JP7178287B2 - 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.

Failure or malfunction of a rechargeable battery is a major problem for equipment that supplies power from rechargeable batteries and for four-wheeled or two-wheeled vehicles that rely on rechargeable batteries to start their engines.

Sudden loss of power due to failure or abnormality of the rechargeable battery poses a reliability problem for autonomous vehicles, which are expected to be realized in the near future.

There are multiple causes for failures or abnormalities in rechargeable batteries. Among them, when "polarity reversal" occurs, in which the positive electrode reaction and the charging reaction are reversed as a result of overdischarge, the rechargeable battery suffers irreparable damage. given and known to lead to failure or anomalies.

As a method of detecting an abnormality in a rechargeable battery represented by such polarity reversal, a method of estimating based on the behavior of the voltage of the rechargeable battery has been proposed, for example, as in Patent Document 1. .

JP-A-06-89743

By the way, in the method disclosed in Patent Document 1, in which polarity reversal is detected using only voltage behavior as an index, it is extremely difficult to accurately discriminate from overdischarge in a range that does not lead to polarity reversal. In this case, there is the problem of overestimating damage to a rechargeable battery that has only suffered a recoverable level of damage.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a rechargeable battery state detecting device and a rechargeable battery state detecting method capable of accurately detecting the occurrence of polarity reversal. and

In order to solve the above-mentioned problems, the present invention provides a rechargeable battery state detection device for detecting the state of a rechargeable battery, comprising a voltage detection unit for detecting the terminal voltage of the rechargeable battery and a current flowing through the rechargeable battery. input means for inputting a signal from a current detection unit to be detected; and based on the signal input from the input means, when the rechargeable battery is being discharged, the terminal voltage of the rechargeable battery is set to a predetermined threshold value. a first determination means for determining that there is an abnormality when the value is less than the above; and a second determination means for determining presence/absence of occurrence of pole reversal based on at least one of them.
With such a configuration, it is possible to accurately detect the occurrence of pole reversal.

Further, the present invention is characterized in that the second determination means determines that polarity reversal has occurred when the internal resistance decreases after the discharge of the rechargeable battery is stopped.
With such a configuration, it is possible to accurately detect the occurrence of pole reversal.

Further, in the present invention, the second determination means determines that polarity reversal has occurred when the terminal voltage increases more moderately than in the case of overdischarge after the discharge of the rechargeable battery is stopped. characterized by
With such a configuration, it is possible to accurately detect the occurrence of pole reversal.

Further, according to the present invention, the second determination means determines whether the internal resistance is constant after the discharge of the rechargeable battery is stopped, or when the terminal voltage changes more rapidly than when the polarity is reversed. is characterized by determining that overdischarge has occurred.
According to such a configuration, polarity reversal and overdischarge can be distinguished and detected.

Further, the present invention is characterized in that a warning is issued to the user when the second determination means determines that the polarity reversal has occurred.
According to such a configuration, it is possible to reliably inform the user of the occurrence of pole reversal.

Further, in the present invention, the rechargeable battery is mounted in a vehicle, and when the second determination means determines that polarity reversal has occurred, when the engine of the vehicle is restarted, the It is characterized by executing control for charging the rechargeable battery.
According to such a configuration, it is possible to reduce the state of pole reversal.

Further, the present invention provides a rechargeable battery state detection method for detecting the state of a rechargeable battery, wherein a voltage detection unit for detecting a terminal voltage of the rechargeable battery and a current detection unit for detecting a current flowing through the rechargeable battery and an input step of inputting a signal of and based on the signal input in the input step, when the terminal voltage of the rechargeable battery is less than a predetermined threshold when the rechargeable battery is being discharged, an abnormality is detected. a first determination step for determining that the rechargeable battery is abnormal, and if an abnormality is determined in the first determination step, after the discharge is stopped, the battery is switched based on at least one of a change in terminal voltage and a change in internal resistance of the rechargeable battery. and a second determination step of determining whether or not a pole is generated.
According to such a method, it is possible to accurately detect the occurrence of pole reversal.

According to the present invention, it is possible to provide a rechargeable battery state detection device and a rechargeable battery state detection method that can accurately detect the occurrence of polarity reversal.

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. It is a figure which shows the change of a terminal voltage when reversal of polarity and overdischarge generate|occur|produce. It is a figure which expands and shows a part of FIG. FIG. 4 is a simplified diagram showing changes in voltage and changes in internal resistance during polarity reversal and during overdischarge; FIG. 2 is an example of a flowchart illustrating the flow of processing executed while an engine is operating in the embodiment shown in FIG. 1; FIG. FIG. 2 is an example of a flowchart illustrating the flow of processing executed after the engine stops in the embodiment shown in FIG. 1; 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 control section 10, a voltage detection section 11, a current detection section 12, a temperature detection section 13, and a discharge circuit 15 as main components. Control the state of charge. Note that the control unit 10, the voltage detection unit 11, the current detection unit 12, the temperature detection unit 13, and the discharge circuit 15 may not be configured separately, but may be configured by integrating some or all of them. In other words, the voltage detection unit 11 may be a portion of the circuit in which a circuit for detecting voltage is incorporated. At least part of the voltage detection unit 11 , the current detection unit 12 , the temperature detection unit 13 , and the discharge circuit 15 may be configured independently of the rechargeable battery state detection device 1 .

Here, the control unit 10 refers to outputs from the voltage detection unit 11, the current detection unit 12, and the temperature detection unit 13, detects the state of the rechargeable battery 14, and controls the voltage generated by the alternator 16. This controls the state of charge of the rechargeable battery 14 . The voltage detection unit 11 detects the terminal voltage of the rechargeable battery 14 and notifies the control unit 10 of it. The control unit 10 does not control the charging state of the rechargeable battery 14 by controlling the voltage generated by the alternator 16. For example, an ECU (Electric Control Unit) (not shown) based on information from the control unit 10 You may make it control a charge state.

The current detection unit 12 detects the current flowing through the rechargeable battery 14 and notifies the control unit 10 of it. The temperature detection unit 13 detects the temperature of the rechargeable battery 14 itself or the ambient temperature and notifies the control unit 10 of it. The discharge circuit 15 is composed of, for example, a semiconductor switch and a resistance element connected in series, and intermittently discharges the rechargeable battery 14 by on/off control of the semiconductor switch by the control unit 10 .

The rechargeable battery 14 is composed of, for example, a lead-acid battery, a nickel-cadmium battery, a nickel-hydrogen battery, or a lithium-ion battery. to power the 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 unit 10 includes a CPU (Central Processing Unit) 10a as a processor, a ROM (Read Only Memory) 10b, a RAM (Random Access Memory) 10c, a communication unit 10d, and an I/F (Interface) 10e. have. Here, the CPU 10a controls each section based on a program 10ba stored in the ROM 10b. The program 10ba has a plurality of instruction groups that can be executed by the CPU 10a. By executing the instruction group, the processing described later can be realized. 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 generated when the program 10ba is executed, and parameters 10ca such as formulas or tables to be described later. The communication unit 10d communicates with an ECU 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 detection unit 11, the current detection unit 12, and the temperature detection unit 13 into digital signals and takes them in, and supplies them to the discharge circuit 15, the alternator 16, the starter motor 18, and the like. A drive current is supplied to control them.

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 the following, detailed operation will be described after the principle of operation of the embodiment of the present invention is described.

First, the principle of operation of this embodiment will be described. FIG. 3 is a diagram showing changes in terminal voltage (hereinafter simply referred to as "voltage") measured over time when the rechargeable battery 14 is reversed during discharge and when overdischarge occurs during discharge. is. In this figure, the horizontal axis indicates time (hr) and the vertical axis indicates the voltage of the rechargeable battery 14 . 4 is an enlarged view of the range from 0 to 2.5 hours in FIG. 3 (the range surrounded by the dashed line in FIG. 3).

In FIGS. 3 and 4, at time T0, discharging is stopped and no charging/discharging occurs (in the case of a vehicle, the engine 17 is stopped). SOC becomes very low), the voltage recovers rapidly. Also, the amplitude of the voltage drop due to the discharge by the discharge circuit 15 that is performed periodically (impulses appearing periodically in FIGS. 3 and 4) is not large.

On the other hand, in the case of polarity reversal indicated by the dashed line (when the positive electrode reaction and the charging reaction are reversed as a result of overdischarge), the voltage recovers more slowly than in the case of overdischarge. Also, the voltage drop due to the discharge (impulse appearing periodically in FIGS. 3 and 4) by the discharge circuit 15 which is performed periodically has a larger amplitude than the overdischarge. Since the discharge by the discharge circuit 15 which is performed periodically is a constant current discharge, a large amplitude of the voltage drop due to the discharge indicates a large internal resistance.

FIG. 5 is an image diagram showing a simplified change in voltage and change in internal resistance at the time of pole reversal and overdischarge. As indicated by the solid line in FIG. 5, during overdischarge, when the discharge is stopped at time T0 during discharge, the voltage recovers rapidly. On the other hand, as shown by the dashed line in FIG. 5, during polarity reversal, when discharge is stopped at time T0 during discharge, the voltage recovers more slowly than during overdischarge (voltage slope is small).

In addition, as indicated by white circles in FIG. 5, during overdischarge, when discharge is stopped at time T0 during discharge, the value of the internal resistance becomes substantially constant. On the other hand, as indicated by black circles in FIG. 5, during polarity reversal, when the discharge is stopped at time T0 during discharge, the value of the internal resistance gradually decreases.

As shown above, when the discharge is stopped after the polarity reversal occurs during the discharge, the voltage recovers more gently than the overdischarge as shown by the broken line, and the internal resistance value gradually decreases. do. On the other hand, when the discharge is stopped after overdischarge occurs during discharge, the voltage recovers rapidly as indicated by the solid line, and the internal resistance maintains a constant value.

Therefore, in the embodiment of the present invention, when the voltage drops below a predetermined threshold during discharging of the rechargeable battery 14, first, it is determined that polarity reversal or overdischarge has occurred, and the CPU 10a of the control unit 10 flags Let F=1. Then, after the discharge is stopped (after the engine 17 is stopped), if the flag F=1, the CPU 10a determines that polarity reversal or overdischarge has occurred, and observes changes in voltage and changes in internal resistance. . As a result, when the voltage rapidly recovers as indicated by the solid line in FIG. 5 and the internal resistance value remains constant as indicated by the white circles, it is determined that the battery is overdischarged. On the other hand, when the voltage gradually recovers as indicated by the dashed line in FIG. 5 and the internal resistance value decreases as indicated by the black circles, it is determined that the polarity is reversed.

As described above, in the present embodiment, when the voltage of the rechargeable battery 14 drops below a predetermined threshold during discharging, the voltage is lowered after the discharge is stopped, instead of making a decision immediately. If the voltage recovers rapidly and the internal resistance value remains constant, it is determined to be a recoverable overdischarge. judge. Therefore, it is possible to prevent erroneous determination of a recoverable overdischarge as a reversal of polarity difficult to recover from.

Next, an example of processing executed in the embodiment of the present invention will be described with reference to FIGS. 6 and 7. FIG. FIG. 6 is a diagram showing a sequence of processes that are performed periodically, for example, when the engine 17 is in operation. When the process of the flowchart shown in FIG. 6 is started, the following steps are executed.

In step S10, the CPU 10a of the control unit 10 determines whether or not the engine 17 is in operation. If it is determined that it is in operation (step S10: Y), the process proceeds to step S11; N) ends the process.

In step S11, the CPU 10a refers to the output of the current detector 12 and measures the current I flowing through the rechargeable battery .

At step S12, the CPU 10a refers to the current I measured at step S11 to determine whether or not the rechargeable battery 14 is discharging. , otherwise (step S12: N), the process is terminated.

In step S13, the CPU 10a measures the voltage (terminal voltage) V of the rechargeable battery 14 by referring to the output of the voltage detection section 11. FIG.

In step S14, the CPU 10a compares the terminal voltage V of the rechargeable battery 14 measured in step S13 with a predetermined threshold value Th. If V<Th is satisfied (step S14: Y), the process proceeds to step S15; In the case of (step S14: N), the process proceeds to step S16. As the threshold Th, when the rechargeable battery 14 is composed of 6 cells, for example, a voltage (for example, 10 V) lower than the voltage of one cell (approximately 2 V) can be used as the threshold. . Of course, other voltages may be set.

In step S15, the CPU 10a substitutes 1 into a flag F which is set to 1 when an abnormality occurs in the rechargeable battery 14 and set to 0 otherwise.

In step S16, the CPU 10a substitutes 0 for the flag F.

According to the above process, when the terminal voltage V of the rechargeable battery 14 becomes less than the predetermined threshold value Th during discharging, the flag F is set to 1 assuming that some abnormality has occurred, and set to 0 otherwise. be done.

Next, an example of processing executed when the engine 17 is stopped will be described with reference to FIG. When the process of the flowchart of FIG. 7 is started, the following steps are executed.

In step S30, the CPU 10a determines whether or not the engine 17 has been stopped. If it is determined that the engine 17 has been stopped (step S30: Y), the process proceeds to step S31; ), the process ends.

In step S31, the CPU 10a determines whether or not the value of the flag F is 1. If F=1 (step S31: Y), the process proceeds to step S32; otherwise (step S31: N ), the process ends.

In step S32, the CPU 10a sets 1 as an initial value to a variable n for counting the number of times of processing.

In step S33, the CPU 10a determines whether or not a predetermined time has elapsed. If it is determined that the predetermined time has elapsed (step S33: Y), the process proceeds to step S34; otherwise (step S33: N). ), the same process is repeated. For example, if several hours have passed, it is judged as Y and the process proceeds to step S34.

In step S34, the CPU 10a controls the discharge circuit 15 to pulse discharge the rechargeable battery 14, for example.

In step S35, the CPU 10a measures the voltage V and the current I during discharging by means of the voltage detection section 11 and the current detection section 12. FIG.

At step S36, the CPU 10a stores the voltage V measured at step S35 in the array variable V(n). For example, if n=1, V(1) stores the current voltage V of rechargeable battery 14 .

In step S37, the CPU 10a calculates the internal resistance R. More specifically, CPU 10a calculates the internal resistance R of rechargeable battery 14 from changes in voltage and current during discharge.

At step S38, the CPU 10a stores the value of the internal resistance R calculated at step S37 in the array variable R(n). For example, if n=1, R(1) stores the current internal resistance R of rechargeable battery 14 .

In step S39, the CPU 10a increments the variable n for counting the number of times of processing by one.

In step S40, the CPU 10a determines whether or not the value of the variable n for counting the number of times of processing is greater than N. If n>N is satisfied (step S40: Y), the process proceeds to step S41; At (step S40: N), the process returns to step S33 and repeats the same processing as described above. A value of about 2 to 20 can be set for N. Of course, other values may be set.

In step S41, the CPU 10a determines whether or not the value of V(n2)-V(n1) (where n2>n1) is a positive value (>0). If S41: Y), the process proceeds to step S42, otherwise (step S41: N), the process ends.

In step S42, when the value of V(n2)-V(n1) (where n2>n1) is less than a predetermined threshold Th1 (when V(n2)-V(n1)<Th1), the CPU 10a determines that the voltage gradually recovers after the discharge is stopped, as indicated by the dashed line in FIG. 5, and proceeds to step S43. Note that n1 and n2 can be the timings of n1 and n2 shown in FIG. Note that Th1 is preferably set to a value smaller than the value of V(n2)-V(n1) during overdischarge.

In step S43, the CPU 10a determines whether the value of R(n) is decreasing over time as indicated by the black circles in FIG. If step S43: Y), the process proceeds to step S44, otherwise (step S43: N), the process ends.

In step S44, the CPU 10a determines that polarity reversal has occurred. That is, when the terminal voltage V of the rechargeable battery 14 becomes less than the predetermined threshold value Th during discharging, and the terminal voltage V gradually increases and the internal resistance R decreases after the discharge is stopped, polarity reversal occurs. determine that there is

In step S45, the CPU 10a outputs information indicating the occurrence of polarity reversal via the communication section 10d. As a result, the upper ECU (Electric Control Unit) recognizes that the polarity reversal has occurred, for example, notifies the user of the occurrence of the polarity reversal and warns the user, and when the engine 17 is started. For example, the alternator 16 is controlled to charge the rechargeable battery 14 with a high current to eliminate polarity reversal.

As described above, according to the process of the flowchart shown in FIG. 7, when the terminal voltage becomes less than the predetermined threshold value Th during discharging of the rechargeable battery 14, it is immediately determined that an abnormality has occurred. Instead, changes in the voltage and the internal resistance are detected after the discharge is stopped, and it is determined that the reversal has occurred when the voltage gradually increases and the internal resistance decreases. As a result, it is possible to prevent a recoverable overdischarge from being erroneously determined as a reversal that is difficult to recover from.

(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 embodiments, after the discharge is stopped, both the internal resistance and the change in the voltage are referred to determine whether or not the polarity reversal has occurred. may For example, if the internal resistance decreases after the discharge is stopped, it may be determined that the polarity reversal has occurred. Further, it may be determined that the polarity inversion has occurred when the voltage gradually increases after the discharge is stopped.

Further, in the above embodiment, when the polarity reversal occurs, the user is notified, but other processes may be executed. For example, at least one of (1) a process of notifying the user of the occurrence of pole reversal to warn him or (2) a process of changing the control of the vehicle may be executed.

More specifically, with respect to (1), when the polarity reversal occurs, the CPU 10a of the control unit 10 outputs information indicating that the polarity reversal has occurred to the ECU (not shown) via the communication unit 10d. A display device (not shown) may display information indicating that the polarity reversal has occurred and information indicating that the rechargeable battery 14 needs to be replaced. Also, an audio warning may be issued at the same time.

Regarding (2), when the CPU 10a of the control unit 10 outputs information indicating that the polarity reversal has occurred to the ECU (not shown) via the communication unit 10d, the chargeable battery state detection device 1 can be charged. The state of the battery 14 (for example, SOF (State of Function)) is detected to determine whether the engine 17 can be restarted. As a result, when it is determined that the engine 17 cannot be restarted, when the user attempts to restart the engine 17, the display device displays information indicating that the engine 17 cannot be restarted due to the reversal of polarity, and the starter The supply of current to the motor 18 is cut off.

On the other hand, when it is determined that the engine 17 can be restarted, the current (dark current) flowing through the load 19 is cut off in order to prevent further consumption of the rechargeable battery 14 . In addition, after the user starts the engine, the charging mode for polarity reversal is entered, the voltage generated by the alternator 16 is increased, and the rechargeable battery 14 can be rapidly charged.

Further, the flowcharts shown in FIGS. 6 and 7 are examples, and needless to say, the present invention is not limited only to these flowcharts.

For example, in the flowchart shown in FIG. 7, it is determined whether or not the curve is the dashed line shown in FIG. 5 by one determination in step S42. You may do so. For example, when the voltage gradients measured over time are ΔV1, ΔV2, ΔV3, . ), and the average value of ΔV1, ΔV2, ΔV3, . . . , ΔVn may be compared with a predetermined threshold value. Alternatively, each of ΔV1, ΔV2, ΔV3, . . . , ΔVn may be compared with a predetermined threshold that decreases with time. Of course, depending on the timing of sampling, such a relationship may not always hold, so the sampling period may be determined appropriately, or the sampling period may be lengthened as the slope becomes smaller. In addition, when polarity reversal occurs, compared to the case of overdischarge, the slope of ΔV continues even after a certain amount of time has passed. You may make it determine with reversal of polarity. Alternatively, if the time from reaching a predetermined voltage V1 to reaching a predetermined voltage V2 (>V1) is equal to or greater than a predetermined threshold value, it may be determined that the polarity is reversed. Furthermore, these multiple determination methods may be combined.

Alternatively, the change in voltage may be fitted by a predetermined function, and determination may be made based on the size of the time constant of the fitting result function. For example, fitting may be performed using an exponential function represented by the following equation (1) or equation (2), and if the obtained time constant τ1 is equal to or greater than a predetermined threshold value, the reversal may be determined. Note that Time in Equation (1) indicates time, and n in Equation (2) indicates the number of times of sampling.

V=−A×exp(−Time/τ1)+B (1)

V=−A×exp(−n/τ1)+B (2)

Also, the threshold value may be variable depending on the temperature and/or SOC, etc., instead of being a fixed value, or the threshold value may be calculated each time depending on the temperature and/or SOC.

Also, after the engine 17 stops, a dark current flows through the load 19 . Therefore, the tendency of the voltage change may differ depending on the influence of the dark current. Therefore, the threshold is determined in consideration of the influence of the dark current, the voltage value corrected for the influence of the dark current is used, or the judgment is suspended when the dark current value is large. good too.

In the above description, changes in voltage have been explained, but changes in resistance values can also be similarly determined using a plurality of thresholds, fitting with a function and determining from a constant value, temperature and/or Alternatively, the threshold may be obtained based on SOC or the like, or the influence of dark current may be considered.

More specifically, R1>R2>R3>, . . . , Rn, where R1, R2, R3, . value decreases with the lapse of time) and Rn asymptotically approaches a predetermined value as n increases, it may be determined that the reversal has occurred.

Alternatively, where ΔR is the change in internal resistance, each of ΔR1, ΔR2, ΔR3, . Of course, depending on the timing of sampling, such a relationship may not always hold, so the sampling period may be determined appropriately, or the sampling period may be lengthened as the slope approaches zero. Alternatively, if the time from reaching a predetermined internal resistance R1 to reaching a predetermined internal resistance R2 (<R1) is less than a predetermined threshold value, it may be determined that the polarity is reversed.

Alternatively, the change in internal resistance may be fitted with a predetermined function, and determination may be made based on the size of the time constant of the fitting result function. For example, fitting is performed using an exponential function shown in the following equation (3) or equation (4), and if the obtained constant C+D is equal to or greater than a predetermined threshold value, it may be determined that the reversal has occurred. Alternatively, when C is equal to or greater than a predetermined threshold value, it may be determined that the reversal has occurred. Alternatively, when the time constant τ2 is less than a predetermined threshold value, it may be determined that the reversal has occurred. Note that Time in Equation (3) indicates time, and n in Equation (4) indicates the number of times of sampling.

R=C×exp(−Time/τ2)+D (3)

R=C×exp(−n/τ2)+D (4)

As for the threshold for determination, as in the case of voltage, instead of being a fixed value, for example, it may be variable depending on temperature and/or SOC, etc., or the threshold may be calculated each time according to temperature and/or SOC, etc. It may be obtained by

Further, similarly to the voltage described above, a dark current flows through the load 19 after the engine 17 stops. Therefore, the change tendency of the internal resistance may differ depending on the influence of the dark current. Therefore, the threshold may be determined in consideration of the influence of the dark current, or the determination may be suspended when the value of the dark current is large.

1 Rechargeable Battery State Detector 10 Control Unit 10a CPU
10b ROM
10c RAM
10d communication unit 10e I/F
REFERENCE SIGNS LIST 11 voltage detector 12 current detector 13 temperature detector 14 rechargeable battery 15 discharge circuit 16 alternator 17 engine 18 starter motor 19 load

Claims (7)

In a rechargeable battery state detection device that detects the state of a rechargeable battery,
input means for inputting signals from a voltage detection section for detecting terminal voltage of the rechargeable battery and a current detection section for detecting current flowing through the rechargeable battery;
First determination means for determining, based on the signal input from the input means, that there is an abnormality when the terminal voltage of the rechargeable battery is less than a predetermined threshold when the rechargeable battery is being discharged. When,
When the first determination means determines that there is an abnormality, a second determination is made based on at least one of a change in terminal voltage and a change in internal resistance of the rechargeable battery to determine whether or not polarity reversal has occurred after stopping discharging. means and
A rechargeable battery state detection device comprising: 2. The state of the rechargeable battery according to claim 1, wherein said second determination means determines that polarity reversal has occurred when said internal resistance decreases after the discharge of said rechargeable battery has stopped. detection device. The second determination means determines that polarity reversal has occurred when the terminal voltage increases more gently than in the case of overdischarge after the discharge of the rechargeable battery has stopped. 3. The rechargeable battery state detection device according to claim 1 or 2. The second determination means determines that overdischarge occurs if the internal resistance is constant or if the terminal voltage changes more rapidly than the polarity reversal after the discharge of the rechargeable battery is stopped. 4. The rechargeable battery state detection device according to claim 1, wherein the rechargeable battery state detection device determines that the battery has been charged. 5. The state of the rechargeable battery according to any one of claims 1 to 4, wherein a user is warned when the second determination means determines that polarity reversal has occurred. detection device. The rechargeable battery is mounted on a vehicle,
When the second determination means determines that the polarity reversal has occurred, when the engine of the vehicle is restarted, control is performed to charge the rechargeable battery.
6. The rechargeable battery state detection device according to any one of claims 1 to 5, characterized in that: In a rechargeable battery state detection method for detecting a state of a rechargeable battery,
an input step of inputting signals from a voltage detection unit that detects the terminal voltage of the rechargeable battery and a current detection unit that detects the current flowing through the rechargeable battery;
A first determination step of determining, based on the signal input in the input step, that an abnormality is occurring when the terminal voltage of the rechargeable battery is less than a predetermined threshold when the rechargeable battery is discharging. When,
If the first determination step determines that there is an abnormality, a second determination is made based on at least one of a change in terminal voltage and a change in internal resistance of the rechargeable battery to determine whether or not polarity reversal has occurred after stopping discharging. a step;
A rechargeable battery state detection method , comprising:

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