JPH06342044A - Battery measuring apparatus - Google Patents

Abstract

PURPOSE:To provide a battery measuring apparatus wherein a cumulative error due to the integration of a current is eliminated by a simple constitution and the residual capacity can be measured precisely. CONSTITUTION:Electric power is supplied to a battery 11 and a load 12 from a solar cell 10, the battery 11 is charged, and electric power is supplied to the load from the battery at night or the like. The current value of a charging current for the battery is sent to an integrator 14, it is integrated, and the residual capacity is computed. In addition, the charging current and a terminal voltage are sent to an inflection-point detection part 15, and the inflection point of an internal resistance which is changed due to a charging operation is detected at the detection part. The residual capacity (correction capacity) of the battery at the inflection point is found in advance. When the inflection point is detected, the output of the integrator is corrected to the correction capacity by a correction-capacity setting part 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery measuring device, and more specifically to a device for measuring various characteristics (performance) such as remaining capacity and life judgment of a battery.

[0002]

2. Description of the Related Art A rechargeable battery (storage battery) is
It is used in various fields such as uninterruptible power supply systems, vehicle-mounted and solar power generation systems. The battery is configured such that the container main body is filled with the electrolytic solution and the electrodes are inserted and arranged in the electrolytic solution.

By the way, it is necessary to know the remaining capacity of the battery to determine whether or not the battery needs to be charged and the amount of charge (time).
Also, it is important for knowing the life judgment and the like, and various types of residual capacity measuring devices have been conventionally proposed. And, as an example, for example, Japanese Unexamined Patent Publication No.
As disclosed in Japanese Patent Laid-Open No. 3-208773, there is a method in which a charging current to a battery and a discharging current when being supplied from a battery to a load are integrated, and a current remaining capacity of the battery is obtained from an integrated amount of the current. . That is, the remaining capacity corresponds to the total amount of electric charge stored in the battery at present, and by integrating the electric current (charge current is positive, discharge current is negative), the charge supply amount and the discharge amount to the battery are calculated. This is because the sum is required.

As a life determining device, as disclosed in, for example, Japanese Patent Laid-Open No. 2-55536, first, a battery is also normally used (when power is supplied from a commercial power source to a load). The battery is charged by a method such as floating charging to bring it into a fully charged state (remaining capacity 100%). Then, a pseudo power failure is generated to supply power from the battery to the load. Measure the terminal voltage of the battery during discharge, find the integrated amount of the output current until the voltage drops to a predetermined voltage, and determine if the integrated amount has reached the predetermined amount to determine whether the battery has reached the end of life. I try to make a decision.

[0005]

However, the above-mentioned conventional ones have the following problems. That is, since the currents are integrated in all cases, if an error occurs in the calculated value that is the basis of the integration, the error is accumulated and accurate measurement cannot be performed. Moreover, not all the energy of the charging current is used for charging (charge accumulation), but a predetermined amount is used for charging according to the charging efficiency. The charging efficiency varies depending on the remaining capacity and also changes depending on the temperature, so that it cannot be accurately grasped, which causes a cumulative error.

By the way, the above-mentioned conventional Japanese Patent Laid-Open No. 63-2 is used.
Japanese Patent Publication No. 08773 proposes the above-mentioned problem of accumulated error and uses a hydrometer in combination as a means for solving the problem. However, in order to carry out such hydrometer measurement, it is necessary to use normal current integration. In addition to the above-mentioned sensors, a complicated sensor is added and the sensor is immersed in an electrolyte solution, and wiring from the electrolyte solution to the outside of the battery is drawn out, resulting in a complicated device configuration. Furthermore, the concentration of the electrolyte varies depending on its location (during charge and discharge, the concentration near the electrode plate is high due to the effect of diffusion due to chemical reactions, and in the equilibrium state, it goes upward due to the difference in the specific gravity of the electrolyte and water. The lower the concentration), the specific gravity also varies from place to place. Therefore, the specific gravity (average value) of the entire electrolytic solution cannot be obtained and the accurate remaining capacity cannot be measured, so that the correction based on the specific gravity is not accurate.

The present invention has been made in view of the above background, and an object of the present invention is to accurately detect that a battery has a predetermined remaining capacity with a simple structure and to accumulate the current with current integration. It is an object of the present invention to provide a battery measuring device capable of instantaneously and accurately measuring various characteristics such as remaining capacity and life judgment by correcting the error.

[0008]

In order to achieve the above-mentioned object, in the battery measuring device according to the present invention, the charge / discharge current of the battery is detected and the integrated amount thereof is obtained, and the remaining amount is calculated based on the integrated amount. In a battery measuring device for measuring capacity, an inflection point detecting means for detecting an inflection point of a terminal voltage and / or an internal resistance of the battery which fluctuates with charging, and the inflection point is detected by the inflection point detecting means. In this case, the remaining capacity calculated based on the integrated amount is corrected to a correction capacity at which the inflection point occurs.

Also, charge / discharge control means for forcibly discharging the battery and then charging it, and inflection point detection means for detecting an inflection point of the terminal voltage and / or internal resistance of the battery which fluctuates with the charging. And a capacity calculation means for calculating the capacity accumulated in the battery from the inflection point to full charge, and the storage capacity of the battery is calculated based on the capacity calculated by the capacity calculation means. It may be configured by a life determining unit that determines the life depending on the size of the.

[0010]

The change in the terminal voltage (internal resistance) during charging has an inflection point that does not rise constantly with an increase in the state of charge (remaining capacity) but rises sharply at a certain point. Then, near the inflection point, the charge state (remaining capacity) does not change in spite of the change in voltage (internal resistance). Therefore, normally, current integration is performed to measure the released or accumulated charge (capacity) to obtain the remaining capacity, but if it passes through the inflection point during charging, it is detected and the inflection point obtained in advance is detected. The remaining capacity at the time of is corrected and the accumulated error is reset.

Further, when the life is judged, the remaining capacity can be made accurate by obtaining the inflection point. Therefore, the inflection point is used to charge the battery from the inflection point to full charge. Calculate the electric charge stored in. This can be done, for example, by integrating the charging current (however, charging efficiency is taken into consideration). Then, based on the calculated electric charge, the electric charge of 100% currently stored in the battery is obtained. This is the power storage capacity, and if this value is low, it means that the degree of deterioration has progressed, so the life is determined by the magnitude of that value.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the battery measuring device according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows a first embodiment of the present invention. As shown in the figure, in this example, a measuring device for obtaining the remaining capacity of the battery applied to the solar power generation system is shown. That is, power is supplied from the power source (solar cell) 10 to the battery 11 and the load 12, and the battery 11 is charged. When electric power cannot be supplied from the solar cell 10 to the load at night, electric charges stored in the daytime battery 11 are discharged, and electric power is supplied from the battery 11 to the load 12.

Further, the charging current i to the battery 11 is detected through the current detector 13, and the detected current i is sent to the integrator 14 which is a remaining capacity calculating section to calculate and output the remaining capacity by integrating the current. As shown in FIG. 2, the integrator 14 may be of a general structure in which an OP amplifier is used and a capacitor is provided in its feedback loop. And the calculation of the remaining capacity in the integrator 14 is
Since it is the same as the above-mentioned conventional one (remaining capacity meter disclosed in Japanese Patent Laid-Open No. 63-208773), detailed description thereof will be omitted.

By the way, in the case of such a solar power generation system, since the solar cell 10 generates power during the daytime, the charging current i flows into the battery 11. Then, the magnitude of the current increases and decreases with the increase and decrease in the amount of sunshine, and therefore increases from a certain time (when the amount of sunshine required for power generation after sunrise) increases, reaches a maximum around noon, and then decreases. When the amount of sunlight required for power generation cannot be obtained after sunset, discharge current flows from the battery. Since this discharge current is in the opposite direction to the above charge current, if the charge current is positive, it becomes negative and a constant current flows. Note that current does not flow when power supply to the load is unnecessary. Therefore, FIG.
As shown in.

The remaining capacity (charge) obtained by integrating the charging current by the integrator 14 gradually increases while the charging current is flowing, as shown in FIG. It will decrease when it is flowing. However, since the cumulative error occurs due to the integration as described above, the remaining capacity obtained by the integrator 14 is shown by the solid line, although the actual remaining capacity changes as shown by the alternate long and short dash line in FIG. However, the error between the two has expanded with the passage of time.

Therefore, in the present invention, the following correcting means is provided in order to eliminate the above accumulated error. That is, first, the change in the terminal voltage of the battery 11 with the increase in the remaining capacity at the time of charging gradually increases at the beginning of charging as shown in FIG. Then gradually increases. The inflection point P at which the rate of increase suddenly changes is the depth DO of charge / discharge.
It is the same regardless of D. Here, DOD refers to the capacity discharged from full charge by the time charging is started. For example, DOD 80% means that 80% of the charge has already been discharged and the charge state (remaining capacity) at the start of charging is This means 20%. Further, in the vicinity of the inflection point P, the amount of change in the charge state is smaller than the change in the voltage, and the charge state can be accurately predicted even with a relatively rough detection.

Therefore, according to the present invention, the inflection point P of the voltage rise at the time of charging is detected, and it is considered that the predetermined charging state (remaining capacity QP) exists at the time of detection, and the result obtained by the integrator 14 is used. The output of the integrator is set to the remaining capacity QP regardless of the correction (correction is made). As a result, even if there is a cumulative error, it is corrected at least every time the inflection point P is passed during charging, and the error is reset.
The reason why the voltage fluctuates in the state where the discharge current is constant is that the internal resistance of the battery 11 fluctuates according to the charging state. To do.

Further, the inflection point P changes as the temperature changes, as shown in FIG. Therefore, in this example, the temperature at the time of detecting the inflection point P is also measured, the remaining capacity QP (T) indicated by the inflection point P is obtained, and the above correction is performed with the value QP (T). I have to.

That is, as shown in FIG. 1, the terminal voltage and the charging current of the battery 11 are input to the inflection point detecting section 15, where the inflection point P of the voltage (internal resistance) is detected, and the detection signal is sent. It is sent to the correction capacity setting unit 16. Then, when the correction capacity setting unit 16 receives the detection signal, the correction capacity setting unit 16
4 is set to a predetermined correction capacity value, and the output of the integrator 14 is changed to the correction capacity value.

Explaining each part in detail, first, the inflection point detecting section 15 detects the inflection point P of the internal resistance which is not affected by the fluctuation of the current because the charging current is not constant in this example. It has become. That is, first, battery 1
The terminal voltage and charging current of 1 are sent to the internal resistance calculation unit 17,
Then, the internal resistance R is calculated by the following formula.

Internal resistance R = terminal voltage / charging current The output of the internal resistance calculating section 17 is sent to a differentiator 18, where the time derivative of the internal resistance R is obtained. That is, since the inflection point P is a point where the internal resistance changes rapidly,
This is because the point where the amount of change (differential value) is the largest becomes the inflection point. However, at the beginning of charging / discharging, the terminal voltage for calculating the internal resistance is changed from the open voltage due to the voltage drop of the internal resistance due to the connection of the load etc. from the open state or the reversal of the direction of the current. Change rapidly in a short time to increase or decrease (Fig. 3 (C))
However, this change is not the desired inflection point. Therefore,
The output of the differentiator 18 is sent to the low-pass filter 19 so as to remove such a variation in a short time.

The output of the low-pass filter 19 is connected to the peak detector 20. This peak detector 2
In the case of 0, a peak of a mountain exceeding a certain threshold value is detected in the differential value change curve obtained by removing unnecessary changes for a short time by the low-pass filter 19, and it is designated as an inflection point P. A detection signal is output when it is determined and the inflection point is detected. Then, changes in the outputs of the respective parts of the inflection point detection unit 15 due to changes in the charging current (FIG. 3 (A)) are shown in FIGS. 4 (A) to 4 (C).

On the other hand, the correction capacity setting unit 16 is based on the relay 21 that closes the contact when receiving the detection signal output from the peak detection unit 20 and the temperature given from the temperature sensor 22 when the relay 21 is closed. And a temperature-capacity converter 23 that determines a correction capacity to be set in the integrator 14. The temperature-capacity conversion unit 23 has a database that stores the relationship of the remaining capacity QP of the inflection point with respect to the temperature T in the form of a graph or table as shown in FIG. 6, and the inflection point corresponding to the detected temperature T. The remaining capacity QP of the above is determined and sent to the integrator 14. As a result, as shown in FIG. 4D, the output of the integrator 14 (shown by the solid line) is corrected at a predetermined timing (shown by the arrow),
It matches the actual remaining capacity (indicated by the one-dot chain line). In addition,
In the case where the integrator 14 is configured as shown in FIG. 2, the correction capacitance QP is set, for example, by temporarily discharging the electric charge of the feedback capacitor of the OP amplifier which constitutes the integrator 14 when there is a detection signal. And the specified remaining capacity QP
It suffices to charge the feedback capacitor with a charge according to the above.

Thus, in this embodiment, the accumulated error of the remaining capacity is corrected based on the information such as the terminal voltage and the charging current of the battery 11 which is originally necessary for detecting the remaining capacity and which can be detected by the sensor having a relatively simple structure. It can be performed. If the charging current is constant (for example, the power source is relatively stable, such as a commercial power source, and is charged separately from the system without being connected to an actual load), the internal resistance calculator 17 of the above-described embodiment is provided. Alternatively, the detected terminal voltage may be input to the differentiator 18.

In a place where the temperature change is small, the temperature sensor 22 and the temperature capacity converter 23 are not provided,
Various modifications can be made, such as setting a fixed correction capacitance when the relay 21 is on.

FIG. 7 shows a second embodiment of the present invention.
In this example, based on the first embodiment described above,
Another auxiliary correction capacity setting unit 24 is provided. That is,
For example, as shown in FIG. 8, when charging / discharging of the battery is repeatedly performed in a region of a low state of charge below the inflection point P, the apparatus of the first embodiment does not pass through the inflection point and is thus corrected. However, the cumulative error is enlarged.

Therefore, in the present example, when the state of charge is low and the remaining capacity is small, the low capacity detecting section 25 detects such a state and closes the contact of the relay 26, and the voltage capacity converting section 2 at that time.
The predetermined correction capacity determined in 7 is set in the integrator 14. That is, the discharge curve gradually decreases when the remaining capacity is high, as shown by the chain double-dashed line in FIG. 8, but sharply decreases when the remaining capacity becomes low. However, there is no inflection point like the charging curve (shown by the one-dot chain line in the figure). The discharge curve also changes with temperature.
Therefore, a conversion table for obtaining the remaining capacity from the terminal voltage, the discharge current, and the temperature is created in advance, and the conversion table is accessed from the three pieces of information input to the voltage / capacity conversion unit 27 to obtain the current remaining capacity and correct it. Come to do.

However, in this correction method, the discharge curve has no inflection point like the charge curve, and the correction capacity is 3
Since the error is large because it is calculated based on one piece of data, a temporary correction should be made at the inflection point of the charging curve. Further, since the low capacity detection unit 25 continues to output the detection signal when the remaining capacity becomes equal to or less than the predetermined threshold value, the temporary correction is always performed while the remaining capacity is low and the integrator is operated as it is. The current integration at 14 will always be invalid. Therefore, for example, when the low capacity state continues, the temporary correction may be performed at a predetermined timing. Since the other configurations and operations (correction performed by using the inflection point of the charging curve) are the same as those in the first embodiment described above, the same reference numerals are given and the description thereof is omitted.

FIG. 9 shows a third embodiment of the present invention. In this embodiment, unlike the above embodiments, an example of a measuring device for determining the life of a battery is shown. As shown in the figure, the battery 11 can be connected to a charging power source 10 'and a discharging load (resistor) 12' via a switch S. Although not shown, this battery can be connected to an actual load or a power source or the like as needed by using other connecting means as in the above-described embodiments.

Then, similarly to each of the above-mentioned embodiments, the charging current detected through the current detector 13 is sent to the integrator 14 'and the inflection point detecting section 15, and this inflection point detecting section 15 is The terminal voltage of the battery 11 is also input. Then, the inflection point detection unit 15 detects the inflection point of the change in the internal resistance during charging based on the given current and voltage.

In this example, unlike the above-described embodiments, the output (detection signal) of the inflection point detecting section 15 is changed to the integrator 1.
It is supposed to be sent to 4 '. Then, the integrator 14 'is adapted to integrate the charging current given after the detection signal is inputted.

Further, the charging / discharging control section 28 for controlling the connection of the switch S is provided, and when the life is judged, first, the switch S is connected to the discharge load 12 'and the battery 11 is connected.
The electric charge stored in the battery 11 is discharged, and then the switch S is connected to the charging power source 10 'to charge the battery 11 until the battery 11 is fully charged. Then, the measured terminal voltage of the battery 11 is also input to the charge / discharge control unit 28. When the terminal voltage reaches a predetermined voltage, it is determined that the battery is fully charged, and the switch S is turned off as shown in the figure. To At this time, a control signal (end) is sent to the integrator 14 '.

When the control signal is input, the integrator 14 'terminates the integration of the charging current and sends the charge Q obtained by the integration up to that time to the life determining unit 29. . That is, the charge Q obtained by the integrator 14 'means the charge accumulated up to 100% from the inflection point. However, since there is a loss component, the actually stored charge has a value obtained by subtracting a predetermined loss component from the integrated value of the current (see FIG. 10C). Then, the loss amount is held in advance as data.

In the life determining unit 29, the storage capacity of this battery is calculated by calculating the capacity for 100% based on the electric charges actually stored by the integrator 14 ', and the storage capacity is calculated. When it becomes less than the predetermined value, it is judged that the life has expired. Specifically, based on the temperature detected by the temperature sensor 22, the charging state (X) at the inflection point
Then, the storage capacity is calculated by the following formula.

Power storage capacity = (100 / (100-X)) Q Here, the operation of this example will be described. First, the charge / discharge control unit 28 is operated to connect the switch S to the discharge load 12 'and fully discharge. Let it be below the point of inflection. Next, the switch S is connected to the charging power source 10 'to charge the battery 11. At this time, the inflection point detection unit 15 is activated to detect the inflection point of the charging curve. Then, the integrator 14 'integrates the charging current from the inflection point to full charge, and obtains the charge Q accumulated during that time. The history of changes in the terminal voltage of the battery 11 at this time is shown in FIG.
As shown in (B). The charge Q thus obtained is sent to the life determining unit 19, where it is determined whether or not the life has expired, and the determination result is displayed on a display unit (not shown).

With this configuration, the life of the battery can be measured with a small amount of discharge in this example, and it is not necessary to discharge the battery from full charge, and the battery can be measured (life judgment based on life). ) Can be done.

[0037]

As described above, in the battery measuring device according to the present invention, various measurements are performed using the inflection point of the charging curve, so that the cumulative error is corrected and corrected with a simple structure. The remaining capacity can be obtained and the life can be determined.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of a battery measuring device according to the present invention.

FIG. 2 is a diagram showing an internal structure of an integrator.

FIG. 3 is a diagram illustrating an operation.

FIG. 4 is a diagram illustrating an operation.

FIG. 5 is a diagram showing a characteristic of a terminal voltage with respect to a charging state (current and temperature are constant).

FIG. 6 is a diagram showing a characteristic of a terminal voltage with respect to a charging state.

FIG. 7 is a diagram showing a second embodiment of the battery measuring device according to the present invention.

FIG. 8 is a diagram showing a characteristic of a terminal voltage with respect to a charge / discharge state.

FIG. 9 is a diagram showing a third embodiment of the battery measuring device according to the present invention.

FIG. 10 is a diagram illustrating an operation.

[Explanation of symbols]

 11 Battery 14 Integrator (means for integrating charging current) 14 'Integrator (capacity calculating means) 15 Inflection point detection part 16 Correction capacity setting part 22 Temperature sensor 25 Low capacity detection part 26 Voltage capacity conversion part (correction capacity calculation) Means) 28 charge / discharge control section 29 life judgment section

Claims (4)

[Claims] 1. A battery measuring device for detecting a charging / discharging current of a battery, obtaining an integrated amount thereof, and measuring a remaining capacity on the basis of the integrated amount, wherein a terminal voltage of the battery and / or an internal voltage which varies with charging. Inflection point detection means for detecting the inflection point of the resistance, and when the inflection point is detected by the inflection point detection means,
A battery measuring device comprising: a correction unit that corrects the remaining capacity calculated based on the integrated amount to a correction capacity at which the inflection point occurs. 2. The correction means comprises temperature detection means and means for determining the correction capacity corresponding to the inflection point of the temperature detected by the temperature detection means, and based on the determined correction capacity. The battery measurement device according to claim 1, wherein the correction is performed by using the battery measurement device. 3. A low capacity detecting means for detecting that charging / discharging is performed in a region having a low remaining capacity, and a discharge of a terminal voltage and / or an internal resistance of the battery which receives an output of the low capacity detecting means. 3. A correction capacity calculating means for calculating an auxiliary correction capacity based on a characteristic, wherein the calculated auxiliary correction capacity is used to correct the remaining capacity calculated based on the integrated amount. Battery measuring device described in. 4. A charge / discharge control means for forcibly discharging the battery and then charging it, and an inflection point detection means for detecting an inflection point of the terminal voltage and / or internal resistance of the battery which fluctuates with the charging. And a capacity calculation means for calculating the capacity accumulated in the battery from the inflection point to full charge, and the storage capacity of the battery is calculated based on the capacity calculated by the capacity calculation means. A battery measuring device equipped with a life judging means for judging the life according to the size of the battery.