JP3778060B2 - Battery remaining capacity calculation method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in a battery remaining capacity calculation method.
[0002]
[Prior art]
Secondary batteries are used in various fields. For efficient operation of the secondary battery, it is necessary to accurately perform charge / discharge control of the secondary battery. For this reason, a method for calculating the remaining capacity (SOC) of the secondary battery with high accuracy is required.
[0003]
Conventionally, as a method for calculating the SOC of such a secondary battery, a method based on current integration of charge / discharge current has been known. However, in such a method based on current integration, for example, in the case of a battery usage mode in which full charge and full discharge are not performed, errors due to a drop in the LSB digit of the CPU for calculating the SOC and a capacity drop due to self-discharge are greatly affected. However, there is a problem that the SOC calculation accuracy of the secondary battery cannot be increased due to high dependency on the current sensor accuracy.
[0004]
For this reason, as disclosed in PCT International Publication No. WO 99/61929, a method for correcting the SOC with the estimated voltage of the battery has been proposed.
[0005]
[Problems to be solved by the invention]
However, in the conventional method of correcting the SOC using the estimated voltage, the SOC estimation accuracy from the voltage may be lowered depending on the SOC region. For this reason, the calculation accuracy of the SOC of the battery depends on the charge / discharge pattern of the battery, and the calculation accuracy of the SOC deteriorates depending on the charge / discharge pattern. This problem is serious because the SOC region where the estimation accuracy of the SOC is low is often the normal use region of the battery.
[0006]
The present invention has been made in view of the above-described conventional problems, and an object thereof is to provide a battery remaining capacity calculation method capable of ensuring high estimation accuracy of SOC without depending on the charge / discharge pattern of the battery.
[0007]
[Means for Solving the Problems]
To achieve the above object, the present invention is fully charged, a method of estimating a battery use forms without full discharge electromotive voltage and the current integrated value and the remaining capacity of the battery (SOC), the battery voltage An electromotive voltage is obtained, a first estimated SOC is obtained from the electromotive voltage, a second estimated SOC is obtained from the integrated current value, and an SOC correction parameter is determined by the battery electromotive voltage, and an SOC value from the battery electromotive voltage is calculated. In the SOC region where the estimation accuracy is low, the SOC correction amount due to the electromotive voltage is small, and in the SOC region where the SOC estimation accuracy from the electromotive voltage is high, the correction amount due to the electromotive voltage is determined to be large, based on the difference between the first estimated SOC and the second estimated SOC, the calculated amount of correction by the PI control using the correction parameters, corrects the second estimated SOC by the correction amount And wherein the door.
[0010]
In the battery remaining capacity calculation method, the correction parameter is determined in advance by creating a map of an electromotive voltage and a correction parameter.
[0011]
In the battery remaining capacity calculation method, a battery temperature factor is included in the map.
[0012]
According to each of the above configurations, when determining the SOC correction parameter based on the electromotive voltage of the battery, in the SOC region where the SOC estimation accuracy from the voltage is high, the correction amount due to the voltage increases, and the SOC estimation accuracy from the voltage In the SOC region where the battery voltage is low, the correction parameter is determined so that the correction amount due to the voltage is small. Therefore, the SOC of the battery can be calculated with high accuracy without depending on the charge / discharge pattern of the battery.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.
[0014]
FIG. 1 is an explanatory diagram of a battery remaining capacity calculation method according to the present invention. In FIG. 1, the charge / discharge current I of the battery is measured (S1), and this is integrated to obtain a current integrated value (S2), and the remaining capacity (SOC) of the battery is calculated from this value (S3). This SOC corresponds to the second estimated SOC according to the present invention. Further, from the measured value of the charge / discharge current I, the charge / discharge polarization voltage is calculated as the voltage fluctuation affected by the past charge / discharge history (S4). Further, a drop voltage (voltage drop) due to the internal resistance of the battery is also calculated from the charge / discharge current I (S5).
[0015]
Next, the battery voltage V is measured (S6), and the electromotive voltage of the battery is calculated from the battery voltage V, the charge / discharge polarization voltage, and the internal resistance drop voltage (S7). Specifically, the battery voltage V is obtained by subtracting the charge / discharge polarization voltage and the internal resistance drop voltage from the battery voltage V.
[0016]
The estimated capacity of the battery is calculated from the relationship between the electromotive voltage calculated in this way and the battery capacity (S8). This estimated capacity corresponds to the first estimated SOC according to the present invention. The relationship between the electromotive voltage and the battery capacity may be obtained for each battery in advance.
[0017]
Next, the remaining capacity of the battery is corrected by PI (proportional, integral) control based on the difference between the first estimated SOC (S8) and the second estimated SOC (S3) obtained from the current integrated value. The amount is calculated (S9). This correction amount is corrected in addition to the second estimated SOC, and an estimated value of SOC is calculated.
[0018]
The SOC correction parameter used for the PI control can be determined from the above-described electromotive voltage of the battery (S10). That is, a map of the electromotive voltage and the correction parameter is created in advance, and the correction parameter is determined based on this map. In this map, as shown in FIG. 1, it is also preferable to include a factor of the battery temperature (S11). Thereby, a correction parameter with higher accuracy can be determined.
[0019]
The correction parameter is determined based on the fact that there are an SOC region where the estimation accuracy is high and a SOC region where the estimation accuracy is low when determining the SOC correction amount from the electromotive voltage of the battery. That is, in the SOC region where the estimation accuracy of the SOC from the electromotive voltage of the battery is low, the correction amount of the SOC due to the electromotive voltage is small, and the correction parameter is determined so that the influence is small. Further, in the SOC region where the estimation accuracy of the SOC from the electromotive voltage is high, the correction amount by the electromotive voltage is increased, and the correction parameter is determined so as to increase the influence. As a result, the estimation accuracy of the SOC of the battery can be maintained high regardless of the region where the SOC of the battery is. As a result, high SOC estimation accuracy can always be ensured regardless of the charge / discharge pattern.
[0020]
【The invention's effect】
As described above, according to the present invention, when the SOC of the battery obtained from the integrated current value is corrected from the electromotive voltage of the battery, the correction amount is large in the SOC region where the estimation accuracy of the SOC from the electromotive voltage is high. Thus, the correction parameter is determined so that the correction amount is small in the SOC region where the estimation accuracy is low. Thereby, SOC estimation accuracy can be improved in all SOC regions, and a highly accurate battery remaining capacity calculation method can be provided regardless of the charge / discharge pattern.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a battery remaining capacity calculation method according to the present invention.

Claims (3)

A method of estimating a remaining capacity (SOC) of a battery from an electromotive voltage and a current integrated value of the battery in a usage pattern in which full charge and full discharge are not performed ,
Obtain the electromotive voltage from the battery voltage,
A first estimated SOC is obtained from the electromotive voltage,
A second estimated SOC is obtained from the current integrated value,
In the SOC region in which the SOC correction parameter is reduced by the electromotive voltage of the battery and the SOC estimation accuracy from the battery electromotive voltage is low, the SOC correction amount by the electromotive voltage is small, and the SOC estimation accuracy from the electromotive voltage is high. In the SOC region, the correction amount due to the electromotive voltage is determined to be large,
Based on the difference between the first estimated SOC and the second estimated SOC, a correction amount is obtained by PI control using the correction parameter;
The battery remaining capacity calculation method, wherein the second estimated SOC is corrected by the correction amount . 2. The battery remaining capacity calculation method according to claim 1, wherein a map of an electromotive voltage and a correction parameter is created in advance and the correction parameter is determined based on the map. 3. The battery remaining capacity calculation method according to claim 2 , wherein a factor of a battery temperature is entered in the map.

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