JP2007245818A - Battery state control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device to carry out state detection of a battery even in supplying electric power to a load from the battery when an engine works. <P>SOLUTION: This battery state control device to carry out state control of the battery loaded on a vehicle is characteristically furnished with a voltage measuring means to measure output voltage of the battery and a battery state detecting means to detect that the battery is in a sate incapable of supplying the electric power required by the load when timely variation of the output voltage is out of a previously set first region in the case when the electric power is supplied to the load at a constant electric current value from the battery when the engine works. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a battery state management system, and more specifically, manages a battery state by detecting a supply power shortage state associated with a decrease in the remaining amount of battery or the progress of deterioration during traveling.

  A battery made of lead-acid battery mounted on a car is used to drive a starter attached to the engine at the start, and when the engine is operating, the power supply to the load is insufficient for the amount of power generated by the generator Power is being supplied from the battery. Therefore, the function of the battery is extremely important both in starting and running the automobile.

  In particular, in recent years, devices that require a large current have been mounted on automobiles, and it is important to stabilize the power supply while the automobile is running. However, when the battery is deteriorated or the remaining capacity is small, a situation occurs in which power cannot be sufficiently supplied to the load. Therefore, various methods for measuring the battery output voltage and output current to measure the remaining amount of the battery or measuring the health level of the battery have been considered.

  For example, Japanese Patent Laying-Open No. 2005-304173 (Patent Document 1) proposes a battery state detection method and a detection device that detect a battery state only by measuring a battery voltage at the time of starting. The battery state detection method disclosed in Patent Document 1 includes a resistance R inherent to an engine start circuit stored in advance, an open circuit voltage Vo measured immediately before engine start, and a discharge voltage at the time of maximum voltage drop at engine start. The battery internal resistance r is calculated from Vst, and the battery health level SOH is detected by applying the calculated internal resistance r to the relationship between the internal resistance r and the health level SOH stored in advance.

  However, even when the engine is in operation, if the battery continues to be used in an excessively discharged state, the battery will deteriorate, and even if it is charged again, the battery may deteriorate and power cannot be supplied to the load. Therefore, it is necessary to detect the state of the battery not only at the time of starting but also during traveling.

  However, in the apparatus and method of Patent Document 1, since the state of the battery is only detected using the output voltage value at the time of starting, the state of the battery changes during engine operation, and the battery is deteriorated or discharged. Even if it becomes, there is a problem that it cannot be detected.

JP-A-2005-304173

  The present invention has been made in view of the above problems, and it is an object of the present invention to provide a system that detects a power state supplied from a battery to a load during engine operation and manages a remaining amount of the battery and a progress state of deterioration. Yes.

In order to solve the above problems, as a first invention,
Voltage measuring means for measuring the output voltage of the battery mounted on the vehicle;
Battery state detecting means for detecting that the battery is in an insufficient supply power state when the amount of change in the output voltage measured at the time of engine operation deviates from a predetermined range of the amount of change; A battery state management system is provided.

  When the engine is operating, it is not sufficient to supply power from the generator to the load, and the state of supplying power from the battery occurs when a load that requires a large current is driving. In this case, the output current flowing from the battery to the load is considered to be constant depending on the amount of current flowing to the load that requires a large current, but the output voltage is almost constant over time due to the decrease in the electromotive force. Decrease with change. The change amount of the decrease in the output voltage represents the deterioration state or discharge state of the battery, and the change amount increases as the battery deteriorates or discharges.

In the present invention, the amount of change in output voltage (slope of the output voltage value with respect to time) during a predetermined time during engine operation is measured, and when the range of the amount of change set in advance is exceeded, the output voltage due to battery deterioration or discharge Is in a state where the battery cannot supply the power required by the load, that is, the remaining amount of the battery is low, or the battery is deteriorated and the supply power is insufficient. Is detected. Note that when power is started to be supplied to the load that requires the large current, the output voltage of the battery rapidly decreases, but the amount of change in the output voltage that is required in the present invention is the load that requires the large current. The amount of change in output voltage in a state where power is continuously supplied is shown.
Thus, the battery state can be managed when the engine is operating only by measuring the output voltage of the battery when the engine is operating.

  The battery state detection means may further detect that the battery is in an insufficient supply power state even when a value obtained by differentiation of the output voltage is out of a preset range.

  A second-order differential value is obtained as a value obtained by differentiation. The second-order differential value with respect to time of the output voltage indicates the speed of battery deterioration, and the state of the battery is detected from this second-order differential value. If the battery continues to supply power while the battery's deterioration state is constant, the slope of the battery's output voltage with respect to time is constant, but the battery's deterioration progresses and the remaining capacity of the battery decreases. Then, polarization occurs in the battery, the capacity of the battery decreases at an accelerated rate, and the slope of the output voltage with respect to time increases. That is, the second order differential value is increased. By comparing the second-order differential value with a predetermined value set in advance, when the slope of the output voltage begins to increase, the battery supplies power to the load before it can actually supply power to the load. It is possible to detect that the state becomes impossible.

As a second invention,
Voltage measuring means for measuring the output voltage of the battery mounted on the vehicle;
Current measuring means for measuring an output current supplied from the battery to the load;
Battery state detecting means for detecting that the battery is in an insufficient supply power state when an internal resistance value of the battery obtained from the output voltage and output current exceeds a predetermined value set in advance. A battery status management system is provided.

  The internal resistance of the battery at the time of engine operation is calculated, and when the internal resistance value exceeds a predetermined value, it is detected that the battery is in an insufficient supply power state. For this reason, it is possible to detect the state of the battery not only at the start but also at the time of engine operation.

The battery state detection means includes
It is preferable that an internal resistance value at the time of starting the engine, which is obtained from the open circuit voltage of the battery at the time of starting the engine, the voltage at the time of the maximum voltage drop and the current value, is set as the predetermined value.

  When the engine is operating, the battery is normally in a charged state, so it is considered that the internal resistance of the battery is smaller than that at the start. Therefore, the state of the battery can be detected more accurately by determining the deterioration state of the battery from the internal resistance at the time of engine operation with the internal resistance value at the time of engine start as the predetermined value.

  When the battery state detection unit detects that the battery is in a supply power shortage state, a control unit may be provided to limit power supply to a load with low importance.

  When determining the deterioration state of the battery, it is configured to have a control means that supplies power only to a highly important load, so even if the battery cannot supply sufficient power to the load during engine operation, Electric power can be supplied.

As described above, in the present invention, the amount of change in the output voltage with respect to time during engine operation (the slope of the output voltage value with respect to time) is measured, and if the range of the normal amount of change set in advance is exceeded, the battery deteriorates. Alternatively, it is detected that the output voltage is reduced due to the discharge, and the battery cannot supply the power required by the load, that is, the battery is in a state of insufficient supply power. Thus, the battery state can be managed when the engine is operating only by measuring the output voltage of the battery when the engine is operating.
Further, by comparing the second-order differential value with respect to the time of the output voltage of the battery and a predetermined value set in advance, the battery cannot actually supply power to the load when the slope of the decrease in the output voltage starts to increase. Before, it can be detected that the battery is in a state of insufficient power supply.
Further, the internal resistance of the battery at the time of engine operation is calculated, and when a predetermined value is exceeded, it is detected that the battery is in a state where it cannot supply the power required by the load. For this reason, it is possible to detect the state of the battery not only at the start but also at the time of engine operation.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of a starting system to which a battery state management device 20 of the present invention is connected.
The battery 1 is connected to the ignition switch 2, and the ON terminal 2 a of the ignition switch 2 is connected to the starter 3. The battery 1 can use a 12V lead battery. The starter 3 is a cell motor or the like that transmits driving force to the engine 4 to start the engine 4, and is connected to a rotating shaft (not shown) of the engine 4. The engine 4 is connected to the generator 5, and the generator 5 is connected to the battery 1. The generator 5 operates when the engine 4 rotates, the electric power of the generator 5 is supplied to the battery 1, and the battery 1 is charged by the generator 5. The battery 1 is connected to an ECU 8.

  A voltage sensor 7 constituting voltage measuring means is attached between the battery 1 and the ignition switch 2 to measure the voltage value of the battery. A signal indicating a voltage value output from the voltage sensor 7 is input to the battery state management device 20. The battery state management device 20 includes an arithmetic processing unit 21 that constitutes a battery state detection unit, a storage unit 22, a control unit 23 that constitutes a control unit, and a display unit 24 that constitutes a warning generation unit. A signal from the voltage sensor 7 is input to the arithmetic processing unit 21. The arithmetic processing unit 21 includes an interface for inputting and outputting signals, an A / D converter, a CPU, and the like (not shown).

  A storage unit 22 is connected to the arithmetic processing unit 21, and the arithmetic processing unit 21 reads data stored in the storage unit 22 and determines the state of the battery. The control unit 23 is connected to the arithmetic processing unit 21 and receives a load control command for supplying power only to an important load necessary for driving the automobile. The control unit 23 is connected to the ECU 8 that is a load, and performs load control on the ECU 8. The display unit 24 is connected to the arithmetic processing unit 21, and gives a warning to the occupant when the battery cannot supply power to the load.

Next, a battery state detection method will be described.
FIG. 2 is a graph showing changes in the battery output voltage Vout with respect to time.
While the automobile is running, the generator 5 connected to the engine 4 supplies electric power to the electric load, and charges the battery 1 when the electric power generation exceeds the electric power required by the load. On the other hand, when the load increases and the power generation amount of the generator 5 is insufficient, power is also supplied from the battery 1.

  Consider a case where the load suddenly increases while the automobile is running, and power is supplied from the battery 1 to the load. In FIG. 2, power is charged from the generator 5 to the battery 1 until time t1, and the battery is fully charged. When a load that requires a large current is applied at time t1, the amount of power generated by the generator 5 is not sufficient, and power is supplied from the battery 1 to the load. At this time, the output voltage Vout of the battery decreases by the voltage drop Vb due to the internal resistance Rb of the battery 1.

  When electric power is supplied from the battery 1 to the load with a constant current value, the output voltage Vout of the battery decreases at a constant rate as time elapses after time t1. The decrease in the output voltage Vout of the battery 1 is mainly caused by a decrease in the electromotive force of the battery 1. The slope at which the output voltage Vout decreases (differential value ΔVst / Δt with respect to the time of Vst) is determined by the deterioration state and the charge state of the battery. As shown in the vicinity of A1 in FIG. 2, in FIG. 2a, the battery is not deteriorated and the state of charge is high, so the inclination of the decrease of the output voltage Vout with respect to time is small, and deterioration and discharge progress like b and c. The slope of the decrease in the output voltage Vout increases.

FIG. 3 shows an example of the slope ΔVst / Δt of the output voltage Vout of the battery 1 with respect to time. a, b, and c correspond to a, b, and c in FIG. FIG. 3 shows the absolute value of the slope. Further, at the time point t1 when the load requiring a large current starts to operate, the output voltage Vout of the battery 1 rapidly decreases, so the magnitude of the gradient ΔVst / Δt temporarily increases, but as shown by A1 In a state in which power is continuously supplied to the load, a substantially constant current is supplied from the battery 1 depending on the amount of current flowing from the battery 1 to the load that requires a large current. Δt does not vary greatly.
Here, a certain value is set as a threshold, and the state of the battery is determined by comparing with a slope ΔVst / Δt of the output voltage Vout of the battery 1.

  In a, the slope ΔVst / Δt of the output voltage Vout of the battery 1 is substantially constant and is smaller than the threshold value, so that it is determined that the battery 1 has not deteriorated. In b, the slope is smaller than the threshold for a while after the time t1, but becomes larger than the threshold when the time elapses. If it exceeds the threshold, it is determined that the battery cannot supply power to the load. In addition, at c, since the slope is already larger than the threshold value at time t1, it is determined that the battery is discharged or deteriorated.

  Further, ΔVst / Δt may change abruptly as in the vicinity of A2 in FIG. This sudden change in ΔVst / Δt is caused by the battery 1 being excessively discharged and being deteriorated. As for the case where the deterioration occurs, the battery 1 that has been deteriorated to some extent but is capable of supplying power to the load is further deteriorated, or the battery 1 that has not deteriorated at first. However, it can be considered that the battery 1 is in a low charge state by continuing to supply power to the load, but the power supply is further continued and the battery 1 deteriorates.

  The deterioration of the battery 1 is caused by the concentration polarization of the battery 1. The gradient (differential value) of the output voltage Vout with respect to time represents the state of polarization, and the second-order differential value, which is the amount of increase in the gradient ΔVst / Δt of the output voltage Vout, represents the rate of increase in polarization. A point where the second-order differential value is larger than a predetermined value is an inflection point of a graph showing the output voltage. The rate of increase in polarization is due to the shape of the battery electrode surface, and is caused by miniaturization, dropout, PbSO4 precipitation, shrinkage due to change in the negative electrode active material, and PbSO4 precipitation due to changes in the positive electrode active material. As the time elapses, the increase amount of the slope ΔVst / Δt of the output voltage Vout of the battery becomes larger, so that the increase rate of polarization becomes larger.

  Therefore, the amount of increase in the slope ΔVst / Δt of the output voltage Vout of the battery, that is, the second derivative of the output voltage Vout of the battery is calculated, and the deterioration of the battery is determined from the second derivative value. FIG. 4 shows the relationship of the second derivative value of the battery output voltage Vout with respect to time. 4 corresponds to a, b, and c in FIGS. 2 and 3, and the time axis is the same as FIG. If the rate of increase in polarization exceeds a predetermined value, it is determined that power cannot be supplied to the load because the battery deteriorates. By using the acceleration of the increase in polarization, which is the second derivative of the output voltage, the vicinity of A1 in FIG. 2 where the output voltage Vout where the battery is not deteriorated is constantly detected is not detected, and the decreasing slope of the output voltage Vout increases. When the deterioration starts, the state of the battery can be detected earlier before the deterioration of the battery actually proceeds greatly.

The operation of the first embodiment will be described.
The voltage sensor 7 measures the output voltage Vout of the battery. The arithmetic processing unit 21 receives the measured voltage value and stores it in the storage unit 22. The arithmetic processing unit 21 obtains the slope ΔVst / Δt of the battery output voltage Vout with respect to time using the previously stored voltage value and the voltage value measured this time. Further, a second-order derivative that is an increase amount of the slope ΔVst / Δt of the output voltage Vout is obtained. The voltage value may be an average value of measurement results obtained by performing a plurality of measurements.

  The storage unit 22 also stores a first threshold value and a second threshold value set in advance. When the slope ΔVst / Δt is greater than the threshold value, the arithmetic processing unit 21 determines that the battery 1 is in a deteriorated or discharged state, and in any case, the supply power is insufficient. Further, the second-order differential value of the output voltage of the battery 1 is compared with the second threshold value to determine the state of the battery 1. Even if it is determined from the comparison between the output voltage slope ΔVst / Δt and the predetermined value that the battery 1 is not deteriorated or discharged, the rate at which the output voltage of the battery 1 decreases as the polarization of the battery 1 progresses with time. It may get bigger. At this time, by comparing the second-order differential value with an appropriate second threshold, when the rate of increase in the polarization of the battery 1 increases, the battery 1 begins to deteriorate due to excessive discharge. It can be detected that power cannot be supplied to the load, and this is determined to be a shortage of power supply.

  That is, it can be detected that the battery 1 is in a state of insufficient power supply only by the slope ΔVst / Δt of the output voltage. However, when the second-order differential value is used, when the slope at which the output voltage decreases further starts to increase, Even before the battery 1 can no longer supply power to the load, strictly speaking, even if the supply power is not insufficient, it is detected that the battery 1 will not be able to supply power to the load in the near future. It can be assumed that the power supply is insufficient.

  If the arithmetic processing unit 21 determines that the supply power is insufficient, the control unit 23 receives a command from the arithmetic processing unit 21 to perform load control. The control unit 23 is connected to the ECU 8, and the control unit 23 limits power supply to the ECU 8. For example, among the plurality of ECUs 8, the control unit 23 continues the operation of important ECUs that are necessary for driving the automobile, and stops the operation of ECUs that are not important. Since the ECU 8 is connected to the battery, power is supplied only to an important ECU that continues to operate, and load control is performed. Further, the display unit 24 displays that the battery cannot supply power to some loads, and informs the passenger of the battery status.

  A second embodiment of the present invention is shown in FIG. In addition to the configuration of the first embodiment, a current sensor 6 constituting current measuring means is connected between the battery 1 and the ignition switch 2. The arithmetic processing unit 21 is different from the first embodiment in that the state of the battery is detected using the internal resistance Rb of the battery. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  When concentration polarization occurs due to deterioration of the battery, the internal resistance Rb increases. Even if the battery is in a discharged state, the internal resistance increases. Therefore, the deterioration or discharge of the battery is determined based on the internal resistance Rb of the battery 1 instead of the gradient ΔVst / Δt of the battery output voltage Vout.

The internal resistance value Rb of the battery 1 can be obtained by various methods using the output voltage Vout and the output current Iout measured using the current sensor 6 and the voltage sensor 7 at each time point. As shown, the internal resistance Rb is a value obtained by subtracting the output voltage Vout measured using the voltage sensor 7 from the open circuit voltage Vo of the battery 1 and dividing this by the output current Iout measured using the current sensor 6.
Internal resistance Rb = (open voltage Vo−output voltage Vout) / current Iout (1)

  When the calculated internal resistance value is larger than a predetermined value, it is determined that the battery 1 is in a deteriorated or discharged state and sufficient power cannot be supplied to the load. The predetermined value is determined in advance with reference to, for example, an internal resistance value when the engine 1 is started.

FIG. 6 shows measured values of battery voltage and current when the automobile is started. Since the battery is unloaded immediately before starting, the battery voltage indicates the value of the open circuit voltage V0. When the ignition key is turned on and the engine is started, a start system is connected to the battery, and a voltage is applied to the start system. At this time, the voltage applied to the starting system is lower than the open circuit voltage of the battery because a voltage drop occurs due to the internal resistance of the battery. At the time of starting, the output voltage value of the battery when the battery voltage drop is maximum, that is, the minimum value of the voltage applied to the starting system is called the lower limit voltage Vst, and the current value at this time is called the inrush current Ist.
At this time, the internal resistance value Rbs at the time of start-up is obtained by Expression (2).
Internal resistance Rbs at start-up = (open voltage V0−lower limit voltage Vst) / inrush current Ist
... Formula (2)

  If the internal resistance Rbs at the start is set to a predetermined value and the internal resistance Rb at the time of engine operation is larger than this value, it is determined that the battery 1 is in a deteriorated or discharged state and cannot supply power to the load. If the battery 1 is charged during engine operation, the internal resistance Rb of the battery during engine operation is the same or smaller than the internal resistance Rbs during startup. Since the internal resistance Rb is considered to increase with time if the battery 1 is deteriorated due to the polarization of the battery 1 and the supply power is insufficient, the internal resistance Rb during engine operation becomes larger than the internal resistance Rbs at the start of the battery. It is determined that 1 cannot supply power to the load. The predetermined value is determined based on the internal resistance Rbs when the engine is started, and may be determined by giving some appropriate margin to the internal resistance Rbs.

The operation of the second embodiment will be described.
When the engine is started, the current sensor 6 and the voltage sensor 7 measure the output voltage and the output current, and input the measured values to the arithmetic processing unit 21. The arithmetic processing unit 21 calculates the internal resistance value Rbs of the battery at the time of start-up using the equation (2) from the open circuit voltage value V0, the lower limit voltage Vst, and the inrush current value Ist, and stores it in the storage unit 22.

  When the engine is operating, the current sensor 6 and the voltage sensor 7 measure the output voltage and the output current, and input the measured values to the arithmetic processing unit 21. When a large load is suddenly applied, the internal resistance Rb is calculated according to the equation (1), and compared with the internal resistance value Rbs at the time of start obtained by the equation (2). If the internal resistance value Rb when the engine is operating is larger than the internal resistance value Rbs at the time of starting, it is determined that the battery is in a deteriorated or discharged state and power cannot be supplied to the load.

  If the arithmetic processing unit 21 determines that the battery is deteriorated or discharged, the control unit 23 receives a command from the arithmetic processing unit 21 to perform load control. The control unit 23 continues the operation for an important ECU necessary for driving the automobile, and stops the operation for an ECU that is not an important ECU. Since the ECU 8 is connected to the battery, power is supplied only to an important ECU that continues to operate, and load control is performed. Further, the display unit 24 displays that the battery cannot supply power to the load, and informs the passenger of the state of the battery.

1 is a block diagram showing a first embodiment of a vehicle power supply control device according to the present invention. It is a graph which shows the change of the output voltage of a battery with respect to time when big load is applied at the time of engine operation. It is a graph which shows the inclination of the battery output voltage with respect to time. It is a graph which shows the 2nd-order differential value of the battery output voltage with respect to time. It is a block diagram which shows 2nd embodiment of the power supply control apparatus for vehicles. It is a graph which shows the change of the voltage at the time of starting, and an electric current.

Explanation of symbols

1 Battery 2 Ignition Key 3 Starter 4 Engine 5 Generator 6 Current Sensor 7 Voltage Sensor 8 ECU
20 battery state management device 21 arithmetic processing unit 22 storage unit 23 control unit 24 display unit

Claims (5)

Voltage measuring means for measuring the output voltage of the battery mounted on the vehicle;
Battery state detecting means for detecting that the battery is in a state of insufficient power supply when a change amount of the output voltage measured at the time of engine operation deviates from a predetermined change amount range. Battery status management system.   2. The battery state management according to claim 1, wherein the battery state detection unit further detects that the battery is in an insufficient supply power state even when a value obtained by differentiation of the output voltage is out of a preset range. system. Voltage measuring means for measuring the output voltage of the battery mounted on the vehicle;
Current measuring means for measuring an output current supplied from the battery to the load;
Battery state detecting means for detecting that the battery is in an insufficient supply power state when an internal resistance value of the battery obtained from the output voltage and output current exceeds a predetermined value set in advance. Battery status management system. The battery state detection means includes
The battery state management system according to claim 3, wherein the predetermined value is an internal resistance value at the time of starting the engine which is obtained from an open circuit voltage of the battery at the time of starting the engine, a voltage and a current value at the time of the maximum voltage drop.   5. The apparatus according to claim 1, further comprising a control unit that restricts power supply to a less important load when the battery state detection unit detects that the battery is in a shortage of supply power. The described battery state management system.

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