JP7269147B2 - Rechargeable battery status detection device and rechargeable battery status detection method - Google Patents

Description

The present invention relates to a rechargeable battery state detection device and a rechargeable battery state detection 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 for accurately determining the remaining capacity by correcting the remaining capacity based on the charging efficiency of the battery, and for accurately executing charging control based on the remaining capacity.

JP-A-03-231175

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

SUMMARY OF THE INVENTION The present invention has been made in view of the circumstances described above, and provides a rechargeable battery state detecting device and a rechargeable battery state detecting method capable of accurately performing charge control regardless of the capacity of the rechargeable battery. intended to provide.

In order to solve the above problems, the present invention provides a rechargeable battery state detection device for detecting the state of a rechargeable battery, in which an estimated value of the capacity of the rechargeable battery is obtained, and based on the estimated value of the capacity, a first estimating means for estimating a charging rate of the rechargeable battery; detecting a current flowing through the rechargeable battery by a current detection value outputted from a current sensor; and a correcting means for correcting the estimated value of the capacity of the rechargeable battery based on the charging rates estimated by the first estimating means and the second estimating means. and.
According to such a configuration, charging control can be performed accurately regardless of the capacity of the rechargeable battery.

Further, the present invention is characterized in that the first estimating means acquires the estimated value of the capacity from outside or calculates the estimated value of the capacity based on the resistance of the rechargeable battery. .
According to such a configuration, it is possible to acquire the estimated value of the capacity depending on the case.

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

In the present invention, the first estimating means measures the voltage and current of the rechargeable battery during discharge, calculates a resistance value that changes in time series based on these values, and uses the calculated resistance value as a primary The capacity is determined from the slope of the obtained linear function by fitting to the function.
With such a configuration, it is possible to obtain the capacity more accurately regardless of the type of rechargeable battery.

In the present invention, the second estimating means determines that the charging rate of the rechargeable battery is fully charged when the charging resistance of the rechargeable battery exceeds a predetermined threshold. do.
With such a configuration, it is possible to accurately obtain the charging rate based on the charging resistance.

Further, the present invention is characterized in that the threshold value is different according to the charging voltage when charging the rechargeable battery.
According to such a configuration, it is possible to accurately determine whether the battery is fully charged even if the charging voltages are different.

Further, according to the present invention, the same threshold value is used, and the charging rate is corrected according to the charging voltage when charging the rechargeable battery.
According to such a configuration, it is possible to accurately obtain the charging rate at the time of full charge.

In the present invention, the correcting means corrects the estimated value of the capacity when the charging rates estimated by the first estimating means and the second estimating means differ by a predetermined threshold or more, or , the capacitance is obtained again from the slope of the linear function.
With such a configuration, it is possible to accurately obtain the capacitance through 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 host device, and charging of the rechargeable battery is controlled based on the supplied correction value of the capacity. and
According to such a configuration, it is possible to accurately determine the capacity of the rechargeable battery and efficiently execute charging control based on the accurate capacity.

The present invention also provides a rechargeable battery state detection method for detecting a state of a rechargeable battery, in which an estimated value of the capacity of the rechargeable battery is obtained, and charging of the rechargeable battery is performed based on the estimated value of the capacity. a first estimation step of estimating a rate; detecting a current flowing through the rechargeable battery by a current detection value output from a current sensor; and estimating the charging rate of the rechargeable battery based on the current detection value. and a correction step of correcting the estimated value of the capacity of the rechargeable battery based on the state of charge estimated in the first and second estimation steps. Characterized by
According to such a configuration, charging control can be performed accurately regardless of the capacity of the rechargeable battery.

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

1 is a diagram showing a configuration example of a rechargeable battery state detection device according to an embodiment of the present invention; FIG. 2 is a block diagram showing a detailed configuration example of a control unit in FIG. 1; FIG. FIG. 4 is a diagram showing voltage and current sampling states during pulse discharge. FIG. 4 is a diagram showing temporal changes in resistance values obtained by the pulse discharge shown in FIG. 3; FIG. 5 is a diagram showing a relationship between a slope value obtained by fitting a linear function to the results shown in FIG. 4 and SOH; FIG. 4 is a diagram showing the relationship between SOC and charging resistance when charging voltages are different; FIG. 4 is a diagram showing the relationship between SOC and charging resistance when charging voltages are different; It is a figure for demonstrating an example of the process performed in embodiment of this invention. FIG. 9 is a diagram for explaining the details of the initial capacity detection process shown in FIG. 8; FIG. FIG. 9 is a diagram for explaining the details of the full charge detection process shown in FIG. 8; FIG. FIG. 9 is a diagram for explaining the details of the initial capacity change processing shown in FIG. 8; FIG. Figure 9 shows a modified embodiment of the process shown in Figure 8; FIG. 4 is a diagram showing an embodiment in which SOC is corrected by charging voltage; FIG. 14 is an example of processing for executing the correction shown in FIG. 13. FIG.

Next, embodiments of the present invention will be described.

(A) Description of Configuration of Embodiment of the Invention FIG. 1 is a diagram showing a power supply system of a vehicle having a rechargeable battery state detection device according to an embodiment of the invention. In this figure, the rechargeable battery state detection device 1 has a controller 10, a voltage sensor 11, a current sensor 12, a temperature sensor 13, and a discharge circuit 15 as main components, and detects the charge state of the rechargeable battery 14. Control. Here, the control unit 10 refers to 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 voltage generated by the alternator 16 to charge the battery. It controls the state of charge of the rechargeable battery 14 . Voltage sensor 11 detects the terminal voltage of rechargeable battery 14 and notifies control unit 10 of it. Current sensor 12 detects the current flowing through rechargeable battery 14 and notifies control unit 10 . The temperature sensor 13 detects the electrolyte of the rechargeable battery 14 or the ambient temperature, and notifies the controller 10 of it. The discharge circuit 15 is composed of, for example, a semiconductor switch and a resistance element or a constant current element connected in series. Discharge according to the command of the device 1 .

The rechargeable battery 14 is composed of a rechargeable battery having an electrolytic solution, such as a lead-acid battery, a nickel-cadmium battery, or a nickel-hydrogen battery, and is charged by an alternator 16 to drive a starter motor 18 to start the engine. Also, power is supplied to the load 19 . Alternator 16 is driven by engine 17 to generate AC power which is converted to DC power by a rectifier circuit to charge rechargeable battery 14 . The alternator 16 is controlled by the controller 10 and is capable of adjusting the generated voltage.

The engine 17 is configured by, for example, a reciprocating engine such as a gasoline engine and a diesel engine, a rotary engine, or the like, and is started by a starter motor 18 to drive drive wheels through a transmission to provide propulsion to the vehicle. to generate electric power. The starter motor 18 is composed of, for example, a direct-current motor, and generates rotational force from electric power supplied from the rechargeable battery 14 to start the engine 17 . The load 19 includes, for example, an electric steering motor, a defogger, a seat heater, an ignition coil, a car audio system, a car navigation system, and the like, and operates with 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 section 10 has a CPU (Central Processing Unit) 10a, a ROM (Read Only Memory) 10b, a RAM (Random Access Memory) 10c, a communication section 10d, and an I/F (Interface) 10e. ing. Here, the CPU 10a controls each section based on a program 10ba stored in the ROM 10b. The ROM 10b is composed of a semiconductor memory or the like, and stores programs 10ba and the like. The RAM 10c is configured by a semiconductor memory or the like, and stores data 10ca such as data generated when executing the program 10ba, mathematical formulas or tables to be described later. The communication unit 10d communicates with an ECU (Electronic Control Unit) or the like, which is a host device, and notifies the host device of 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 takes them in, and supplies drive currents 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, etc. may be executed by the ECU. It is not limited to the configuration of FIG.

In addition, although one CPU 10a is provided in the example of FIG. 2, distributed processing may be executed by a plurality of CPUs. Alternatively, the CPU 10a may be replaced by a DSP (Digital Signal Processor), FPGA (Field Programmable Gate Array), ASIC (Application Specific Integrated Circuit), or the like. Alternatively, the processing may be performed by a computer on a server using a general-purpose processor or cloud computing that executes the functions by loading a software program. In addition, 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, operation of the embodiment of the present invention will be described. In addition, below, after explaining the outline of the operation|movement of embodiment of this invention, detailed operation|movement is demonstrated.

First, an outline of the operation of the embodiment will be described. In this embodiment, when the rechargeable battery 14 installed in the vehicle is replaced with a new rechargeable battery 14 due to deterioration, for example, the rechargeable battery 14 after replacement is assumed to be When the rechargeable battery 14 has an initial capacity different from the nominal capacity, or when the rechargeable battery 14 has an initial capacity different from the nominal capacity due to neglect or the like, it can be detected and corrected. The capacity of the rechargeable battery 14 indicates the amount of electricity that can be extracted from the battery, and is represented by Ah (ampere hour), for example. In addition, the amount of electricity that can be extracted from the rechargeable battery 14 decreases as it deteriorates. Therefore, the capacity in the initial state where deterioration does not occur is defined as the initial capacity. Also, the nominal capacity means, for example, the capacity described in the catalog.

As an example, assume that the rechargeable battery 14 of the vehicle has been replaced due to deterioration over time due to use. In this 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 performs operations described later due to the interruption and restart of the power supply.

That is, the control unit 10 acquires information on the recommended initial capacity of the rechargeable battery 14 (hereinafter referred to as "recommended initial capacity") from the ECU (not shown) of the vehicle. For example, 50Ah is acquired as the information on the recommended initial capacity. The CPU 10a of the control unit 10 sets the recommended initial capacity to 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 the 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 indicates time, and the vertical axis indicates current or voltage. First, the CPU 10a measures the pre-discharge voltage Vb and the pre-discharge current Ib. Next, the CPU 10a controls the discharge circuit 15 to cause the rechargeable battery 14 to pulse-discharge. At this time, the CPU 10a samples the outputs of the voltage sensor 11 and the current sensor 12 at predetermined intervals. In the example of FIG. 3, sampling is performed at timings t1, t2, t3, .

Next, the CPU 10a converts the time-series voltage values V(tn) sampled at timings t1, t2, t3, . Divide to obtain the time-series resistance value R(tn). Instead of using the voltage value as it is, the drop voltage ΔV(tn) from the pre-discharge start voltage Vb is obtained, and this drop voltage ΔV(tn) is divided by the current value I(tn). A series resistance value R(tn) may be obtained.

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

f(tn)=a·tn+b (1)

FIG. 4 shows actual measurements for several types of rechargeable batteries 14 . In FIG. 4, batt1,2, batt3,4, and batt5,6 indicate rechargeable batteries of the same initial capacity (or nominal capacity), and batt1,2 indicate medium initial capacity rechargeable batteries. and batt3,4 and batt5,6 denote rechargeable batteries with initial capacities greater than batt1,2. 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 slope does not change 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. As shown in FIG. The horizontal axis of FIG. 5 indicates the slope a of the linear function, and the vertical axis indicates the SOH (State of Health). In addition, the rhombus (SOH_ini) in the figure indicates the measured initial capacity, and the circle (SOH_nom) indicates the nominal capacity. Nominal capacity and slope have a coefficient of determination on the order of 0.8. Also, the actually measured initial capacity and the slope have a coefficient of determination of about 0.8. Thus, the nominal value or the measured value of the initial capacity of the rechargeable battery 14 and the slope have a high correlation.

Therefore, in the present embodiment, when information about the recommended initial capacity cannot be obtained from the ECU, the slope a is obtained based on the equation (1) from the voltage value and the current value in the pulse discharge, and from the value of this slope a , the initial capacity IC of the rechargeable battery 14 is obtained. The relationship between the slope 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 state of charge (SOC) of the rechargeable battery 14 and defines it as SOCa. More specifically, the CPU 10a refers to the output of the current sensor 12 and integrates the current input/output to/from the rechargeable battery 14 to obtain the current integrated value IV. 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 the SOC, and calculates the charging rate SOC0 based on the initial capacity IC and the current integrated value IV. is obtained and this is defined as SOCa (=SOC0+IV/IC).

The CPU 10 a of the control unit 10 refers to the SOCa calculated based on the integrated value of the current, and controls the charging of the rechargeable battery 14 by the alternator 16 .

The CPU 10a of the control unit 10 determines whether or not the battery is fully charged by being charged by the alternator 16, based on changes in charging resistance, which will be described later. Note that "fully charged" refers to a state in which the rechargeable battery 14 is fully charged. For example, when the rechargeable battery 14 is new, it is charged to the nominal value. It means that the battery has been charged to the SOH at the point in time.

Here, there is a relationship between the SOC of the rechargeable battery 14 and the voltage generated by the alternator 16 as shown in FIG. 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 while the voltage generated by the alternator 16 is varied. In this figure, the solid curve shows the relationship between the SOC and the charging resistance of the rechargeable battery 14 when charged at a voltage of 15.5V, and the dashed curve with short intervals shows the relationship when charged at a voltage of 14.5V. and the long dashed curve shows the relationship between SOC and charging resistance when charged at a voltage of 13.5V. Here, the charging resistance is the voltage V applied to the rechargeable battery 14 when charging the rechargeable battery 14, the open circuit voltage OCV, and the resistance R obtained from the current I (=(V-OCV)/I). 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 reaches approximately 30 mΩ or more. That is, 30 mΩ is used as a threshold value, and whether or not the battery is fully charged can be determined by comparing this threshold value with the charging resistance. However, when the charging voltage is 14.5 V or 13.5 V, the SOC is less than 100% when the charging resistance is 30 mΩ. For this reason, when the voltage generated by the alternator 16 is not fixed but fluctuates, if the same threshold value is used to determine full charge, an accurate determination cannot be made.

Therefore, in the embodiment of the present invention, as shown in FIG. 7, by using a threshold that varies according to the generated voltage (=charged voltage) of the alternator 16, even if the generated voltage changes, the chargeable battery 14 is fully charged. I'm 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, and when the generated voltage is 14.5 V, the determination is made using the threshold Th2. When the voltage is 13.5V, the threshold Th3 is used for determination. According to such a method, even if the voltage generated by the alternator 16 changes, it is possible to accurately detect that the rechargeable battery 14 is fully charged.

When it is detected that the charging rate of the rechargeable battery 14 has reached the fully charged state, the CPU 10a sets SOCb=100%, which is the charging rate for full charging, and compares it with the charging 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, if SOCa=SOCb, 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 processing to re-estimate the initial capacity of the rechargeable battery 14. FIG. For example, re-estimating the initial capacity when the ambient temperature is within a predetermined range (for example, about 25°C plus or minus 5°C) to reduce errors due to temperature, or when charging from a low charging rate Since the full charge detection cannot be performed normally in this case, it is possible to re-estimate the initial capacity when the battery is charged from a high charging rate. This allows an accurate initial capacity to be estimated. By repeating the process until the difference between SOCa and SOCb becomes less than the predetermined threshold value, a more accurate initial capacity can be obtained.

When an accurate initial capacity is obtained as described above, charging control is performed based on this initial capacity, thereby preventing overcharging, for example, and improving fuel efficiency. Also, by preventing overdischarge, it is possible to prevent the engine 17 from being unable to restart, for example.

Details of the processing performed in the embodiment of the present invention will now be described with reference to FIGS. 8 to 11. FIG.

FIG. 8 is a flowchart for explaining an example of the main processing that is executed after the rechargeable battery 14 is replaced. When the process 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, for example, information such as 50Ah is obtained.

In step S11, the CPU 10a determines whether or not information acquisition was successful in step S10. If it is determined to be successful (step S11: Y), the process proceeds to step S13; otherwise (step S11: N ), the process proceeds to step S12.

In step S<b>12 , the CPU 10 a executes processing for 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 full charge detection processing for determining whether or not the rechargeable battery 14 is fully charged. The details of this process will be described later with reference to FIG.

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

In step S15, the CPU 10a obtains SOCa based on the initial capacity SOC0, the current integrated value IV obtained while the engine 17 is running, 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 the SOC, and calculates the charging rate based on the initial capacity IC and the current integrated value IV. and set this to SOCa (=SOC0+IV/IC).

In step S16, the CPU 10a obtains the absolute value of the difference between the state of charge SOCa obtained in step S15 and the state of charge SOCb detected by the full charge detection process in step S13 (|SOCa−SOCb|), and calculates this as dSOC. and

In step S17, the CPU 10a determines whether or not the dSOC obtained in step S16 is less than a predetermined threshold Th. If so (step S17: N), the process proceeds to step S18.

In step S<b>18 , the CPU 10 a executes processing for changing the initial capacity IC of the rechargeable battery 14 . Details of this process will be described later with reference to FIG.

Next, details of the "initial capacity estimation process" shown in step S12 of FIG. 8 will be described with reference to FIG. When the process 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 start 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. FIG. Methods of pulse discharge include, for example, a method of discharging via a resistive element and a method of discharging via a constant current circuit. In the latter method, since a constant current flows, it is possible to simplify the process of calculating the resistance value, which will be described later. Also, by limiting the current value, the load on the rechargeable battery 14 can be reduced.

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

At step S34, the CPU 10a measures the current of the rechargeable battery 14. FIG. More specifically, the CPU 10a refers to the output of the current sensor 12, measures the current I(tn) of the rechargeable battery 14 at timing tn, 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 since the start of the pulse discharge. If it is determined that the predetermined time has elapsed (step S35: Y), the process proceeds to step S36. In the case of (step S35: N), the process returns to step S33 and repeats the same processing as in the above case. For example, as shown in FIG. 3, when sampling has been completed N times, it is judged as Y and the process proceeds to step S36.

At step S36, the CPU 10a terminates 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(tn). More specifically, the CPU 10a divides the time-series voltage value V(tn) measured in step S33 by the time-series current value I(tn), thereby obtaining the time-series resistance value R(tn). demand. The obtained time-series resistance values R(tn) are stored in the RAM 10c as data 10ca.

In step S38, the CPU 10a fits the time-series resistance value R(tn) obtained in step S37 with the linear function f(tn) shown in the above equation (1) to obtain coefficients a and b. More specifically, for example, by using least squares calculation or Kalman filter calculation, linear function fitting can be performed to 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.

At step S40, the initial capacity IC of the rechargeable battery 14 is estimated based on the coefficient a obtained at step S39. More specifically, as shown in FIG. 5, since there is a correlation between the initial capacity of the rechargeable battery 14 and the slope a, the initial capacity IC of the rechargeable battery 14 is estimated based on the correlation. be able to.

In the above process, the resistance value is obtained by directly dividing the voltage value measured in step S33 by the current value measured in step S34. The resistance value R(tn) may be obtained by dividing the differential voltage ΔV(tn) obtained by subtracting Vb by the current value I(tn).

Also, the change in the resistance value of the rechargeable battery 14 due to the temperature is stored in the ROM 10b as a table, the temperature of the rechargeable battery 14 is detected by referring to the output of the temperature sensor 13, and based on the detected temperature, The resistance value obtained in step S37 may be temperature-corrected. Such a method can prevent errors from occurring due to temperature.

Next, the details of the "full charge detection process" shown in step S13 of FIG. 8 will be described with reference to FIG. When the process 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 and determines whether or not the rechargeable battery 14 is being charged by the alternator 16. If it is determined that the battery is being charged (step S50: Y), Otherwise (step S50: N), the same process is repeated. Note that if the battery is not being charged, the process may be terminated instead of repeating the same process.

In step S<b>51 , 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 obtained.

In step S52, the control unit 10 calculates the charging resistance R. More specifically, the current I obtained in step S50, the generated voltage V obtained in step S51, and, for example, the voltage of the rechargeable battery 14 after a predetermined time has passed 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 Th for determining whether or not the battery is fully charged to Th' based on the generated voltage V obtained in step S51. More specifically, by multiplying the reference threshold Th by g(V), the threshold Th is corrected by Th'=Th×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, if the threshold value Th1 when the generated voltage V=15.5 V is used as a reference threshold Th, when the generated voltage V=14.5 V, Th′=Th1×g(V)= Th2, and when the generated voltage V=13.5 V, g(V) is set so that Th'=Th1×g(V)=Th3.

In the above example, only the generated voltage V is considered, but the threshold value Th may be corrected in consideration of the temperature of the rechargeable battery 14 detected by the temperature sensor 13, for example. . Specifically, a function g(V, θ) having the generated voltage V and the temperature θ as variables may be used for correction 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 if R≧Th' is satisfied (step S54: Y) Otherwise (step S54: N), the process proceeds to step S56.

In step S55, the control unit 10 determines full charge (SOCb=100%). As a result, the control unit 10 stops driving the alternator 16 by the engine 17 .

At step S56, the controller 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, thereby continuing charging until the rechargeable battery 14 is fully charged.

According to the above process, the reference threshold value Th is corrected according to the generated voltage of the alternator 16, and the fully charged state can be determined based on the corrected threshold value Th′. The state of charge can be accurately determined.

Next, details of the "initial capacity change process" shown in step S18 of FIG. 8 will be described with reference to FIG. When the process 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 fully charged. Note that this process is the same as the process shown in FIG. 10, so the description thereof will be omitted.

In step S71, the CPU 10a determines whether or not the fully charged state is determined by the process of step S70. At step S72:N), the process returns to step S70 to repeat the same process.

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

In step S73, the CPU 10a determines whether or not the initial capacity obtained initially has changed as a result of the estimation in step S72. If not, go to step S74, otherwise (step S73: N), return to the original process. For example, if the initial capacity estimated in step S72 has changed compared to 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 charging control based on the changed initial capacity. As a result, the ECU executes charging control based on the changed initial capacity, so that overcharging and overdischarging can be prevented.

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-described embodiment is merely an example, and needless to say, the present invention is not limited to the case described above. For example, in the above embodiment, in step S18 of FIG. 8, the initial capacitance is re-estimated and changed. For example, as shown in FIG. You may make it return and repeat the same process.

That is, in the process shown in FIG. 12, when compared with FIG. 8, the process of step S18 is omitted and the process of step S90 is added. If it is determined in step S17 that dSOC<Th, the process proceeds to step S90 to decrease or increase the initial capacity IC by a predetermined amount (eg, 5Ah), and then returns to step S13. As a result, SOCa changes, so the process is repeated until dSOC<Th. Through the above processing, the correct initial capacity of the rechargeable battery 14 after replacement can be obtained as in FIG.

Further, in the above embodiment, as shown in FIG. 7, different Th1 to Th3 are used for each voltage of the alternator 16 to determine full charge. However, for example, as shown in FIG. Using Th, SOC1 to SOC3, which differ for each voltage, may be applied as the full charge value.

FIG. 14 is a diagram showing a flowchart for applying SOC1 to SOC3, which are different for each voltage, as the full charge value, as shown in FIG. 14, steps S53 to S56 are omitted 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 to be satisfied (step S101: Y), the process proceeds to step S102, otherwise (step S101: N). return to the original processing.

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

In step S<b>103 , the CPU 10 a corrects the reference SOC according to the voltage generated by the alternator 16 . For example, as shown in FIG. 13, when the generated voltage is 13.5V, the reference SOC is corrected to SOC1, and when the generated voltage is 14.5V, the reference SOC is corrected to SOC2. If it is 15.5V, the reference SOC is corrected to SOC3. Specifically, when the reference SOC=SOC3, if the generated voltage is 15.5V, SOC3 is calculated by SOC3=1×reference SOC, and if the generated voltage is 14.5V, SOC2=α1. SOC2 is obtained from x reference SOC, and when the generated voltage is 13.5V, SOC3 is obtained from SOC3=α2×reference SOC. Note 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. FIG.

In each of the above embodiments, the charging resistance R is calculated by dividing the difference between the charging voltage V and the open circuit voltage OCV by the charging current I. It may be calculated by taking St and polarization Pl into consideration. 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 embodiments, the charging resistance is used to detect full charge, but the determination may be made based on the charging current. Specifically, from the start of charging until the terminal voltage reaches a predetermined voltage value, constant-current charging is performed in which the charging current is substantially constant. After the terminal voltage reaches a predetermined voltage value, the battery is switched to constant voltage charging in which charging is performed with the terminal voltage kept substantially constant. After switching to constant voltage charging, the charging current generally decreases as the battery approaches full charge. Then, when the charging current drops to a predetermined current value (current threshold), the duration time 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 (determination time). It may also be determined that the rechargeable battery has reached a predetermined state.

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. The resistance of the rechargeable battery 14 may be determined when the starter motor 18 is energized.

Further, in the above embodiment, when the rechargeable battery 14 is replaced with a new one, the above-described processing of FIG. 9 and the like is executed. 9 and the like are executed to detect whether the capacity of the rechargeable battery 14 has decreased from the initial capacity, and if it has decreased, the capacity after the decrease is used to obtain an accurate SOC. can ask. As a result, even when deterioration occurs, overcharge or overdischarge can be prevented.

In the above embodiment, the capacity of the rechargeable battery 14 is estimated from the slope a of the linear function. The capacity may be estimated from the average value of .

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

1 Rechargeable Battery State 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 a rechargeable battery state detection device that detects the state of a rechargeable battery,
a first estimating means for obtaining an estimated value of the capacity of the rechargeable battery and estimating the state of charge of the rechargeable battery based on the estimated value of the capacity;
a second estimating means for detecting the current flowing through the rechargeable battery by a current detection value output from a current sensor and estimating the charging rate of the rechargeable battery based on the current detection value;
a correcting means for correcting the estimated value of the capacity of the rechargeable battery based on the charging rate estimated by the first estimating means and the second estimating means;
A rechargeable battery state detection device comprising: wherein the first estimating means obtains an estimated value of the capacity from outside or calculates an estimated value of the capacity based on the resistance of the rechargeable battery;
2. The rechargeable battery state detection device according to claim 1, wherein: The first estimating means measures the voltage and current of the rechargeable battery during discharge, calculates the resistance value based on these values, and obtains the capacity based on the calculated resistance value. Item 3. The rechargeable battery state detection device according to item 2. The first estimating means measures the voltage and current of the rechargeable battery during discharge, calculates the resistance value that changes in time series based on these, and fits the calculated resistance value to a linear function, 4. The rechargeable battery state detection device according to claim 3, wherein the capacity is obtained from the obtained slope of the linear function. 5. The second estimating means determines that the charging rate of the rechargeable battery is fully charged when the charging resistance of the rechargeable battery exceeds a predetermined threshold. The rechargeable battery state detection device according to any one of Claims 1 to 3. 6. The rechargeable battery state detection device according to claim 5, wherein the threshold value is different according to the charging voltage when charging the rechargeable battery. 6. The rechargeable battery state detection device according to claim 5, wherein the same threshold value is used, and the charging rate is corrected according to the charging voltage when charging the rechargeable battery. The correcting means corrects the estimated value of the capacity, or corrects the slope of the linear function when the charging rates estimated by the first estimating means and the second estimating means differ by a predetermined threshold or more. 5. The rechargeable battery state detecting device according to claim 4, wherein said capacity is obtained again from . 1. The correction value of the capacity corrected by the correction means is supplied to a higher-level device, and charging of the rechargeable battery is controlled based on the supplied correction value of the capacity. 9. The rechargeable battery state detection device according to any one of 8. In a rechargeable battery state detection method for detecting a state of a rechargeable battery,
a first estimating step of obtaining an estimated value of the capacity of the rechargeable battery and estimating a state of charge of the rechargeable battery based on the estimated value of the capacity;
a second estimation step of detecting a current flowing through the rechargeable battery by a current detection value output from a current sensor and estimating the charging rate of the rechargeable battery based on the current detection value;
a correction step of correcting the estimated value of the capacity of the rechargeable battery based on the state of charge estimated in the first estimation step and the second estimation step;
A rechargeable battery state detection method, comprising:

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