JP2003149307A - Method for calculating battery remaining capacity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for calculating a remaining capacity of a battery to ensure high estimation accuracy of the state of charge (SOC) without relying on a charging/discharging pattern of the battery. SOLUTION: The SOC of the battery is calculated by integrating a charging/ discharging current I of the battery, and starting voltage of the battery is calculated to obtain the estimated capacity of the battery. A PI control calculates a correcting amount from the difference between the SOC and the estimated capacity and correct the SOC. A correcting parameter used by the PI control is determined based on the starting voltage of the battery: the parameter is small for a SOC region having a low estimation accuracy of the SOC from the starting voltage, and large for a SOC region having a high estimation accuracy. Thus, estimation accuracy of the remaining capacity of the battery improves for all SOC regions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method for calculating the remaining capacity of a battery.

[0002]

2. Description of the Related Art Secondary batteries have been used in various fields, but in order to operate the secondary batteries efficiently, it is necessary to accurately control the charging and discharging of the secondary batteries. For this,
A method for calculating the state of charge (SOC) of the secondary battery with high accuracy is required.

Conventionally, as a method of 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, in the case of a battery usage mode in which full charge and full discharge are not performed, for example, an error due to a drop in the LSB digit of the CPU for calculating the SOC or a decrease in capacity due to self-discharge has a great influence. However, there is a problem that the accuracy of calculating the SOC of the secondary battery cannot be increased because of the high dependence on the accuracy of the current sensor.

Therefore, PCT international publication WO99 / 61
As disclosed in No. 929, the estimated voltage of the battery causes S
A method of correcting OC has been proposed.

[0005]

However, in the conventional method of correcting the SOC by the above estimated voltage, the SOC is
In some cases, the estimation accuracy of the SOC from the voltage becomes low depending on the region. Therefore, there is a problem that 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. Since the SOC region in which the SOC estimation accuracy is low is a battery normal use region in many cases, this problem is serious.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide a battery remaining capacity calculation method which does not depend on the charge / discharge pattern of the battery and can ensure a high SOC estimation accuracy. It is in.

[0007]

In order to achieve the above object, the present invention is a method for estimating the remaining capacity (SOC) of a battery from the electromotive voltage of the battery and the integrated current value, Is used to determine the SOC correction parameter, and the SOC obtained from the current integrated value is corrected using the correction parameter.

In the battery remaining capacity calculation method described above, the SOC is corrected by obtaining the electromotive voltage from the battery voltage, obtaining the first estimated SOC from the electromotive voltage, and obtaining the second estimated SOC from the integrated current value. 1st estimated SOC and 2nd estimated SO
It is characterized in that a correction amount is obtained from a difference from C using a correction parameter, and the second estimated SOC is corrected by the correction amount.

According to each of the above configurations, when the SOC correction parameter is determined by the electromotive voltage of the battery, the S from the voltage is determined.
In the SOC region where the estimation accuracy of OC is high, the correction amount due to the voltage becomes large, and the estimation accuracy of SOC from the voltage is low.
In the OC region, the correction parameter is determined so that the correction amount by the voltage becomes small, so that the SOC of the battery can be calculated with high accuracy without depending on the charge / discharge pattern of the battery.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

FIG. 1 shows an explanatory view of a battery remaining capacity calculation method according to the present invention. In FIG. 1, the charging / discharging current I of the battery is measured (S1), and this is integrated to obtain an integrated current value (S2), and the remaining capacity (SOC) of the battery is calculated from this value (S3). This SOC is the second aspect of the present invention.
Corresponding to the estimated SOC of Further, the charge / discharge polarization voltage is calculated from the measured value of the charge / discharge current I as a voltage fluctuation amount affected by the past charge / discharge history (S4). Further, the drop voltage (voltage drop) due to the internal resistance of the battery is also calculated from the charge / discharge current I (S5).

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 electromotive voltage of the battery is obtained by subtracting the charge / discharge polarization voltage and the internal resistance drop voltage from the battery voltage V.

The estimated capacity of the battery is calculated from the relationship between the electromotive voltage thus calculated 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 in advance for each battery.

Next, based on the difference between the first estimated SOC (S8) and the second estimated SOC (S3) obtained from the integrated current value, PI (proportional, integral) control is performed to allow the battery to remain. A correction amount of capacity is calculated (S9). This correction amount is added to the second estimated SOC and corrected to calculate an estimated SOC value.

The SOC correction parameter used for the PI control can be determined from the above-mentioned battery electromotive voltage (S10). That is, a map of the electromotive voltage and the correction parameter is created in advance, and the correction parameter is determined by this map. Note that, as shown in FIG. 1, it is also suitable to include a factor of the battery temperature in this map (S11). This makes it possible to determine the correction parameter with higher accuracy.

The above-mentioned correction parameter increases the estimation accuracy in determining the SOC correction amount from the electromotive voltage of the battery S
It is determined based on the fact that there is an OC region and a lower SOC region. That is, in the SOC region where the accuracy of SOC estimation from the electromotive voltage of the battery is low, the SOC due to the electromotive voltage is
The correction parameter is determined so that the correction amount becomes smaller and its influence becomes smaller. In addition, SOC from electromotive voltage
In the SOC region where the estimation accuracy of is high, the correction amount by the electromotive voltage is increased, and the correction parameter is determined so that the influence thereof becomes high. This makes it possible to maintain high estimation accuracy of the SOC of the battery regardless of the region of the SOC of the battery. As a result, a high SOC estimation accuracy can always be ensured regardless of the charge / discharge pattern.

[0017]

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, S with high accuracy of SOC estimation from the electromotive voltage is used.
The correction parameter is determined such that the correction amount is large in the OC region and the correction amount is small in the SOC region where the estimation accuracy is low. As a result, the 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 drawings]

FIG. 1 is an explanatory diagram of a battery remaining capacity calculation method according to the present invention.

Claims (2)

[Claims] 1. A method of estimating a state of charge (SOC) of a battery from an electromotive voltage of a battery and an integrated current value, wherein a correction parameter of SOC is determined by the electromotive voltage of the battery, and the correction parameter is used. The SOC calculated from the integrated current value is corrected to calculate the remaining battery capacity. 2. The battery remaining capacity calculation method according to claim 1, wherein the SOC is corrected by obtaining an electromotive voltage from a battery voltage, obtaining a first estimated SOC from the electromotive voltage, and calculating a second value from the integrated current value. The estimated SOC of is calculated, and from the difference between the first estimated SOC and the second estimated SOC,
A battery remaining capacity calculation method, characterized in that a correction amount is obtained using the correction parameter, and the second estimated SOC is corrected by the correction amount.