JP4827470B2 - Battery status monitoring device - Google Patents

Description

  The present invention relates to a battery state monitoring device that monitors the state of a battery mounted on an automobile.

  In recent years, various loads driven by a large current, such as electric power steering (hereinafter referred to as “EPS”), have been mounted on automobiles. For example, when driving an EPS, a current of several hundred amperes flows instantaneously, so that the voltage drop of the battery is also large. Therefore, when the battery is deteriorated, a sufficient drive current cannot be supplied from the battery to the EPS, and the operation of the EPS becomes unstable. Therefore, it is necessary to accurately monitor the degree of deterioration of the battery and prompt the user to replace the battery or the like promptly when the battery has deteriorated to such an extent that the load drive is hindered.

  The present invention has been made in view of such circumstances, and an object thereof is to obtain a battery state monitoring device capable of accurately monitoring the degree of deterioration of a battery.

A battery state monitoring device according to a first aspect of the present invention is a battery state monitoring device that monitors the state of a battery mounted on an automobile, and detects a voltage sensor that detects an output voltage of the battery and an output current of the battery. Including a drop due to the diffusion polarization of the battery based on the current sensor, the voltage value detected by the voltage sensor during the cranking period at the time of engine start , and the open circuit voltage value of the battery, Obtaining a voltage drop amount of the battery ; and further, a current value detected by the current sensor in the cranking period, a plurality of voltage drop amounts of the battery obtained with respect to a plurality of times in the cranking period, and the battery Any driving time based on the current value flowing through the load when driving a predetermined load by Characterized in that it comprises a processing unit for determining a predicted voltage drop amount of the battery at the time of driving the load.

The battery state monitoring apparatus according to a second aspect of the invention is the battery state monitoring apparatus according to the first aspect of the invention, particularly when the predicted voltage drop amount of the battery is equal to or greater than a predetermined threshold value. It further comprises an output unit for outputting information indicating that the information is received.

  According to the battery state monitoring apparatus of the first aspect of the present invention, it is possible to obtain the amount of voltage drop of the battery including not only the amount of drop caused by the internal resistance of the battery but also the amount of drop caused by the diffusion polarization of the battery. it can. Accordingly, it is possible to accurately monitor the degree of deterioration of the battery.

Furthermore, according to the battery state monitoring device according to the first aspect of the present invention, it is possible to obtain the predicted voltage drop amount of the battery when the load is driven by the battery by detecting the output current of the battery with the current sensor. In addition, the predicted voltage drop amount of the battery can be obtained when the engine is started. Therefore, it is possible to determine at the time of engine start whether or not the battery has deteriorated to the extent that the driving of the load is hindered. Furthermore, since the predicted voltage drop amount of the battery when the load is driven with an arbitrary driving time can be obtained, it is possible to broaden the load targets for which the predicted voltage drop amount can be obtained.

According to the battery state monitoring apparatus according to the second aspect of the present invention, when the battery has deteriorated to such an extent that the load drive is hindered, it is possible to promptly prompt the user to replace the battery.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the element which attached | subjected the same code | symbol in different drawing shall show the same or corresponding element.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing the configuration of the battery state monitoring apparatus according to Embodiment 1 of the present invention. As shown in FIG. 1, the battery state monitoring apparatus according to the first embodiment is configured to include a voltage sensor 2, a current sensor 3, a processing unit 4, a storage unit 5, and an output unit 6, and is provided in an automobile. The state (degree of deterioration) of the mounted battery 1 is monitored.

  The voltage sensor 2 detects the output voltage of the battery 1. The current sensor 3 detects the output current of the battery 1. Both the output voltage value of the battery 1 detected by the voltage sensor 2 and the output current value of the battery 1 detected by the current sensor 3 are input to the processing unit 4. The storage unit 5 is configured by a nonvolatile memory or the like. The storage unit 5 stores data necessary for data processing performed by the processing unit 4. The processing unit 4 includes a CPU and the like, and performs various types of data processing for monitoring the state of the battery 1. The output unit 6 is configured by a liquid crystal display device, for example, and outputs a determination result of the state of the battery 1 and the like.

  A starter 8 is connected to the battery 1 via an ignition switch 7. Further, a large current load 9 (typically referred to as EPS in the first embodiment) 9 is connected to the battery 1. Both the starter 8 and the EPS 9 are driven by the battery 1.

  By turning on the ignition switch 7, the battery 1 and the starter 8 are brought into conduction, and the engine starting operation is started.

  FIG. 2 is a diagram illustrating changes in the output voltage and output current of the battery 1 when the engine is started. For comparison, FIG. 2 shows a characteristic K1 related to the new battery 1 and a characteristic K2 related to the deteriorated battery 1. The characteristics K1 and K2 are created by the processing unit 4 based on the detection values of the voltage sensor 2 and the current sensor 3. Specifically, the output voltage value and the output current value of the battery 1 are measured by the voltage sensor 2 and the current sensor 3 at a minute time interval, and the measurement results at each time point are connected in a curve.

  Referring to FIG. 2, immediately after the ignition switch 7 is turned on, an inrush current flows from the battery 1 to the starter 8, so that the output current value of the battery 1 increases instantaneously and the output voltage value instantaneously increases. Decrease (points P1, P2). Thereafter, when the back electromotive force of the starter 8 is generated, the output voltage value of the battery 1 gradually increases and the output current value gradually decreases. Then, after a cranking period in which the increase and decrease in the output voltage value and the output current value are repeated a plurality of times, the output voltage value of the battery 1 returns to the open circuit voltage value VO (point P5).

  In FIG. 2, the straight line L1 is a straight line connecting the points P1 and P5, the straight line L2 is a straight line connecting the points P2 and P5, and the straight line L4 is a straight line representing the open circuit voltage value VO. The straight line L3 is a voltage drop line caused by the internal resistance of the starter 8 and the wiring resistance between the starter 8 and the battery 1. Points P3 and P4 are arbitrary measurement points on the characteristics K1 and K2 within the cranking period. In the example shown in FIG. 2, among the four turning points found on the characteristics K1 and K2 within the cranking period, the last turning point in time (that is, the time point when viewed from the points P1 and P2). Are defined as points P3 and P4, respectively.

  FIG. 3 is a diagram illustrating points P1 to P5 and straight lines L1, L2, and L4 extracted from FIG. In the case of a new battery 1, the processing unit 4 shown in FIG. 1 calculates the voltage difference between the open circuit voltage value VO and the voltage value at the point P3 as the voltage drop amount VA of the battery 1. As shown in FIG. 3, the voltage VA is the sum of the voltage Va1 (the difference voltage between the straight line L4 and the straight line L1) and the voltage Va2 (the voltage difference between the straight line L1 and the point P3). Here, the voltage Va1 corresponds to the voltage drop caused by the internal resistance of the battery 1, and the voltage Va2 corresponds to the voltage drop caused by the diffusion polarization of the battery 1.

  Similarly, regarding the deteriorated battery 1, the processing unit 4 calculates a voltage difference between the open circuit voltage value VO and the voltage value at the point P4 as the voltage drop amount VB of the battery 1. As shown in FIG. 3, the voltage VB is the sum of the voltage Vb1 (the difference voltage between the straight line L4 and the straight line L2) and the voltage Vb2 (the difference voltage between the straight line L2 and the point P4). Here, the voltage Vb1 corresponds to a voltage drop caused by the internal resistance of the battery 1, and the voltage Vb2 corresponds to a voltage drop caused by the diffusion polarization of the battery 1.

  Thus, the voltage of the battery 1 including not only the voltage drop due to the internal resistance of the battery 1 (voltage Va1, Vb1) but also the voltage drop due to the diffusion polarization of the battery 1 (voltage Va2, Vb2). By obtaining the drop amounts VA and VB, the degree of deterioration of the battery 1 can be accurately monitored.

  FIG. 4 is a diagram showing the point P3 and the straight line L4 extracted from FIG. The straight line LA is a straight line connecting the points P3 and P5. The current value Ix is a current value that flows through the EPS 9 when the battery 9 drives the EPS 9. Regarding the straight line LA, the voltage value when the current value is Ix is Vx1. The voltage of the difference between the open circuit voltage value VO and the voltage value Vx1 corresponds to the predicted voltage drop amount Vy1 of the battery 1 when driving the EPS 9. As described above, the processing unit 4 uses the current value I1 detected by the current sensor 3 during the cranking period, the voltage drop amount VA corresponding to the current value I1, and the current flowing through the EPS9 when the battery 9 drives the EPS9. Based on the value Ix, the predicted voltage drop amount Vy1 of the battery 1 when driving the EPS 9 can be obtained. Expressed by the formula, Vy1 = VA × Ix / I1. For example, when the current value I1 is 200A and the current value Ix is 100A, the predicted voltage drop amount Vy1 is ½ of the voltage drop amount VA.

  In addition, the storage unit 5 stores a threshold voltage Vth of a voltage drop amount corresponding to the EPS 9. The processing unit 4 compares the calculated predicted voltage drop amount Vy1 with the threshold voltage Vth. When the predicted voltage drop amount Vy1 is equal to or higher than the threshold voltage Vth, information indicating that the battery 1 is deteriorated is output from the output unit 6. For example, a message prompting the user to replace the battery 1 is displayed on the screen of the output unit 6 that is a display device. However, since FIG. 4 corresponds to a new battery 1 and the predicted voltage drop amount Vy1 is smaller than the threshold voltage Vth, such display is not performed.

  FIG. 5 shows the point P4 and the straight line L4 extracted from FIG. The straight line LB is a straight line connecting the points P4 and P5. Regarding the straight line LB, the voltage value when the current value is Ix is Vx2. The voltage difference between the open circuit voltage value VO and the voltage value Vx2 corresponds to the predicted voltage drop amount Vy2 of the battery 1 when the EPS 9 is driven. Similar to FIG. 4, the processing unit 4 obtains the predicted voltage drop amount Vy2 based on the current value I2, the voltage drop amount VB, and the current value Ix. Expressed by the formula, Vy2 = VB × Ix / I2.

  The processing unit 4 compares the predicted voltage drop amount Vy2 with the threshold voltage Vth, and outputs information indicating that the battery 1 is deteriorated when the predicted voltage drop amount Vy2 is equal to or higher than the threshold voltage Vth. Output from unit 6. FIG. 5 corresponds to the deteriorated battery 1, and the predicted voltage drop amount Vy <b> 2 is larger than the threshold voltage Vth, so that such information is output from the output unit 6.

  As described above, according to the battery state monitoring apparatus of the first embodiment, not only the voltage drop (Va1, Vb1) due to the internal resistance of the battery 1 but also the diffusion of the battery 1 as shown in FIG. The voltage drop amounts VA, VB of the battery 1 at the time of starting the engine can be obtained including the voltage drop (Va2, Vb2) due to the polarization. Accordingly, it is possible to accurately monitor the degree of deterioration of the battery 1.

  Further, by detecting the output current of the battery 1 by the current sensor 3, as shown in FIGS. 4 and 5, the predicted voltage drop amounts Vy1 and Vy2 of the battery 1 when the EPS 9 is driven by the battery 1 can be obtained. it can. Moreover, the predicted voltage drop amounts Vy1 and Vy2 of the battery 1 can be obtained when the engine is started. Therefore, it can be determined in advance at the time of engine start before driving the EPS 9 whether the battery 1 has deteriorated to such an extent that the driving of the EPS 9 is hindered.

  Further, when it is determined that the battery 1 has deteriorated to such an extent that the driving of the EPS 9 is hindered, a message to that effect is output from the output unit 6 to prompt the user to replace the battery 1 promptly. It becomes possible.

  In the above description, the predicted voltage drop amounts Vy1 and Vy2 of the battery 1 are calculated using the voltage values of the points P3 and P4 on the characteristics K1 and K2 within the cranking period. However, the voltage at the points P3 and P4 is calculated. Instead of the value, an average value of the output voltage value of the battery 1 in the cranking period may be used.

Embodiment 2. FIG.
In the first embodiment, the estimated voltage drop amounts Vy1 and Vy2 of the battery 1 when driving the EPS 9 are obtained on the assumption that the driving time of the starter 8 by the battery 1 and the driving time of the EPS 9 are substantially equal. On the other hand, in the second embodiment, the predicted voltage drop amount of the battery 1 when the load 9 is driven for an arbitrary load 9 that is driven with a driving time different from the driving time of the starter 8 by the battery 1. A battery state monitoring device capable of obtaining the above will be described.

  FIG. 6 is a diagram showing changes in the output voltage and output current of the battery 1 when the engine is started. The horizontal axis is time, and the vertical axis is voltage value and current value. FIG. 6 shows a voltage waveform G1 and a current waveform G2 related to a new battery 1 (including almost a new one). The voltage waveform G1 and the current waveform G2 are created by the processing unit 4 based on the detection values of the voltage sensor 2 and the current sensor 3. Specifically, the output voltage value and the output current value of the battery 1 are measured by the voltage sensor 2 and the current sensor 3 at a minute time interval, and the measurement results at each time point are connected in a curve.

Points P _{1 to} P ₄ are arbitrary measurement points on the voltage waveform G1 and the current waveform G2 within the cranking period. A plurality of (four in the example shown in FIG. 6) valleys appear in the voltage waveform G1 within the cranking period, and a plurality (four) peaks in the current waveform G2 corresponding to this. Appears. Points at the bottom of the valleys in the voltage waveform G1 (the peaks of the peaks in the current waveform G2) are defined as points P _{1 to} P ₄ . For example, at the point P ₁ , the time is T ₁ , the voltage value is V ₁ , and the current value is I ₁ . Similarly, the points P ₂ , P ₃ , and P ₄ have time T ₂ , T ₃ , T ₄ , voltage values V ₂ , V ₃ , V ₄ , and current values I ₂ , I ₃ , I ₄ , respectively. .

The horizontal axis of the graph shown in FIG. 6 is time, and the vertical axis is voltage value and current value. As in FIG. 2, the horizontal axis is current value and the vertical axis is voltage value. Is the graph of FIG. Of the eight turning points found on the characteristic K within the cranking period, the second, fourth, sixth and eighth turning points in time when viewed from the point P ₀ corresponding to the lower limit voltage are respectively points. This corresponds to P ₁ , P ₂ , P ₃ and P ₄ .

FIG. 8 is a diagram in which the points P _{1 to} P ₄ and P5 and the straight line L4 are extracted from FIG. 7 in the same manner as FIG. The voltage difference between the open-circuit voltage value VO and the voltage values V ₁ , V ₂ , V ₃ , V ₄ of the points P ₁ , P ₂ , P ₃ , P ₄ is the voltage drop amount VA ₁ , VA _{2 of the} battery 1. , VA ₃ , VA ₄ . The straight lines LA ₁ , LA ₂ , LA ₃ , LA ₄ are straight lines connecting the points P ₁ , P ₂ , P ₃ , P ₄ and the point P 5, respectively. The current value Ix is a current value that flows through the load 9 when the battery 9 drives the load 9. Regarding the straight lines LA ₁ , LA ₂ , LA ₃ , LA ₄ , the voltage values when the current value is Ix are Vx1 ₁ , Vx1 ₂ , Vx1 ₃ , Vx1 ₄ , respectively. The difference voltage between the open-circuit voltage value VO and each of the voltage values Vx1 ₁ , Vx1 ₂ , Vx1 ₃ , Vx1 ₄ is the battery 1 when driving the load 9 at the drive times T ₁ , T ₂ , T ₃ , T ₄ , respectively. Corresponding to the predicted voltage drop amounts Vy1 ₁ , Vy1 ₂ , Vy1 ₃ , and Vy1 ₄ . As in the first embodiment, the predicted voltage drop amounts Vy1 _{1 to} Vy1 ₄ correspond to the current values I _{1 to} I ₄ detected by the current sensor 3 in the cranking period and the current values I _{1 to} I ₄ . Based on the voltage drop amounts VA _{1 to} VA _{4 to be performed} and the current value Ix flowing through the load 9 when the load 9 is driven by the battery 1, it can be obtained by the processing unit 4.

FIG. 9 is a graph showing the time dependence of the predicted voltage drop amount with respect to the graph shown in FIG. The horizontal axis is time, and the vertical axis is voltage value. The processing unit 4 plots the voltage values Vx1 ₁ , Vx1 ₂ , Vx1 ₃ , and Vx1 ₄ corresponding to the times T ₁ , T ₂ , T ₃ , and T ₄ and approximates the transition by a straight line LC. Regarding the straight line LC, the voltage value when the time is Ts is Vx1s. The processing unit 4 obtains a predicted voltage drop amount Vy1s of the battery 1 when driving the load 9 with an arbitrary drive time Ts as a voltage difference between the open voltage value VO and the voltage value Vx1s.

  As in the first embodiment, the processing unit 4 compares the calculated predicted voltage drop amount Vy1s with a predetermined threshold voltage that is set and stored in advance according to the load 9, and calculates the predicted voltage drop amount Vy1s. Is equal to or higher than the threshold voltage, information indicating that the battery 1 is deteriorated is output from the output unit 6.

According to the battery state monitoring apparatus according to the second embodiment, the processing unit 4, for a plurality of times T ₁ through T ₄ in cranking period, the voltage drop VA ₁ to VA ₄ of the battery 1 respectively By obtaining, the predicted voltage drop amount Vy1s of the battery 1 when the load 9 is driven with an arbitrary drive time Ts is obtained. Therefore, the predicted voltage drop amount Vy1s of the battery 1 when the load 9 is driven with an arbitrary drive time Ts as well as the EPS 9 whose drive time is approximately equal to the drive time of the starter 8 can be obtained. Can be expanded.

It is a block diagram which shows the structure of the battery state monitoring apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the change of the output voltage and output current of the battery 1 at the time of engine starting. It is the figure which extracted and showed points P1-P5 and the straight lines L1, L2, L4 from FIG. It is the figure which extracted and showed the point P3 and the straight line L4 from FIG. It is the figure which extracted and showed the point P4 and the straight line L4 from FIG. It is a figure which shows the change of the output voltage and output current of the battery 1 at the time of engine starting. FIG. 7 is a diagram obtained by rewriting the graph shown in FIG. 6 into a graph in which the horizontal axis represents current values and the vertical axis represents voltage values. The point P ₁ to P ₄ from 7 is a diagram showing an extracted P5 and linear L4. FIG. 9 is a graph showing the time dependence of the predicted voltage drop amount with respect to the graph shown in FIG. 8.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery 2 Voltage sensor 3 Current sensor 4 Processing part 5 Memory | storage part 6 Output part 7 Ignition switch 8 Starter 9 EPS (load)

Claims (2)

A battery state monitoring device for monitoring a state of a battery mounted on an automobile,
A voltage sensor for detecting the output voltage of the battery;
A current sensor for detecting the output current of the battery;
A voltage drop amount of the battery including a drop due to the diffusion polarization of the battery based on a voltage value detected by the voltage sensor in a cranking period at the time of engine start and an open voltage value of the battery Furthermore, the current value detected by the current sensor in the cranking period, the plurality of voltage drop amounts of the battery determined for a plurality of times in the cranking period, and a predetermined load by the battery A battery state monitoring device comprising: a processing unit that obtains a predicted voltage drop amount of the battery when driving the load in an arbitrary driving time based on a current value flowing through the load when driving . The battery state monitoring apparatus according to claim 1 , further comprising: an output unit that outputs information indicating that the battery has deteriorated when the predicted voltage drop amount of the battery is equal to or greater than a predetermined threshold value .

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