JPH11135159A - Detecting method of remaining capacity of secondary battery and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable detection of remaining capacity, even in loading and to prevent an accumulation of measurement errors. SOLUTION: A charging/discharging electric-power quantity is calculated, based on a battery current flowing through a secondary battery 10, and a remaining capacity is calculated by adding/subtracting the charging/discharging power quantity to/from the total capacity set up in advance or the remaining capacity calculated at the last time. Also, an estimated remaining capacity of a terminal voltage is determined based on the terminal voltage, in the case that a battery current does not flow through the secondary battery 10 for more than one hour because of the stop of an electric vehicle, and the calculated remaining capacity is corrected based on the estimated remaining capacity of the terminal voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for detecting the remaining capacity of a secondary battery.

[0002]

2. Description of the Related Art In the field of electric vehicles, for example, detecting and displaying the remaining capacity of a secondary battery indicates the cruising distance of the vehicle, and therefore it is desirable that the remaining capacity be as accurate as possible. Here, since there is a certain relationship between the remaining capacity and the open terminal voltage of many secondary batteries, the remaining capacity can be grasped fairly accurately by measuring the open terminal voltage.

However, according to this method, the remaining capacity cannot be measured while the electric vehicle in which the load is connected to the secondary battery is running. There is a problem that the remaining capacity can be accurately detected only when the open terminal voltage of the battery is stabilized. Therefore, it is desired to be able to detect the remaining capacity even when the load is connected to the secondary battery,
As a remaining capacity detecting device for that purpose, for example, Japanese Patent Application Laid-Open
No. 3,368,401 is known.
This configuration measures the load current of the battery, calculates the utilization rate in consideration of the battery temperature, and calculates and displays the current remaining capacity calculated from the utilization rate and the load current from the previous remaining capacity. It is. According to this configuration, the remaining capacity can be sequentially displayed even while the electric vehicle is running.

[0004]

However, in this type of residual capacity detecting device, measurement errors are unavoidable. Therefore, even if resetting is made at the time of full charge, errors are accumulated until the next full charge. The disadvantage is that the results must be inaccurate. In particular, when charging and discharging are repeated without reaching full charge, there is no chance of resetting the error, so that there has been a problem that the detection accuracy is further reduced. Therefore, the present invention provides a method for detecting the remaining capacity of a secondary battery, which can detect the remaining capacity even when the load is connected, and further minimize the accumulation of measurement errors. It is intended to provide the device.

[0005]

According to a first aspect of the present invention, there is provided a method for measuring the remaining capacity of a secondary battery, comprising calculating a charge / discharge power amount based on a discharge current and a charge current flowing through the secondary battery and presetting the charge / discharge power amount. The remaining capacity is calculated by adjusting the charge / discharge power amount from the total capacity or the remaining capacity calculated last time, based on the terminal voltage when the discharge current and the charge current do not substantially flow to the secondary battery for a predetermined time or more. The present invention is characterized in that a terminal voltage estimated remaining capacity is determined, and the calculated remaining capacity is corrected based on the terminal voltage estimated remaining capacity thus determined.

According to a second aspect of the present invention, there is provided an apparatus for measuring a remaining capacity of a secondary battery, comprising: a current detecting means for detecting a discharging current and a charging current flowing through the secondary battery; and a discharging current and a charging current detected by the current detecting means. A variable capacity calculating means for calculating the charge / discharge power based on the remaining capacity calculating means for calculating the remaining capacity by adjusting the charge / discharge power from a predetermined total capacity or a previously calculated remaining capacity; ,
A terminal voltage measuring means for measuring a terminal voltage of the secondary battery; and a terminal voltage estimated remaining capacity estimated from the terminal voltage when the discharge current and the charge current do not substantially flow through the secondary battery for a predetermined time or more. It is characterized by including a remaining capacity determining means and a correcting means for correcting the remaining capacity calculated by the remaining capacity calculating means based on the estimated terminal voltage remaining capacity. According to a third aspect of the present invention, in the remaining capacity measuring device, a display unit for sequentially displaying the remaining capacity of the secondary battery, and an average value calculating means for calculating an average value of a predetermined number of calculation results of the remaining capacity. Wherein the average value calculated by the average value calculation means is displayed on the display unit.

[0007]

According to the first and second aspects of the present invention, when the load or the charging power source is connected to the secondary battery, the battery is charged based on the discharge current and the charging current flowing through the secondary battery. The remaining capacity is calculated by calculating the discharge power and adding or subtracting the charge / discharge power from the preset total capacity or the previously calculated remaining capacity. Therefore, it is possible to sequentially measure the remaining capacity that changes with the progress of discharging or charging. When the discharge current and the charge current do not substantially flow through the secondary battery for a predetermined time or more due to, for example, a long stop of the electric vehicle, the terminal voltage estimated remaining capacity is determined based on the terminal voltage, and thus determined. The calculated remaining capacity is corrected based on the terminal voltage estimated remaining capacity. Therefore, even if there is an error in the remaining capacity measured based on the calculation of the charge / discharge power, the error is corrected based on the relatively accurate estimated terminal voltage remaining capacity, and the error accumulates. It is possible to prevent an accurate remaining capacity from being measured.

According to the third aspect of the present invention, the display unit displays the average value of the remaining capacity calculated by the average value calculation means, so that the remaining capacity is calculated from the value calculated based on the battery current. Even when the value is replaced with a value determined based on the terminal voltage, the displayed value does not change abruptly, and display unnaturalness is eliminated.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a remaining capacity detecting device for a power battery of an electric vehicle will be described in detail with reference to the drawings.

In FIG. 1, reference numeral 10 denotes a secondary battery for powering an electric vehicle, for example, a lithium ion type in which charge and discharge are repeated by inserting and extracting lithium ions in a negative electrode, and a number of cells are connected in series. It is configured. This is charged by the charging circuit 11 through the backflow prevention diode 12 and supplies power to the electric vehicle through the output terminal 13. The charge / discharge line to the secondary battery 10 is provided with a magnetic field detection type current detecting means 14 using, for example, a Hall element, and the battery current IB (discharge current and charge current) flowing through the secondary battery 10 is thereby provided. Can be detected. Further, each cell is provided with terminal voltage measuring means 15 for measuring the terminal voltage of the secondary battery 10 as a value for each cell.
Temperature detecting means 16 for detecting the temperature of 0 is provided.

The signals from the current detecting means 14, the terminal voltage measuring means 15 and the temperature detecting means 16 are CP
U20. And this C
The PU 20 has an EPRO storing each table described later.
M21 and a display 22 as a display unit installed on a meter panel in the driver's seat are connected, and the remaining capacity of the secondary battery 10 calculated by a procedure described in detail below is displayed on the display 2.
2 is displayed. For example, the CPU 20 always executes the processing shown in FIG.
The charge / discharge current measurement routine shown in FIG. That is,
First, the battery current IB measured by the current detecting means 14
Is read (step S1), and this and a predetermined reference current I
a, the state of the secondary battery 10 is determined based on the magnitude relationship with -Ia (step S2). Since the reference current Ia is set to a value corresponding to a relatively small discharge current when the electric vehicle is stopped, "Y" in step S2 means that the current is not flowing to the power motor and the electric current is not flowing. This means that the car is stopped and this is, for example, 1
If it has continued for more than the time, the battery state flag is set to "open" (steps S3, S4). Further, the fact that "N" is obtained in step S2 and "Y" is obtained in step S5 means that a large load current flows and the motor of the electric vehicle is driven. Be executed. In addition, since “N” in step S5 means that the charging current is flowing into the secondary battery 10 (during charging or regeneration by the charging circuit 11), the charging current integration routine S7 is executed.

The above-described discharge current integration routine has the contents shown in FIG. That is, here, the discharge counter DCR
(Set to 0 when fully charged) by integrating the battery current IB measured every second (step S6).
1) Add the discharge power to the discharge counter DCR. In this embodiment, next, the integrated value of the discharge counter DCR is compared with, for example, twice the value of the battery design capacity DC (total capacity of the secondary battery 10) (step S62). This step S62 is to prevent errors from accumulating when charging and discharging are repeated without reaching full charge for a long period of time. Then, the next charge / discharge integration routine is repeated. The fact that "Y" is obtained in step S62 means that the count value of the discharge counter DCR is abnormally large.
As shown at 68, the discharge counter DCR, the charge counter CR, and the remaining capacity RM of the parameter are reset.

On the other hand, the charging current integration routine S7 performed during charging or regeneration of the secondary battery 10 has the contents shown in FIG. That is, the battery current IB (charge current) measured every second is added to the charge counter CR (set to 0 when the battery is fully charged) (step S7).
1) Add the charging power to the charging counter CR. In this embodiment, next, the integrated value of the charge counter CR is compared with, for example, 1.5 times the value of the discharge counter DCR (step S72). This step S72 also
This is to prevent the accumulation of errors when charging and discharging are repeated without reaching full charge for a long period of time. In a normal case, the value is "N", so the process returns as it is to return to the next charge. The discharge integration routine is repeated.
Since "Y" in step S72 means that the count value of the charge counter CR is abnormally large, it is determined that the battery is fully charged, the charge counter CR is set to 0, the discharge counter DCR is set to 0, and the remaining capacity is set. RM is reset to the battery design capacity DC (step S73).

By executing the charge / discharge current measurement routine as described above, the discharge counter DCR and the charge counter C
In R, the amount of discharged power and the amount of charged power (charge / discharge power) based on the time of full charge are integrated. That is, by executing the above-described charge / discharge current measurement routine, the CPU 20 functions as a variable capacity calculation unit that calculates the charge / discharge power amount based on the battery current IB detected by the current detection unit 14.

In this embodiment, the remaining capacity calculation routine shown in FIGS. 5 and 6 is executed, for example, every 5 seconds, and the remaining capacity of the secondary battery 10 is displayed on the display 22. First, signals from the current detecting means 14 and the temperature detecting means 16 are read (step S21), and a design capacity DC corresponding to the current / temperature is read from a design capacity table (step S22). This design capacity table is created in advance as a ratio to a rated value using temperature and discharge current as parameters as shown in FIG.
It is stored in OM21. Thus, the design capacity DC at the current and temperature is determined.

Next, the magnitude relationship between the discharge power DCR and the charge power CR considering the charging efficiency (0.9) is determined (step S23), and the former (DCR) is replaced with the latter (0. 0).
9 × CRD) and the difference (DCR−
On the condition that (0.9 × CR) is smaller than the design capacity DC (step S24), a value obtained by subtracting the discharge power DCR from the design capacity DC and further adding 0.9 times the charge power CR is obtained. The remaining capacity RM of the secondary battery 10 is calculated (Step S25). That is, by executing the above steps, the CPU 20 calculates the remaining capacity by adding or subtracting the charge / discharge power from the predetermined total capacity (design capacity DC) or the remaining capacity RM calculated last time. It also works as

If the charging power (0.9 × CR) is larger than the discharging power DCR (step S23).
(N)) It is considered that the battery is overcharged and cannot be originally provided, and the state of charge RM is regarded as a fully charged state, and the remaining capacity RM is set as the design capacity DC (step S26). The difference (DCR−0.9 × CR) is larger than the design capacity DC (“N” in step S24) because overdischarge is not possible due to overdischarge.
M is set to 0 (step S27).

Thereafter, it is determined whether or not the battery state flag is "open" and the discharge power DCR is greater than 1.5 times the design capacity DC (step S28). Since the battery state flag is not "open" while the electric vehicle is running, the determination result is "N", and the remaining capacity ratio SOC (%) is calculated in step S29. Then, for example, a moving average of eight times of the remaining capacity ratio SOC is calculated (step S29), and the calculation result is displayed every moment on the display 22 of the driver's seat.

During running of the electric vehicle, the secondary battery 10 may be charged by regenerative braking, and the secondary battery 10 is charged from an external power source as appropriate. Therefore,
If the above-described charge / discharge current is measured and only the remaining capacity is calculated based on the current, an error is accumulated and an incorrect detection result is obtained. Therefore, in the present embodiment, the secondary battery 1
Focusing on the fact that there is a close relationship between the residual capacity of 0 and its open terminal voltage, the terminal is determined based on the terminal voltage when the discharge current or the charge current does not substantially flow through the secondary battery 10 for a predetermined time or more. The estimated voltage remaining capacity is determined, and the calculated remaining capacity RM is corrected based on the terminal voltage estimated remaining capacity thus determined.

That is, for example, when the electric vehicle stops and
When the time equal to or longer than the time has elapsed, the terminal voltage of the secondary battery 10 is stabilized, and the determination result is “Y” in step S28. Then, first, each cell voltage output from the voltage detecting means is read by the CPU 20 (step S31),
The estimated discharge amount ODCR is read from the estimated discharge amount table based on the minimum value among them (step S32). This estimated discharge amount table is created in advance as a ratio (%) to the rated value using the open circuit voltage of the cell as a parameter as shown in FIG. Then, based on this, the terminal voltage estimated remaining capacity OVRM is calculated from the design capacity DC based on the estimated discharge amount ODCR.
Is determined (step S33), and based on this, the remaining capacity ratio SOC (%) is calculated (step S34). That is, the CPU 20 and the EPROM 2
1 is a terminal voltage estimated remaining capacity OVR estimated from the terminal voltage when the load current does not substantially flow through the secondary battery 10 by the CPU 20 executing the above-described steps.
It functions as a remaining capacity determination unit that detects M.

Next, the remaining capacity RM is replaced with the above-mentioned terminal voltage estimated remaining capacity OVRM, and the charge counter CR is set to 0.
And discharge counter DCR is set to (DC-O
VRM) (step S35). With this,
The CPU 20 functions as a correction unit, and the process proceeds to step S33.
The calculated remaining capacity RM is corrected based on the terminal voltage estimated remaining capacity OVRM determined in the above, and the remaining capacity RM becomes accurate. Thereafter, the remaining capacity ratio S is determined in steps S29 and S30 in the same manner as when the electric vehicle is running.
The moving average of the last eight OCs is calculated (average calculating means), and the value is displayed on the display 22.

As described above, according to the present embodiment, the charge / discharge power amount is calculated based on the discharge current and the charge current flowing through the secondary battery 10 when the load or the charging power supply is connected to the secondary battery 10. And preset design capacity DC
Alternatively, the remaining capacity RM is calculated by adjusting the charge / discharge power amount from the previously calculated remaining capacity RM. Therefore, the remaining capacity RM changes with the progress of the discharge or charge.
Can be measured sequentially.

When the discharge current and the charge current do not substantially flow through the secondary battery 10 for one hour or more due to, for example, an electric vehicle stopping for a long time, the terminal voltage is estimated to remain based on the terminal voltage (minimum cell voltage). The capacity OVRM is determined, and the terminal voltage estimated remaining capacity O thus determined is determined.
Remaining capacity RM calculated as described above based on VRM
Is corrected.

Therefore, even if there is an error in the remaining capacity RM calculated based on the measurement of the charging / discharging current, the error does not greatly accumulate and is corrected based on the relatively accurate terminal voltage estimated remaining capacity OVRM. Therefore, it is possible to prevent the accumulation of errors and the detection of an incorrect remaining capacity RM.

In this embodiment, the display 22
For example, since the average value of the last eight times is displayed, it is possible to prevent the displayed remaining capacity ratio SOC from suddenly changing and to eliminate unnaturalness on the display. There are advantages.

<Other Embodiments>

The present invention is not limited to the embodiments described above and shown in the drawings, but can be carried out in various modifications without departing from the scope of the invention. The embodiments described below also cover the technical scope of the present invention. Belongs to. (1) In the above embodiment, the temperature of the secondary battery is detected, and the design capacity DC is corrected based on the temperature. However, if the detection accuracy of the remaining capacity is not so required, this may be omitted. Good. Conversely, to further increase the detection accuracy, the discharge capacity may be determined with higher accuracy by adding the temperature parameter to the estimated discharge amount table indicating the relationship between the open terminal voltage and the discharge capacity. If the discharge efficiency at the time of discharge and the charge efficiency at the time of charge are determined using temperature as a parameter, the remaining capacity can be detected with higher accuracy.

(2) In the above embodiment, an example is shown in which the present invention is applied to a lithium ion type secondary battery. However, the type of battery is not limited to this, and there is a predetermined relationship between the open terminal voltage and the remaining capacity. It can be widely applied to various types of batteries.
Further, the present invention is not limited to the one that detects the remaining capacity of a secondary battery for an electric vehicle, and can be applied to portable electronic devices such as a portable personal computer and a mobile phone.

(3) In the above embodiment, a table prepared in advance is read in determining the design capacity DC according to the battery current IB and the temperature and determining the estimated discharge amount ODCR in accordance with the terminal voltage. The present invention is not limited to this, and the design capacity and the estimated discharge amount may be converted into a function using the battery current and the terminal voltage as parameters, and may be calculated and calculated as needed.

(4) In the above embodiment, the calculated value of the remaining capacity ratio SOC is sequentially displayed on the display. However, the present invention is not limited to this. For example, the remaining capacity ratio SOC may be set to a predetermined value (or a plurality of values). When it has reached, a lamp may be turned on, or a notification may be given by a synthesized voice.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart showing a charge / discharge current measurement routine;

FIG. 3 is a flowchart showing a discharge current integration routine;

FIG. 4 is a flowchart showing a charging current integration routine;

FIG. 5 is a flowchart showing a part of a remaining capacity calculation routine;

FIG. 6 is a flowchart showing another part of the remaining capacity calculation routine.

FIG. 7 is a table showing a design capacity table;

FIG. 8 is a table showing an estimated discharge amount table;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Secondary battery 14 ... Current detection means 15 ... Terminal voltage measurement means 20 ... CPU (variable capacity calculation means, remaining capacity calculation means,
(Remaining capacity determination means, correction means, average value calculation means) 22 ... display (display unit)

Claims (3)

[Claims] 1. A method for detecting a remaining capacity of a secondary battery, comprising: calculating a charge / discharge power amount based on a discharge current and a charge current flowing through the secondary battery; The remaining capacity is calculated by adjusting the charge / discharge power amount from the remaining capacity, and the terminal voltage is estimated based on the terminal voltage when the discharge current and the charge current do not substantially flow through the secondary battery for a predetermined time or more. And correcting the calculated remaining capacity on the basis of the terminal voltage estimated remaining capacity thus determined. 2. A method for detecting a remaining capacity of a secondary battery, comprising: current detection means for detecting a discharge current and a charge current flowing through the secondary battery; and a discharge current and a charge detected by the current detection means. A variable capacity calculating means for calculating a charge / discharge power amount based on a current; and a remaining capacity calculating means for calculating a remaining capacity by adding or subtracting the charge / discharge power amount from a predetermined total capacity or a previously calculated remaining capacity. Terminal voltage measuring means for measuring a terminal voltage of the secondary battery; and a terminal voltage estimation residual estimated from a terminal voltage when a discharge current and a charge current do not substantially flow through the secondary battery for a predetermined time or more. A remaining capacity determining means for determining a capacity; and a correcting means for correcting the remaining capacity calculated by the remaining capacity calculating means based on the terminal voltage estimated remaining capacity. Rechargeable battery remaining capacity detection device. A display unit for sequentially displaying the remaining capacity of the secondary battery; and an average value calculating means for calculating an average value of a predetermined number of calculation results of the remaining capacity, wherein the display unit displays the average value. 3. The apparatus according to claim 2, wherein an average value calculated by the calculation means is displayed.