JPH06242193A - Remaining capacity meter - Google Patents

Abstract

PURPOSE:To detect the accurate remaining capacity of a battery. CONSTITUTION:The nonrotating state of a motor 14 is detected by a tachometer 28, and a processing section 26 thereby detects the stopping of a vehicle, and the release voltage of a main battery 10 is measured on the then output of a voltmeter. Since the release voltage has a fixed connection with the remaining capacity of a battery, the then remaining capacity of the battery is computed on the release voltage. On the other hand, the processing section 26 integratingly computes the discharge quantity of the main battery 10 on the output of an ammeter 20. The deterioration rate of the battery and its actual full charging capacity are computed on both remaining capacity decided from the release voltage during stopping and discharging capacity. In addition, the accurate charged state (SOC) and the remaining capacity can be constantly detected by means of the computed full charging capacity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a remaining capacity meter for detecting the degree of deterioration of a battery and measuring the remaining capacity in consideration of the detected degree of deterioration of the battery.

[0002]

2. Description of the Related Art Conventionally, an electric vehicle driven by a motor has been known and has been drawing attention from the viewpoint of low pollution. This electric vehicle is equipped with a battery as an energy source, and it is necessary to measure the state of charge of this battery. That is, the battery is consumed by driving the motor,
When the remaining capacity approaches 0, the vehicle cannot run. Therefore, it is necessary to charge the battery when the remaining capacity falls below a predetermined value, and it is essential to measure the state of charge.

Therefore, various kinds of charge capacity measuring devices have been conventionally known, in which the charge / discharge amount of a battery is integrated by a power integrator and compared with a known electric capacity of the battery to charge the battery. A power integrating SOC meter that measures a state (SOC) is known. According to the SOC meter of this type, the battery itself does not need to be modified, and the SOC meter is reset by full charge due to regular charging, so that the SOC can be measured relatively accurately.

However, this SOC meter is premised on that the capacity for full charge does not change, and if the SOC meter changes due to deterioration of the battery, the accuracy deteriorates. In particular, when the SOC is low, that is, when the discharge progresses, the remaining capacity obtained by subtracting the discharged electric capacity from the fully charged capacity becomes considerably inaccurate.

On the other hand, Japanese Unexamined Patent Publication No. 63-261179 discloses an auxiliary battery for an automobile, which detects the degree of deterioration of the battery. In this device, the differential internal resistance of the battery is obtained from the battery voltage or the like when discharging a large current. Since this differential internal resistance has a good correlation with the residual capacity, the residual capacity is obtained from the measured differential internal resistance. Further, the average current when the set voltage at which the voltage regulator is operating is reached is calculated.
The average current when the set voltage is reached is smaller as the full charge capacity is larger and the remaining capacity is larger. Therefore, the full charge capacity is obtained from the residual capacity obtained from the differential internal resistance and the average current when the set voltage is reached, and the deterioration degree is detected by comparing with the nominal full charge capacity.

By detecting the degree of deterioration in this way, the SOC and the remaining capacity can be accurately detected. In the normal case, the remaining capacity is represented by the electric capacity Ah, and the SOC is represented by% of the remaining capacity with respect to the full charge capacity.

[0007]

However, in order to detect the degree of battery deterioration according to the above conventional example, it is necessary to measure the average charging current when the set voltage at which the voltage regulator operates is reached. Since the auxiliary battery of a normal gasoline vehicle can be constantly charged during traveling, the voltage regulator is frequently operated. But,
An electric vehicle mainly discharges when it is running, is not in a high charge state, and cannot measure the average charging current when the set voltage is reached. Further, even during charging, the constant voltage is only at the end of charging, and the remaining capacity at that time cannot be accurately known.

Therefore, the above-mentioned conventional example has a problem that the deterioration degree of the main battery for driving the motor in the electric vehicle cannot be detected. In addition, there is a problem that the remaining battery capacity cannot be accurately detected in consideration of the degree of deterioration.

The present invention has been made to solve the above-mentioned problems, and provides a remaining capacity meter capable of detecting the deterioration level of a battery and accurately detecting the remaining capacity in consideration of this. The purpose is to do.

[0010]

SUMMARY OF THE INVENTION The present invention is a remaining capacity meter for detecting the degree of deterioration of a battery for driving a motor of an electric vehicle, which is an open circuit for detecting an open circuit voltage of a battery from a battery voltage when a vehicle is stopped. A voltage detecting means, a stop-time remaining capacity detecting means for detecting a remaining capacity of the battery from the detected open circuit voltage, a discharging electric capacity detecting means for detecting a discharging electric capacity of the battery based on an integrated value of a discharging current of the battery, It has a full charge capacity calculating means for calculating the full charge capacity of the battery from the remaining capacity at the time of stop and the discharged electric capacity, and a deterioration degree calculating means for calculating the deterioration degree from the obtained full charge capacity and the nominal full charge capacity. It is characterized by

Further, the present invention is a remaining capacity meter for measuring the remaining capacity of a battery for driving a motor of an electric vehicle, which is an open circuit voltage detecting means for detecting the open circuit voltage of the battery from the battery voltage when the vehicle is stopped. And a remaining capacity during stop for detecting the remaining capacity of the battery from the detected open circuit voltage, a discharging capacity detecting means for detecting the discharging capacity of the battery based on the integrated value of the discharging current of the battery, and a remaining capacity during stopping. A full charge capacity calculating means for calculating the full charge capacity of the battery from the capacity and the discharged electric capacity; and a remaining capacity detection means for calculating the remaining capacity of the battery from the calculated full charge capacity and the detection value of the discharged electric capacity detection means. It is characterized by having.

[0012]

As described above, the voltage of the battery originally depends on the remaining capacity of the battery, but the battery voltage normally measured changes due to the influence of the discharge current or the like. However, in an electric vehicle, when the vehicle is stopped, there is no discharging current or charging current due to regenerative braking. Therefore, the open circuit voltage of the battery can be measured. Therefore, in the present invention, the open circuit voltage is obtained from the battery voltage when the vehicle is stopped, and the remaining capacity at the time of stop is detected from this.

On the other hand, in the present invention, the discharge electric capacity for integrating the discharge current amount of the battery is detected. Therefore, the remaining capacity can be detected by subtracting the discharged electric capacity from the full charge capacity, and the SOC can be detected by dividing the remaining capacity by the full charge capacity.

Here, in the present invention, the full charge capacity is not fixed to the nominal capacity, but is changed according to the measurement. That is, the actual full charge capacity can be calculated by adding the remaining capacity at the time of stop and the discharged electric capacity at that time. Therefore, the degree of deterioration of the battery can be detected by comparing this full charge capacity with the nominal full charge capacity. In addition, the full charge capacity at the time of calculating the remaining capacity from the discharge electric capacity described above can be corrected to obtain an accurate remaining capacity.

If the calculation of the full charge capacity is performed at only one point, the error becomes large, so it is desirable to obtain the full charge capacity from the remaining capacity at a plurality of different points for discharging electricity. In particular, it is preferable to detect the degree of deterioration such as after the ignition switch is turned off after the traveling ends and to correct the full charge capacity.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a main part configuration of an electric vehicle to which a state-of-charge meter according to the present invention is applied.
Is composed of a lead-acid battery and outputs its output from the inverter 12
Supply to. The inverter 12 includes a plurality of switching elements, converts the supplied DC power into a predetermined AC power, and supplies the AC power to the motor 14. The motor 14 is composed of an AC induction motor and is operated with an output according to the electric power supplied from the inverter 12. Wheels are connected to the output shaft of the motor 14 through a gear unit or the like (not shown), and the electric vehicle travels according to the output of the motor 14.

On the other hand, an ammeter 20, a voltmeter 22 and a thermometer 24 are connected to the main battery 10. The measured values of the ammeter 20, voltmeter 22 and thermometer 24 are
It is supplied to the processing unit 26. The operating condition of the motor 14 is detected by the tachometer 28, and the rotation speed signal is supplied to the processing unit 26.

Then, the processing unit 26 performs a predetermined arithmetic processing in accordance with each of the supplied signals to calculate the degree of deterioration of the main battery 10, the remaining capacity and the SOC. A display unit 30 is connected to the processing unit 26, and the remaining capacity and SOC of the main battery 10 are displayed here. Therefore, the driver sees the display on the display unit 30 and
It is possible to know the remaining capacity and SOC of the main battery 10, and it is possible to judge the travelable distance and the necessity of charging.

Here, the calculation of the degree of deterioration performed in the processing unit 26 will be described. FIG. 2 shows an example of the relationship between the open circuit voltage and the remaining capacity of a lead battery. Thus, the open circuit voltage increases as the remaining capacity increases. On the other hand, in an electric vehicle,
The main battery 10 is in a state of being disconnected from the load. That is, all the switching elements in the inverter 12 are in the off state, and the battery voltage measured by the voltmeter 22 when the vehicle is stopped becomes the open circuit voltage. Therefore, for the main battery 10 to be mounted, if the relationship between the remaining capacity and the open-circuit voltage is checked in advance and the relationship as shown in FIG. 2 is stored as a map, the output of the voltmeter 22 when the vehicle is stopped causes
The processing unit 26 can calculate the remaining capacity of the main battery 10 at that time. In order to detect the open circuit voltage accurately, a switch or the like may be provided to positively disconnect the main battery 10 from the load when measuring the open circuit voltage.

On the other hand, the processing unit 26 integrates the discharge amount and the charge amount supplied from the ammeter 20 to obtain the SOC.
Is constantly detected. That is, SOC = (full charge capacity−discharge amount−self discharge amount + charge amount)
/ SOC is calculated based on the formula of full charge capacity. Here, as the full charge capacity, the nominal full charge capacity is initially used,
It is updated at any time depending on the degree of deterioration of the main battery 10 described later.
Further, the discharge amount and the charge amount are calculated based on the measurement value of the ammeter 20, and the charge amount depends on the current during normal regenerative braking. Further, the self-discharge amount is unique to the battery, and is calculated by multiplying the self-discharge amount per time, which is obtained in advance, by the elapsed time from full charge.

In this way, when the SOC and the SOC when the vehicle is stopped are obtained, the full charge capacity at that time is obtained from this relationship. That is, as shown in FIG.
From the SOC at the time of obtaining the state of charge, the relationship between the two is plotted and this straight line is extended to obtain the state of charge at the time of SOC 100%. The remaining capacity when the SOC is 100% is the full charge capacity. The calculation of the full charge capacity is performed when a certain amount of data is accumulated. In addition, this calculation obtains a straight line by the method of least squares, and
It is sufficient to obtain the remaining capacity when C is 100%. Since the discharge amount at that time is known from the SOC at the time of measuring the remaining capacity, the full charge capacity is calculated from the sum of this discharge amount and the remaining capacity, and a certain number of these are collected to obtain an average value. good. As described above, the accuracy of the obtained full charge capacity can be improved by obtaining the full charge capacity after a certain amount of data is collected without obtaining the full charge capacity by one measurement. In this way, the processing unit 26 can know the full charge capacity of the main battery 10 at a predetermined frequency.

Therefore, the deterioration degree can be calculated by the deterioration degree = 1-full charge capacity / nominal capacity. In addition, by using the updated full charge capacity to obtain the SOC as described above, an accurate SOC considering the degree of deterioration of the battery can be obtained.
Can be calculated.

Furthermore, the remaining capacity can be calculated from the remaining capacity = full charge capacity × SOC.

Therefore, the processing unit 24 supplies the remaining capacity, SOC, degree of deterioration, etc., obtained in this way, to the display unit 28, where they are displayed. Therefore, the driver can accurately grasp the situation of the main battery 10 by looking at the display unit 28. The relationship between the open circuit voltage and the remaining capacity of the battery changes depending on the temperature at that time. That is, it is known that the lower the temperature, the less the remaining capacity. Therefore, the detected value of the remaining capacity based on FIG. 2 may be corrected by the battery temperature.

Next, an example of the operation for calculating the remaining capacity of the battery described above will be described with reference to FIG. First,
From the detection values of the ammeter 20, the voltmeter 22, and the thermometer 24,
The current flowing in the main battery 10, the battery voltage and the battery temperature are taken in (S1). Then, the current values are integrated, correction is made according to the detected battery temperature (S2), and the remaining capacity and SOC are obtained (S3). As a result, the processing unit 2
4 can recognize the remaining capacity and SOC, and can perform display by this.

Next, it is determined whether the key switch is on (S4). Then, if the key switch is on, it is determined whether or not the battery is in an open state when the electric vehicle is traveling and is stopped by a signal (S5).
This is performed by the output of the tachometer 28 or the like. Alternatively, the output from a speed sensor or the like may be used. Then, when the battery is left unattended, the deterioration degree is measured as described above (S6). That is, the remaining capacity is obtained from the relationship of FIG. 2, and the SOC at that time is input to the memory. Then, when there is a certain amount of data about the deterioration level input in the memory, the deterioration level is detected and the full charge capacity is updated. Then, based on the thus-obtained full charge capacity, the remaining capacity and SOC are updated and display output is performed (S7). The deterioration degree may be updated at a predetermined frequency such as when the battery is fully charged.

On the other hand, when the key switch is off in S4 and when the display output in S7 ends, it is determined whether or not charging is in progress (S8). If the battery is being charged, it is determined whether the battery is fully charged (S9). If the battery is fully charged, the integrated current amount is reset (S1).
0). Here, the judgment of full charge is made based on the current change during charging, the time thereof, and the like.

In this way, the full-charge capacity of the battery can be updated by using the battery voltage (open voltage) while the vehicle is stopped, so that the remaining capacity, S, according to the degree of deterioration of the battery, S
OC detection can be performed.

When the open circuit voltage is obtained while the battery is left standing, it takes some time (about several minutes) until the open circuit voltage is stabilized. Therefore, for example, it is preferable to estimate the open circuit voltage value from the voltage change for 1 minute after leaving.

[0030]

As described above, according to the remaining capacity meter of the present invention, the actual full charge capacity at that time can be detected by detecting the battery open-circuit voltage when the vehicle is stopped. Therefore, it is possible to detect the degree of deterioration using this, and it is possible to accurately detect the remaining battery capacity in consideration of the degree of deterioration.

Further, the open circuit voltage itself when the vehicle is stopped can be measured only intermittently, but since the SOC by the integration of the electric quantity can always be carried out, the full charge capacity is updated from the intermittent open circuit voltage. You can always know the accurate remaining capacity.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an overall configuration of an embodiment.

FIG. 2 is a characteristic diagram showing a relationship between an open circuit voltage and a remaining capacity.

FIG. 3 is an explanatory diagram illustrating a method of calculating a degree of deterioration.

FIG. 4 is a flowchart showing operations of deterioration degree calculation and remaining capacity calculation.

[Explanation of symbols]

 10 Main Battery 12 Inverter 14 Motor 20 Ammeter 22 Voltmeter 24 Thermometer 26 Processing Section 28 Display Section

Claims (2)

[Claims] 1. A remaining capacity meter for detecting the degree of deterioration of a battery for driving a motor of an electric vehicle, which comprises an open circuit voltage detecting means for detecting an open circuit voltage of the battery based on a battery voltage when the vehicle is stopped. Remaining capacity detection means at the time of stop to detect the remaining capacity of the battery from the open circuit voltage, Discharge capacity detection means to detect the discharge capacity of the battery based on the integrated value of the discharge current of the battery, Remaining capacity at the time of stop, discharge A remaining capacity characterized by having a full charge capacity calculating means for calculating the full charge capacity of the battery from the electric capacity, and a deterioration degree calculating means for calculating the degree of deterioration from the full charge capacity and the nominal full charge capacity. Total. 2. A remaining capacity meter for measuring a remaining capacity of a battery for driving a motor of an electric vehicle, which is an open circuit voltage detecting means for detecting an open circuit voltage of the battery from a battery voltage when the vehicle is stopped. Remaining capacity detecting means for detecting the remaining capacity of the battery from the detected open circuit voltage, discharging electric capacity detecting means for detecting the discharging electric capacity of the battery based on the integrated value of the discharging current of the battery, and the remaining capacity at stopping. A full charge capacity calculating means for calculating the full charge capacity of the battery from the discharged electric capacity, and a remaining capacity detecting means for calculating the remaining capacity of the battery from the calculated full charge capacity and the detection value of the discharge electric capacity detecting means, A residual capacity meter characterized by having.