JP5089510B2 - Secondary battery state detection method, state detection device, and secondary battery power supply system - Google Patents

Description

  The present invention relates to a state detection method for detecting a state of a secondary battery, and more particularly to a technical field of a state detection method, a state detection device, and a secondary battery power supply system for detecting a state of charge of a secondary battery. It is.

  In recent years, many electrical devices have been used to further improve the safety and comfort of automobiles, and the importance of secondary battery power sources mounted in response thereto is increasing. As an example, safety-related parts such as electric brakes are being controlled by electricity, and idling stops are made at intersections in response to energy saving and carbon dioxide emission regulations. It has become. Thus, as the importance of the secondary battery power source increases, a technique for estimating the charging rate of the secondary battery with high accuracy is strongly desired.

  As a method for estimating the charging rate (SOC) of the secondary battery, a method using the open-circuit voltage (OCV) when the secondary battery is stable is known. Here, the open end voltage is a voltage when both terminals of the secondary battery are opened and not energized. It is known that there is a substantially linear relationship between the stable OCV and the SOC, and a method for estimating the SOC from the measured value of the OCV by using this relationship is disclosed.

  As an example, Patent Document 1 discloses a method for obtaining a charging rate by estimating a stable OCV. Here, a coefficient of an exponential decay function of the fourth or higher order that approximates the OCV time characteristic of the secondary battery is determined, and the OCV convergence value of the secondary battery is obtained based on at least the determined coefficient, and based on the OCV convergence value. Estimating the charging rate.

JP 2005-43339 A

  During charging and discharging, the voltage of the secondary battery deviates from the stable OCV due to polarization. Moreover, polarization does not immediately disappear with the end of charge / discharge, but gradually relaxes over time. Therefore, if the OCV after charge / discharge is measured and the SOC is estimated from the relationship between the stable OCV and the SOC, the SOC cannot be accurately estimated due to the influence of polarization. The influence of polarization occurs not only in liquid secondary batteries but also in sealed secondary batteries and primary batteries (only discharge).

  Patent Document 1 proposes a method of estimating a stable voltage (voltage convergence value) using a battery voltage measured for a predetermined time after the end of charge / discharge. However, in the detection method described in Patent Document 1, a voltage change (state change in the battery) that can be detected within a predetermined time for measuring the voltage after charging / discharging is reflected in an exponential decay function that is a time characteristic of the battery voltage. However, it is difficult to reflect the phenomenon that changes over a much longer time than the predetermined time due to, for example, the movement of the reactant in the battery, in the exponential decay function. For this reason, there exists a problem that the estimation precision of stable voltage falls and the estimation error of SOC increases as a result.

  Therefore, the present invention has been made to solve these problems, and a secondary battery that corrects voltage changes due to polarization, including changes that are difficult to detect in a short time, and performs secondary battery state detection with high accuracy. It aims at providing the state detection method of a battery, a state detection apparatus, and a secondary battery power supply system.

  A first aspect of a state detection method for a secondary battery according to the present invention is a state detection method for a secondary battery that performs state detection by estimating a voltage correction value for correcting a voltage change due to polarization of the secondary battery, A plurality of voltage measurement values of the secondary battery are acquired in a period from the end of charging / discharging of the secondary battery until a predetermined voltage measurement time elapses, and the secondary battery with the elapsed time from the end of charging / discharging as a variable. A coefficient of a voltage approximation formula for calculating a voltage of the battery is determined using the plurality of voltage measurement values, and a voltage change rate calculation formula for calculating a voltage change rate of the secondary battery is derived from the voltage approximation formula, The voltage change rate of the secondary battery at the time of voltage measurement time is calculated, and the voltage change rate is substituted into a first correlation equation representing the correlation between the voltage change rate and the voltage correction value created in advance. A correction value is calculated.

  In another aspect of the method for detecting a state of a secondary battery according to the present invention, the coefficient of the voltage approximation formula is determined by sequentially calculating each time the voltage measurement value is acquired.

  In another aspect of the method for detecting a state of a secondary battery according to the present invention, the voltage change rate calculation formula is a first derivative of the voltage approximation formula.

  In another aspect of the method for detecting a state of the secondary battery according to the present invention, the voltage measurement time is a predetermined first voltage measurement time TM1 or a predetermined second measurement time TM2 (<TM1). Thus, the elapsed time until charging / discharging is started again is any shorter time.

  Another aspect of the secondary battery state detection method of the present invention is characterized in that the first correlation equation includes at least one of the temperature of the secondary battery and the charge rate SOC as a variable. To do.

  Another aspect of the secondary battery state detection method of the present invention is characterized in that the charge rate SOC calculated immediately before is used for the calculation of the first correlation equation.

  According to another aspect of the method for detecting the state of the secondary battery of the present invention, the absolute value of the current measurement value of the secondary battery is not more than a predetermined current threshold even after the voltage measurement time has elapsed. The update is performed using a predetermined attenuation calculation expression that is a function of an elapsed time since the previous calculation.

  In another aspect of the secondary battery state detection method of the present invention, the attenuation calculation expression is further a function of the temperature of the secondary battery.

Another aspect of the secondary battery state detection method of the present invention is characterized in that the stable voltage of the secondary battery is estimated using the voltage correction value as at least one correction amount.
The stable voltage here is different from the stable open-circuit voltage (stable OCV), and is a voltage when charging / discharging is substantially stopped for a long time in a state where a load is connected to the battery terminal. The voltage has no effect.

  According to another aspect of the method for detecting a state of the secondary battery of the present invention, the charge rate SOC and the stable voltage of the secondary battery are expressed in advance by a second correlation formula, and the calculation is performed in the second correlation formula. The charging rate SOC is estimated by substituting a stable voltage.

  The first aspect of the secondary battery state detection device of the present invention is a state detection sensor that measures the voltage, current, and temperature of the secondary battery, and the correlation between the voltage change rate of the secondary battery and the voltage correction value. A storage unit that stores in advance a first correlation equation to be expressed, and a plurality of voltage measurement values are acquired from the state detection sensor in a period from when charging / discharging of the secondary battery is completed until a predetermined voltage measurement time elapses And determining a coefficient of a voltage approximation formula for calculating the voltage of the secondary battery using the elapsed time from the end of charge / discharge as a variable, using the plurality of voltage measurement values, and calculating the voltage of the secondary battery from the voltage approximation formula. A voltage change rate calculation formula for calculating a change rate is derived to calculate a voltage change rate of the secondary battery at the time when the voltage measurement time has elapsed, and the voltage change rate is substituted into the first correlation equation to calculate the voltage An arithmetic processing unit for calculating a correction value. To.

  A first aspect of the secondary battery power supply system according to the present invention includes the secondary battery and the secondary battery state detection device described above.

  According to the state detection method, the state detection device, and the secondary battery power supply system of the present invention, the voltage change due to polarization is estimated by accurately estimating the voltage correction value from the voltage change rate after the end of charge / discharge. It is possible to provide a secondary battery state detection method, a state detection device, and a secondary battery power supply system that perform correction and detect the state of the secondary battery with high accuracy.

  Configurations of a secondary battery state detection method, a state detection device, and a secondary battery power supply system in a preferred embodiment of the present invention will be described in detail with reference to the drawings. In addition, about each component which has the same function, the same code | symbol is attached | subjected and shown for simplification of illustration and description.

  A method for detecting the state of the secondary battery according to the first embodiment of the present invention will be described below. The secondary battery remains polarized for a while after charging and discharging, and the voltage is not stable. In the state detection method of this embodiment, a voltage correction value for correcting a voltage change due to the influence of such polarization is estimated, and the state detection is performed by correcting the voltage measurement value with this voltage correction value and estimating a stable voltage. Is going. Furthermore, it is possible to estimate the charging rate using the correlation between the stable voltage and the charging rate, and to detect the state such as the charging rate of the secondary battery.

  The inventor has found that there is a correlation as shown in FIG. 1 between the voltage correction value for correcting the influence of polarization and the voltage change rate. FIG. 1 shows the correlation between the vertical axis with voltage correction value ΔV [V] for polarization and the horizontal axis with voltage change rate m [mV / sec]. In the present embodiment, such a correlation is used to estimate the voltage correction value for polarization with high accuracy.

  The voltage change of the secondary battery due to the polarization after the end of charging / discharging varies greatly depending on the previous charging / discharging history. An example of the voltage change after completion | finish of charging / discharging is shown in FIG. In the figure, the vertical axis represents the battery voltage of the secondary battery, and the horizontal axis represents the voltage change due to polarization relaxation when the elapsed time from the end of charge / discharge. Here, the voltage change after completion | finish of charging / discharging is each shown by the codes | symbols 21-25 about five cases from which the temperature of a secondary battery differs in the charging / discharging log | history before completion | finish of charging / discharging. For comparison, the stable voltage of the secondary battery is denoted by reference numeral 20. As for the charge / discharge history, assuming a secondary battery installed in a car, the battery is almost fully charged while driving (during generator operation), discharged or substantially charged after the engine is stopped (after generator stopped). In this case, there is no discharge.

The voltage change 21 indicates a change with time in voltage when charging / discharging is completed with almost no discharge after charging is completed. In the case of the voltage change 22, the charging / discharging is finished after a little discharging after the charging is finished. Further, the discharge capacity after completion of charging increases in the order of voltage changes 23, 24, and 25. In particular, in the case of voltage change 25, the discharge capacity is large and the voltage at the end of discharge is lower than the stable voltage 20. .
If the discharge continues, the voltage change gradually approaches the stable voltage 20 from below. In this case, the same correction can be made by extending the voltage change rate m to a positive value in FIG.

  As for the voltage change after the end of charging / discharging, the voltage immediately after the end of charging / discharging decreases as the immediately preceding discharge capacity increases, and the subsequent voltage increase increases and the increase period also increases. Thus, the voltage change after the end of charge / discharge is greatly different depending on the charge / discharge history immediately before the end of charge / discharge, and the stable voltage 20 is estimated from the difference from the stable voltage 20, that is, the voltages 21 to 25 having the influence of polarization. The voltage correction values for doing so differ greatly. Since the secondary battery before the end of charging / discharging is considered to perform extremely various charging / discharging, it is extremely difficult to determine the voltage correction value according to the history before the end of charging / discharging.

  However, it can be seen from FIG. 2 that when a certain amount of time (TM2) has elapsed since the end of charging / discharging, the voltage changes in a direction in which the voltage decreases almost uniformly. The voltage decrease rate increases as the difference from the stable voltage 20 increases. Therefore, the correlation between the change rate m of the voltage changes 21 to 25 when a predetermined time (TM1) after the end of charge / discharge has elapsed and the voltage correction value ΔV which is the difference between the stable voltage 20 at that time is shown in FIG. Reference numeral 10 indicates. FIG. 1 shows that the voltage correction value ΔV changes uniquely with the voltage change rate m.

  Therefore, in the state detection method of the present embodiment, the voltage correction value ΔV is calculated or estimated using the voltage characteristics of the secondary battery as described above. That is, the voltage change rate m at a predetermined elapsed time is calculated from the voltage measurement value after the end of charge / discharge, and the voltage correction value ΔV is obtained from the voltage change rate m calculated using the correlation shown in FIG. As shown in FIG. 2, the predetermined elapsed time for calculating the voltage change rate m needs to be longer than at least the elapsed time TM2 at which the voltage decreases almost uniformly. The longer the predetermined elapsed time is, the smaller the influence of the charging / discharging history before the end of charging / discharging is, but the voltage change rate m is also decreased, and there is a possibility that the accuracy is lowered, and it takes time until the voltage correction value ΔV is calculated. There is also a problem that it takes too much.

  Therefore, in the present embodiment, an elapsed time is determined in advance so that the voltage can be reduced uniformly and the accuracy of the voltage change rate m can be secured to some extent (suitable for applying the correlation of FIG. 1). 1 measurement time TM1. After charge / discharge is completed, a plurality of voltage measurements are acquired for a period until the first measurement time TM1 elapses. When the first measurement time TM1 is reached, the voltage change rate m is calculated at that time, and the calculated voltage The voltage correction value ΔV is calculated from the change rate m using the correlation shown in FIG.

  Alternatively, an elapsed time TM2 in which the voltage decreases substantially uniformly after the end of charge / discharge is set in advance as the second measurement time, and the voltage from the second measurement time TM2 to the first measurement time TM1 Every time the measurement value is acquired, the voltage change rate m at the time when the measurement time TM1 has elapsed is estimated and updated, and the voltage correction value ΔV is estimated from the estimated voltage change rate m using the correlation shown in FIG. Thereby, the estimated value of voltage correction value (DELTA) V can be obtained from the time of 2nd measurement time TM2 before 1st measurement time TM1 passes.

  Further, even when charging / discharging is resumed in the middle of reaching the first measurement time TM1 after the second measurement time TM2 has elapsed, the voltage change rate m updated immediately before the resumption of charge / discharge is used. The correction value ΔV can be estimated. When the voltage correction value ΔV is estimated as described above, the stable voltage can be estimated by correcting the voltage estimation value when the measurement time TM1 has elapsed.

  In this embodiment, the voltage change rate m is approximated by a voltage approximation expression using a predetermined function in order to obtain the voltage change rate m from the voltage change with time after the end of charging and discharging as shown in FIG. A voltage change rate calculation formula for calculating the voltage change rate m is derived from the voltage approximation formula. Specifically, the first derivative of the voltage approximation formula can be used as the voltage change rate calculation formula. When the elapsed time from the end of charge / discharge is t and the voltage approximation formula is FV (t), the voltage approximation formula FV (t) can be expressed as follows using an exponential function, for example.

FV (t) = A1 * exp (A5 * t) + A2 * exp (A6 * t)
+ A3 * exp (A7 * t) + A4 * exp (A8 * t) + A9 (1)
Here, A1 to A9 are fitting parameters.

When the voltage approximation formula is defined as described above, the voltage change rate calculation formula can be the first derivative of the voltage approximation formula FV (t) shown below.
FV ′ (t) = A1 * A5 * exp (A5 * t)
+ A2 * A6 * exp (A6 * t)
+ A3 * A7 * exp (A7 * t)
+ A4 * A8 * exp (A8 * t) (2)
Accordingly, the voltage change rate m in the first measurement time TM1 is calculated by the following equation.
m = FV ′ (TM1) (3)

  The voltage changes 21 to 25 shown in FIG. 2 are fitted using the voltage approximation formulas FV (t), respectively, and the coefficients A1 to A8 determined respectively are used at the time t of the first derivative FV ′ (t). Each voltage change rate m is calculated by substituting the first measurement time TM1. The point indicated by reference numeral 10 in FIG. 1 indicates the correlation between the voltage change rate m and the voltage correction value ΔV when the first measurement time TM1 = 1770 seconds.

  The correlation between the voltage correction value ΔV and the voltage change rate m shown in FIG. 1 can also be expressed by the first correlation equation using a predetermined function. When the first correlation equation is FD (m), FD (m) can be determined by fitting the actual measurement data 10 shown in FIG. 1 using a predetermined function. In FIG. 1, the first correlation equation FD (m) determined by fitting is indicated by reference numeral 11. An exponential function, a polynomial, or the like can be used as a function that forms the first correlation equation FD (m).

  The first correlation equation FD (m) is preferably formed so as to include at least one of the temperature Temp and the charging rate SOC of the secondary battery as a variable. In particular, the voltage change shown in FIG. 2 is faster when the temperature Temp of the secondary battery is high, and is slower when the temperature Temp is low. As a result, the correlation between the voltage change rate m shown in FIG. 1 and the voltage correction value ΔV also differs. The example shown in FIG. 1 is when the temperature Temp of the secondary battery is 25 ° C. Since the voltage change speed varies depending on the temperature Temp, the first measurement time TM1 (and the second measurement time TM2) for calculating the voltage change rate m is also preferably changed depending on the temperature Temp.

  When the first correlation equation FD (m) includes the charging rate SOC of the secondary battery as a variable, the charging rate SOC used for calculating the first correlation equation FD (m) SOC can be used.

  The fitting of the voltage approximate expression FV (t) can be performed using all the voltage measurement values acquired so far when the first measurement time TM1 is reached after the end of charge / discharge, or the second measurement time TM2 Each time a voltage measurement value is acquired after the elapse of time, the voltage measurement value acquired so far may be used for sequential fitting. When sequential fitting is performed each time a voltage measurement value is acquired, the voltage change rate m at the time when the measurement time TM1 has elapsed is estimated even before the first measurement time TM1 is reached, and the first voltage change rate m is estimated from the estimated voltage change rate m. The voltage correction value at the time when the measurement time TM1 has elapsed can be estimated using the correlation equation.

  The voltage change rate m in the first measurement time TM1 can be calculated from, for example, the first measurement time TM1 and a plurality of voltage measurement values before and after the first measurement time TM1. However, the voltage change is small at the time of the first measurement time TM1, and the voltage measurement error greatly affects the calculation result of the voltage change rate. On the other hand, when fitting the voltage approximation equation with high accuracy using the measurement data acquired during the first measurement time TM1 and calculating the voltage change rate using this, the influence of the voltage measurement error And the voltage change rate can be calculated with high accuracy. Further, as described above, when the fitting of the voltage approximation formula is sequentially performed, the voltage correction value ΔV can be estimated even before the first measurement time TM1 is reached.

  As described above, regardless of the charge / discharge history before the end of charge / discharge, in any case of the voltage changes 21 to 25 shown in FIG. 2, the voltage monotonously after at least the second measurement time TM2 has elapsed. It decreases and approaches the stable voltage 20. Then, when the time-dependent change of the voltage correction value ΔV after the time when the first measurement time TM1 is reached is normalized by the voltage correction value ΔV at the same point, the attenuation curve as shown in FIG. Draw.

  In the present embodiment, the attenuation curve shown in FIG. 3 is represented by an attenuation calculation expression G (t) (reference numeral 30), and when the voltage correction value ΔV is calculated when the first measurement time TM1 has elapsed, the subsequent voltage correction values are calculated. ΔV is calculated using the attenuation calculation formula G (t). FIG. 3 shows the change over time of the voltage correction value when the horizontal axis is the elapsed time after the first measurement time TM1 and the vertical axis is the normalized voltage correction value ΔV when the first measurement time TM1 has elapsed. ing.

The voltage correction value ΔV after the first measurement time TM1 has elapsed is calculated using the same attenuation calculation formula G (t) regardless of the magnitude of the voltage correction value ΔV calculated when the first measurement time TM1 has elapsed. However, when the temperature Temp of the secondary battery changes, the speed of attenuation of the voltage correction value ΔV changes, so the same attenuation calculation expression G (t) cannot be used. Therefore, in the present embodiment, the attenuation calculation equation G (t) includes the secondary battery temperature Temp as a variable, and the voltage correction value ΔV at the subsequent elapsed time t from the voltage correction value ΔV when the first measurement time TM1 has elapsed. ΔV ′ is calculated by the following equation.
ΔV ′ = ΔV * G (t) (4)

The attenuation calculation expression G (t) shown in FIG. 3 can be formed as the following expression using an exponential function, for example.
G (t) = exp (B * t) (5)
In this case, the time t does not necessarily have to be an elapsed time from the time when the first measurement time TM1 has elapsed. Then, when the voltage correction value ΔV ′ is calculated, the voltage correction value ΔV ″ when the time t2 further elapses can be calculated with ΔV in Expression (4) as ΔV ′ and t as t2.

  The voltage correction value ΔV calculated as described above can be used to obtain the stable voltage of the secondary battery. The stable voltage is obtained by subtracting the voltage correction value ΔV from the voltage measurement value at the time when the voltage correction value ΔV is calculated. Moreover, since the stable voltage has a predetermined correlation with the charging rate SOC of the secondary battery, the charging rate SOC of the secondary battery can be estimated from the stable voltage using a predetermined correlation equation. As a method for detecting the state of the secondary battery using this SOC, it is possible to determine whether the charging rate is properly maintained or whether charging is required.

  There is a correlation as shown in FIG. 4 between the stable voltage (Vt) and the charging rate SOC. This correlation is expressed using the second correlation equation FS (Vt), and the charging rate SOC is calculated by substituting the stable voltage Vt obtained above into the second correlation equation FS (Vt). Then, the calculated SOC is compared with a predetermined threshold SOCth. When the SOC is equal to or higher than the SOCth, it is determined that an appropriate charging rate is maintained. When the SOC is lower than the SOCth, it is determined that charging is necessary. it can.

  The process flow of the secondary battery state detection method of the present embodiment will be described with reference to the flowchart shown in FIG. The secondary battery state detection method of the present embodiment calculates a voltage correction value ΔV that is the difference between the measured voltage and the stable voltage at the time when the first measurement time TM1 has elapsed since the end of charge / discharge. The voltage correction value ΔV after the first measurement time TM1 can be calculated by multiplying the previously calculated voltage correction value ΔV by an attenuation calculation expression G (t) using the subsequent elapsed time t.

  In the processing flow shown in FIG. 5, processing is performed periodically at time intervals ΔT. First, in step S1, an elapsed time T from the end of charge / discharge is initialized to zero. In the next step S2, a voltage measurement value Vm and a current measurement value Im of the secondary battery are obtained from a predetermined state detection sensor.

  In step S3, it is determined whether or not the absolute value | Im | of the current measurement value is larger than a predetermined threshold value Ith. If the absolute value | Im | is larger than the predetermined threshold value Ith, charging / discharging is resumed. Determine and return to the initialization of step S1. On the other hand, if the absolute value | Im | is equal to or smaller than the predetermined threshold value Ith, it is determined that charging / discharging is in a resting state (a state where charging / discharging is substantially not performed), and the process proceeds to step S4.

  In step S4, the time interval ΔT is added to the elapsed time T to calculate the elapsed time T from the end of charge / discharge. In subsequent step S5, it is determined whether or not the elapsed time T has reached the first measurement time TM1, and if the elapsed time T has not reached the first measurement time TM1, the process proceeds to step S6. When the elapsed time T matches the first measurement time TM1, the process proceeds to step S7, and when the elapsed time T exceeds the first measurement time TM1, the process proceeds to step S9.

  When the process proceeds to step S6 in the determination of step S5, the voltage measurement value Vm is stored and the process proceeds to the next cycle. When the process proceeds to step S7, the voltage approximate expression FV (T) is fitted using the plurality of voltage measurement values stored after the completion of charge / discharge in step S7. In the subsequent step S8, the voltage change rate m is calculated by substituting the first measurement time TM1 into the first derivative FV ′ (T) of the fitted voltage approximate expression FV (T). Furthermore, the voltage correction value ΔV is calculated by substituting the calculated voltage change rate m into the first correlation equation FD (m).

  When the process proceeds to step S9 in the determination of step S5, the voltage correction value attenuated during the time interval ΔT by multiplying the voltage correction value ΔV calculated in the previous cycle by the attenuation calculation formula G (ΔT). ΔV is calculated.

  When the voltage correction value ΔV is calculated in step S8 or step S9, the stable voltage Vt is calculated by subtracting the voltage correction value ΔV from the voltage measurement value Vm in step S10. Further, the charging rate SOC is estimated by substituting this stable voltage Vt into the second correlation equation FS (Vt). In step S11, the estimated charging rate SOC is compared with a predetermined threshold SOCth, and when the SOC is greater than SOCth, it is determined that the secondary battery is in a good state of charge (step S12). It is determined that charging is necessary (step S13). Thereafter, the process proceeds to the next cycle.

  Although the time interval ΔT is constant here, it is preferable that ΔT is appropriately changed according to the flow because the optimal time interval differs depending on the flow of processing. As an example, the time interval for determining whether or not it is in a resting state in step S3 is set to 1 second or less, and the time interval for storing the voltage measurement value Vm for fitting (step S6) is set to about several tens of seconds to 1 minute. The time interval for updating the voltage correction value ΔV (step S9) can be about 1 hour.

  A battery state detection device and a battery power supply system according to an embodiment of the present invention will be described below with reference to FIG. The battery power supply system 100 of the present embodiment includes a battery 101 and a battery state detection device 110 of the present embodiment. Further, the battery state detection device 110 according to the present embodiment includes a state detection sensor 111, an arithmetic processing unit 112, and a storage unit 113.

  The state detection sensor 111 includes a voltage sensor 111a, a current sensor 111b, and a temperature sensor 111c that measure the voltage, current, and temperature of the battery 101, respectively. The storage unit 113 stores in advance the first correlation equation FD (m), the second correlation equation FS (Vt), the attenuation function G (t), and the like necessary for the calculation in the calculation processing unit 112.

  The arithmetic processing unit 112 reads the first correlation equation FD (m), the second correlation equation FS (Vt), the attenuation function G (t), and the like from the storage unit 113, and then executes the above-described operation with the unit time ΔT as a cycle. The process by the battery state detection method of a form is performed. That is, for each unit time ΔT, the voltage, current, and the like of the battery 101 are read from the state detection sensor 111, and the state of charge is detected by estimating the charge rate SOC of the battery 101 according to the processing procedure shown in FIG. Thereby, it becomes possible to detect the shortage of charging of the battery 101 at an early stage.

  In addition, the description in this Embodiment shows an example of the state detection method of the secondary battery which concerns on this invention, a state detection apparatus, and a secondary battery power supply system, It is not limited to this. The detailed configuration and detailed operation of the secondary battery state detection method and the like in the present embodiment can be changed as appropriate without departing from the spirit of the present invention.

It is a graph which shows the correlation with the voltage change rate used with the state detection method of the secondary battery which concerns on embodiment of this invention, and a voltage correction value. It is a graph which shows an example of the voltage change of the secondary battery after completion | finish of charging / discharging. It is a graph which shows an example of the change of the voltage correction value after the time of predetermined time having passed since the end of charging / discharging. It is a graph which shows an example of the correlation of the stable voltage and charging rate of a secondary battery. It is a flowchart which shows the flow of a process of the state detection method of the secondary battery which concerns on embodiment. It is a block diagram which shows the schematic structure of the secondary battery state detection apparatus and secondary battery power supply system which concern on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Secondary battery power supply system 101 Secondary battery 110 Secondary battery state detection apparatus 111 State detection sensor 111a Voltage sensor 111b Current sensor 111c Temperature sensor 112 Operation processing part 113 Storage part

Claims (12)

A state detection method for a secondary battery that performs state detection by estimating a voltage correction value for correcting a voltage change due to polarization of the secondary battery,
Obtaining a plurality of measured voltage values of the secondary battery in a period from the end of charging / discharging of the secondary battery until a predetermined voltage measurement time elapses;
A coefficient of a voltage approximation formula for calculating the voltage of the secondary battery with the elapsed time from the end of charge / discharge as a variable is determined using the plurality of voltage measurement values,
Deriving a voltage change rate calculation formula for calculating the voltage change rate of the secondary battery from the voltage approximation formula to calculate the voltage change rate of the secondary battery at the time when the voltage measurement time has elapsed,
A method for detecting a state of a secondary battery, wherein the voltage correction value is calculated by substituting the voltage change rate into a first correlation equation representing a correlation between a voltage change rate and a voltage correction value created in advance. The method for detecting a state of a secondary battery according to claim 1, wherein the coefficient of the voltage approximation formula is sequentially calculated and determined each time the voltage measurement value is acquired. The secondary battery state detection method according to claim 1, wherein the voltage change rate calculation formula is a first derivative of the voltage approximation formula. The voltage measurement time is either a predetermined first voltage measurement time TM1 or an elapsed time until charging / discharging is started again after a predetermined second measurement time TM2 (<TM1). The method for detecting a state of a secondary battery according to any one of claims 1 to 3, wherein the time is short. The secondary correlation according to any one of claims 1 to 4, wherein the first correlation equation includes at least one of a temperature and a charge rate SOC of the secondary battery as a variable. Battery state detection method. The state detection method for a secondary battery according to claim 5, wherein the charge rate SOC calculated immediately before is used for the calculation of the first correlation equation. If the absolute value of the current measurement value of the secondary battery is not more than a predetermined current threshold even after the voltage measurement time has elapsed, a predetermined attenuation calculation that is a function of the elapsed time since the previous voltage correction value was calculated It updates using a type | formula. The state detection method of the secondary battery of any one of the Claims 1 thru | or 6 characterized by the above-mentioned. The secondary battery state detection method according to claim 7, wherein the attenuation calculation formula is further a function of the temperature of the secondary battery. The secondary battery state detection method according to any one of claims 1 to 8, wherein a stable voltage of the secondary battery is estimated using the voltage correction value as at least one correction amount. The charging rate SOC and the stable voltage of the secondary battery are expressed in advance by a second correlation equation, and the charging rate SOC is estimated by substituting the calculated stable voltage into the second correlation equation. The method for detecting a state of a secondary battery according to claim 9. A state detection sensor for measuring the voltage, current, and temperature of the secondary battery;
A storage unit that stores in advance a first correlation equation representing a correlation between a voltage change rate of the secondary battery and a voltage correction value;
A plurality of voltage measurement values are acquired from the state detection sensor in a period from the end of charging / discharging of the secondary battery until a predetermined voltage measurement time elapses, and the secondary time using the elapsed time from the end of charging / discharging as a variable A coefficient of a voltage approximation formula for calculating a voltage of the battery is determined using the plurality of voltage measurement values, and a voltage change rate calculation formula for calculating a voltage change rate of the secondary battery is derived from the voltage approximation formula, An arithmetic processing unit that calculates a voltage change rate of the secondary battery at the time when a voltage measurement time elapses, and calculates the voltage correction value by substituting the voltage change rate into the first correlation equation. Secondary battery state detection device. A secondary battery power supply system comprising: the secondary battery; and the secondary battery state detection device according to claim 11.

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