JP5466564B2 - Battery degradation estimation method, battery capacity estimation method, battery capacity equalization method, and battery degradation estimation apparatus - Google Patents

Description

  The present invention relates to a battery deterioration estimation method for estimating the remaining capacity and life of a secondary battery such as a lithium ion battery, a battery capacity estimation method for estimating the battery capacity from the battery deterioration estimation method, and the battery capacity estimation method The present invention relates to a battery capacity equalizing method and a battery deterioration estimating device for equalizing a remaining capacity or a chargeable capacity of a secondary battery.

  The capacity reduction rate of the secondary battery is a half that is proportional to the half power of the energization current amount (current integrated value) of the secondary battery or the half power of the secondary battery leaving time. The power law is known. That is, if the square root of the energizing current amount obtained by integrating the energizing current (current amount) of the secondary battery with time is obtained, the deterioration state (or capacity reduction rate) of the secondary battery can be estimated. Therefore, the deterioration state of a secondary battery built in a personal computer (PC) or terminal device used in a normal temperature state (for example, about 25 ° C.) can be easily estimated from the amount of energized current and the time for which it is left. Can do.

  In addition, by determining the accumulated charge amount based on the passage of time of the charge / discharge current without interrupting the power supply from the secondary battery and without discharging the secondary battery to the discharge end state, A technique capable of estimating the full charge capacity or the remaining capacity (remaining capacity) is also disclosed (see, for example, Patent Document 1). That is, in the secondary battery, there is a difference between the calculated remaining capacity and the actual remaining capacity when charging and discharging are repeated. However, according to the technique disclosed in Patent Document 1, the secondary battery is used. The actual remaining capacity (or full charge capacity) of the secondary battery can be estimated from the accumulated charge amount.

JP 2009-52974 A

  However, when estimating the capacity reduction rate (or capacity maintenance rate) of the secondary battery based on the half-power law of the energization current amount and the standing time, it is a half of the energization current amount depending on each temperature condition. The proportional characteristic between the power and the capacity reduction rate is different. For example, in the case of a secondary battery built in an electronic device such as a PC used in a normal temperature state (about 25 ° C.), the capacity decrease rate corresponding to the amount of energization current is uniquely determined from one proportional characteristic graph. Can be sought. However, since the secondary battery mounted on a vehicle or the like has a large change in environmental temperature from about −30 ° C. to + 65 ° C., the proportional characteristic between the half of the energization current amount and the capacity reduction rate is the temperature condition. Each will be different.

  That is, when the use conditions such as the temperature of the secondary battery are different, the capacity reduction rate (or capacity maintenance rate) is also different. In other words, when estimating the capacity decrease rate (or capacity maintenance rate) of a secondary battery used in different environmental temperatures from the energization current amount, the temperature is a parameter and the energization current amount is half the power. Many characteristic tables showing the relationship with the capacity reduction rate must be prepared. Further, even when the SOC (State of Charge) is different, the proportional characteristic between the half of the energization current amount and the capacity reduction rate is different, so a large number of characteristic tables must be prepared. Therefore, the number of characteristic tables for estimating the capacity reduction rate (or capacity maintenance rate) from the amount of energizing current of the secondary battery increases, and the usability of the characteristic table for estimating battery deterioration becomes extremely poor.

  In the technique disclosed in Patent Document 1, the actual full charge capacity and the remaining capacity can be obtained from the accumulated charge amount of the secondary battery. However, the battery capacity reduction rate depends on the environmental temperature and SOC (State of Charge). Therefore, it is necessary to obtain the capacity reduction rate of the battery using the environmental temperature and SOC as parameters. For example, if the temperature is high, the capacity reduction rate of the battery increases, and if the SOC is large, the capacity reduction rate of the battery increases. Therefore, the actual full charge capacity is determined from the accumulated charge amount of the secondary battery for each temperature and SOC. It is necessary to calculate the remaining capacity. That is, in order to estimate the actual full charge capacity and remaining capacity, it is necessary to determine the accumulated charge amount of the secondary battery for each temperature condition and SOC level. The estimation means is not easy to use.

  The present invention has been made in view of such problems, and the capacity maintenance rate of the secondary battery is determined based on the half-law of the energization current amount even if the use condition of the secondary battery is different. Battery degradation estimation method that can be uniquely estimated, battery capacity estimation method for estimating battery capacity from the battery degradation estimation method, and remaining capacity or rechargeable capacity of secondary battery is equalized from the battery capacity estimation method It is an object of the present invention to provide a battery capacity equalization method and a battery deterioration estimation device.

  In order to achieve the above object, a battery deterioration estimation method according to claim 1 of the present invention is a battery deterioration estimation method for estimating a level of capacity deterioration of a secondary battery, and affects the capacity deterioration of the secondary battery. Corresponding to each of a plurality of use conditions, a first procedure for integrating the amount of current flowing through the secondary battery or the elapsed time over a predetermined period, and the secondary under a single use condition A second procedure for calculating a degradation coefficient indicating a ratio of a degradation rate of the secondary battery in the plurality of usage conditions to a degradation rate of the battery for each of the corresponding usage conditions; and The current integrated value or elapsed time integrated for each of the plurality of use conditions is corrected by the deterioration coefficient calculated for each of the plurality of use conditions corresponding in the second procedure, and the current integration for the single use condition is corrected. Value or Based on the third procedure for conversion to elapsed time, the integrated current value or elapsed time converted in the third procedure, and the deterioration rate in the single use condition, the level of capacity deterioration of the secondary battery And a fourth procedure for estimating.

  According to this method, in the first procedure, for each of a plurality of use conditions corresponding to each of the temperature width and the SOC width, a current integrated value (energized current amount) obtained by integrating the current amount over a predetermined period is obtained. Further, the current integrated value is converted to a value obtained by dividing the current to a half power. In the second procedure, a plurality of use conditions (for example, respective temperature widths) when the deterioration coefficient in a deterioration mode (for example, a reference deterioration mode at 25 ° C.) in a single use condition is set to 1. And the SOC width). Then, in the third procedure, a reference for each of a plurality of use conditions (for example, for each temperature width and SOC width) based on a deterioration coefficient table and a table of values obtained by multiplying the current integrated value by a power of two. An energization amount integration table corresponding to the deterioration mode is created. Finally, in the fourth step, the level of capacity deterioration of the secondary battery is estimated using the energization amount integration table corresponding to the reference deterioration mode and the deterioration rate under a single use condition. Thereby, the subdivided use conditions (that is, the respective conditions of a plurality of temperature ranges and SOC widths) are unified into a single use condition (for example, the temperature range and the SOC range at 25 ° C.). be able to. In this way, the use conditions that affect the deterioration of the secondary battery can be subdivided. As a result, the deterioration of the secondary battery can be estimated with high accuracy.

  A battery capacity estimation method according to claim 2 of the present invention is a battery capacity estimation method for estimating the capacity of the secondary battery based on the battery deterioration estimation method according to claim 1, wherein the fourth On the basis of the level of capacity deterioration of the secondary battery estimated in the procedure, a fifth procedure for estimating the capacity maintenance rate of the secondary battery, the capacity maintenance rate estimated in the fifth procedure, and the second And a sixth procedure for estimating the current capacity of the secondary battery based on the initial capacity of the secondary battery.

  According to this method, it is possible to easily estimate the capacity maintenance rate of the secondary battery based on the level of capacity deterioration estimated by the battery deterioration estimation method realized in the first aspect of the invention. Therefore, the current capacity of the secondary battery can be uniquely estimated from the capacity maintenance rate and the initial capacity of the secondary battery.

  A battery capacity equalization method according to claim 3 of the present invention is based on the battery capacity estimation method according to claim 2, and the battery capacity equalization for equalizing the remaining capacity or the chargeable capacity of the secondary battery. A seventh procedure for estimating the SOC of the secondary battery, an SOC estimated in the seventh procedure, and a current capacity of the secondary battery estimated in the sixth procedure. Based on the eighth procedure for calculating the remaining capacity or rechargeable capacity of the secondary battery, the remaining capacity or rechargeable capacity of the secondary battery calculated in the eighth procedure and other secondary batteries Based on the ninth procedure for comparing the remaining capacity or the chargeable capacity, and the comparison result by the ninth procedure, the remaining capacity or chargeable capacity of the secondary battery and the remaining capacity of the other secondary battery or And a tenth procedure for equalizing the chargeable capacity. And butterflies.

  According to this method, based on the estimated value of the current capacity of the secondary battery estimated by the battery capacity estimation method realized in the invention according to claim 2 and the SOC, the remaining capacity or charge of the secondary battery The possible capacity can be calculated. Therefore, by comparing the remaining capacity or rechargeable capacity of the secondary battery with the remaining capacity or rechargeable capacity of another secondary battery, the remaining capacity or rechargeable capacity of the secondary battery It becomes possible to equalize the remaining capacity or the chargeable capacity.

  A battery deterioration estimation apparatus according to claim 4 of the present invention is a battery deterioration estimation apparatus that estimates a level of capacity deterioration of a secondary battery, and is a plurality of use conditions that affect the capacity deterioration of the secondary battery. Corresponding to each, an integration means for integrating the amount of current flowing through the secondary battery, or the elapsed time over a predetermined period, and the plurality of the plurality of secondary batteries with respect to the deterioration rate of the secondary battery under a single use condition Deterioration coefficient calculating means for calculating a deterioration coefficient indicating a ratio of deterioration rates of the secondary batteries under use conditions for each of a plurality of corresponding use conditions, and current integration integrated by the integration means for each of the plurality of use conditions The value or elapsed time is corrected by the deterioration coefficient calculated for each of a plurality of use conditions corresponding to the deterioration coefficient calculating means, and converted into an integrated current value or elapsed time in the single use condition. Conversion means, and capacity deterioration estimation means for estimating the level of capacity deterioration of the secondary battery based on the integrated current value or elapsed time converted by the conversion means and the deterioration rate under the single use condition. It is characterized by providing.

  According to this configuration, the integration means obtains a current integrated value (energization current amount) obtained by integrating the current amount over a predetermined period for each of a plurality of use conditions corresponding to each of the temperature width and the SOC width, Furthermore, the current integrated value is converted into a value obtained by dividing the current to a half power. A plurality of use conditions (for example, respective temperature ranges) when the deterioration coefficient calculation means sets the deterioration coefficient to 1 when the deterioration mode is in a single use condition (for example, the reference deterioration mode at 25 ° C.). And the SOC width). Then, the conversion means is based on the deterioration coefficient table and a table of values obtained by multiplying the current integrated values by a power of two, and the reference deterioration mode for each of a plurality of use conditions (for example, for each temperature width and SOC width). A corresponding energization amount integration table is created. Finally, the capacity deterioration estimation means estimates the level of capacity deterioration of the secondary battery using the energization amount integration table corresponding to the reference deterioration mode and the deterioration speed under a single use condition. Thereby, the subdivided use conditions (that is, the respective conditions of a plurality of temperature ranges and SOC widths) are unified into a single use condition (for example, the temperature range and the SOC range at 25 ° C.). be able to. In this way, the use conditions that affect the deterioration of the secondary battery can be subdivided. As a result, the deterioration of the secondary battery can be estimated with high accuracy.

  According to the present invention, the degradation factor indicating the ratio of the degradation rate of the secondary battery in a plurality of usage conditions to the degradation rate of the secondary battery in a single usage condition is used to subdivide the temperature and SOC. The usage conditions of the secondary battery are unified. This makes it possible to subdivide the use conditions that affect the deterioration of the secondary battery, so that it is possible to estimate the deterioration with high accuracy. In other words, subdivided use conditions (for example, use conditions for a plurality of temperature ranges and a plurality of SOC widths) are simply changed to a single use condition (for example, a temperature range and an SOC width at 25 ° C.). Can be unified. In this way, the use conditions that affect the deterioration of the secondary battery can be subdivided. As a result, the deterioration of the secondary battery can be estimated with high accuracy.

It is a block diagram which shows the structure of the battery deterioration estimation apparatus applied to each embodiment of this invention. It is a block diagram which shows the internal structure of the capacity | capacitance maintenance factor calculator shown in FIG. It is a figure which shows the division | segmentation table which divided | segmented the temperature of use conditions, and use SOC width | variety into three divisions, respectively, in order to obtain | require the deterioration rate of a secondary battery. It is a cycle characteristic figure which shows the relational characteristic of capacity maintenance rate (%) to energization current amount (Ah) which is experimental data for obtaining the deterioration rate of a secondary battery. FIG. 5 is a cycle characteristic diagram showing a relational characteristic of capacity retention ratio (%) with respect to the half power (Ah ^1/2 ) of the energization current amount created based on the cycle characteristic diagram of FIG. 4. FIG. 6 is a diagram showing a deterioration rate / classification table obtained from the slope of each cycle characteristic shown in FIG. 5. It is a figure which shows the degradation coefficient and division | segmentation table calculated | required from the deterioration speed and division | segmentation table shown in FIG. It is a figure which shows the electric current integrated value and the division | segmentation division table which showed the energizing current amount (current integrated value) which flowed per unit sampling time calculated for every division | segmentation of the temperature range and SOC width | variety of a secondary battery. FIG. 9 is a diagram showing a current integrated value half-power / segmentation table in which an energized current amount (current integrated value) is converted to a half power based on the current integrated value / segmentation table of FIG. 8. It is a figure which shows the electric current integrated value 1/2 power and division | segmentation table which converted the value [Ah1 ^{/ 2} ] of the energization current amount into [ ^1/2 ] the standard deterioration mode. It is a flowchart which shows the flow of the preparatory process for performing the battery deterioration estimation method which concerns on 1st Embodiment of this invention. It is a flowchart which shows the flow of the calculation process of the battery degradation estimated value at the time of an energization current integration in the battery degradation estimation method which concerns on 1st Embodiment of this invention. It is a flowchart which shows the flow of the calculation process of the battery deterioration estimated value at the time of leaving of a secondary battery in the battery deterioration estimation method which concerns on 1st Embodiment of this invention. It is a flowchart which shows the flow of the calculation process of the battery degradation estimated value at the time of electricity supply and the time of leaving in the battery degradation estimation method which concerns on 1st Embodiment of this invention. It is a cycle characteristic figure of the experimental data which shows the relation of the capacity maintenance rate to the energization amount integrated value (energization current amount) in the standard deterioration condition. FIG. 16 is a cycle characteristic diagram illustrating a relational characteristic of a capacity maintenance ratio with respect to a half power of an energization amount integrated value (energization current amount) created based on the cycle characteristic diagram of FIG. 15. It is a model figure for demonstrating the relationship of the capacity | capacitance of LIB (lithium ion battery), an open circuit voltage (OCV), and deterioration. It is a model figure for demonstrating the cell capacity estimation method applied to 2nd Embodiment of this invention. It is a SOC-voltage characteristic diagram of each cell for demonstrating the method of drawing out the capacity | capacitance of an assembled battery to the maximum.

  The battery deterioration estimation method of the present invention is configured to determine the deterioration state of the secondary battery due to energization and the deterioration state of the secondary battery due to neglect without depending on the use conditions such as temperature and SOC. The relationship between the half current of the current integrated value) and the capacity maintenance ratio is converted to a single axis, and the capacity maintenance ratio of the secondary battery is uniquely estimated. That is, the battery deterioration conditions subdivided according to temperature conditions and SOC states are combined into one type of battery deterioration condition by using a deterioration coefficient. As a result, conditions (temperature conditions and SOC states) that affect battery deterioration can be subdivided, so that it is possible to estimate the deterioration of the secondary battery with high accuracy.

  Hereinafter, several embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted.

"Definition of terms"
First, definitions of terms used in the battery deterioration estimation method according to each embodiment of the present invention will be described.
The “deterioration rate” is a capacity deterioration rate of the secondary battery for each use condition such as temperature and SOC. The unit of this capacity deterioration rate is a straight line of the deterioration rate obtained from the energization current amount represented by [% / Ah ^1/2 ] or [% / times ^1/2 ] or the 1/2 power of elapsed time. It is a slope, and the larger the value, the faster the deterioration rate.

The “deterioration coefficient” is a speed multiple of a deterioration rate due to a difference in use conditions of the secondary battery that affects the battery deterioration with respect to the reference deterioration mode. For example, when the deterioration rate in the reference deterioration mode is 1.2% / Ah ^1/2 and the deterioration rate under any use condition is 2.4% / Ah ^1/2 , the deterioration coefficient is 2.0, The deterioration rate under the use condition is twice as high as the half power of the energization current amount in the reference deterioration mode.

  “SOC” is a charge rate of the secondary battery expressed by (remaining capacity / full charge capacity) × 100. For example, it is a capacity ratio that is currently charged when the battery capacity (Ah) that can be discharged from full charge to full discharge is 100%, with full charge being 100% and full discharge being 100%.

  “1C” is a current value when a capacity (Ah) capable of discharging the secondary battery from full charge to full discharge is discharged in one hour. Usually, the nominal capacity is written in the secondary battery, and 1C is calculated from the nominal capacity. For example, in the case of a secondary battery having a nominal capacity of 5 Ah, 1C is 5A.

  “CC-CV (Constant Current-Constant Voltage) charging” means charging at a specified current value up to the target voltage, and after reaching the target voltage, charging is performed while keeping the target voltage constant. It is a charging method.

  “CC (Constant Current) discharge” is a discharge method in which discharge is performed at a specified current value up to a target voltage.

<Configuration of battery deterioration estimation device>
Next, the configuration of the battery deterioration estimation apparatus for realizing the battery deterioration estimation method according to each embodiment of the present invention will be described. FIG. 1 is a block diagram showing a configuration of a battery deterioration estimation apparatus applied to each embodiment of the present invention. As shown in FIG. 1, the battery deterioration estimation device 1 includes a secondary battery 2 such as a lithium ion battery, a temperature sensor 3 that detects the temperature of the secondary battery 2, and a voltage detector 4 that detects the voltage of the secondary battery 2. A current detector 5 for detecting a charging current and a discharging current of the secondary battery 2, an SOC calculator 6 for calculating an SOC value, a time measuring means 7 for measuring an energization time of the current flowing through the secondary battery 2, and the secondary battery The capacity maintenance factor calculator 8 that calculates the capacity maintenance factor 2 and the storage medium 9 that stores the calculation results calculated by the capacity maintenance factor calculator 8 are provided.

  The SOC calculator 6 calculates the SOC value based on the voltage of the secondary battery 2 detected by the voltage detector 4 and the charge / discharge current of the secondary battery 2 detected by the current detector 5. The capacity maintenance ratio calculator 8 includes temperature information of the temperature sensor 3, voltage information of the voltage detector 4, current information of the current detector 5, SOC value calculated by the SOC calculator 6, and energization time measured by the time measuring means 7. Based on the above, the capacity maintenance rate of the secondary battery 2 is calculated.

  FIG. 2 is a block diagram showing an internal configuration of the capacity maintenance ratio calculator 8 shown in FIG. As shown in FIG. 2, the capacity maintenance ratio calculator 8 calculates the amount of current flowing through the secondary battery 2 or the elapsed time corresponding to each of a plurality of use conditions that affect the capacity deterioration of the secondary battery 2. The integration means 8a for integrating over a predetermined period corresponds to the deterioration coefficient indicating the ratio of the deterioration rate of the secondary battery 2 under a plurality of use conditions to the deterioration rate of the secondary battery 2 under a single use condition. Deterioration coefficient calculation means 8b for each of a plurality of use conditions to be calculated, and current integrated value or elapsed time accumulated by the integration means 8a for each of the plurality of use conditions for each of the plurality of use conditions corresponding to the deterioration coefficient calculation means 8b. The conversion means 8c which corrects by the deterioration coefficient calculated in the above and converts it into the current integrated value or elapsed time under a single use condition, the current integrated value or elapsed time converted by the conversion means 8c and the single use condition Based on the definitive degradation rate, and a capacity deterioration estimating unit 8d for estimating the level of capacity deterioration of the secondary battery 2. The level of capacity deterioration corresponds to the capacity reduction rate or capacity maintenance rate of the secondary battery.

<How to determine the degradation rate>
Next, how to determine the deterioration rate, which is the rate of capacity deterioration of the secondary battery, will be described. The deterioration rate varies depending on the use conditions (for example, temperature, use SOC width, energization current, etc.) of the secondary battery. For this reason, it is necessary to obtain a deterioration rate for each use condition having a different deterioration rate. As an example, a description will be given of the condition division and how to obtain the deterioration coefficient when the temperature of the use condition and the use SOC width are dominant in the deterioration rate.

  FIG. 3 is a diagram illustrating a classification table in which the temperature width and the usage SOC width of the use conditions are divided into three sections in order to obtain the deterioration rate of the secondary battery. That is, as shown in FIG. 3, as an example of the division when the operation temperature range of the battery is −30 to 65 ° C. and the used SOC width (hereinafter simply referred to as the SOC width) is 0 to 100%, Each SOC width is divided into three sections. Here, the temperature width (° C.) is divided into three sections of −30 to 25 ° C., 25 to 45 ° C., and 45 to 65 ° C., and the SOC width (%) is 0 to 40%, 40 to 70%, and Divide into 3 categories of 70-100%. Note that the accuracy of deterioration rate estimation becomes higher as these sections are further classified, and the accuracy of estimation of deterioration rate is lower as the conditions are roughly classified.

  As a method of obtaining the deterioration rate, for example, under the conditions of each temperature width and each SOC width shown in FIG. 3, a cycle of 1C CC-CV charge which is a current value capable of discharging the battery capacity in 1 hour → 1C CC discharge cycle The total accumulated integrated amount (energized current amount (Ah)) at that time is plotted on the horizontal axis, and the capacity retention rate (%) is plotted on the vertical axis.

  FIG. 4 is a cycle characteristic diagram showing a relational characteristic of the capacity retention rate (%) with respect to the energization current amount (Ah), which is experimental data for obtaining the deterioration rate of the secondary battery. That is, FIG. 4 shows the relationship between nine energization current amounts (Ah) and capacity maintenance ratios (%) based on the division table in which the temperature range and the SOC range shown in FIG. It is the cycle characteristic figure plotted. In addition, since it is necessary to obtain the deterioration rate of the reference deterioration mode, in the cycle characteristic diagram of FIG. 4, 1C CC-CV charge → 1C CC discharge when the temperature is 25 ° C. and the SOC width is 0 to 100%. The cycle is plotted as the reference degradation mode.

  As can be seen from the cycle characteristic diagram of FIG. 4, in the same SOC width (for example, SOC = 0 to 40%), the capacity retention rate (%) tends to decrease as the temperature increases. However, since the relationship between the energization current amount (Ah) and the capacity retention rate (%) shown in FIG. 4 is a non-linear characteristic, the magnitude of the decreasing tendency of the capacity retention rate (%), that is, the deterioration rate is determined. It is difficult to make a quantitative comparison.

Therefore, by plotting the horizontal axis as the 1/2 power of the total energization integrated amount (energization current amount) and the vertical axis as the capacity maintenance ratio (%) based on the data obtained in the cycle characteristic diagram of FIG. It is possible to linearize the relationship between the value (Ah ^1/2 ) of the energization current amount and the capacity maintenance ratio (%) by linear interpolation. As a result, the degradation rate for each temperature width and SOC width section is determined by the slope of the linear characteristic with the horizontal axis representing the 1/2 power of the total energization amount (energization current amount) and the vertical axis representing the capacity retention rate (%). Can be easily obtained.

FIG. 5 is a cycle characteristic diagram showing a relational characteristic of the capacity retention ratio (%) with respect to the half power (Ah ^1/2 ) of the energization current amount created based on the cycle characteristic diagram of FIG. The energization current amount is ½ power (Ah ^1/2 ), and the vertical axis indicates the capacity retention rate (%). As shown in FIG. 5, the relationship between the ½ power (Ah ^1/2 ) of the energization current amount and the capacity retention rate (%) is a linear characteristic, and therefore the slope at which the capacity retention rate (%) is inclined. Thus, the deterioration rate can be easily obtained. That is, as shown in FIG. 5, when the horizontal axis is set to the half power of the energization current amount, the gradient for each of the temperature width and the SOC width becomes the deterioration rate, and the unit of the deterioration speed is [% / Ah ^{1 / 2} ].

FIG. 6 is a diagram showing a deterioration rate / classification table obtained from the slope of each cycle characteristic shown in FIG. The unit of the deterioration rate is [% / Ah ^1/2 ]. In addition, the deterioration rate table of FIG. 6 also shows the deterioration rate (0.199 [% / Ah ^1/2 ]) in the reference deterioration mode when the temperature is 25 ° C. and the SOC width is 0 to 100%. Yes. That is, as shown in the deterioration rate / classification table of FIG. 6, the higher the SOC width value in the same temperature range, the higher the deterioration rate, and the higher the temperature range value in the same SOC width. It can be seen that the deterioration rate is high.

However, since the deterioration rate obtained from the deterioration rate / table of FIG. 6 becomes nine types of deterioration rates depending on the combination of the temperature width category and the SOC width category, all temperature ranges (-30 to + 65 ° C.) and all In the SOC range (0 to 100%), the deterioration rate with respect to the half power (Ah ^1/2 ) of the energization current amount cannot be uniquely determined. Therefore, the capacity maintenance ratio is uniquely estimated by following the procedure described below.

<How to determine the degradation factor>
The ratio of the degradation rate of each category to the degradation rate of the standard degradation mode (0.199 [% / Ah ^1/2 ]) is obtained from the degradation rate classification table for each category shown in FIG. Deterioration coefficient under any use condition. In other words, the deterioration coefficient of an arbitrary use condition can be obtained by the following equation (1).
(Deterioration coefficient of arbitrary use condition) = (Deterioration rate of arbitrary use condition [% / Ah ^1/2 ]) ÷ (Deterioration rate of reference deterioration mode [% / Ah ^1/2 ]) (1)

  FIG. 7 is a diagram showing a degradation coefficient / classification table obtained from the degradation rate / classification table shown in FIG. That is, when the deterioration coefficient is obtained from the deterioration rate / classification table of FIG. 5 by the above-described equation (1), the deterioration coefficient of each use condition is as shown in the deterioration coefficient / classification table of FIG. However, since the degradation coefficients shown in the degradation coefficient / classification table of FIG. 7 are nine types of degradation coefficients depending on the temperature width classification and the SOC width classification, handling them as they are is not convenient.

<Data collection method>
As shown in the block diagram of FIG. 1, in the battery deterioration estimation device 1 of the secondary battery 2 such as a lithium ion battery, the voltage detector 4, the current detector 5 connected to the capacity maintenance factor calculator 8, and Each temperature sensor 3 constantly monitors voltage, current, and temperature information of the secondary battery 2. Also, the SOC calculator 6 calculates the current SOC value based on the voltage detected by the voltage detector 4 and the charge / discharge current detected by the current detector 5, and this SOC value is calculated as a capacity maintenance ratio calculator. Therefore, the SOC state when the secondary battery 2 is used can always be grasped. In addition, since the temperature of the secondary battery 2 is constantly monitored by the temperature sensor 3, the temperature of the secondary battery 2 can be always grasped when the battery deterioration estimation device 1 is in operation. Furthermore, the capacity maintenance rate calculator 8 can calculate the energization current amount (Ah) of the secondary battery 2 based on the current value detected by the current detector 5 and the time information by the time measuring means 7.

The energization current amount (current integrated amount) per unit sampling time can be obtained by the following equation (2).
(Energizing current flowing per unit sampling time [Ah / sampling time]) =
(Total amount of current that is energized [Ah]) ÷ (current sampling time [Hr]) (2)

  The energization current amount [Ah / sampling time] flowing per unit sampling time calculated based on the equation (2) is integrated for each condition according to the temperature and SOC value of the secondary battery at the time of measurement. .

  FIG. 8 is a diagram showing a current integration value / classification table indicating the amount of energization current (current integration value) flowing per unit sampling time, calculated for each category of the temperature width and SOC width of the secondary battery. FIG. 7 also shows the total current integrated amount (total current amount) obtained by summing the energized current amounts (current integrated values) of the respective sections. That is, FIG. 8 shows the respective energized current amounts (current integrated values) divided according to the temperature width and SOC width conditions when 8000 Ah is used as the total current integrated amount (total current amount) of the secondary battery. [Ah] is shown.

<Deterioration estimation>
Next, the deterioration of the secondary battery is estimated using the deterioration coefficient calculated as shown in FIG. 7 and the energized current amount (current integrated value) sampled as shown in FIG. First, the energization current amount (current integrated value) under each use condition shown in FIG. FIG. 9 is a diagram showing a half-current / segmentation table of current integration values obtained by converting energization current amounts (current integration values) to 1/2 power based on the current integration value / segmentation table of FIG. . That is, FIG. 9 shows the current integrated value half-power / classification obtained by multiplying the energized current quantity (current integrated value) to the half power based on the energizing current quantity (current integrated value) classification table of FIG. It is a figure which shows a division | segmentation table.

Further, the value [Ah ^1/2 ] obtained by multiplying the energized current amount (current integrated value) of each use condition shown in FIG. 9 by ^1/2 and the respective use conditions obtained from the deterioration coefficient / classification table shown in FIG. The product with the degradation coefficient corresponding to is calculated for each category. Thereby, in each use condition, it can convert into the value [Ah1 ^{/ 2} ] which multiplied the energization current amount (current integrated value) equivalent to the reference | standard deterioration mode of 25 degreeC conversion to the 1/2 power.

FIG. 10 is a diagram showing a current integrated value 1/2 power / classification table in which the value [Ah ^1/2 ] of the energization current amount is converted to a value corresponding to the reference deterioration mode. That is, FIG. 10 multiplies the value [Ah ^1/2 ] obtained by multiplying the energization current amount (current integrated value) shown in FIG. 9 by ^1/2 and the deterioration coefficient shown in FIG. 7 for each corresponding use condition. 5 is a table showing the energization current amount (current integrated value) 1/2 power [Ah ^1/2 ] corresponding to the reference deterioration mode at 25 ° C.

Next, the sum total of the values obtained by raising the energization current amount corresponding to the reference deterioration mode calculated from all the usage conditions of the temperature width and the SOC width to the power of 1/2 is obtained and recorded in the table of FIG. That is, as shown in FIG. 10, the sum total of the values obtained by raising the energization current amount corresponding to the reference deterioration mode calculated from all the use conditions to the power of ½ is 333.487 [Ah ^1/2 ].

Then, the sum of values obtained by raising the energization current amount corresponding to the reference deterioration mode shown in FIG. 10 to the power of ½ (335.487 [Ah ^1/2 ]) and the deterioration rate (0.199 of the reference deterioration mode shown in FIG. 6). Based on [% / Ah ^1/2 ]), the current capacity retention rate estimated value Y [%] is calculated by the following equation (3).

Capacity maintenance factor estimated value Y [%] = 100− (total sum of energization current amount raised to half power [Ah ^1/2 ]) × (deterioration rate in reference deterioration mode [% / Ah ^1/2 ]) ( 3)
Substituting specific numerical values into equation (3), the sum of the values obtained by raising the energization current amount to the power of 1/2 is 335.487 [Ah ^1/2 ] from FIG. 10, and the deterioration rate of the reference deterioration mode is 6 is 0.199 [% / Ah ^1/2 ],
Capacity maintenance rate estimated value Y [%] = 100-335.487 [Ah ^1/2 ]) × 0.199 [% / Ah ^1/2 ]) = 33.238 [%].
That is, the capacity retention rate estimated value Y can be uniquely determined as 33.238 [%] regardless of conditions such as temperature and SOC width.

《Application example》
Next, as an application example, separation of the battery deterioration estimation method based on the standing time will be described. The battery deterioration estimation method described above is applied only to deterioration due to energization of the secondary battery. However, in actuality, the deterioration phenomenon of the secondary battery includes deterioration due to the standing time (that is, a change with time that occurs even when the current is not supplied) in addition to the deterioration due to the current supply.

  Therefore, similarly to the above-described concept, the neglected deterioration rate is obtained by a test for each leaving time and the SOC state at that time, and the neglected deterioration coefficient is calculated therefrom. Then, by counting and integrating the temperature and the SOC state in a state where the secondary battery is not used as a system, it is possible to obtain the estimated capacity maintenance rate based on the standing time as described above.

  When calculating the estimated capacity maintenance rate based on the neglected time, for example in the case of a vehicle, the time is counted by an ECU (Electric Control Unit) or an absolute clock (ordinary clock) built in the control system. To calculate the absolute time from the next ignition ON. The temperature is calculated by assuming that the temperature is left at the modeled temperature. Then, the temperature for the time calculated by counting the time is added to the modeled temperature.

  Specifically, the temperature count is stored as the temperature when the ignition is turned off, the temperature when the ignition is turned on the next time is sampled, and the temperature when the ignition is turned off and the temperature when the ignition is turned on are calculated by counting the time. The interpolation time is linearly interpolated with the left standing time, and the residence time under the temperature condition is calculated for each. The count adds the stay time for each temperature calculated by the temperature count to each condition.

<Another plan for conversion to energized current amount in the standard deterioration mode>
Next, another method of converting the energization current amount (energization amount) in the reference deterioration mode obtained in the above-described FIG. 10 will be described. That is, in the above-described battery deterioration estimation method, as an example of the conversion implementation method, the horizontal axis is a value [Ah ^1/2 ] obtained by multiplying the current carrying amount (energization amount) to the half power, and the vertical axis is the capacity maintenance. When the rate was [%], the slope obtained by linear interpolation of the characteristic graph was defined as the deterioration rate, and the relative speed ratio was defined as the deterioration coefficient. However, in another plan, the deterioration rate and the deterioration coefficient are not linearly interpolated based on a value [Ah ^1/2 ] obtained by multiplying the energization current amount (energization amount) on the horizontal axis by the 1/2 power, as shown in FIG. A normal energizing current amount (energizing amount) [Ah] is used as it is on the horizontal axis.

That is, when expressed by a mathematical expression, if the deterioration rate linearly interpolated using the 1/2 power law of the current carrying amount is a, Y = 100−a · X.
Y is a capacity retention rate (%), X is, for example, a value [Ah ^1/2 ] obtained by multiplying the energization current amount by 1/2, and a is a deterioration coefficient.

On the other hand, when a normal energization current amount (energization amount) [Ah] as shown in FIG. 4 when the energization current integrated amount is not raised to the 1/2 power, Y = 100−a ² · X. Note that Y is a capacity maintenance rate (%), X is, for example, an energization integrated amount (Ah), and a is a deterioration coefficient.
Therefore, when counting without the 1/2 power of the reference X axis, the values of the deterioration rate and the deterioration coefficient obtained in FIGS. The battery deterioration can be uniquely estimated regardless of the width.

<Flow of battery degradation estimation method>
Next, a procedure for calculating the capacity maintenance rate by executing the battery deterioration estimation method of the present embodiment will be described in detail using a flowchart. FIG. 11 is a flowchart showing a flow of a preparatory process for executing the battery deterioration estimation method according to the first embodiment of the present invention. Therefore, the flow of the flowchart of FIG. 11 will be described with reference to the battery deterioration estimation device 1 shown in FIG. As a precondition, it is assumed that the ignition (IG) is in the ON state, various information necessary for calculating the capacity retention rate estimation value has been acquired, and the ECU of the vehicle is in a normal state.

  In FIG. 11, when performing periodic processing as a preparation step for executing the battery deterioration estimation method, first, the capacity maintenance ratio calculator 8 acquires the battery temperature information of the secondary battery 2 via the temperature sensor 3. (Step S1). Next, the capacity maintenance ratio calculator 8 acquires the SOC value of the secondary battery 2 calculated by the SOC calculator 6 based on the voltage information detected by the voltage detector 4 and the current information detected by the current detector 5. (Step S2). Further, the capacity maintenance rate calculator 8 calculates the amount of energization current (energization current × time) during one sampling period based on the time information counted by the time measuring means 7 and the current information detected by the current detector 5. Obtain (step S3).

  Next, the capacity maintenance rate calculator 8 searches the elapsed time integration table based on the battery temperature information acquired in step S1 and the SOC value acquired in step S2 based on the time information of the time measuring means 7 (step S4). ). Then, the accumulated time recorded in the corresponding elapsed time accumulated table is counted up (step S5).

  Further, the capacity maintenance rate calculator 8 searches the discharge current amount integration table based on the battery temperature information acquired in step S1 and the SOC value acquired in step S2 based on the time information of the time measuring means 7 (step S6). ). Then, the integrated current amount recorded in the corresponding discharge current amount integration table is counted up (step S7).

  Next, the flow of the process for calculating the estimated battery deterioration value by integrating the energization current amount will be described. FIG. 12 is a flowchart showing a flow of a battery deterioration estimated value calculation process at the time of integration of energized current in the battery deterioration estimating method according to the first embodiment of the present invention.

  As shown in FIG. 12, when calculating the deterioration degree of the secondary battery at the time of energization current accumulation, first, the capacity maintenance rate calculator 8 acquires an energization amount accumulation table. That is, an energization amount integration table (1/2 current integration value / division table) of the current integration value shown in FIG. 9 is obtained (step S11). Furthermore, the capacity maintenance ratio calculator 8 acquires the deterioration coefficient table of the energization amount shown in FIG. 7 (step S12). Then, the energization amount integration table acquired in step S11 and the deterioration coefficient table acquired in step S12 are multiplied by the values of the corresponding categories (columns) to create the energization amount integration table corresponding to the reference deterioration mode shown in FIG. (Step S13).

Next, for the energization amount integration table corresponding to the reference deterioration mode created in step S13 (FIG. 10), the total energization amounts of all the sections are calculated to obtain 335.487 [Ah ^1/2 ] (step S14). Further, 0.199 [% / Ah ^1/2 ] is retrieved as the deterioration rate of the reference deterioration mode from the deterioration rate table shown in FIG. 6 (step S15). Then, the energization amount obtained in step S14 is multiplied by the sum (335.487 [Ah ^1/2 ]) and the deterioration rate (0.199 [% / Ah ^1/2 ]) of the reference deterioration mode searched in step S15. In addition, the deterioration degree of the secondary battery is calculated (step S16). Specifically, the capacity maintenance rate estimated value Y [%] can be calculated based on the above-described equation (3).

  Then, in step S16, when the degree of deterioration of the secondary battery (that is, the estimated battery deterioration value at the time of integrating the energizing current of the secondary battery) is calculated, the energizing current integrating table (that is, the current accumulated value 1 of FIG. The data (current integration value) in the / square table is reset to the initial state (step S17).

  The relationship between each step and each procedure in claim 1 is that step S11 corresponds to the first procedure, step S12 corresponds to the second procedure, and steps S13 to S15 correspond to the third procedure. Further, step S16 corresponds to a fourth procedure.

  Next, the flow of the process for calculating the estimated battery deterioration value when the secondary battery is left will be described. FIG. 13 is a flowchart showing a flow of a battery deterioration estimation value calculation process when the secondary battery is left in the battery deterioration estimation method according to the first embodiment of the present invention.

  In FIG. 13, when performing the calculation process of the degree of deterioration by the discharge time, the capacity maintenance ratio calculator 8 first obtains a left time integration table of the total discharge amount when left. That is, a neglected time integration table similar to the current square value 1/2 table shown in FIG. 9 is acquired (step S21). Further, the capacity maintenance rate calculator 8 obtains the deterioration coefficient table of the leaving time as shown in FIG. 7 (step S22). Then, the neglected time integration table acquired in step S21 and the deterioration coefficient table acquired in step S22 are multiplied by the corresponding category (column) value, and the neglected time integration table corresponding to the reference deterioration mode as shown in FIG. 10 is obtained. Create (step S23).

Next, regarding the neglected time integration table (corresponding to FIG. 10) corresponding to the reference deterioration mode created in step S23, the neglected period discharge amount of all the sections is summed and recorded in the table (step S24). Further, the deterioration rate [% / Ah ^1/2 ] of the reference deterioration mode is searched from the deterioration rate table of the standing time as shown in FIG. 6 (step S25). Then, the total amount [Ah ^1/2 ] of the discharge amount obtained in step S24 is multiplied by the deterioration rate [% / Ah ^1/2 ] of the reference deterioration mode searched in step S25, and the above equation (3) is obtained. Based on this, a capacity maintenance rate is calculated (step S26).

  In step S26, when the degree of deterioration of the secondary battery (that is, the estimated battery deterioration value when the secondary battery is left) is calculated, the discharge amount integration table (that is, 1/2 of the current integration value shown in FIG. 9). The data (discharge amount integrated value) of the power table is reset to the initial state (step S27).

FIG. 14 is a flowchart showing a flow of calculation processing of an estimated battery deterioration value when energized and left in the battery deterioration estimation method according to the first embodiment of the present invention.
As shown in FIG. 14, when calculating the degree of deterioration of the secondary battery in consideration of deterioration both during energization and when left unattended, first, the capacity maintenance rate calculator 8 acquires an energization amount integration table. That is, an energization amount integration table (1/2 of the current integration value / division table) of the current integration value as shown in FIG. 9 is acquired (step S31). Further, the capacity maintenance rate calculator 8 obtains an energization amount deterioration coefficient table as shown in FIG. 7 (step S32).

  Then, the energization amount integration table corresponding to the reference deterioration mode as shown in FIG. 10 is obtained by multiplying the values of the corresponding categories (columns) for the energization amount integration table acquired in step S31 and the deterioration coefficient table acquired in step S32. Create (step S33). With respect to the energization amount integration table corresponding to the reference deterioration mode created in step S33 (FIG. 10), the energization amounts of all the sections are summed (step S34).

  Next, in order to take into account the deterioration at the time of leaving, a left time integration table of time integration at the time of leaving is acquired. That is, a neglected time integration table similar to the current square value 1/2 table as shown in FIG. 9 is acquired (step S35). Further, the capacity maintenance rate calculator 8 obtains a deterioration coefficient table of the leaving time as shown in FIG. 7 (step S36). Then, the neglected time integration table acquired in step S35 and the deterioration coefficient table acquired in step S36 are multiplied by the corresponding category (column) values, and the neglected time integration table corresponding to the reference deterioration mode as shown in FIG. 10 is obtained. Create (step S37). Then, the capacity maintenance rate calculator 8 converts the neglected time accumulated value of the neglected time accumulated table into the energization amount accumulated value, and calculates the sum of the converted values (step S38).

The conversion from the neglected time integrated value to the energized amount integrated value is performed by multiplying the discharged time integrated value by the energized amount integrated conversion coefficient. The energization amount integration conversion coefficient is obtained by the following equation, for example.
Energization amount integration conversion coefficient = (Charge amount integration value in the reference deterioration mode 1 / 2-gradient of capacity retention rate graph) / (Discharge time integration value in the reference deterioration mode 1/2 power-capacity maintenance rate graph) Slope)

  The slope of the energization amount integrated value in the standard deterioration mode minus the 1/2 power of the capacity maintenance ratio, and the slope of the discharge time integrated value in the reference deterioration mode minus the half of the capacity maintenance ratio are as follows. Can be obtained.

  FIG. 15 is a cycle characteristic diagram of experimental data showing the relationship of the capacity retention rate to the current carrying amount integrated value (energizing current amount) under the reference deterioration condition. The horizontal axis represents the current carrying amount accumulated value (Ah), and the vertical axis represents the capacity maintenance. The rate (%) is shown. That is, this figure is a cycle characteristic diagram in which the cycle of 1C CC-CV charge → 1C CC discharge in the reference deterioration mode is plotted. However, as can be seen from FIG. 15, since the relationship between the energization amount integrated value and the capacity maintenance rate is a non-linear characteristic, the slope of the energization amount integrated value-capacity maintenance rate graph and the discharge time integrated value-capacity It is difficult to uniquely determine the slope of the maintenance rate graph.

However, the capacity maintenance rate (deterioration speed) of the secondary battery can be uniquely obtained by raising the energization amount integrated value by a factor of 1/2 using FIG. FIG. 16 is a cycle characteristic diagram showing a relational characteristic of the capacity retention ratio with respect to the half power of the energization amount integrated value (energization current amount) created based on the cycle characteristic diagram of FIG. The value raised to the power of 1/2 (Ah ^1/2 ) and the vertical axis represents the capacity retention rate (%). That is, as shown in FIG. 16, since the relationship between the energization current amount to the half power and the capacity retention rate is a linear characteristic, the slope of the energization amount integrated value-capacity retention rate graph and the discharge time integration The slope of the value-capacity retention ratio graph can be uniquely determined.

The capacity maintenance rate calculator 8 adds the sum obtained in step S34 and the sum obtained in step S38 (step S39). Further, the deterioration rate of the reference deterioration mode is searched from the deterioration rate table shown in FIG. 6, and the deterioration degree of the secondary battery is calculated by multiplying the searched deterioration rate by the sum of the energization amounts obtained in step S39. (Step S40).
In step S40, when the degree of deterioration is calculated in consideration of deterioration both during energization and when the secondary battery is energized, the energization amount accumulation table created in step S34 and the leaving time accumulation table created in step S37. The data is reset to the initial state (step S41).
As described above, it is possible to calculate the capacity maintenance rate in consideration of deterioration both during energization and when left unattended.

  In the first embodiment, the estimation of the battery deterioration due to energization and the estimation of the battery deterioration due to neglecting are performed by converting the data to one axis (for example, equivalent to the reference deterioration mode) without depending on conditions such as temperature and SOC. The method for estimating deterioration (in terms of the amount of energization) has been described. Thereby, for example, the deterioration level of a lithium ion battery or the like can be accurately estimated. In other words, since the capacities of all the battery cells constituting the assembled battery can be estimated with high accuracy, the capacities of the secondary batteries connected in series can be maximized. Therefore, in the second embodiment, a method for maximizing the capacity of secondary batteries connected in series will be described.

  That is, using the cell capacity estimation method described in the first embodiment, the capacities of all cells are estimated individually. Further, the SOC of each cell is estimated, and the capacity that can be charged before full charge (hereinafter, chargeable capacity) is calculated. And the capacity | capacitance of all the cells is compared, the cell which needs discharge based on a capacity | capacitance reference value is specified, and the cell concerned is discharged, and the balance of the whole battery capacity is adjusted. Thereby, the maximum capacity as an assembled battery can be drawn. In other words, by accurately estimating the capacity of all the pond cells that make up the assembled battery, it is possible to perform equalization based on the capacity standard from the equalization based on the voltage, so that the maximum capacity of the assembled battery can be extracted. It becomes. Hereinafter, a method of extracting the maximum capacity as an assembled battery using the cell capacity estimation method will be described in detail.

  Generally, the maximum energy can be extracted from the assembled battery by measuring each cell voltage of the assembled battery and adjusting the variation of each cell voltage by charging or discharging each cell. Such a voltage equalization circuit for an assembled battery is widely known. In addition, when there is no variation in the capacity of each cell, the maximum energy is extracted from the assembled battery by adjusting the variation in each cell voltage by constantly monitoring the voltage variation and equalizing the voltage. Can do.

However, the capacity of each cell in the assembled battery is not necessarily the same due to the individual difference of secondary batteries, the arrangement location, and the like. Therefore, there is known a technique for performing equalization corresponding to variation in capacity by limiting timing for equalizing voltages. For example, by equalizing the voltage when fully charged, the capacity of the assembled battery can be maximized even if the capacity of the assembled battery varies. A technique for equalizing cell capacity by such voltage control is, for example,
JP-A-2000-14031, JP-A-2006-42555, JP-A-2001-178003, JP-A-2005-151679, and the like.

  Although it is possible to maximize the capacity of the assembled battery by a general method including each of the above publications, in order to limit the conditions for voltage equalization (for example, voltage equalization on the fully charged side) In some cases, the operation time of the equalization circuit is short, or the desired operation time cannot be increased. Therefore, for example, when the cell voltages are equalized by discharging, it is necessary to increase the capacity of the circuit to be discharged so that equalization can be performed within a limited operation time.

<Cell capacity estimation method>
Lithium ion batteries (hereinafter referred to as LIB) have greatly different deterioration rates depending on conditions such as the temperature of the use environment, the standing time, the energization amount, the energization current magnitude, and the voltage (SOC). In addition, the capacity maintenance rate (deterioration degree) of LIB is proportional to the ½ power of the energization current amount and the standing time. Therefore, the degradation coefficient (the gradient coefficient with respect to the ½ power of the energization amount and the standing time) is obtained by dividing the temperature, voltage, and magnitude of the energization current into conditions.

  Then, for each use condition, the energization amount equivalent to the reference deterioration mode obtained by multiplying the value obtained by accumulating the standing time and the energization current amount to the 1/2 power (see FIG. 9) and the deterioration coefficient (see FIG. 7). The values (see FIG. 10) are summed and converted to a standard deterioration rate to estimate the degree of deterioration of the secondary battery. Thereby, irrespective of the above-mentioned use conditions, the capacity deterioration rate of each cell can be calculated by uniquely estimating the capacity deterioration rate of the LIB.

  The deterioration rate of the secondary battery varies depending on the amount of energization current and the standing time, and the deterioration rate also varies depending on the staying voltage (or SOC) and temperature. However, in either case, the 1/2 power law is followed. Therefore, by giving a coefficient to each use condition having a different deterioration rate, the horizontal axis can be adjusted to the reference use condition (for example, 25 ° C.). Thereby, it is possible to unify the deterioration levels used in combination under the use conditions having different deterioration rates.

  Here, the relationship between the LIB capacity, the open circuit voltage (OCV), and the deterioration will be briefly described. FIG. 17 is a model diagram for explaining the relationship between LIB battery capacity, open circuit voltage (OCV), and deterioration. As shown in FIG. 17, when LIB is a cup, as shown in FIG. 17A, the battery capacity (Ah) is represented by a volume V that can be stored in the cup, and the open circuit voltage (OCV) is represented by a water level h. be able to. Here, the phenomenon in which the usable battery capacity (Ah) decreases due to the deterioration of the LIB from the initial state is represented by a cup as shown in the initial state of FIG. The height H and the water level h are not changed, and the cup cross-sectional area S is reduced to S0. That is, even if the LIB deteriorates and the battery capacity decreases (that is, even if the cup volume decreases from V to V0), the relationship between the SOC and the voltage does not change, so the volume (or water volume) V at the water level h. Can not be measured.

<Cell capacity estimation method>
(1) The integrated amount ΔAh of the current discharged (or charged) during a certain period and the SOC change amount ΔSOC before and after that are measured. Thereby, ΔAh / ΔSOC = cell capacity. However, in order to estimate the cell capacity by this method, it is necessary to measure the OCV in order to measure the SOC before and after discharging (or charging) with high accuracy. However, since it takes 1 hour or more for the battery after energization to exhibit a predetermined open circuit voltage (OCV), it is necessary to use EV (Electric Vehicle) or HEV (Hybrid Electric Vehicle). It is difficult to do.

  (2) Battery deterioration is estimated by a change in the internal resistance of the secondary battery. In this case, although it is possible to relate the internal resistance and the capacity deterioration, the internal resistance largely varies depending on the temperature, the SOC, the energization history, and the like, so it is difficult to estimate the battery deterioration with high accuracy.

  Therefore, a capacity estimation method for estimating the cell capacity with high accuracy will be described. Here, in order to simplify the description, an assembled battery including two cells A and B connected in series will be described. FIG. 18 is a model diagram for explaining a cell capacity estimation method applied to the second embodiment of the present invention.

In FIG. 18, the capacity of cell A is A, the capacity of cell B is B, the SOC of cell A is A _SOC , and the _SOC of cell B is B _SOC . Further, the remaining capacity of the cell A is a, the remaining capacity of the cell B is b, the remaining chargeable capacity of the cell A is a ₀ , and the remaining chargeable capacity of the cell B is b ₀ .

Here, the capacity relation and the SOC relation between the cell A and the cell B are as follows.
A = B (1)
A <B (2)
Furthermore, in the case of (2),
A _SOC > B _SOC (3)
A _SOC = B _SOC (4)
A _SOC <B _SOC (5)

In the case of (1), the capacity of the assembled battery can be maximized by setting the capacity to A = B ( _SOC = A _SOC = B _SOC ).
When the capacity of (2) is A <B and the SOC of (3) is A _SOC > B _SOC , the cell A is discharged and A _SOC = B _SOC if the normal equalization method is used. be able to.

However, in the embodiment of the present invention, the following equalization process is performed. That is,
When the SOC of (3) is A _SOC > B _SOC and the remaining capacity is a ≧ b, the cell A is discharged so that the remaining capacity becomes a = b. Furthermore, when the battery is connected to the charger and is in a chargeable state, both the cells A and B are fully charged without losing the usable capacity of the battery pack by charging the battery pack while discharging the cell A. Thus, not only the capacity of the cells A and B but also the energy capacity of the cells A and B can be maximized.

Next, when the SOC of (3) is A _SOC > B _SOC and the remaining capacity is a <b, equalization is not performed in the normal state. Furthermore, when the battery is connected to the charger and is in a chargeable state, both the cells A and B are fully charged without losing the usable capacity of the battery pack by charging the battery pack while discharging the cell A. Thus, not only the capacity of the cells A and B but also the energy capacity of the cells A and B can be maximized.

  Here, when charging the battery pack while discharging the cell A, if the normal equalization method is used, the cell A is further discharged from the state where the remaining capacity is a <b after the cell voltage is equalized. On the contrary, the usable capacity of the assembled battery is reduced. However, according to the method of the present embodiment, even when the assembled battery is charged while discharging the cell A, it is possible to prevent a decrease in the usable capacity of the assembled battery.

Next, when the SOC of (4) is A _SOC = B _SOC , equalization is not performed in the normal state. Furthermore, when it is connected to the charger and is in a chargeable state, both the cells A and B are fully charged without losing the usable capacity of the assembled battery by charging the assembled battery while discharging the cell A. Thus, not only the capacity of the cells A and B but also the energy capacity of the cells A and B can be maximized.

Next, when the SOC of (5) is A _SOC <B _SOC and the remaining chargeable capacity is a ₀ > b ₀ , the cell B is set such that the remaining chargeable capacity is a ₀ = b ₀ To discharge. Further, when the SOC of (5) is A _SOC <B _SOC and the remaining chargeable capacity is a ₀ ≦ b ₀ , equalization is not performed in the normal state. Furthermore, when the charger is connected and is in a chargeable state, both the cells A and B are fully charged without losing the usable capacity of the assembled battery by charging the assembled battery while discharging the cell A. Thus, not only the capacity of the cells A and B but also the energy capacity of the cells A and B can be maximized.

Here, a specific example of a method for extracting the capacity of the assembled batteries connected in series to the maximum will be described. FIG. 19 is an SOC-voltage characteristic diagram of each cell for explaining a method of maximizing the capacity of the assembled battery. The horizontal axis represents SOC (%), and the vertical axis represents open-circuit voltage (OCV) (V). Represents. Here, in order to simplify the description, an assembled battery composed of two cells will be described. Assume that the capacity of cell 1 is 10 Ah, the capacity of cell 2 is 6 Ah, and as shown in FIG. 19, the SOC of cell 1 is 50% and the SOC of cell 2 is 40%. Therefore,
The chargeable capacity of the cell 1 is 10 [Ah] × (100−50) [%] = 5 Ah
The chargeable capacity of the cell 2 is 6 [Ah] × (100−40) [%] = 3.6 Ah.
It is.

  In this case, in order to equalize the voltage variation at the time of full charge, it is necessary to discharge 1.4 Ah (chargeable capacity of the cells 1 and 2) from the cell 2. That is, as shown in FIG. 19, since the voltage of the cell 1 is 3.65V and the voltage of the cell 2 is 3.55V, since the voltage of the cell 1 is apparently higher, the cell 1 is discharged. Although it seems necessary, discharging the cell 2 due to the variation in capacity can maximize the energy of the assembled battery.

  That is, in order to draw out energy to the maximum as an assembled battery, basically, the voltage is equalized toward a condition (for example, when fully charged) where the capacity of each cell is to be equalized. Therefore, even if the voltage is low compared to other cells at low SOC, the voltage is higher than other cells due to capacity variation at full charge (that is, due to small capacity). However, in the above-described method, it has been detected that discharging is necessary only at full charge. Therefore, in the present embodiment, by ascertaining whether discharge is possible and necessary discharge capacity at all times, it is possible to draw out energy to the maximum as an assembled battery.

  As described above, according to the cell capacity estimation method according to the second embodiment of the present invention, it is not necessary to limit the operating condition of the equalization circuit for equalizing the cell capacity, and for equalization. The capacity of the element (resistive element in the case of equalization by discharge) can be reduced. Further, apparently, even a cell having a low voltage can easily determine a cell that needs to be discharged. Furthermore, it is possible to easily calculate the capacity that needs to be discharged for each cell.

  The present invention has been specifically described above based on the two embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

  Since the battery deterioration estimation method of the present invention can uniquely estimate the deterioration level even if the use conditions of the secondary battery are different, the battery deterioration estimation method is not limited to the on-vehicle secondary battery, but the entire world with different environmental temperatures. It can be effectively used for estimating deterioration of a secondary battery used as a power source for industrial equipment.

DESCRIPTION OF SYMBOLS 1 Battery deterioration estimation apparatus 2 Secondary battery 3 Temperature sensor 4 Voltage detector 5 Current detector 6 SOC calculator 7 Time measuring means 8 Capacity maintenance factor calculator 8a Accumulation means 8b Deterioration coefficient calculation means 8c Conversion means 8d Capacity deterioration estimation means 9 Storage medium

Claims (4)

A battery deterioration estimation method for estimating a level of capacity deterioration of a secondary battery,
Corresponding to each of a plurality of use conditions affecting the capacity deterioration of the secondary battery, a first procedure for integrating the amount of current flowing through the secondary battery, or the elapsed time over a predetermined period;
A second degradation coefficient indicating a ratio of a degradation rate of the secondary battery in the plurality of usage conditions to a degradation rate of the secondary battery in a single usage condition is calculated for each of the corresponding usage conditions. And the steps
The current integrated value or elapsed time accumulated for each of the plurality of use conditions in the first procedure is corrected by the deterioration coefficient calculated for each of the plurality of use conditions corresponding to the second procedure, A third procedure for converting into an integrated current value or elapsed time under one use condition;
And a fourth procedure for estimating the level of capacity deterioration of the secondary battery based on the integrated current value or elapsed time converted in the third procedure and the deterioration rate in the single use condition. A battery deterioration estimation method characterized by the above. A battery capacity estimation method for estimating a capacity of the secondary battery based on the battery deterioration estimation method according to claim 1,
A fifth procedure for estimating a capacity maintenance rate of the secondary battery based on the level of capacity deterioration of the secondary battery estimated in the fourth procedure;
A battery capacity estimation comprising: a sixth procedure for estimating a current capacity of the secondary battery based on the capacity maintenance rate estimated in the fifth procedure and the initial capacity of the secondary battery. Method. A battery capacity equalization method for equalizing a remaining capacity or a chargeable capacity of the secondary battery based on the battery capacity estimation method according to claim 2,
A seventh procedure for estimating the SOC of the secondary battery;
An eighth procedure for calculating a remaining capacity or a chargeable capacity of the secondary battery based on the SOC estimated in the seventh procedure and the current capacity of the secondary battery estimated in the sixth procedure; When,
A ninth procedure for comparing the remaining capacity or chargeable capacity of the secondary battery calculated in the eighth procedure with the remaining capacity or chargeable capacity of another secondary battery;
And a tenth procedure for equalizing the remaining capacity or chargeable capacity of the secondary battery and the remaining capacity or chargeable capacity of the other secondary battery based on the comparison result of the ninth procedure. A method for equalizing battery capacity. A battery deterioration estimation device for estimating the level of capacity deterioration of a secondary battery,
In accordance with each of a plurality of use conditions affecting the capacity deterioration of the secondary battery, an integrating means for integrating the amount of current flowing through the secondary battery, or an elapsed time over a predetermined period;
A deterioration factor for calculating a deterioration factor indicating a ratio of the deterioration rate of the secondary battery in the plurality of use conditions to the deterioration rate of the secondary battery in a single use condition for each of the corresponding use conditions. A calculation means;
The current integrated value or elapsed time integrated by the integration means for each of the plurality of use conditions is corrected by the deterioration coefficient calculated for each of the plurality of use conditions corresponding to the deterioration coefficient calculation means, and the single use condition Conversion means for converting the current integrated value or elapsed time at
Capacity degradation estimating means for estimating the level of capacity degradation of the secondary battery based on the integrated current value or elapsed time converted by the conversion means and the degradation rate under the single use condition. Battery degradation estimation device.

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