JPH10255857A - Remaining capacity meter for storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize an error at the time of estimating the remaining capacity of a storage battery. SOLUTION: The discharging current and terminal voltage of a storage battery 1 are measured by a measuring instrument 5, and the measured data are inputted into a remaining capacity meter body 4 through an A/D converter 6. In the remaining capacity meter body 4, using the inputted measured data, open-circuit estimated voltage is estimated by obtaining a primary regression expression between the discharging current and terminal voltage of the storage battery 1, and the remaining capacity of the storage battery is estimated from a remaining capacity estimation curve which is indicated with a relation between the estimated open-circuit voltage and discharging electric energy. In the case of estimating the estimated open-circuit voltage, if the estimated open-circuit voltage estimated this time is larger than the estimated open-circuit voltage estimated at the previous time, the estimated open-circuit voltage estimated this time is not used, and the estimated open-circuit voltage estimated at the previous time is used. The remaining capacity estimation curve is moved so that the remaining capacity estimation curve may include data, such as the obtained estimated open-circuit voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a storage battery remaining capacity meter, and more particularly, to measuring the remaining capacity of a storage battery mounted on an electric vehicle, such as the remaining power, remaining power, remaining mileage, and remaining operating time. The present invention relates to a battery remaining capacity meter that can be estimated during storage.

[0002]

2. Description of the Related Art Conventionally, as a storage battery remaining capacity meter for an electric vehicle, there has been known a storage battery remaining capacity meter for temporarily measuring the voltage of a storage battery during discharging or at rest and judging the storage battery remaining capacity. ing. This is mainly to measure the open circuit voltage during pause and estimate the remaining capacity from the relationship between the preset open circuit voltage and the remaining capacity.

However, such a fixed method has a great influence on the usage of the battery at the time, the state of the battery, the ambient temperature, and the like, so that accurate estimation is impossible.

Accordingly, a method for estimating the remaining capacity of a storage battery as described below has been proposed by the same applicant (JP-A-5-242915). First, the amount of power consumption for a fixed time from the start of traveling is determined, and a regression equation between the discharge current of the storage battery and the terminal voltage near the end of the fixed time is determined. From the regression equation, an estimated open circuit voltage is obtained, and a regression equation between the estimated open circuit voltage and the power consumption is obtained. Next, the estimated open-circuit voltage and the predetermined open-circuit voltage at the end of discharge in the following running are applied to the above-described regression equation, the discharge power amount corresponding to each is obtained, and the remaining power amount is obtained from the difference. Estimate the remaining capacity of the storage battery.

[0005]

However, in the above prior art, it is unclear how to determine the value of the open circuit voltage corresponding to the usage limit of the electric vehicle, and a large error occurs in the estimation of the remaining capacity. Has occurred. In other words, as the discharge of the storage battery increases, the open-circuit voltage generally decreases monotonically, and the remaining capacity also shows a monotonous decreasing trend. However, this is a factor that increases the estimation error.

An object of the present invention is to provide a storage battery remaining capacity meter capable of reducing the estimation error when the remaining capacity of the storage battery is estimated.

[0007]

In order to achieve the above object, a storage battery remaining capacity meter according to the present invention comprises a measuring means for measuring a discharge current and a terminal voltage of a storage battery mounted on an electric vehicle;
While taking in measurement data one by one from the measurement means,
A discharge power amount calculating means for calculating a discharge power amount of the storage battery based on the taken measurement data; and a measurement data taken from the measurement means one by one. Open-circuit voltage estimating means for obtaining a relational expression between the discharge current and the terminal voltage of the storage battery using the latest measurement data taken in time, and estimating the estimated open-circuit voltage of the storage battery one by one from the relational expression; and As a result of estimating the estimated open circuit voltage by the means one by one, if the estimated open circuit voltage of the current estimation is smaller than the estimated open circuit voltage of the previous estimation, the estimated open circuit voltage of the current estimation is
When the estimated open-circuit voltage estimated this time is larger than the estimated open-circuit voltage estimated last time, the open-circuit voltage selecting means for selecting the estimated open-circuit voltage estimated last time, the estimated open-circuit voltage selected by the open-circuit voltage selecting means and the discharge power While taking in the latest data of the discharge power amount calculated by the amount calculation means, the remaining capacity estimation curve indicated by the relationship between the estimated open-circuit voltage and the discharge power amount and set in advance includes the obtained latest data. And a remaining capacity estimating means for moving the remaining capacity estimation curve and estimating the current remaining capacity of the storage battery based on the remaining capacity estimation curve after the movement.

According to the above configuration, the provision of the open-circuit voltage selecting means ensures that the value of the estimated open-circuit voltage estimated by the open-circuit voltage estimating means is larger than the value of the previously estimated estimated open-circuit voltage. Means that the estimated open circuit voltage of the previous estimation is selected. As a result, the estimated open circuit voltage monotonically decreases with an increase in the discharge of the storage battery, and the remaining capacity can have a monotonous decreasing tendency.

Further, when the remaining capacity estimation curve is used at the discharge start time when the number of measurement points is small, there may be a problem that the remaining capacity estimation curve is not suitable. Such an inconvenience can be avoided by such a movement.

The remaining capacity estimating means obtains a correlation coefficient between the discharge current of the storage battery and the terminal voltage, and estimates the remaining capacity of the storage battery when the absolute value of the correlation coefficient becomes a predetermined value or less. It has a function to stop doing.

Further, the remaining capacity estimating means calculates the remaining capacity estimation curve based on a change in the remaining capacity estimation curve accompanying the repetition of discharging / charging.
It also has a function of determining the life of the storage battery.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a storage battery remaining capacity meter according to the present invention. In the figure, reference numeral 1 denotes a storage battery mounted on an electric vehicle, which supplies electric power to an electric motor 2. The electric motor 2 is driven to rotate by the electric power supply, and the electric driving vehicle is driven by transmitting the rotation driving force to the drive system 3.

The electric vehicle is equipped with a remaining capacity meter main body 4. In the present embodiment, a personal computer is used as the remaining capacity meter main body 4. Then, the discharge current and the terminal voltage of the storage battery 1 are measured by the measuring device 5, and the measurement data is input to the remaining capacity meter main body 4 via the A / D converter 6. At the same time, the number of rotations of the rotating part of the drive system 3 (for example, the output shaft of the transmission) is detected by the detector 7, and the detection result is also input to the remaining capacity meter main body 4 via the A / D converter 6. Note that, instead of the rotating part of the drive system 3, the number of rotations of the electric motor 2 may be directly detected, and the detection result may be input to the remaining capacity meter main body 4.

In the A / D converter 6, the analog data of the discharge current and the terminal voltage of the storage battery 1 from the measuring device 5 and the analog data of the rotation speed of the drive system 3 from the detector 7 are converted into digital data. Is done.

The remaining capacity meter main body 4 calculates the remaining capacity kWh of the storage battery 1 from the data of the discharge current and the terminal voltage of the storage battery 1 and the rotation speed of the drive system 3 which are converted into digital data.
And the remaining capacity% and the mileage km of the electric vehicle are calculated, and the calculation result is converted to an LC provided in the remaining capacity meter main body 4.
It is displayed on the D screen 8.

Further, the remaining capacity kWh and the possible travel distance k
The remaining amount data relating to the remaining capacity of m is output and displayed via the D / A converter 9 on an instrument 10 or the like mounted on the electric vehicle. The measurement data of the discharge current and the terminal voltage of the storage battery 1 and the rotation speed of the drive system 3 input to the remaining capacity meter main body 4 as digital data through the A / D converter 6 are transmitted through the RS-232C11. The data is output to another personal computer 12.

FIG. 2 shows the remaining capacity meter main body 4 and its peripheral devices, ie, A / D converter 6, D / A converter 9, and RS-2.
It shows a detailed configuration such as 32C11. As shown in the figure, an A / D converter 6, a D / A converter 9, and an RS-232C11 are connected to the remaining capacity meter main body 4. Also,
CPU 4A, ROM 4
B, a RAM 4C, and an I / O 4D are provided, and an LCD screen 8 and a switch 13 are connected to the I / O 4D. Also,
A calendar 14 and a backup RAM 15 are connected to the remaining capacity meter main body 4.

Next, the operation of the storage battery remaining capacity meter having the above configuration will be described. While the vehicle is running, the discharge current and the terminal voltage of the storage battery 1 are measured by the measuring device 5, and the rotation speed of the driving type is detected by the detector 7. Then, the analog data of the discharge current, the terminal voltage, and the number of revolutions are input to the A / D converter 6, converted into digital data, taken into the battery remaining capacity meter main body 4, and stored in the RAM 4C.

The storage battery remaining capacity meter main body 4 stores the storage battery 1 based on the data of the discharge current and the terminal voltage taken in one by one.
Is calculated. This calculation result is also stored in the RAM 4C.

The storage battery remaining capacity meter main body 4 discharges the storage battery 1 by using the latest measurement data taken during a certain period of time from the present to the past among the data of the discharge current and the terminal voltage taken in each time. A first-order regression equation between the current and the terminal voltage is obtained. For example, when the discharge current and the terminal voltage taken in are plotted with (○) marks, the result as shown in FIG. 3 is obtained. In FIG. 3, the rightmost plot point is the latest data, and the data elapses from measurement to the left. In FIG. 3, there are seven plot points. If the latest data is newly plotted on the right side, the data plotted on the leftmost side is discarded. As a result, the latest measurement data taken in a certain period of time from the present to the past is plotted. Then, based on the plotted result, a first-order regression equation between the discharge current and the terminal voltage is obtained by equation (1).

Y = rx + En (1) where, x: discharge current y: terminal voltage r: regression coefficient En: estimated open circuit voltage

In the above equation (1), the estimated open circuit voltage E
n is obtained as a y-intercept. In this case, the estimated open circuit voltage En generally decreases monotonically with an increase in the discharge of the storage battery 1. That is, as shown in FIG. 4, the estimated open circuit voltage En2 estimated this time is usually smaller than the estimated open circuit voltage En1 estimated last time. However, due to differences in running patterns and the like, as shown in FIG. 5, the estimated open circuit voltage E estimated this time is more than the estimated open circuit voltage En1 estimated last time.
There is a case where n2 becomes large. If an estimated open-circuit voltage larger than the previously estimated open-circuit voltage is used, when the remaining capacity of the storage battery 1 is estimated, the estimation error increases.

Therefore, in this embodiment, when the estimated open-circuit voltage estimated this time is smaller than the estimated open-circuit voltage estimated last time (case of FIG. 4), the estimated open-circuit voltage estimated this time is used. When the estimated open-circuit voltage is higher than the previously estimated open-circuit voltage (in the case of FIG. 5), a selection circuit that employs the last-estimated estimated open-circuit voltage is provided inside the remaining capacity meter main body 4.

Next, inside the storage battery remaining capacity meter main body 4, the selected estimated open-circuit voltage and the latest data of the discharge power stored in the RAM 4C are fetched, and the relationship between the estimated open-circuit voltage and the discharge power is obtained. The remaining capacity estimation curve shown is determined. The basic shape of the remaining capacity estimation curve is preset as a reference estimation curve as shown in FIG. The reference estimation curve is set by the quadratic regression equation as in equation (2).

Y = a + bx + cx ² (2) where, x: discharge electric energy y: estimated open circuit voltage a, b, c: constants.

When the estimated open-circuit voltage and the amount of discharge power obtained in FIG. 3 are plotted with (□) marks, a result as shown in FIG. 6 is obtained. In FIG. 6, the rightmost plot point is the latest data, and the further to the left, the older the data.

The reference estimation curve is moved so as to pass through each plot point each time a plot point is obtained from the estimated open circuit voltage and the discharge power amount. That is, FIG.
In, when the leftmost plot point is obtained, the reference estimation curve is translated so as to pass through the plot point. The estimated curve after the parallel movement is referred to as a modified estimated curve. Further, when the second plot point from the left is obtained, the corrected estimated curve is translated so as to pass through the plot point. Such an operation is repeated every time a plot point is obtained.

In FIG. 6, the second plot point from the right is the one obtained last time, and the rightmost plot point is the one obtained this time. Then, by moving the previously corrected estimated curve passing through the previously obtained plot points in parallel and passing through the currently obtained plot points, the current corrected estimated curve can be obtained.

Here, the movement of the estimation curve will be described in detail with reference to FIG. As shown in FIG. 7, first, the previously corrected estimated curve is translated in the x-axis direction by dx,
The object is translated in the y-axis direction so as to pass through the point A, which is the plot point obtained this time. As a result, the previous correction estimation curve is translated in the oblique direction, and the current correction estimation curve is formed.

When the current corrected estimated curve is formed as described above, the lower limit value of the estimated open circuit voltage is determined.
This lower limit value is determined using the correlation coefficient between the discharge current of the storage battery and the terminal voltage as shown in FIGS. FIG. 9 is a graph obtained by collecting and plotting a large number of measurement data of the discharge current and the terminal voltage of the storage battery. As can be seen from FIG. 9, the plot points are dense in a range where the discharge current is relatively small (left half side of the figure), and the discharge current and the terminal voltage are almost linear. The plot points are discrete in an extremely large range (right half of the figure), and the discharge current and the terminal voltage do not have a linear relationship.

Therefore, when the correlation coefficient between the discharge current and the terminal voltage is obtained, the absolute value of the correlation coefficient becomes substantially 1 in a range where the discharge current is relatively small, but when the discharge current increases, the correlation coefficient becomes larger. Is smaller than 1. Then, when the absolute value of the correlation coefficient becomes smaller than 1, the lower limit value is set, and the estimation of the estimated open circuit voltage is stopped as shown in FIG. As a result, when the absolute value of the correlation coefficient becomes equal to or less than the predetermined value, the estimation of the remaining capacity of the storage battery is stopped.

Finally, in FIG. 6, the discharge power amount when the reference estimation curve intersects the lower limit value is x0, the discharge power amount when the current correction estimation curve intersects the lower limit value is x1, and the measured discharge amount is x1. Is x2, the remaining capacity (kWh), the remaining capacity (%), and the possible travel distance (km) of the storage battery 1
Are respectively obtained as follows.

Remaining capacity (kWh) = x1-x2 Remaining capacity (%) = 100 (x1-x2) / x0 Travelable distance (km) = km / kWh · Remaining capacity (kW)
h)

Next, an example of estimating the remaining capacity (kWh) and the remaining travelable distance (km) will be described. FIG. 10 shows an example of estimating the remaining capacity (kWh), and FIG. 11 shows an error in the remaining capacity. In this example, the time average value of the estimation error is 5.8% of the total kWh (4.98 kWh).

FIG. 12 shows an example of estimating the remaining mileage (km), and FIG. 13 shows the error of the mileage.
In this example, the time average value of the estimation error is the total km (2
7.7 km for 9.4 km).

Further, the life of the storage battery 1 can be determined from the change in the estimation curve. That is, as shown in FIG. 6, since the storage battery 1 deteriorates with repetition of discharge and charge, the possible discharge amount (that is, the discharge power amount x1) generally decreases. Therefore, for example, if the value of the discharge power amount x1 after charging and before the start of discharge falls below 80% of the discharge power amount x0 which is a possible discharge amount in a new state, it is determined that the storage battery 1 has reached the end of its life.

[0037]

As described above, according to the present invention,
It is possible to highly accurately estimate the remaining capacity of the storage battery even during traveling, and it is possible to avoid over-discharging of the battery due to the vehicle getting stuck on the road or the vehicle running unreasonably.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a storage battery remaining capacity meter according to the present invention.

FIG. 2 is a main part configuration diagram of a storage battery remaining capacity meter according to the present invention.

FIG. 3 is a diagram for explaining a method of estimating an estimated open circuit voltage.

FIG. 4 is a diagram showing an example in which an estimated open circuit voltage monotonically decreases.

FIG. 5 is a diagram showing an example in which an estimated open circuit voltage increases.

FIG. 6 is a diagram for explaining a method of estimating a state of charge.

FIG. 7 is a diagram for explaining a method of moving an estimated curve.

FIG. 8 is a diagram showing changes in an estimated open circuit voltage and a correlation coefficient.

FIG. 9 is a diagram showing an example in which a discharge current and a terminal voltage are plotted.

FIG. 10 is a diagram showing an example of estimating a remaining capacity.

FIG. 11 is a diagram showing a residual capacity error.

FIG. 12 is a diagram showing an example of estimating a remaining travelable distance.

FIG. 13 is a diagram showing a remaining travelable distance error.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Storage battery 2 Motor 3 Drive system 4 Residual capacity meter main body 5 Measuring instrument 6 A / D converter 7 Detector 8 LCD screen 9 A / D converter 11 RS-232C

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Atsushi Fukui 7-17-17, Maygaoka Minami, Suita-shi, Osaka (72) Inventor Tetsuya Hayashida 19-18, Minami-Akutagawa-cho, Takatsuki-shi, Osaka 3-25

Claims (3)

[Claims] A measuring means for measuring a discharge current and a terminal voltage of a storage battery mounted on an electric vehicle;
A discharge power amount calculating unit that calculates a discharge power amount of the storage battery based on the taken measurement data, and while taking measurement data one by one from the measurement unit,
Among the acquired measurement data, a relational expression between the discharge current and the terminal voltage of the storage battery is obtained by using the latest measurement data acquired at a certain time retroactively from the present, and the estimated open circuit of the storage battery is obtained from the relational expression. Open-circuit voltage estimating means for estimating the voltage one by one, and as a result of estimating the estimated open-circuit voltage by the open-circuit voltage estimating means one by one, when the estimated open-circuit voltage of the current estimation is smaller than the estimated open-circuit voltage of the previous estimation, When the estimated open-circuit voltage of the current estimation is larger than the estimated open-circuit voltage of the previous estimation, the open-circuit voltage selecting means for selecting the estimated open-circuit voltage of the previous estimation, and the estimated open-circuit voltage selected by the open-circuit voltage selecting means. While the latest data of the discharge power amount calculated by the discharge power amount calculation means is fetched, the remaining capacity estimation indicated by the relationship between the estimated open circuit voltage and the discharge power amount is set in advance. A remaining capacity estimating means for moving the remaining capacity estimation curve so that the curve includes the acquired latest data, and estimating the current remaining capacity of the storage battery based on the remaining capacity estimation curve after the movement; A remaining capacity meter for a storage battery, comprising: 2. The storage battery remaining capacity meter according to claim 1, wherein the remaining capacity estimation means obtains a correlation coefficient between a discharge current and a terminal voltage of the storage battery, and an absolute value of the correlation coefficient is equal to or less than a predetermined value. A remaining battery capacity meter that stops estimating the remaining capacity of the storage battery when the condition becomes. 3. The storage battery remaining capacity meter according to claim 1, wherein said remaining capacity estimating means determines the life of said storage battery based on a change in said remaining capacity estimation curve accompanying repetition of discharging and charging. Battery remaining capacity meter.