JP2015204131A - Specific gravity estimation device and specific gravity estimation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a specific gravity estimation device and a specific gravity estimation method in which conversion can be made to a highly accurate charging rate when calculating the charging rate of a lead storage battery.SOLUTION: A specific gravity estimation device 10 includes a first open voltage calculation unit 11 for calculating the variation of a charging rate determined by current integration, and converting into a first open voltage OCVi, a second open voltage calculation unit 12 for calculating the second open voltage OCVv on the basis of the current and the terminal voltage of a lead storage battery B, an error estimation unit 36 for estimating the error of the first open voltage on the basis of the first open voltage and second open voltage, and a specific gravity conversion unit 16 for converting a value, obtained by subtracting an error estimated in the error estimation unit from the first open voltage, into a specific gravity.

Description

  The present invention relates to a specific gravity estimation device and a specific gravity estimation method for a lead storage battery with improved estimation accuracy.

  A vehicle such as an automobile is often equipped with a rechargeable battery (secondary battery, hereinafter simply referred to as “battery”). Such a battery stores (charges) electrical energy obtained by converting mechanical kinetic energy transmitted from an engine or the like with an alternator, and supplies (discharges) electrical energy to a motor for driving the vehicle. . At this time, the state of charge (SOC), which is the internal state quantity of the battery, needs to be accurately calculated so that the driver of the vehicle can accurately grasp the travelable distance and the like.

  For example, the invention of Patent Document 1 obtains a charging rate by a current integration method and an open-circuit voltage estimation method, and corrects an error model so that the error is minimized by a Kalman filter (so-called sensor fusion technology). To calculate a highly accurate charging rate.

JP 2013-238402 A

  Here, a lead storage battery is often used as a battery mounted on a vehicle. The invention of Patent Document 1 can also be applied to lead-acid batteries, but requires calculation processing using a conversion table (OCV-SOC conversion table) when determining a charging rate from an open circuit voltage (OCV). . When the conversion table is used, there is a possibility that the accuracy is lowered as compared with, for example, linear conversion.

  An object of the present invention made in view of the above problems is to provide a specific gravity estimation device and a specific gravity estimation method for calculating specific gravity that can be converted into a highly accurate charge rate when calculating the charge rate of a lead storage battery. It is to provide.

  In order to solve the above problem, a specific gravity estimation device according to a first aspect of the present invention is a specific gravity estimation device for a lead storage battery, and calculates a change amount of a charging rate obtained by a current integration method to obtain a first open circuit voltage. A first open-circuit voltage calculating unit for converting; a second open-circuit voltage calculating unit for calculating a second open-circuit voltage based on a current and a terminal voltage of the lead storage battery; the first open-circuit voltage and the second open-circuit voltage; An error estimation unit that estimates an error of the first open-circuit voltage based on the open-circuit voltage of the first and a specific gravity conversion that converts a value obtained by removing the error estimated by the error estimation unit from the first open-circuit voltage into a specific gravity It is characterized by including a part.

  The specific gravity estimation device according to a second aspect of the invention further includes a temperature correction unit that corrects the specific gravity converted by the specific gravity conversion unit according to the temperature of the lead storage battery in the specific gravity estimation device of the first aspect of the invention.

  The specific gravity estimation apparatus according to a third aspect of the present invention is the specific gravity estimation apparatus according to the first or second aspect, wherein the error estimation unit estimates an error of the first open circuit voltage using a Kalman filter.

  A specific gravity estimation method according to a fourth aspect of the present invention is a specific gravity estimation method for a lead storage battery, and (A) calculates a change amount of a charging rate obtained by a current integration method and converts it into a first open circuit voltage. A step of (B) calculating a second open-circuit voltage based on the current and terminal voltage of the lead-acid battery; and (C) based on the first open-circuit voltage and the second open-circuit voltage, And (D) converting a value obtained by removing the error estimated in step (C) from the first open voltage into specific gravity. To do.

  In addition, according to the specific gravity estimation apparatus according to the first aspect of the invention, the error estimation unit for estimating the error of the first open circuit voltage is included. The error estimation unit can estimate the error of the first open-circuit voltage based on the first open-circuit voltage using the current integration method and the second open-circuit voltage using the open-circuit voltage estimation method. That is, since the error of the first open circuit voltage can be corrected by the second open circuit voltage, the error can be obtained with high accuracy. Further, the specific gravity conversion unit converts a value obtained by removing the error estimated by the error estimation unit from the first open circuit voltage into specific gravity. The charge rate and specific gravity of the lead storage battery have a linear relationship. Therefore, the charge rate can be obtained by linear conversion from the specific gravity of the lead storage battery. For example, compared to the case of using a conversion table, the error during conversion is reduced, so that conversion to a highly accurate charge rate is possible.

  Moreover, according to the specific gravity estimation apparatus which concerns on 2nd invention, the temperature correction | amendment part which correct | amends specific gravity according to the temperature of lead acid battery is included, and specific gravity in the predetermined temperature which has a linear expression and the charge rate of lead acid battery is obtained. Can be generated. Therefore, the charging rate can be obtained immediately by linear conversion from the generated specific gravity, and a highly convenient specific gravity estimation device can be provided.

  Further, according to the specific gravity estimation apparatus according to the third aspect of the invention, the error of the first open circuit voltage is estimated using a Kalman filter suitable for self-correcting internal parameters. Therefore, the error can be estimated easily and with high accuracy.

  In addition, according to the specific gravity estimation method according to the fourth aspect of the invention, the method includes a step of estimating an error of the first open circuit voltage. In this step, the error of the first open-circuit voltage can be estimated based on the first open-circuit voltage using the current integration method and the second open-circuit voltage using the open-circuit voltage estimation method. That is, since the error of the first open circuit voltage can be corrected by the second open circuit voltage, the error can be obtained with high accuracy. Also included is another step of converting the value obtained by removing the error estimated in this step from the first open circuit voltage into specific gravity. The charge rate and specific gravity of the lead storage battery have a linear relationship. Therefore, the charge rate can be obtained by linear conversion from the specific gravity of the lead storage battery. For example, compared to the case of using a conversion table, the error during conversion is reduced, so that conversion to a highly accurate charge rate is possible.

It is a block diagram which shows the specific gravity estimation apparatus which concerns on this embodiment. It is a figure which shows the relationship of the open circuit voltage, specific gravity, and charging rate of a lead acid battery. It is a figure which shows the specific gravity-charge rate characteristic of a lead acid battery. It is a figure which illustrates the equivalent circuit model of the battery used with an OCVv calculation part. It is a flowchart which shows the process of the specific gravity estimation apparatus which concerns on this embodiment. It is a block diagram which shows the charging rate estimation apparatus of a comparative example.

Embodiments of the present invention will be described below.
(overall structure)
First, the overall configuration of the specific gravity estimation apparatus 10 of the present embodiment will be described with reference to FIG. The specific gravity estimation device 10 is connected to a battery B mounted on a vehicle such as an automobile. The battery B is a lead storage battery, stores (charges) electrical energy obtained by converting mechanical kinetic energy with an alternator (not shown), and supplies (discharges) electrical energy to a vehicle drive motor (not shown). The battery B may be charged by receiving, for example, regenerative power generated when the vehicle decelerates from the alternator. The specific gravity estimation device 10 calculates the specific gravity that can be converted into the charging rate of the battery B. The specific gravity estimation device 10 can calculate the specific gravity of the battery B that is charged and discharged during operation of the vehicle. Here, the operation of the vehicle means a state in which the engine of the vehicle is running and is running or stopped for movement.

  The specific gravity estimation apparatus 10 includes an OCVi calculation unit 11, an OCVv calculation unit 12, an open circuit voltage correction unit 14, a specific gravity conversion unit 16, and a temperature correction unit 18. As an outline, the specific gravity estimation device 10 calculates the specific gravity of the lead storage battery, which is different from the prior art in that the specific gravity is calculated based on an open circuit voltage using two different methods. Each open circuit voltage is calculated by the OCVi calculation unit 11 and the OCVv calculation unit 12, and the open circuit voltage correction unit 14 performs error correction using these open circuit voltages. Therefore, it is possible to estimate the open-circuit voltage with high accuracy, and as a result, it is possible to obtain the charging rate of the battery B with high accuracy. The terminal voltage VB of the battery B is detected by a voltage sensor (not shown) and output to the specific gravity estimation device 10. In addition, the current IB of the battery B is detected by a current sensor (not shown) and output to the specific gravity estimation device 10. Further, the temperature TB of the battery B is detected by a temperature sensor (not shown) and output to the specific gravity estimation device 10.

  The OCVi calculation unit 11 receives the current IB of the battery B, and outputs a first open circuit voltage OCVi based on the change rate ΔSOCi of the charging rate obtained by the current integration method. The OCVi calculation unit 11 corresponds to the first open-circuit voltage calculation unit of the present invention.

  The OCVi calculation unit 11 includes a current integration unit 32 and an OCVi conversion unit 34. The current integrating unit 32 receives the current IB of the battery B and obtains the change rate ΔSOCi of the charging rate by the current integrating method. The current integration method is a method of calculating the charge rate by obtaining the charge amount by integrating the current IB with time. The current integrating unit 32 may obtain the change rate ΔSOCi of the charging rate after separating the current IB into a charging current having a positive value and a discharging current having a negative value. Here, in the current integration method, processing for adding the initial value of the battery B is also generally performed. However, the current integration unit 32 does not add the initial value, and the change rate ΔSOCi (the amount of charge obtained by time integration of the current IB is calculated as the battery amount). (Value obtained by dividing by the full charge capacity of B).

The OCVi conversion unit 34 converts the change amount ΔSOCi of the charging rate into an open circuit voltage change amount ΔOCV. Then, the initial value OCV ₀ of the open voltage of the battery B is added to generate the first open voltage OCVi. The OCVi conversion unit 34 includes a multiplier, and generates a change amount ΔOCV of the open-circuit voltage by multiplying the change amount ΔSOCi of the charging rate by the coefficient ci. Here, the coefficient ci is determined by the open-circuit voltage difference of 100% to 0% of the charging rate of the battery B, the charging efficiency (or discharging efficiency) of the battery B, the number of cells constituting the battery B, and the like. For example, for a battery B cell, if the open-circuit voltage difference between the charging rate of 100% and 0% is 0.18 [V], and the battery B has a configuration in which six cells are connected in series, the coefficient ci is It is given by multiplying numerical values. Further, if the coefficient ci is determined in consideration of the charging efficiency according to the charging rate, the change amount ΔOCV of the open-circuit voltage can be obtained more accurately.

Further, the OCVi conversion unit 34 includes an adder, and adds the initial value OCV ₀ of the open circuit voltage of the battery B to the change amount ΔOCV of the open circuit voltage to generate the first open circuit voltage OCVi. The initial value OCV ₀ is a value of the open circuit voltage of the battery B when the current integrating unit 32 receives the current IB of the battery B and starts integration. For example, it is assumed that the current integration unit 32 starts integration when the battery B is fully charged. At this time, the initial value OCV ₀ is calculated as 12.72 [V] obtained by multiplying the open circuit voltage 2.12 [V] corresponding to the charging rate of 100% by 6 of the number of cells (see FIG. 2).

  The OCVv calculation unit 12 receives the terminal voltage VB and the current IB of the battery B, and generates the second open circuit voltage OCVv by the open circuit voltage estimation method. The second open circuit voltage OCVv is obtained by applying a current IB to an equivalent circuit (hereinafter referred to as “battery model”) of the battery B included in the OCVv calculation unit 12. A configuration example of the battery model will be described later. The OCVv calculation unit 12 corresponds to the second open circuit voltage calculation unit of the present invention.

  The open-circuit voltage correction unit 14 receives the first open-circuit voltage OCVi from the OCVi calculation unit 11 and the second open-circuit voltage OCVv from the OCVv calculation unit 12, estimates the error Ea of the first open-circuit voltage OCVi, and A value obtained by removing (subtracting) the estimated error Ea from the open circuit voltage OCVi of 1 is output as the corrected open circuit voltage OCV. The corrected open circuit voltage OCV corresponds to “a value obtained by removing the error estimated by the error estimation unit from the first open circuit voltage” of the present invention.

The open-circuit voltage correction unit 14 includes an error estimation unit 36. The error estimation unit 36 receives a value (subtraction value E ₀ ) obtained by subtracting the first open circuit voltage OCVi from the second open circuit voltage OCVv by the subtractor. Error estimator 36 estimates the error Ea by a technique to correct by comparing the value estimated by the error model and the subtracted value E _0. In the present embodiment, since the error estimation unit 36 estimates the error Ea using a Kalman filter, it is possible to obtain the corrected open circuit voltage OCV with high accuracy. Details of the Kalman filter used in the error estimation unit 36 will be described later.

Density conversion unit 16 receives the corrected open-circuit voltage OCV, and converts the specific gravity to output the original estimated specific gravity SG _0. Here, although a specific example will be described later, in a lead storage battery such as the battery B, the open circuit voltage and the specific gravity are in a linear relationship. Therefore, the conversion processing in the specific gravity converter 16, it is not necessary to use a conversion table, it is possible to calculate the original estimated specific gravity SG ₀ without reducing the accuracy.

The temperature correction unit 18 receives the temperature TB of the battery B and the original estimated specific gravity SG ₀ and generates an estimated specific gravity SG. The temperature correction unit 18 performs temperature correction for correcting the original estimated specific gravity SG ₀ to a specific gravity of a predetermined temperature (for example, 20 ° C.) based on the temperature TB of the battery B. Although a specific example will be described later, in a lead storage battery such as the battery B, the specific gravity and the charging rate are in a linear relationship, and by storing a simple calculation formula, the charging rate can be obtained from the specific gravity of 20 ° C., for example. . Therefore, the specific gravity estimation device 10 outputs the estimated specific gravity SG so that the subsequent circuit can be easily converted into the charge rate SOC.

For example, as shown in FIG. 1, the charging rate estimation device can be configured simply by adding a simple circuit (linear conversion unit 20) that performs linear conversion to the subsequent stage of the specific gravity estimation device 10. The linear conversion unit 20 does not need to use a conversion table, and can reduce the calculation processing load of the entire charging rate estimation apparatus including the specific gravity estimation apparatus 10 as compared with a comparative example described later. Here, although the specific gravity estimation apparatus 10 includes the temperature correction unit 18 in the present embodiment, the original estimated specific gravity SG ₀ may be output without including the temperature correction unit 18 as another embodiment. At this time, for example, the temperature correction may be performed by the linear conversion unit 20 together with the conversion to the charging rate SOC.

  As described above, the overall configuration of the specific gravity estimation device 10 has been described with reference to FIG. 1, but in the following, in order to clarify the advantages, the comparison with the charge rate estimation device 1010 of the comparative example is performed, and the lead storage battery The details of the OCVv calculation unit 12 and the open-circuit voltage correction unit 14 will be described, and then the processing of the specific gravity estimation device 10 will be described.

(Contrast with comparative example)
A charging rate estimation device (hereinafter referred to as a “charging rate estimation device including the specific gravity estimation device 10”) configured by the specific gravity estimation device 10 and the linear conversion unit 20 of the present embodiment of FIG. 1 and a comparative example of FIG. The charging rate estimation apparatus 1010 will be described in comparison.

  FIG. 6 is a block diagram illustrating a charging rate estimation apparatus 1010 of the comparative example. In addition, the same code | symbol is attached | subjected about the same element as FIG. 1, and detailed description is abbreviate | omitted. The charging rate estimation device 1010 estimates the charging rate of the battery B that is charged and discharged during operation of the vehicle. Note that the charging rate estimation apparatus 1010 does not perform temperature correction, so the temperature TB of the battery B is not detected. In addition, the charging rate estimation apparatus 1010 can also target batteries B (for example, lithium ion batteries) other than lead storage batteries to estimate the charging rate.

  The charging rate estimation apparatus 1010 includes an OCVv calculation unit 1012, an SOCi calculation unit 1017, an SOCv conversion unit 1018, and a charging rate correction unit 1015. Here, the OCVv calculation unit 1012 corresponds to the OCVv calculation unit 12 of the specific gravity estimation device 10 and outputs the second open circuit voltage OCVv.

  The SOCi calculating unit 1017 adds up the current to obtain ΔSOCi, adds the initial value of the charging rate SOC, and outputs the first charging rate SOCi. The SOCv conversion unit 1018 receives the second open circuit voltage OCVv, performs a conversion process using the conversion table, and outputs a second charge rate SOCv.

  The charging rate correction unit 1015 receives the first charging rate SOCi and the second charging rate SOCv instead of the first open circuit voltage OCVi and the second open circuit voltage OCVv, and replaces the corrected open circuit voltage OCV with it. Except for the output of the charge rate SOC, the configuration is the same as the open-circuit voltage correction unit 14 of the “charge rate estimation device including the specific gravity estimation device 10”.

  In the charging rate estimation apparatus 1010 of the comparative example, the charging rate correction unit 1015 outputs the charging rate SOC. Therefore, the charging rate estimation device 1010 of the comparative example does not include the specific gravity conversion unit 16, the temperature correction unit 18, and the linear conversion unit 20 included in the “charging rate estimation device including the specific gravity estimation device 10”.

  In summary, the charging rate estimation device 1010 of the comparative example includes the SOCv conversion unit 1018, but the “charging rate estimation device including the specific gravity estimation device 10” does not include these conversion units, the specific gravity conversion unit 16, temperature The charge rate SOC of the lead storage battery is calculated using the correction unit 18 and the linear conversion unit 20. That is, the “charge rate estimation device including the specific gravity estimation device 10” calculates the charge rate SOC by obtaining the specific gravity once from the first open circuit voltage OCVi and the second open circuit voltage OCVv.

  The method of the “charge rate estimation device including the specific gravity estimation device 10” that once converts to specific gravity seems to be less efficient in calculation than the comparative example. However, as will be described later, all calculations performed in the specific gravity conversion unit 16, the temperature correction unit 18 and the linear conversion unit 20 according to the characteristics of the lead storage battery follow a linear expression. Therefore, it is not necessary to execute a calculation process using a conversion table such as the SOCv conversion unit 1018 of the comparative example. That is, when the battery B is a lead storage battery, by using the “charge rate estimation device including the specific gravity estimation device 10”, it is possible to convert the charge rate to a highly accurate charge rate, and as a whole, the calculation processing load is reduced. Can be reduced.

(Characteristics of lead-acid battery and specific calculation formula)
Below, the characteristic of a lead acid battery is demonstrated with reference to FIG. 2, FIG. Further, specific calculation formulas in the specific gravity conversion unit 16 and the temperature correction unit 18 will be described. FIG. 2 is a diagram showing the relationship between the charge rate of the lead storage battery, the specific gravity at 20 ° C., and the open circuit voltage. Moreover, FIG. 3 is a figure which shows the specific gravity-charge rate characteristic of a lead storage battery. First, as shown in FIG. 3, in a lead storage battery, the specific gravity and the charging rate have a linear relationship, and when the specific gravity is 1.1, the charging rate (SOC) is 0% and the specific gravity is 1.28. The charging rate (SOC) is 100%. And also when taking the specific gravity between these, a charge rate is easily computable.

  Furthermore, it is known that in lead-acid batteries, there is also a linear relationship between specific gravity and open circuit voltage. Specifically, as can be seen from FIG. 2, when 0.84 is added to the specific gravity value, there is a relationship that becomes equal to the open circuit voltage value [V]. That is, in the lead storage battery, the conversion from the open circuit voltage to the specific gravity and the conversion from the specific gravity to the charge rate can be performed using a primary expression.

  In addition, the open circuit voltage here is the value per cell of a lead acid battery. Actually, in a vehicle or the like, a plurality of cells are connected in series and used to supply a high voltage (for example, 12.72 [V] when six cells having a charging rate of 100% are connected in series). May be. However, for the sake of simplicity, the following description will be made using an open circuit voltage per cell.

Next, specific calculation formulas in the specific gravity conversion unit 16 and the temperature correction unit 18 will be described. The specific gravity conversion unit 16 receives the corrected open-circuit voltage OCV [V], performs conversion according to the following equation (1), and outputs the original estimated specific gravity SG _0.
SG ₀ = OCV−0.84 (1)

Further, the temperature correction unit 18 receives the original estimated specific gravity SG ₀ and the temperature TB [° C.] of the battery B, performs conversion according to the following formula (2), and outputs the estimated specific gravity SG converted to a specific gravity of 20 ° C. To do.
SG = SG ₀ + 0.0007 × (TB−20) (2)
In other words, the temperature correction in the temperature correction unit 18 also has a linear relationship as shown in Expression (2).

  Although a specific calculation formula is omitted, as described with reference to FIG. 3, the conversion from the estimated specific gravity SG to the charge rate SOC in the linear conversion unit 20 is also performed according to the linear expression. As described above, in the specific gravity conversion unit 16, the temperature correction unit 18, and the linear conversion unit 20 of the specific gravity estimation device 10 of the present embodiment, it is not necessary to use the conversion table. Therefore, the charging rate estimation device including the specific gravity estimation device 10 is accurate. High charge rate can be generated.

(OCVv calculation unit)
FIG. 4 is an equivalent circuit (battery model) of the battery B. The battery model includes a resistance R0 that sets a direct current component such as an electrolyte resistance and an ohmic resistance, a resistance R1 that is set as a reaction resistance that represents a dynamic behavior in a charge transfer process, C1 that is set as an electric double layer, diffusion R2 and C2 set to represent dynamic behavior in the process. Here, although the equivalent circuit model of the primary parallel circuit in the charge transfer process and the secondary parallel circuit in the diffusion process is represented, the order is set as necessary.

  When the current IB is input to the battery model, each parameter R0, R1, R2, C1, and so on of the battery model is set by an adaptive mechanism (not shown) so that there is no difference between the terminal voltage VB of the battery B and the terminal voltage estimated value VBm of the battery model. By sequentially correcting C2, a battery model that matches the current state of the battery B can be obtained.

  The OCVv calculation unit 12 calculates the overvoltage VR from the estimated parameters R0, R1, R2, C1, and C2 and the current IB, and calculates the open circuit voltage OCV by subtracting the overvoltage VR from the terminal voltage VB. The calculated open circuit voltage OCV corresponds to the second open circuit voltage OCVv of FIG.

  Here, the adaptive mechanism for sequentially correcting the parameters R0, R1, R2, C1, and C2 may be, for example, a Kalman filter. The Kalman filter is a filter suitable for self-correcting internal parameters, and is used for sequential parameter estimation. Details of parameter estimation by the Kalman filter are described in, for example, Japanese Patent Application No. 2013-502943 of the present applicant.

(Open voltage correction unit)
The open-circuit voltage correction unit 14 (see FIG. 1) includes the error estimation unit 36 as described above. The error estimator 36 uses a Kalman filter to compare the difference in error estimated by the error model with the subtraction value E _0, and if there is a difference between the two, this difference is multiplied by the Kalman gain and fed back. The estimation error is corrected so that is minimized. This is repeated sequentially to estimate the true open-circuit voltage error (error Ea). As described above, the Kalman filter is a filter suitable for self-correcting internal parameters, and the error Ea can be estimated easily and with high accuracy. The details of parameter estimation by the Kalman filter are described in, for example, Japanese Patent Application No. 2013-502943 of the present applicant, and instead of the charging rate calculated by each of the current integration method and the open-circuit voltage estimation method, The first open circuit voltage OCVi and the second open circuit voltage OCVv are used.

(About processing of specific gravity estimation device)
In the specific gravity estimation apparatus 10 of the present embodiment, an estimated specific gravity SG that can be converted into a highly accurate charging rate can be calculated according to the following process. FIG. 5 is a flowchart showing the processing of the specific gravity estimation device 10 provided in the battery B mounted on the vehicle. First, the specific gravity estimation device 10 stands by until the vehicle starts operating (No in step S2). When the vehicle starts to operate (Yes in Step S2), the specific gravity estimation device 10 acquires the terminal voltage VB, current IB, and temperature TB of the battery B (Step S4).

  The specific gravity estimation device 10 calculates a first open-circuit voltage OCVi and a second open-circuit voltage OCVv based on the current integration method and the open-circuit voltage estimation method. That is, ΔSOCi is calculated by the current integration method and converted to the first open circuit voltage OCVi (step S6), and the second open circuit voltage OCVv is calculated based on the terminal voltage VB and the current IB (step S8).

  Next, the specific gravity estimation device 10 corrects an error model by a Kalman filter based on the first open circuit voltage OCVi and the second open circuit voltage OCVv (so-called sensor). A highly accurate error Ea is estimated by the fusion technique (step S10). Here, the error Ea is an error of the first open circuit voltage OCVi.

Thereafter, the specific gravity estimation device 10 converts the first estimated open circuit voltage OCVi into the original estimated specific gravity SG ₀ using the value obtained by removing the error Ea (the corrected open circuit voltage OCV in FIG. 1) according to the above equation (1). (Step S12). Then, the specific gravity estimation device 10 corrects the temperature of the original estimated specific gravity SG ₀ based on the temperature TB of the battery B according to the equation (2), and generates an estimated specific gravity SG corresponding to a specific gravity of 20 ° C. (step) S14). Thereafter, the specific gravity estimation device 10 ends the series of processes when the operation of the vehicle stops (Yes in Step S16), and returns to Step S4 if the vehicle is operating (No in Step S16).

  As described above, according to the specific gravity estimation device 10 and the specific gravity estimation method of the present embodiment, not only the first open circuit voltage OCVi based on the value obtained by the current integration method (change amount ΔSOCi of the charging rate) but also the open circuit voltage The specific gravity (estimated specific gravity SG) of the lead storage battery is calculated based also on the second open circuit voltage OCVv obtained by the estimation method. For example, in the current integration method, errors may accumulate over time and the accuracy may be lowered. However, since the correction by the second open-circuit voltage OCVv by the open-circuit voltage estimation method is possible, the error Ea is obtained with high accuracy. be able to. Therefore, it is possible to calculate the specific gravity with high accuracy, and as a result, it is possible to convert the charge rate with high accuracy. Moreover, the charge rate SOC and the specific gravity of the lead storage battery are in a linear relationship. The charge rate SOC can be obtained by linear conversion from the specific gravity of the lead storage battery (estimated specific gravity SG). For example, compared to the case where a conversion table is used, the error during conversion is reduced, so conversion to a highly accurate charge rate SOC is possible. Is possible. Furthermore, in general, in lead-acid batteries, the target specific gravity (target specific gravity) is changed depending on the destination (for cold regions, high-temperature regions, etc.). According to the specific gravity estimation apparatus 10 of this embodiment, since specific gravity is output, the lead acid battery can be easily adjusted according to the target specific gravity of each destination.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, functions and the like included in each means and step can be rearranged so as not to be logically contradictory, and a plurality of means and steps can be combined into one or divided.

DESCRIPTION OF SYMBOLS 10 Specific gravity estimation apparatus 11 OCVi calculation part 12 OCVv calculation part 14 Open circuit voltage correction part 16 Specific gravity conversion part 18 Temperature correction part 20 Linear conversion part 32 Current integration part 34 OCVi conversion part 36 Error estimation part B Battery

Claims (4)

A specific gravity estimation device for a lead storage battery,
A first open-circuit voltage calculation unit that calculates a change amount of the charging rate obtained by the current integration method and converts the change into a first open-circuit voltage;
A second open-circuit voltage calculation unit for calculating a second open-circuit voltage based on the current and terminal voltage of the lead storage battery;
An error estimation unit that estimates an error of the first open-circuit voltage based on the first open-circuit voltage and the second open-circuit voltage;
A specific gravity estimation device including a specific gravity conversion unit that converts a value obtained by removing the error estimated by the error estimation unit from the first open circuit voltage into specific gravity. The specific gravity estimation apparatus according to claim 1,
The specific gravity estimation apparatus further including a temperature correction unit that corrects the specific gravity converted by the specific gravity conversion unit according to the temperature of the lead storage battery. In the specific gravity estimation apparatus according to claim 1 or 2,
The error estimation unit is a specific gravity estimation device that estimates an error of the first open-circuit voltage using a Kalman filter. A method for estimating the specific gravity of a lead storage battery,
(A) calculating a change amount of the charging rate obtained by the current integration method and converting it to a first open-circuit voltage;
(B) calculating a second open circuit voltage based on the current and terminal voltage of the lead storage battery;
(C) estimating an error of the first open-circuit voltage based on the first open-circuit voltage and the second open-circuit voltage;
(D) A specific gravity estimation method including a step of converting a value obtained by removing the error estimated in step (C) from the first open circuit voltage into specific gravity.

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