JP2010060300A - Method of detecting charged state of secondary battery, and charged state detector and equipment having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely detect a charged state of a secondary battery used by repeating charging/discharging in a vehicle, or the like. <P>SOLUTION: A detection method of a charged state of a secondary battery detects a charged state (SOC) of the secondary battery according to the charged capacity (CHGCAP) obtained by integrating a charge/discharge current to the secondary battery charged and discharged repeatedly in a vehicle, or the like in time and the discharged capacity (DISCAP). In the detection method, charging efficiency (η) is obtained from voltage (V) and internal resistance (DC-IR) of the secondary battery and the charged capacity (CHGCAP) is corrected by the charging efficiency (η), thus precisely detecting the charged state of the secondary battery. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for detecting a state of charge of a secondary battery, a state of charge detection device, and a device using this device.

  Various secondary batteries such as lead storage batteries, Ni-MH batteries, and Li secondary batteries are used as power sources for backup, automobiles, and various electric vehicles. In order to inform the users of the devices using these secondary batteries of the usable time or usable period of the devices, and further to recover the regenerative power to the secondary batteries as in recent hybrid vehicles. Various methods for detecting the state of charge (SOC) of the secondary battery have been proposed in order to control the state of charge (SOC) to an intermediate state such as 50 to 70%.

  Here, the state of charge (SOC) is a parameter commonly used in various secondary batteries including lead-acid batteries, and the secondary battery capacity and remaining capacity. The ratio is generally expressed as a percentage. That is, the SOC when the secondary battery is in a fully charged state is 100%, and the SOC in a fully discharged state is expressed as 0%. The amount of electricity discharged during complete discharge differs depending on the discharge current and the discharge end voltage, and therefore the designer appropriately sets the discharge pattern of the device used, its current value, and the discharge end voltage value. The SOC when the secondary battery is completely discharged under the set discharge conditions is defined as 0%.

  For example, the SOC of a lead storage battery has a strong correlation with the sulfuric acid concentration in the electrolyte solution inside the battery and the open circuit voltage, based on the principle of operation of the lead storage battery. In addition, other Ni-MH secondary batteries and Li secondary batteries also have such a correlation because the correlation between the open circuit voltage and the SOC, in particular, the Li secondary battery has a strong correlation between the open circuit voltage and the SOC. Various SOC detection methods have been proposed. Further, by detecting the charging current and discharging current of the secondary battery and integrating them with time, the amount of charge electricity and the amount of discharge electricity are obtained, and the SOC of the secondary battery is directly calculated from these balances. A method to find it has been proposed.

For example, Patent Document 1 discloses a method for obtaining a remaining capacity of a battery from an electrolyte specific gravity of a lead storage battery and an integrated value of charge / discharge current. In particular, it has been shown that a value obtained by multiplying a charging current value by a time integrated value of a charging current value is adopted for the amount of charging electricity. This charging efficiency is obtained in advance from the relationship between the SOC and temperature and the charging efficiency. It is shown that it is obtained by referring to a table that has been stored.
JP-A-6-281711

  However, in the method of Patent Document 1, the concentration of sulfuric acid in the electrolytic solution is not uniform immediately after charge / discharge of the lead storage battery or in a state where the electrolytic solution is stratified, and as a result, there is a problem that the SOC cannot be accurately detected. . In addition, although the charging efficiency is considered in the detection of the SOC, there is a correlation between the charging efficiency and the SOC and the temperature with respect to the method for obtaining the charging efficiency, but the accuracy of the charging efficiency obtained from the SOC and the temperature alone is It was not sufficient and could not be said to be sufficient for more accurate SOC detection. Moreover, such a subject was a subject common also to other secondary batteries other than lead acid battery. The present invention provides a method for detecting the state of charge of a secondary battery that solves such problems and further improves detection accuracy.

  In order to solve the above-described problem, the invention according to claim 1 of the present invention provides a charge electric quantity (CHGCAP) obtained by integrating a charge / discharge current to a secondary battery that is repeatedly charged / discharged over time, and A method for detecting a state of charge of a secondary battery from a quantity of discharged electricity (DISCAP) to detect a state of charge (SOC) of the secondary battery, the voltage V of the secondary battery and an internal resistance (DC-IR) A method for detecting the state of charge of a secondary battery, characterized in that charging efficiency (η) is obtained and the amount of charged electricity (CHGCAP) is corrected by the charging efficiency (η).

  Further, the invention according to claim 2 of the present invention is the method for detecting the state of charge of the secondary battery according to claim 1, wherein the DC internal resistance obtained by the preset voltage (V) of the secondary battery and the DC method is used. From the table showing the relationship between (DC-IR) and charging efficiency (η), the voltage (V) and the DC internal resistance (DC-IR) are obtained, and the charging efficiency (η) is determined with reference to the table. It is characterized by obtaining.

  Moreover, the invention according to claim 3 of the present invention is the secondary battery charge state detection method according to any one of claims 1 to 2, wherein the charge / discharge current and battery voltage of the secondary battery are measured at a predetermined time interval Δt. The charge current I when the current to the secondary battery transitions from discharge to charge and the battery voltage (V) at that time are measured as a pseudo open circuit voltage OCV, and the charge current I and the At least two pairs of pseudo open circuit voltage (OCV) data pairs (I, OCV) are measured, and the internal current is determined from the relationship between the charging current I obtained from the data pairs and the pseudo open circuit voltage (OCV). The resistance (DC-IR) is obtained.

  According to a fourth aspect of the present invention, in the method for detecting a charged state of the secondary battery according to any one of the first to second aspects, the charge / discharge current and the battery voltage of the secondary battery are measured at a predetermined time interval Δt. The charge current obtained by measuring the charge current I when the current to the secondary battery transitions from discharge to charge and the battery voltage (V) at that time as a pseudo open circuit voltage OCV. I and the pseudo open circuit voltage (OCV) data pair (I, OCV), the charging current I ′ measured after the predetermined time interval Δt of the data pair, and the battery voltage (V ′ at that time) ) As the above-described pseudo open circuit voltage OCV ′, and the internal resistance based on the relationship between the charging current I obtained from the data pair (I ′, OCV ′) obtained from the pseudo open circuit voltage OCV ′ and the pseudo open circuit voltage (OCV). (DC-IR) is obtained.

  Further, according to a fifth aspect of the present invention, in the method for detecting a charged state of a secondary battery according to any one of the first to fourth aspects, the state of charge (SOC) is determined by a self-discharge amount that is generated while charging and discharging are not performed. ) Is corrected.

  Further, the invention according to claim 6 of the present invention is the secondary battery charge state detection method according to claim 5, wherein the temperature (T) of the secondary battery or the ambient temperature (Ta) around the secondary battery. The self-discharge amount is corrected by at least one of the above.

  Further, according to a seventh aspect of the present invention, in the method for detecting a charged state of the secondary battery according to any one of the first to sixth aspects, the temperature (T) of the secondary battery or the ambient temperature (Ta ) Is used to correct the charging efficiency (η).

  Moreover, the invention which concerns on Claim 8 of this invention shows the charge condition detection apparatus of the secondary battery which detects a charge condition by the charge condition detection method of the secondary battery of Claims 1-7.

  Further, an invention according to claim 9 of the present invention shows an apparatus including the secondary battery charge state detection device according to claim 8.

  According to the first to eighth aspects of the present invention, there is a remarkable effect that the detection accuracy of the charged state of the secondary battery can be greatly improved. According to the invention of claim 9 of the present invention, the secondary battery charge state detection device of the present invention is used for a vehicle, a power supply device, etc. Since the SOC control is possible, it is possible to improve the fuel efficiency of the vehicle. In addition, by using the charge state detection device of the present invention in a power supply device that combines a secondary battery with a wind power generator or another independent power source such as a fuel cell, the output from the power supply device can be stabilized. Can do.

(First embodiment of the present invention)
The secondary battery charge state detection method according to the present invention detects the SOC of the secondary battery by integrating the charging current and the discharge current flowing in the secondary battery over time.

  When charging a lead storage battery, a Ni-MH battery, or a Li secondary battery, the charging efficiency decreases due to the decomposition reaction of the electrolyte of the charging current, and the change in the electrode density of the negative electrode in the Li secondary battery. Therefore, the amount of charge (CHGCAP) spent for charging the active material is smaller than the amount of charge (CAP) obtained by actually integrating the charge current. Therefore, even if the charging current is integrated, the amount of charged electricity Qt actually consumed for charging the active material cannot be detected, so that the SOC detection accuracy decreases.

In the present invention, (CHGCAP / CAP) is obtained as the charging efficiency (η), and the charging electric quantity (CAP) obtained as the integrated value of the charging current is corrected by this charging efficiency (η). (CAP) multiplied by charging efficiency (η) to actually charge the active material for the charging reaction (Li ⁺ ion or H ⁺ ion transfer in Li secondary battery or Ni-MH battery) The quantity of electricity CHGCAP is obtained.

  The feature of the present invention is a method for obtaining the charging efficiency (η), and in the present invention, the charging efficiency (η) is obtained from the battery voltage V and the internal resistance during charging (DC-IR). It is in. In the present invention, DC-IR indicates internal resistance measured by the direct current method, and can be obtained from the voltage and current of the secondary battery or the amount of change thereof using Ohm's law.

  Hereinafter, in this embodiment, an example in which a lead storage battery (hereinafter referred to as a battery) is used as the secondary battery will be described.

  First, in step (S0) of the flow shown in FIG. 1, the battery capacity (Q) and SOC initial value in the SOC = 100% state of the battery to be measured are set. For example, the battery capacity (Q) can be measured by setting the battery to SOC = 100% with the battery fully charged, discharging from the fully charged state until the battery is fully discharged (SOC = 0%). Thereafter, if the measurement is started with the battery charged to a fully charged state (SOC = 100%), the initial state SOC may be set to 100%. Also, the SOC is not limited to 100%, and if the amount of electricity corresponding to 0.5 × Q is discharged from the SOC 100% state, the SOC is 50%. Therefore, if the SOC is measured from this state, the SOC = 50% is sufficient. In any case, it is most convenient to supplement the measurement battery to a fully charged state and set the initial SOC = 100%.

Next, CAP, DISCAP, and CHGCAP described later are initialized, that is, CAP = 0, DISCAP = 0, and CHGCAP = 0. Further, the charging efficiency (η), that is, the ratio of the amount of electricity A that is actually charged to the active material and the amount of electricity B that is energized to charge the battery, obtained by the integrated value of the charging current value (A / B) is the charging efficiency (η), and its initial value η ₀ is set. In many cases, the charging efficiency (η) is a value less than 1, but the initial value η ₀ can be set to 1 for convenience. Further, it is not essential to set η ₀ to 1, and it can be set to a value such as 0.95, for example.

  As the charging efficiency (η), a percentage of the ratio (A / B) may be used. However, the charging efficiency (η) in this specification uses the value of the ratio (A / B). Η is 0 or more and 1 or less.

  Next, the charge / discharge current (I) and the battery voltage (V) are measured (step (S1)), and the absolute value | I | of the charge / discharge current is multiplied by the unit time Δt to obtain | I | X Δt is set as CAP, and (CAP = | I | × Δt) is stored in a storage unit such as a memory or a hard disk ((S2)).

  The unit time Δt for the measurement is preferably as short as possible, but is limited by the processing speed of the microcomputer executing the flow shown in FIG. Can be set within the range.

  Next, based on the sign of the current (I) measured in step (S1), it is determined whether the current I is a charging current, a discharging current, or I = 0. It should be noted that I> 0 may be charged and I <0 may be discharged, but the opposite is true for control, that is, I <0 is charged and I> 0 is charged. Based on the above, it is only necessary to determine whether the battery has been discharged or charged.

  In the above-described step (S3), when the battery is discharged (not including 0) by the sign of the current I (not including 0), the CAP measured in step (S2) is defined as the discharge electricity quantity DISCAP ( DISCAP = CAP), and 0 is substituted into the charged electricity amount CHGCAP (CHGCAP = 0) ((S10)).

  Thereafter, the retained SOC is updated. That is, in step (S11), arithmetic processing is performed according to the equation shown in Equation 1.

  Then, the updated SOC, that is, the SOC on the left side in the above equation 1 is output as the current SOC (step (S12)). In addition, when displaying the SOC at 100%, it is necessary to multiply 100 in the second term of the right side of Equation 1 by (CHGCAP-DISCAP) / Q, but as the SOC notation, the fully charged SOC is 1 When the SOC in the fully discharged state is set to 0, (CHGCAP-DISCAP) / Q may be multiplied by 1. Such a notation method of the SOC can be appropriately selected.

  And from step (S12), it returns to step (S1) again, and the electric current (I) and battery voltage (V) which flow into a battery again are measured. In step (S2), the step current (I) is multiplied by the unit time Δt in the same manner as described above to obtain CAP. Here, since the case where the current (I) is a discharge is described above, the case where the current (I) is 0 will be described below.

  When I = 0, since self-discharge proceeds during unit time Δt, the amount of decrease in SOC due to self-discharge can be calculated as DISCAP as shown in Equation 2 (step (S10-2)). )).

  In step (S10-2), 0 is assigned to CHGCAP simultaneously with the setting of DISCAP (CHGCAP = 0). Then, after step (S10-2) is completed, the process proceeds to step (S11), and the updated SOC is calculated as shown in Equation 1 above. After the process proceeds to (S12), the updated SOC is output. After (step (S12)), it returns to step (S1) again.

Needless to say, by providing the step (S10-2) when I = 0, the self-discharge when the battery is left for a long time can be reflected in the SOC, which is preferable for more accurate SOC determination. For example, in a lead storage battery, the capacity decreases due to self-discharge, and the SOC decreases by about 0.1% per day. Since such a self-discharge amount varies depending on the type of battery, a constant k may be set according to the type of battery. For example, as described above, the k value when the SOC is reduced by 0.1% due to the amount of self-discharge per day is set to a value of 1.157 × 10 ⁻⁹ msec ⁻¹ .

  Furthermore, the self-discharge rate is accelerated by an increase in battery temperature T or ambient temperature Ta. For example, in a lead storage battery, when the rate of decrease in SOC due to self-discharge in a 25 ° C. atmosphere is 0.1% / day, the self-discharge rate becomes 1.9 to 2 times as the temperature increases by 10 ° C. That is, since the self-discharge rate increases exponentially with respect to the temperature, the battery temperature T or the ambient temperature Ta around the battery can be measured, and the k value can be corrected based on the temperature T or Ta. More preferred. In addition, this is not limited to lead-acid batteries, and the same applies to other secondary batteries.

  In addition, the structure which provides the step (S10-2) which calculates the fall of SOC which arises by the self discharge in this I = 0 is not an essential structure in this invention. The configuration in which the step (S10-2) is provided is preferably applied in a case where the rest period is long in addition to charging / discharging and the self-discharge is so large that the SOC detection cannot be ignored. For example, this applies to automobiles, HEVs, and EVs. In these applications, by adding the configuration of step (S10-2), it is possible to accurately correct the SOC decrease due to self-discharge and to further increase the SOC detection accuracy. In particular, since the Ni-MH battery and the Ni-Cd battery have a larger self-discharge amount in the same period than other secondary batteries, by using the configuration of step (S10-2), More accurate SOC detection is possible.

  On the other hand, batteries used for power supply applications that are combined with independent power sources such as wind power generation, fuel cells, gas turbine power generation, etc., are always charged and discharged, and the downtime is not so long. In some cases, it is not necessary to consider the amount of discharge. In such a case, step (S10-2) may be omitted. In this case, in step (S3), it may be determined that I = 0 is discharged and the process proceeds to step (S10).

  Next, when it is determined in step (S3) that the battery is charged, the process proceeds from step (S3) to step (S4). In step (S4), it is determined in step (S3) in the previous flow whether the discharge is determined, the charge is determined, or the first charge is performed.

  In step (S4), when discharge is detected in step (S3) of the previous flow, the process proceeds from step (S4) to step (S5). In step (S5), battery voltage value V stored in step (S1) is set to pseudo open circuit voltage OCV. The OCV detected for the first time is referred to as OCV1 for convenience, and the battery voltage value V is substituted into OCV1, that is, OCV1 = V. Note that the current value I at this time is the charging current value I1 obtained for the first time, which is I1 for convenience. That is, I1 = I. And I1 and OCV1 are memorize | stored by a memory | storage means as a data pair (I1, OCV1). When the previous flow is discharging and the current flow is charging, the current I used for charging is a sufficiently small value, and the voltage value V at this time is regarded as a pseudo open circuit voltage value. In the present invention, the voltage value V at this time is set to the pseudo open circuit voltage OCV.

  When step (S5) is the first time after completion of step (S5), the data pair of I and OCV is in a state where one data pair of (I1, OCV1) has been acquired. In this embodiment, in order to detect DC-IR, as described later, at least two (I, OCV) data pairs are required. Therefore, when step (S5) is the first time, as described above, 1 It is impossible to detect DC-IR with the data of one OCV.

Therefore, in the embodiment of the present invention, when step (S5) is the first time (YES in step (S5-2)), the charging efficiency (η) is the initial value of η set in step (S0), that is, The above-described η ₀ (for example, η ₀ = 1) is employed (step (S6)). That is, η = η ₀ is set. In the actual flow, after step (S5) is completed, the process proceeds to step (S5-2). When step (S5-2) is the first time, the process proceeds to step (S6), and η = η ₀ You only have to set it.

  Then, the process proceeds from step (S6) to step (S7). In step (S6) to step (S7), calculation of CHGCAP and initialization of DISCAP are performed according to the following equation (3).

  The CAP in Equation 3 is the CAP obtained as | I | × Δt in step (S2). After step (S7) is completed, the process proceeds to step (S11) described above to update the SOC, and then outputs the updated SOC in step (S12). Then, as described above, step (S12) is followed by step. Return to (S1).

  Next, after shifting to step (S2), the determination of discharging / charging is performed again in step (S3). Here, for convenience of description of the embodiment, when the determination of discharging is made in step (S3) in the current flow after the determination of discharging is made in step (S3) in the previous flow, that is, the step ( A case will be described in which it is determined in S4) that “previous time is discharging”.

  In such a case, the present invention shifts from step (S4) to step (S5). In step (S5), the current I and the voltage V measured in step (S1) are changed to the current I2 and the pseudo open circuit voltage OCV2, respectively. And

  Since the current I2 is also a current immediately after shifting from discharging to charging, it is close to 0 like the current I1, and the OCV2 that is the voltage at this time can be handled as a pseudo open circuit voltage.

  Therefore, after the start of (S0) of the SOC detection flow shown in FIG. 1, the charging performed after the discharge is performed twice, so that the charging current I close to 0 and the current − that can be regarded as the open circuit voltage OCV− Two pairs of voltage data are obtained, namely (I1, OCV1) and (I2, OCV2). In step (S5), at least the data pair at the time of the previous charge is stored. Then, the data pair (I1, OCV1) referenced from the stored data and the data pair (I2, OCV2) stored in step (S1) are passed through the next step (S5-2) to step (S6-2). To provide.

  Then, in step (S6-2), if these two pairs of data are plotted on a graph with the current I on the horizontal axis and the pseudo open circuit voltage OCV on the vertical axis as shown in FIG. A DC-IR value that is an internal resistance value obtained by a direct current method can be obtained as an absolute value. For the sake of convenience, the graph of FIG. 2 is shown, but actually, there is no need to draw the graph, and the DC-IR value can be obtained by the calculation shown in the following equation 4. Then, the obtained DC-IR value is stored (step (S6-2)).

  In this example, the data pair of the current I and the pseudo-open circuit voltage OCV is two pairs. However, the data pair is DC or the slope of a straight line connecting these data pairs by the least square method or the like with three or more pairs. -IR value can also be calculated, and the accuracy of DC-IR can be further increased. However, in that case, in step (S5), there is a function of storing data pairs at the time of past charging according to the number of data pairs used. For example, when the DC-IR is calculated using five data pairs, the past four (I, OCV) data pairs are stored, and these data pairs are the latest data pair step ( Needless to say, the (I, OCV) data pair stored in S1) may be calculated together.

  Of the plurality of (I, OCV) data pairs in step (S5), the most recently obtained (I, OCV) data pair is the time when the latest (I, OCV) data pair is obtained. Needless to say, if the data is erased sequentially, the necessary storage capacity can be saved.

  What is most characterized in the present invention is the DC-IR value obtained in step (S6) and stored in step (S7), and the latest voltage V value at that time, that is, the DC-IR value. The charging efficiency (η) is obtained from the latest voltage V value (corresponding to the pseudo open circuit voltage OCV) measured in step (S1) in the flow in which the DC-IR value is updated, and the DC-IR value is updated. And the latest DC-IR value stored and updated in step (S6-2) and the updated latest voltage V value (pseudo-open circuit voltage OCV) stored in step (S5). In step (S8), the charging efficiency (η) is obtained.

  In the present invention, as an example, as shown in FIG. 3A, a relationship between DC-IR and voltage V (pseudo-open circuit voltage OCV) is obtained in advance, and a table showing these relationships in the storage means. Should be remembered. By referring to the table with the updated latest DC-IR value and the voltage V (pseudo-open circuit voltage OCV) value at the time when the latest DC-IR value is obtained, the charging efficiency (η) (Step (S8)), the process proceeds to the next step (S8-2). In this step (S8-2), the charging efficiency (η) obtained in the previous flow is changed to the latest The charging efficiency (η) is updated, and the value is stored in the storage means (step S8-2).

  Thereafter, the process proceeds from step (S8-2) to step (S9), the charge electricity amount CHGCAP is corrected with the charge efficiency (η) corrected in step (S9), and the SOC is updated in step (S11). After that, the process returns to step (S1) through step (S12) (output of updated SOC).

  In calculating and updating the charging efficiency (η), the present invention calculates the charging efficiency (η) based on a pre-measured table as shown in FIG. 3A from DC-IR and voltage V (pseudo-open circuit voltage OCV). ). According to such a method, the SOC can be detected with higher accuracy than the method of obtaining the charging efficiency η from the SOC and the temperature. In an experiment conducted separately by the present inventors, the SOC detection accuracy is ± 5% by the method according to the present embodiment, and the SOC is detected by a method obtained from the SOC and temperature as described in Patent Document 1. The accuracy was ± 11%, and a remarkable effect of improving the SOC detection accuracy was obtained with respect to the conventional method.

  Further, in the present invention, when obtaining the charging efficiency (η) from the DC-IR and the voltage V, the table shown in FIG. 3A (for 25 ° C.) is changed to FIG. 3B (for 40 ° C.). As shown in FIG. 3C (for 60 ° C.), temperature detection means such as a thermistor for measuring the battery temperature T or the ambient temperature Ta around the battery is provided at the same time. A table to be used can be selected according to the temperature T or the ambient temperature Ta. More preferably, the charging efficiency (not shown in FIG. 3 (a), FIG. 3 (b) and FIG. 3 (c)) is stored in advance by multiple regression analysis from these tables. η) is a function of DC-IR, voltage V and temperature T or temperature Ta, that is, charging efficiency (η) = f (DC-IR, V, T) or charging efficiency (η) = g (DC-IR, More preferably, the charging efficiency (η) is calculated by the multiple regression equation. The table shown in FIGS. 3A to 3C shows an example applied to a specific lead-acid battery, and it goes without saying that the table is modified according to the type and model of the secondary battery. Yes.

  The detection accuracy of the SOC obtained by the charging efficiency (η) obtained by the multiple regression equation considering the temperature T or the ambient temperature Ta is ± 1.8%, and the conventional SOC and temperature described in Patent Document 1 are described. Therefore, it is possible to detect the SOC with extremely high accuracy with respect to the method of detecting the SOC by obtaining the charging efficiency.

  Next, in the embodiment of the present invention, the flow when the previous flow is charging in step (S4) will be described. When it is determined that the battery is charged, the process proceeds from step (S3) to step (S4). In step (S4), the case where it is determined that the battery is discharged in step (S3) in the previous flow is described above. As described above, the process proceeds from step (S4) to step (S5).

  If it is determined in step (S3) that the battery is charged, the process proceeds from step (S3) to step (S4). In step (S4), as described above, it is determined in step (S3) in the previous flow whether the discharge is determined, the charge is determined, or the first charge is performed. The case where it is determined that the battery is discharged in step (S4) and the battery is determined to be charged in step (S4) of the next flow is as described above.

  Here, a case where the first flow is charging and a case where the previous flow is charging and the next flow is also charging will be described.

In the first step (S3) of the flow shown in FIG. 1, in the case of charging, the process proceeds from step (S3) to step (S4), and then proceeds to step (S6). After that, as described above, in step (S7), the initial value η ₀ is adopted as the charging efficiency (η). This is because the updated charging efficiency (η) is not obtained at the first charging.

  In the flow shown in FIG. 1, when the previous flow is charging and this time is also charging, the process proceeds to step (S4-2). In step (S4-2), the presence or absence of the updated charging efficiency η stored in step (S8-2) is referred to. If the updated charging efficiency η exists, the process proceeds to step (S9). After the SOC is updated in step (S11), the updated SOC is output (step (S12)), and the process returns to step S1 again.

  In order to help understand the first embodiment of the present invention described above, FIG. 4 shows an example of a charge / discharge pattern of a secondary battery to which the present invention is applied. Moreover, the figure which expanded a part of the charging / discharging pattern is shown in FIG.

  In the flow shown in FIG. 1 that has been described up to now, as far as the DC-IR measurement method is concerned, on the charging side (A part and B part in FIG. 4) of the transition from discharging to charging in FIG. The charge current I and the battery voltage V at that time are measured as a pseudo open circuit voltage OCV, and at least two points of this data pair (I, OCV) are measured. The relationship between the charge current I and the pseudo open circuit voltage V The absolute value of the slope of the straight line connecting these two points is measured as DC-IR. Such a method corresponds to claim 3 of the present application.

  More specifically, the details of the A part and the B part shown in FIG. 4 will be described with reference to FIG. The voltage (V) and current (I) of the secondary battery are measured at predetermined time intervals Δt. In the A part, an example is shown in which the transition to charging (a2) is started after the start Δt of discharge (a1), and in the same part B, the transition is made to charging (b2) after the start Δt of discharge (b1).

  In the first embodiment of the present invention, the battery voltage V at the time of charging (a2) by the charging current I1 performed following the discharging (a1) is measured as a pseudo battery voltage OCV1, and data (I1, OCV1) is obtained. In the part B where the pair is acquired and the transition is made from the next discharge to the charge, the charge current I2 in the charge (b2) performed following the discharge (b1) and the battery voltage V at this time are set as the pseudo battery voltage OCV2 , (I2, OCV2), two data pairs can be obtained. As the current-voltage relationship, a DC-IR value can be obtained as an absolute value of the slope obtained by plotting the two data pairs.

  In the present invention, the timing for obtaining DC-IR is measured when the current is small and very close to the open circuit voltage value. That is, since the condition for measuring the DC-IR is substantially constant, the accuracy of the DC-IR value is increased in obtaining the charging efficiency η from the DC-IR and the pseudo OCV, and as a result, the charging efficiency (η) is measured. The accuracy increases, and the final target SOC detection accuracy can be increased.

(Second embodiment of the present invention)
In the second embodiment of the present invention, the DC-IR measurement timing is changed in the first embodiment, and the DC-IR measurement is a method corresponding to claim 4. .

  That is, in the details of the part A shown in FIG. 5, the battery voltage V at the time of charging (a2) by the charging current I1 performed following the discharge (a1) is measured as a pseudo battery voltage OCV1, and (I1, OCV1) The battery voltage V at the charging current I1.1 in the charging (a3) performed following the charging (a2) is measured as a pseudo battery voltage OCV1.1, and (I1.1, OCV1. 1) to obtain the data pair That is, since two pairs of data can be obtained at the stage of transition from discharging to charging, thereafter, as in the first embodiment, the slope of the plot of the two pairs of data is plotted as the current-voltage relationship. A DC-IR value can be obtained as an absolute value. In the B section, it is possible to obtain a DC-IR value as well.

  Therefore, in the second embodiment, the measurement frequency of the DC-IR value is at least approximately twice or more that in the first embodiment, so the update frequency of the charging efficiency (η) is also doubled. However, one of the two data pairs is measured at a position close to the open circuit voltage, but the measurement is performed when the other data pair is slightly separated from the open circuit voltage. However, the amount of increase in the variation (tolerance) is at most about 1.2 times that of the first embodiment. Therefore, also in the second embodiment, the SOC of the secondary battery can be obtained with higher accuracy than the method disclosed in Patent Document 1. Furthermore, since there is an advantage that the SOC update output frequency is twice that of the first embodiment, it may be appropriately selected from these methods according to the characteristics of the secondary battery and the charge / discharge conditions.

  Although this invention described the example applied to the lead acid battery, if it is a secondary battery with a correlation between SOC and battery voltage, it can be applied to another secondary battery on the measurement principle. Needless to say. However, among secondary batteries, it is suitable for a lead storage battery or a lithium secondary battery in which the correlation between the SOC and the battery voltage is clear.

  Although only the method has been described for the first and second embodiments of the present invention, a person skilled in the art can create a program according to the method using a programming language that runs on a personal computer. The secondary battery state-of-charge detection device of the present invention can be easily configured relatively easily.

  In the first embodiment, the flowchart of the method for detecting the state of the secondary battery is shown, but it is within the scope of the claims of the present invention, and is described in the claims of the present invention. It is apparent that modifications within a range that does not depart from the configuration are possible, and such modifications are also included in the scope of the present invention.

  According to the configuration of the present invention described above, there is a remarkable effect that the detection accuracy of the charged state of the secondary battery can be greatly improved. Further, by using the secondary battery state of charge detection device of the present invention for a vehicle, a power supply device, etc., for example, when the vehicle is mounted, it is possible to perform optimal SOC control of the secondary battery, thereby improving the fuel efficiency of the vehicle. There is an effect. In addition, by using the charge state detection device of the present invention in a power supply device that combines a secondary battery with a wind power generator or another independent power source such as a fuel cell, the output from the power supply device can be stabilized. Can do.

  INDUSTRIAL APPLICABILITY The present invention is suitable as a state detection method and apparatus for a secondary battery that is repeatedly charged and discharged, such as a hybrid vehicle or a power source that combines an independent power source and a secondary battery. Suitable for the equipment used.

The figure which shows the detection flow of the charge condition by this invention The figure which shows the relationship between electric current-pseudo open circuit voltage (A) A diagram showing a table for obtaining charging efficiency (η) from OCV and DCIR at a temperature of 25 ° C. (b) A diagram showing a table for obtaining charging efficiency (η) from OCV and DCIR at a temperature of 0 ° C. (c) ) A table showing a table for obtaining charging efficiency (η) from OCV and DCIR at a temperature of 40 ° C. The figure which shows an example of the current-time characteristic of a secondary battery The figure which shows some details of an example of the current-time characteristic of a secondary battery

Claims (9)

The charge state (SOC) of the secondary battery is determined from the charge amount (CHGCAP) obtained by integrating the charge / discharge current to the secondary battery that is repeatedly charged and discharged over time and the discharge amount (DISCAP). A method for detecting a charge state of a secondary battery to be detected,
The charging efficiency (η) is obtained from the voltage (V) and internal resistance (DC-IR) of the secondary battery,
A method for detecting a state of charge of a secondary battery, wherein the charge electricity amount (CHGCAP) is corrected by the charge efficiency (η). From the preset table showing the relationship between the voltage (V) of the secondary battery and the DC internal resistance (DC-IR) determined by the DC method and the charging efficiency (η), the voltage (V) and the internal voltage The charge state detection method of the secondary battery according to claim 1, wherein a resistance (DC-IR) is obtained and the charging efficiency (η) is obtained by referring to the table. Measuring the charge / discharge current and battery voltage of the secondary battery at a predetermined time interval Δt;
A charging current I when the current to the secondary battery shifts from discharging to charging; and
The battery voltage (V) at that time is measured as a pseudo open circuit voltage OCV,
Measure at least two pairs of data pairs (I, OCV) of the charging current I and the pseudo open circuit voltage (OCV),
3. The secondary battery according to claim 1, wherein the internal resistance (DC-IR) is obtained from a relationship between a charging current I obtained from the data pair and a pseudo open circuit voltage (OCV). 4. Charge state detection method. Measuring the charge / discharge current and battery voltage of the secondary battery at a predetermined time interval Δt;
A charging current I when the current to the secondary battery shifts from discharging to charging; and
A data pair (I, OCV) of the charging current I and the pseudo open circuit voltage (OCV) obtained by measuring the battery voltage (V) at that time as the pseudo open circuit voltage OCV,
The data pair (I ′) obtained by measuring the charging current I ′ measured after the predetermined time interval Δt of the data pair and the battery voltage (V ′) at that time as the pseudo open circuit voltage OCV ′. , OCV ') and the internal resistance (DC-IR) is determined from the relationship between the charging current I obtained from the pseudo open circuit voltage (OCV). Battery charge state detection method. 5. The method for detecting a state of charge of a secondary battery according to claim 1, wherein the state of charge (SOC) is corrected by an amount of self-discharge that occurs while charging and discharging are not performed. 6. The method for detecting a charged state of a secondary battery according to claim 5, wherein the self-discharge amount is corrected by at least one of a temperature (T) of the secondary battery and an ambient temperature (Ta) around the secondary battery. 7. The secondary according to claim 1, wherein the charging efficiency (η) is corrected by at least one of a temperature (T) of the secondary battery and an ambient temperature (Ta) around the lead-acid battery. Battery charge state detection method. The secondary battery charge state detection apparatus which detects a charge state by the charge state detection method of the secondary battery of Claims 1-7. The apparatus provided with the charge condition detection apparatus of the secondary battery of Claim 8.

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