R (tun) by the linear function f (tun) shown in the following equation (1) to obtain the coefficients a and b. Specifically, the coefficients a and b are obtained by performing fitting by the minimum square calculation or the Kalman filter calculation.

f (tun) = a · tun + b ··· (1)

FIG. 4 shows actual measurement values for a plurality of types of rechargeable batteries 14. In FIG. 4, bats 1, 2, bats 3, 4, and bats 5 and 6 show rechargeable batteries having the same initial capacity (or nominal capacity), respectively, and batts 1 and 2 are rechargeable batteries having a medium initial capacity. , And butts 5 and 6 indicate rechargeable batteries having an initial capacity larger than that of butts 1 and 2. As shown in these figures, the resistance value differs depending on the capacity of the rechargeable battery, but if the capacity is the same, the inclination hardly changes even if the type is different.

FIG. 5 is a diagram showing the relationship between the slope of the linear function and the initial capacity of the rechargeable battery 14. The horizontal axis of FIG. 5 shows the slope a of the linear function, and the vertical axis shows the SOH (State of Health). Further, the diamond shape (SOH_ini) in the figure indicates the actually measured initial capacity, and the circle (SOH_nom) indicates the nominal capacity. The nominal capacity and the slope have a coefficient of determination of about 0.8. Further, the actually measured initial capacity and the slope have a coefficient of determination of about 0.8. As described above, the nominal value or the actually measured value of the initial capacity of the rechargeable battery 14 has a high correlation with the inclination.

Therefore, in the present embodiment, when the information on the recommended initial capacitance cannot be obtained from the ECU, the slope a is obtained from the voltage value and the current value in the pulse discharge based on the equation (1), and after replacement from the value of the slope a. The initial capacity IC of the rechargeable battery 14 of the above is obtained. The relationship between the inclination a and the initial capacity can be obtained in advance by actual measurement and stored in the ROM 10b.

Next, the CPU 10a obtains the charge rate SOC (State of Charge) of the rechargeable battery 14, and uses this as the SOC. More specifically, the CPU 10a obtains the integrated current value IV by referring to the output of the current sensor 12 and integrating the currents input and output to and from the rechargeable battery 14. Further, the CPU 10a obtains SOC0, which is the charging rate at the start of charging, based on the correlation between the open circuit voltage OCV (Open Circuit Voltage) and SOC, and the charging rate is based on the initial capacitance IC and the integrated value IV of the current. Is obtained, and this is designated as SOCa (= SOC0 + IV / IC).

The CPU 10a of the control unit 10 controls to charge the rechargeable battery 14 by the alternator 16 with reference to the SOCa calculated based on the integrated value of the current.

The CPU 10a of the control unit 10 determines whether or not the battery is fully charged by being charged by the alternator 16 from a change in the charging resistance described later. The fully charged state means that the rechargeable battery 14 is fully charged. For example, when the rechargeable battery 14 is new, it means that it has been charged to the nominal value, and when it has deteriorated over time, it means that it has been charged. It means that the battery has been charged to SOH at the time.

Here, there is a relationship as shown in FIG. 6 between the SOC of the rechargeable battery 14 and the generated voltage of the alternator 16. FIG. 6 is a diagram showing the relationship between the SOC of the rechargeable battery 14 and the charging resistance when the rechargeable battery 14 is charged by changing the generated voltage of the alternator 16. In this figure, the solid line curve shows the relationship between the SOC of the rechargeable battery 14 and the charging resistance when charged at a voltage of 15.5 V, and the broken line curve with a short interval shows the relationship when charged at a voltage of 14.5 V. The relationship between the SOC and the charging resistance is shown, and the long-interval dashed curve shows the relationship between the SOC and the charging resistance when charging at a voltage of 13.5V. Here, the charging resistance refers to the voltage V applied to the rechargeable battery 14 when charging the rechargeable battery 14, the open circuit voltage OCV, and the resistance R (= (V-OCV) / I) obtained from the current I. To say.

In FIG. 6, when the charging voltage is 15.5 V, it can be determined that the battery is fully charged (SOC = 100%) when the charging resistance becomes about 30 mΩ or more. That is, 30 mΩ is used as the threshold value, and it can be determined whether or not the battery is fully charged by comparing the threshold value with the magnitude of the charging resistance. However, when the charging voltage is 14.5V or 13.5V, the SOC is less than 100% when the charging resistance is 30mΩ. Therefore, when the generated voltage of the alternator 16 is not fixed and fluctuates, if the full charge is determined using the same threshold value, an accurate determination cannot be made.

Therefore, in the embodiment of the present invention, as shown in FIG. 7, by using a threshold value that fluctuates according to the generated voltage (= charging voltage) of the alternator 16, the rechargeable battery 14 is full even when the generated voltage changes. I am trying to detect charging. For example, in the example of FIG. 7, when the generated voltage of the alternator 16 is 15.5 V, the determination is made using the threshold Th1. When the generated voltage is 14.5 V, the determination is made using the threshold Th2 to generate power. When the voltage is 13.5V, the threshold Th3 is used for determination. According to such a method, even if the generated voltage of the alternator 16 changes, it is possible to accurately detect that the rechargeable battery 14 is in a fully charged state.

When it is detected that the charge rate of the rechargeable battery 14 is in a fully charged state, the CPU 10a sets SOCb = 100%, which is the charge rate related to full charge, and compares it with the charge rate SOCa obtained by integrating the current. .. As a result, when SOCa = SOCb, it is determined that the initial capacity IC of the rechargeable battery 14 after replacement is the same as the recommended initial capacity. Alternatively, if the recommended initial capacity cannot be obtained from the ECU, it is determined that the estimated initial capacity IC of the rechargeable battery 14 after replacement is correct.

On the other hand, when SOCa = SOCb, it is estimated that the initial capacity IC of the rechargeable battery 14 after replacement is different from the recommended initial capacity, or the estimated initial capacity IC of the rechargeable battery 14 after replacement is incorrect. Therefore, the CPU 10a executes a process of re-estimating the initial capacity of the rechargeable battery 14. For example, when the environmental temperature is within a predetermined range (for example, about 25 ° C plus or minus 5 ° C) in order to reduce the error due to temperature, the initial capacity estimation is re-executed, or when charging is performed from a low charge rate. Since full charge detection cannot be performed normally, it is possible to re-execute the estimation of the initial capacity when charging from a high charge rate. This makes it possible to estimate an accurate initial capacity. By repeating the process until the difference value between SOCa and SOCb becomes less than a predetermined threshold value, a more accurate initial capacitance can be obtained.

When an accurate initial capacity is obtained as described above, by performing charge control based on this initial capacity, for example, overcharging can be prevented, so that fuel efficiency can be improved. Further, by preventing over-discharging, for example, it is possible to prevent the engine 17 from being unable to restart.

Next, the details of the processing executed in the embodiment of the present invention will be described with reference to FIGS. 8 to 11.

FIG. 8 is a flowchart for explaining an example of the main processing executed after the rechargeable battery 14 is replaced. When the processing of the flowchart shown in FIG. 8 is started, the following steps are executed.

In step S10, the CPU 10a acquires information on the recommended initial capacity from the ECU of the vehicle. As a result, information such as 50 Ah is obtained.

In step S11, the CPU 10a determines whether or not the information acquisition was successful in step S10, and if it is determined that the information acquisition was successful (step S11: Y), the process proceeds to step S13, and in other cases (step S11: N). ) Proceeds to step S12.

In step S12, the CPU 10a executes a process of estimating the initial capacity IC of the rechargeable battery 14. The details of this process will be described later with reference to FIG.

In step S13, the CPU 10a executes a full charge detection process for determining whether or not the rechargeable battery 14 is in a fully charged state. The details of this process will be described later with reference to FIG.

In step S14, the CPU 10a proceeds to step S15 when it is detected that the rechargeable battery 14 is fully charged as a result of the process of step S13 (step S14: Y), and proceeds to other cases (step S14: Y). In N), the process returns to step S13 and the same process is repeated.

In step S15, the CPU 10a obtains SOCa based on the initial capacity SOC0, the integrated value IV of the current obtained while the engine 17 is operating, and the initial capacity IC. More specifically, the CPU 10a obtains SOC0, which is the charging rate at the start of charging, based on the correlation between the open circuit voltage OCV and SOC, and determines the charging rate based on the initial capacitance IC and the integrated value IV of the current. Obtain it, and set this as SOCa (= SOC0 + IV / IC).

In step S16, the CPU 10a obtains an absolute value (| SOCa-SOCb |) of the difference between the charge rate SOCa obtained in step S15 and the charge rate SOCb detected by the full charge detection process in step S13, and this is dSOC. And.

In step S17, the CPU 10a determines whether or not the dSOC obtained in step S16 is less than a predetermined threshold value Th, and if dSOC <Th (step S17: Y), the process is terminated, and other than that. In the case (step S17: N), the process proceeds to step S18.

In step S18, the CPU 10a executes a process of changing the initial capacity IC of the rechargeable battery 14. The details of this process will be described later with reference to FIG.

Next, with reference to FIG. 9, the details of the “initial capacity estimation process” shown in step S12 of FIG. 8 will be described. When the processing of the flowchart shown in FIG. 9 is started, the following steps are executed.

In step S30, the CPU 10a refers to the output of the voltage sensor 11 and detects the pre-discharge voltage Vb shown in FIG.

In step S31, the CPU 10a refers to the output of the current sensor 12 and detects the pre-discharge current Ib shown in FIG.

In step S32, the CPU 10a controls the discharge circuit 15 to start pulse discharge of the rechargeable battery 14. As a method of pulse discharge, for example, there are a method of discharging via a resistance element and a method of discharging via a constant current circuit. In the latter method, since a constant current flows, the process of calculating the resistance value, which will be described later, can be simplified. Further, by limiting the current value, the load on the rechargeable battery 14 can be reduced.

In step S33, the CPU 10a measures the voltage of the rechargeable battery 14. More specifically, the CPU 10a refers to the output of the voltage sensor 11, measures the voltage V (tun) at the timing tun of the rechargeable battery 14, and stores it in the RAM 10c as data 10ca.

In step S34, the CPU 10a measures the current of the rechargeable battery 14. More specifically, the CPU 10a refers to the output of the current sensor 12, measures the current I (tun) at the timing tun of the rechargeable battery 14, and stores it in the RAM 10c as data 10ca.

In step S35, the CPU 10a determines whether or not a predetermined time has elapsed from the start of pulse discharge, and if it is determined that a predetermined time has elapsed (step S35: Y), the process proceeds to step S36, and other than that. In the case of (step S35: N), the process returns to step S33 and the same process as described above is repeated. For example, as shown in FIG. 3, when N times of sampling is completed, it is determined as Y and the process proceeds to step S36.

In step S36, the CPU 10a ends the pulse discharge. More specifically, the CPU 10a controls the discharge circuit 15 to end the pulse discharge.

In step S37, the CPU 10a obtains a time-series resistance value R (tun). More specifically, the CPU 10a divides the time-series voltage value V (tun) measured in step S33 by the time-series current value I (tun) to obtain the time-series resistance value R (tun). Ask. The obtained time-series resistance value R (tn) is stored in the RAM 10c as data 10ca.

In step S38, the CPU 10a fits the time-series resistance value R (tun) obtained in step S37 by the linear function f (tun) shown in the above equation (1) to obtain the coefficients a and b. More specifically, for example, by using the least square operation or the Kalman filter operation, it is possible to perform fitting of a linear function and obtain coefficients a and b.

In step S39, the CPU 10a acquires the coefficient a, which is the slope of the linear function obtained in step S38.

In step S40, the initial capacity IC of the rechargeable battery 14 is estimated based on the coefficient a acquired in step S39. More specifically, as shown in FIG. 5, since the rechargeable battery 14 has a correlation between the initial capacity and the inclination a, the initial capacity IC of the rechargeable battery 14 is estimated based on the correlation. be able to.

In the above processing, the resistance value is obtained by directly dividing the voltage value measured in step S33 by the current value measured in step S34. For example, the voltage before discharge start is obtained from the measured voltage value. The resistance value R (tun) may be obtained by dividing the difference voltage ΔV (tun) obtained by subtracting Vb by the current value I (tun).

Further, the change in the resistance value due to the temperature of the rechargeable battery 14 is stored in the ROM 10b as a table, the temperature of the rechargeable battery 14 is detected with reference to the output of the temperature sensor 13, and the temperature of the rechargeable battery 14 is detected based on the detected temperature. The resistance value obtained in step S37 may be temperature-corrected. According to such a method, it is possible to prevent the occurrence of an error due to temperature.

Next, with reference to FIG. 10, the details of the “full charge detection process” shown in step S13 of FIG. 8 will be described. When the processing of the flowchart shown in FIG. 10 is started, the following steps are executed.

In step S50, the control unit 10 refers to the output of the current sensor 12, determines whether or not the rechargeable battery 14 is being charged by the alternator 16, and determines that the rechargeable battery 14 is being charged (step S50: Y). Proceeds to step S51, and in other cases (step S50: N), the same process is repeated. If charging is not in progress, the process may be terminated instead of repeating the same process.

In step S51, the control unit 10 refers to the output of the voltage sensor 11 and acquires the generated voltage V of the alternator 16. As a result, for example, a voltage such as 15.5V is acquired.

In step S52, the control unit 10 calculates the charging resistance R. More specifically, the current I acquired in step S50, the generated voltage V acquired in step S51, and, for example, the voltage of the rechargeable battery 14 when a predetermined time has elapsed since the vehicle was stopped are measured. It can be obtained by R = (V-OCV) / I using the open circuit voltage OCV obtained in.

In step S53, the control unit 10 corrects the threshold value Th for determining whether or not the battery is fully charged to Th'based on the generated voltage V acquired in step S51. More specifically, the threshold Th is corrected by Th'= Th × g (V) by multiplying the reference threshold Th by g (V). Note that g (V) is a function whose value increases as the value of the generated voltage V decreases. In the example of FIG. 7, assuming that the threshold Th1 when the generated voltage V = 15.5 V is the reference threshold Th, when the generated voltage V = 14.5 V, Th'= Th1 × g (V) = When Th2 and the generated voltage V = 13.5V, g (V) is set so that Th'= Th1 × g (V) = Th3.

In the above example, only the generated voltage V is taken into consideration, but for example, the threshold value Th may be corrected in consideration of the temperature of the rechargeable battery 14 detected by the temperature sensor 13. .. Specifically, the function g (V, θ) with the generated voltage V and the temperature θ as variables may be used to correct by Th ′ = Th × g (V, θ).

In step S54, the control unit 10 compares the charging resistance R calculated in step S52 with the corrected threshold value Th'obtained in step S53, and when R ≧ Th'is satisfied (step S54: Y). Proceeds to step S55, and otherwise proceeds to step S56 (step S54: N).

In step S55, the control unit 10 determines that the battery is fully charged (SOCb = 100%). As a result, the control unit 10 stops driving the alternator 16 by the engine 17.

In step S56, the control unit 10 determines that the battery is not fully charged. As a result, the control unit 10 continues to drive the alternator 16 by the engine 17 until the rechargeable battery 14 is fully charged.

According to the above processing, the reference threshold value Th is corrected according to the power generation voltage of the alternator 16, and the fully charged state can be determined based on the corrected threshold value Th'. Therefore, even if the power generation voltage changes, it is full. The charging state can be accurately determined.

Next, with reference to FIG. 11, the details of the “initial capacity change process” shown in step S18 of FIG. 8 will be described. When the processing of the flowchart shown in FIG. 11 is started, the following steps are executed.

In step S70, the CPU 10a executes a "full charge detection process" for detecting whether or not the rechargeable battery 14 is in a fully charged state. Since this process is the same as the process shown in FIG. 10, the description thereof will be omitted.

In step S71, the CPU 10a determines whether or not it is determined to be in a fully charged state by the process of step S70, and if it is determined to be in a fully charged state (step S71: Y), the process proceeds to step S72, and in other cases (step S71: Y). In step S72: N), the process returns to step S70 and the same process is repeated.

In step S72, the CPU 10a executes an "initial capacity estimation process" for estimating the initial capacity of the rechargeable battery 14. Since this process is the same as the process shown in FIG. 9, the description thereof will be omitted.

In step S73, as a result of the estimation in step S72, the CPU 10a determines whether or not the initial capacity obtained at the first time has changed, and when it is determined that the initial capacity obtained at the first time has changed (step S73: Y). Proceeds to step S74, and returns to the original process in other cases (step S73: N). For example, when the initial capacity estimated in step S72 changes as compared with the recommended initial capacity acquired in step S10 of FIG. 10 or the initial capacity estimated in step S12, it is determined as Y. The process proceeds to step S74.

In step S74, the CPU 10a notifies, for example, the ECU that the initial capacity has changed.

In step S75, the CPU 10a notifies, for example, the ECU to perform charge control based on the initial capacity after the change. As a result, since the ECU executes charge control based on the initial capacity after the change, it is possible to prevent overcharging or overdischarging.

As described above, according to the processing of the flowcharts shown in FIGS. 8 to 11, the operation of the present embodiment described above can be realized.

(C) Description of Modified Embodiment The above embodiment is an example, and it goes without saying that the present invention is not limited to the cases described above. For example, in the above embodiment, the initial capacity is re-estimated and changed in step S18 of FIG. 8, but for example, as shown in FIG. 12, the value of the initial capacity IC is increased or decreased to step S13. You may go back and repeat the same process.

That is, in the process shown in FIG. 12, the process in step S18 is omitted and the process in step S90 is added as compared with FIG. Here, if it is determined in step S17 that dSOC <Th, the process proceeds to step S90, the initial capacitance IC is decreased or increased by a predetermined amount (for example, 5 Ah), and the process returns to step S13. As a result, SOCa changes, so the process is repeated until dSOC <Th, and when dSOC <Th is satisfied, Y is determined and the process ends. By the above processing, as in FIG. 8, the accurate initial capacity of the rechargeable battery 14 after replacement can be obtained.

Further, in the above embodiment, as shown in FIG. 7, the full charge is determined by using Th1 to Th3, which are different for each voltage of the alternator 16, but for example, as shown in FIG. 13, the same threshold value is used. By using Th, SOC1 to SOC3, which are different for each voltage, may be applied as a full charge value.

FIG. 14 is a diagram showing a flowchart in which SOC1 to SOC3, which are different for each voltage, are applied as full charge values, as shown in FIG. As compared with FIG. 10, in FIG. 14, steps S53 to S56 are excluded, and steps S101 to S103 are added.

Here, in step S101, the CPU 10a determines whether or not R ≧ Th is satisfied, and if it is determined that the condition is satisfied (step S101: Y), the process proceeds to step S102, and in other cases (step S101: N). Returns to the original processing.

In step S102, the CPU 10a sets a reference SOC that serves as a reference for correction.

In step S103, the CPU 10a corrects the reference SOC according to the generated voltage of the alternator 16. For example, as shown in FIG. 13, when the generated voltage is 13.5 V, the reference SOC is corrected to SOC1, and when the generated voltage is 14.5 V, the reference SOC is corrected to SOC2, and the generated voltage is increased. If it is 15.5V, the reference SOC is corrected to SOC3. Specifically, when the reference SOC = SOC3, the SOC3 is obtained by SOC3 = 1 × reference SOC when the generated voltage is 15.5 V, and SOC2 = α1 when the generated voltage is 14.5 V. × The SOC2 is obtained by the reference SOC, and when the generated voltage is 13.5V, the SOC3 = α2 × The SOC3 is obtained by the reference SOC. It should be noted that α2 <α <1.

As described above, according to the process of FIG. 14, the SOC can be set according to the generated voltage V.

Further, in each of the above embodiments, the charging resistance R is calculated by dividing the difference value between the charging voltage V and the open circuit voltage OCV by the charging current I. For example, the rechargeable battery 14 is stratified. It may be calculated by adding St and polarization Pl. That is, the charging resistance R may be obtained based on the following equation (2).

R = (V-OCV-St-Pl) / I ... (2)

Further, in the above embodiment, the full charge is detected by using the charging resistor, but the determination may be made based on the charging current. Specifically, constant current charging is performed in which the charging current is substantially constant from the start of charging until the terminal voltage reaches a predetermined voltage value. After the terminal voltage reaches a predetermined voltage value, the terminal voltage is set to be substantially constant and the charging is switched to the constant voltage charging. After switching to constant voltage charging, the charging current usually decreases as it approaches full charge. Then, when the charging current drops to a predetermined current value (referred to as the current threshold value), the duration during which the charging current is equal to or less than the current threshold value is obtained, and when this duration reaches the predetermined time (referred to as the determination time). It may be determined that the rechargeable battery has reached a predetermined state.

Further, in the above embodiment, the internal resistance of the rechargeable battery 14 is obtained from the voltage and current during discharge by the discharge circuit 15, but when the current flows through the load 19 instead of the discharge circuit 15 (for example,). The resistance of the rechargeable battery 14 may be determined (when a current flows through the starter motor 18).

Further, in the above embodiment, when the rechargeable battery 14 is replaced with a new one, the process shown in FIG. 9 or the like described above is executed, but even if the rechargeable battery 14 is not replaced with a new one, the process is executed. By executing the processes shown in FIG. 9 and the like to detect whether the capacity of the rechargeable battery 14 has decreased from the initial capacity, and if it has decreased, the reduced capacity is used to obtain an accurate SOC. Can be sought. As a result, it is possible to prevent overcharging or overdischarging even when deterioration occurs.

Further, in the above embodiment, the capacity of the rechargeable battery 14 is estimated from the slope a of the linear function. For example, the capacity is estimated from the intercept b of the linear function, or the resistance value R (tun). The capacity may be estimated from the average value of.

Further, in the above embodiment, in step S16 and step S17 of FIG. 8, when the absolute value dSOC of the difference value between SOCa and SOCb is smaller than the predetermined threshold value Th, the process of changing the initial capacitance is executed. However, for example, the determination may be made based on the value obtained by dividing dSOC by SOCb (or SOCa), or the determination may be made based on these ratios.

1 Rechargeable battery status detector 10 Control unit 10a CPU
10b ROM
10c RAM
10d communication unit 10e I / F
11 Voltage sensor 12 Current sensor 13 Temperature sensor 14 Rechargeable battery 15 Discharge circuit 16 Alternator 17 Engine 18 Starter motor 19 Load

Claims (10)

In the rechargeable battery status detector that detects the status of the rechargeable battery,
A first estimation means for acquiring an estimated value of the capacity of the rechargeable battery and estimating the charge rate of the rechargeable battery based on the estimated value of the capacity.
A second estimation means that detects the current flowing through the rechargeable battery by the current detection value output from the current sensor and estimates the charge rate of the rechargeable battery based on the current detection value.
A correction means for correcting the estimated value of the capacity of the rechargeable battery based on the charge rate estimated by the first estimation means and the second estimation means.
A rechargeable battery state detector characterized by having. The first estimation means obtains the estimated value of the capacity from the outside, or calculates the estimated value of the capacity based on the resistance of the rechargeable battery.
The rechargeable battery state detecting device according to claim 1. The first estimation means is characterized in that the voltage and current during discharge of the rechargeable battery are measured, a resistance value is calculated based on these, and the capacity is obtained based on the calculated resistance value. Item 2. The rechargeable battery state detection device according to item 2. The first estimation means measures the voltage and current while the rechargeable battery is discharging, calculates the resistance value that changes in time series based on these, and fits the calculated resistance value to a linear function. The rechargeable battery state detecting device according to claim 3, wherein the capacity is obtained from the obtained slope of the linear function. The second estimation means is characterized in that, when the charging resistance of the rechargeable battery exceeds a predetermined threshold value, it is determined that the charging rate of the rechargeable battery is fully charged. The rechargeable battery state detection device according to any one of the above items. The rechargeable battery state detecting device according to claim 5, wherein the threshold value is different depending on the charging voltage when charging the rechargeable battery. The rechargeable battery state detecting device according to claim 5, wherein the threshold value uses the same value and is corrected to a different charging rate according to the charging voltage when charging the rechargeable battery. When the charge rate estimated by the first estimation means and the second estimation means are different by a predetermined threshold value or more, the correction means corrects the estimated value of the capacity or the inclination of the linear function. The rechargeable battery state detecting device according to claim 4, wherein the capacity is obtained again from the above. Claims 1 to 1, wherein the correction value of the capacity corrected by the correction means is supplied to a higher-level device, and the rechargeable battery is charge-controlled based on the correction value of the supplied capacity. 8. The rechargeable battery state detection device according to any one of 8. In the rechargeable battery status detection method for detecting the status of a rechargeable battery,
The first estimation step of acquiring the estimated value of the capacity of the rechargeable battery and estimating the charge rate of the rechargeable battery based on the estimated value of the capacity,
A second estimation step in which the current flowing through the rechargeable battery is detected by a current detection value output from the current sensor, and the charge rate of the rechargeable battery is estimated based on the current detection value.
A correction step for correcting the estimated value of the capacity of the rechargeable battery based on the charge rate estimated in the first estimation step and the second estimation step.
A rechargeable battery state detection method comprising.

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