JP6969307B2 - Management device, power storage system, method of equalizing the remaining capacity of the power storage element, method of estimating the internal state of the power storage element - Google Patents

Description

The present invention relates to a technique for equalizing the capacity of a power storage element and a technique for estimating an internal state.

When a plurality of power storage elements are connected in series and used, capacity variation may occur between the power storage elements.

Generally, when a capacity difference occurs between the storage elements, the storage elements having a high SOC calculated from the battery voltage at the time of charging are subjected to resistance discharge to equalize the capacities. The following Patent Document 1 is a document that discloses a technique relating to capacity equalization.

Japanese Unexamined Patent Publication No. 2007-110841

Self-discharge is one of the reasons for the variation in the remaining capacity, and it has been required to eliminate the variation in the remaining capacity due to the self-discharge. Further, in order to enhance the safety of the power storage system, it has been required to estimate the internal state of the power storage element and utilize it for the management of the power storage element.
The present invention has been completed based on the above circumstances, and an object of the present invention is to equalize the remaining capacity of the power storage element and to estimate the internal state.

A management device for a plurality of energy storage elements connected in series, wherein the plurality of energy storage elements have an invariant region in which the correlation characteristic does not change before and after deterioration in the residual capacity-voltage correlation characteristic, and the plurality of the energy storage elements. For the element, the arrival time from the first voltage of the first measurement point to the second voltage of the second measurement point in the invariant region is measured, and the plurality of the storage elements are based on the measured arrival time. Performs equalization processing to equalize the remaining capacity of. Equalization is to make the difference in the remaining capacity of the power storage element smaller than the state before the equalization process.

A management device for a plurality of energy storage elements connected in series, wherein the plurality of energy storage elements have an invariant region in which the correlation characteristic does not change before and after deterioration in the residual capacity-voltage correlation characteristic, and the plurality of the energy storage elements. For the element, the arrival time from the first voltage of the first measurement point to the second voltage of the second measurement point in the invariant region is measured, and the plurality of the storage elements are based on the measured arrival time. Estimate the internal state of.

These techniques can be applied to a method of equalizing the remaining capacity of the power storage element and a method of estimating the internal state of the power storage element. Further, it can be applied to a power storage system including a power storage element, a uniform circuit, and a management device. Further, it can be realized by various embodiments such as an equalization program for equalizing the remaining capacity of the power storage element, an estimation program for the internal state of the power storage element, and a recording medium on which these programs are recorded.

In this configuration, the capacity between the power storage elements can be equalized. In addition, the internal state of the power storage element can be estimated.

Side view of the automobile in the first embodiment Battery perspective An exploded perspective view of the battery Block diagram showing the electrical configuration of the battery Circuit diagram of equalization circuit Graph showing the residual capacity-OCV correlation characteristic of the lithium ion secondary battery Graph showing the residual capacity-OCV correlation characteristic of the lithium ion secondary battery Graph showing changes in positive electrode potential Graph showing changes in the potential of the negative electrode Graph showing the residual capacity-OCV correlation characteristic of the lithium ion secondary battery Graph showing changes in positive electrode potential Graph showing changes in the potential of the negative electrode Graph showing the residual capacity-OCV correlation characteristic of the lithium ion secondary battery Flow chart of battery monitoring process The figure which shows the arrival time of each lithium ion secondary battery The figure which shows the self-discharge amount of each lithium ion secondary battery Graph showing residual capacity-voltage correlation characteristics of lithium-ion secondary battery

A management device for a plurality of energy storage elements connected in series, wherein the plurality of energy storage elements have an invariant region in which the correlation characteristic does not change before and after deterioration in the residual capacity-voltage correlation characteristic, and the plurality of energy storage elements. With respect to the element, the arrival time from the first voltage of the first measurement point to the second voltage of the second measurement point in the invariant region is measured, and a plurality of storage elements remain based on the measured arrival time. Performs equalization processing to equalize the capacity.

The arrival time until the power storage element changes from the first voltage at the first measurement point to the second voltage at the second measurement point has a correlation with the self-discharge of the power storage element. In this configuration, since the equalization process is performed based on the arrival time, it is possible to eliminate the generation of the remaining capacity difference of the power storage element due to the variation in self-discharge. Moreover, since the first measurement point and the second measurement point are points in the invariant region where the correlation characteristics do not change before and after deterioration, the relationship between the arrival time and the self-discharge amount is kept constant regardless of the presence or absence of deterioration. Dripping. That is, if the amount of self-discharge is the same (constant current), the arrival time is the same regardless of the presence or absence of deterioration. Therefore, the self-discharge amount can be accurately detected from the arrival time regardless of the presence or absence of deterioration, and the remaining capacity of the power storage element can be accurately equalized.

The equalization process may be performed before the start of charging or at the start of charging. In this configuration, since the equalization process is performed before the start of charging or at the start of charging, charging can be performed in a state where the capacity variation is small. Therefore, it is possible to further suppress that some of the power storage elements are charged in the overcharged region.

A management device for a plurality of energy storage elements connected in series, wherein the plurality of energy storage elements have an invariant region in which the correlation characteristic does not change before and after deterioration in the residual capacity-voltage correlation characteristic, and the plurality of energy storage elements. With respect to the element, the arrival time until the change from the first voltage of the first measurement point to the second voltage of the second measurement point in the invariant region F is measured, and the plurality of storage elements are based on the measured arrival time. Estimate the internal state of.

In this configuration, the internal state of the power storage element can be estimated. Therefore, the power storage element can be managed and controlled according to the estimated internal state.

When the arrival time is shorter than the threshold value, the power storage element may be determined to be abnormal due to an internal short circuit. In this configuration, it is possible to determine whether or not there is an internal short circuit in the power storage element. Therefore, it is possible to suppress the continuation of the use of the power storage element causing an internal short circuit, and thus the safety is enhanced.

When the plurality of power storage elements can be regarded as no current or no current, the arrival time when the power storage element discharges from the first voltage of the first measurement point to the second voltage of the second measurement point in the invariant region. Should be measured.

In this configuration, the arrival time due to the self-discharge of the power storage element can be obtained. Therefore, since the self-discharge amount can be accurately detected, the remaining capacity of the power storage element can be accurately equalized. In addition, the internal state of the power storage element can be accurately determined.

The power storage element can be a lithium ion secondary battery in which the positive electrode material is lithium iron phosphate and the negative electrode material is graphite. The iron phosphate-based lithium ion secondary battery has a flat plateau region in the residual capacity-OCV characteristic. In the plateau region, it is difficult to detect the voltage difference of the lithium ion secondary battery, and there is a problem that the method of detecting and equalizing the difference in the remaining capacity from the voltage difference cannot be applied. In this configuration, it is possible to detect the difference in remaining capacity due to self-discharge from the arrival time by measuring the arrival time with two points where there is a voltage change such as the end point of the plateau region as measurement points. It is possible to eliminate the occurrence of a difference in the remaining capacity of the next battery.

<Embodiment 1>
1. 1. Explanation of Battery FIG. 1 is a side view of an automobile, FIG. 2 is a perspective view of the battery, FIG. 3 is an exploded perspective view of the battery, and FIG. 4 is a block diagram showing an electrical configuration of the battery.

As shown in FIG. 1, the automobile 1 includes a battery 20 which is a power storage device. As shown in FIG. 2, the battery 20 has a block-shaped battery case 21, and the battery case 21 houses an assembled battery 30 composed of a plurality of secondary batteries B1 to B4 and a control board 28. ing.

As shown in FIG. 3, the battery case 21 has a box-shaped case body 23 that opens upward, a positioning member 24 that positions a plurality of secondary batteries B1 to B4, and a middle of being mounted on the upper part of the case body 23. It is configured to include a lid 25 and an upper lid 26. As shown in FIG. 3, a plurality of cell chambers 23A in which the secondary batteries B1 to B4 are individually housed are provided in the case main body 23 side by side in the X direction.

As shown in FIG. 3, the positioning member 24 has a plurality of bus bars 27 arranged on the upper surface thereof, and the positioning member 24 is arranged on the upper portions of the plurality of secondary batteries B1 to B4 arranged in the case main body 23. As a result, the plurality of secondary batteries B1 to B4 are positioned and connected in series by the plurality of bus bars 27.

As shown in FIG. 2, the inner lid 25 has a substantially rectangular shape in a plan view. A pair of terminal portions 22P and 22N to which harness terminals (not shown) are connected are provided at both ends of the inner lid 25 in the X direction. The pair of terminal portions 22P and 22N are made of a metal such as a lead alloy, 22P is a positive electrode side terminal portion and 22N is a negative electrode side terminal portion.

An accommodating portion 25A is provided on the upper surface of the inner lid 25. The control board 28 is housed inside the housing portion 25A of the inner lid 25, and by mounting the inner lid 25 on the case main body 23, the secondary battery B and the control board 28 are connected to each other. ing. Further, the upper lid 26 is attached to the upper part of the inner lid 25 so as to close the upper surface of the accommodating portion 25A accommodating the control board 28.

The electrical configuration of the battery 20 will be described with reference to FIG. The battery 20 includes an assembled battery 30, a current cutoff device 37, a current sensor 41, a voltage detection unit 45, an equalization circuit 70, a warning lamp 80, and a management device 50 for managing the assembled battery 30.

The assembled battery 30 is composed of four lithium ion secondary batteries B1 to B4 connected in series. The lithium ion secondary battery B is an example of the "storage element" of the present invention.

The assembled battery 30, the current sensor 41, and the current cutoff device 37 are connected in series via the energization paths 35P and 35N. The current sensor 41 is arranged in the negative electrode energization path 35N and the current cutoff device 37 is arranged in the positive electrode energization path 35P. The current sensor 41 is connected to the negative electrode side terminal portion 22N, and the current cutoff device 37 is connected to the positive electrode side terminal portion 22P. Has been done.

The battery voltage of the lithium ion secondary batteries B1 to B4 is about 3.5 [V], and the total voltage Ev of the assembled battery 30 is about 14V. The battery 20 is for starting the engine.

The current sensor 41 is provided inside the battery case 21 and detects the current I flowing through the assembled battery 30. The current sensor 41 is electrically connected to the management device 50 by a signal line, and the output of the current sensor 41 is taken into the management device 50.

The voltage detection unit 45 is provided inside the battery case 21 and detects the battery voltages V1 to V4 of the lithium ion secondary batteries B1 to B4 and the total voltage Ev of the assembled battery 30. The voltage detection unit 45 is electrically connected to the management device 50 by a signal line, and the output of the voltage detection unit 45 is taken into the management device 50.

The current cutoff device 37 can be configured by a contact switch (mechanical type) such as a relay or a semiconductor switch such as an FET or a transistor. The current cutoff device 37 opens and closes the current-carrying path 35P of the positive electrode.

The equalization circuit 70 is individually provided for the lithium ion secondary batteries B1 to B4. As shown in FIG. 5, the equalization circuit 70 includes a discharge resistor R and a discharge switch SW. When the discharge switch SW is turned on, the lithium ion secondary battery B is discharged via the discharge resistance R. By discharging the lithium ion secondary battery B having a large capacity, the remaining capacity C between the lithium ion secondary batteries B1 to B4 can be equalized.

The management device 50 includes a CPU (central processing unit) 51 having a calculation function, a memory 53 for storing various information, a ROM 54, a time measuring unit 55 for measuring time, a communication unit 57, and the like, and is provided on the control board 28. ing. The ROM 54 stores a program for executing the battery monitoring process (S10 to S100) shown in FIG. The program can be stored in a recording medium such as a CD-ROM and transferred.

The communication unit 57 is provided for communication with the vehicle ECU (Electronic Control Unit) 100 mounted on the automobile 1. After mounting on the vehicle, the communication unit 57 is connected to the vehicle ECU 100 by a signal line, and the management device 50 can receive information about the vehicle such as the operating state of the engine from the vehicle ECU 100.

The management device 50 monitors the current of the assembled battery (lithium ion secondary battery B) 30 based on the output of the current sensor 41. Further, based on the output of the voltage detection unit 45, the voltages V1 to V4 of the lithium ion secondary batteries B1 to B4 and the total voltage Ev of the assembled battery 30 are monitored. In addition, the management device 50 performs equalization processing (S90) and abnormality determination (S100), which will be described later. Since the battery 20 includes a plurality of lithium ion secondary batteries B1 to B4 connected in series and a management device 50, it corresponds to the "storage system" of the present invention.

2. 2. Characteristics of Lithium Ion Secondary Battery The lithium ion secondary battery B is, for example, an iron phosphate-based lithium ion secondary battery in which lithium iron phosphate (LiFePO4) is used as a positive electrode active material and graphite is used as a negative electrode active material.

FIG. 6 is a diagram showing the correlation characteristics of the residual capacity-OCV of the iron phosphate-based lithium ion secondary battery B. OCV (Open Circuit Voltage) means an open circuit voltage. Further, SOC (state of cAHrge) is a charged state, and is a ratio of the remaining capacity C to the fully charged capacity Co.

SOC = C / Co ... (1)
C is the remaining capacity and Co is the fully charged capacity.

The iron phosphate-based lithium ion secondary battery B has a low change region AL in which the change amount of OCV with respect to the change amount of the remaining capacity C is relatively low, and a high change region AH in which the change amount is relatively high. Specifically, the end of charging (initial stage of discharging) in which the SOC is 95% or more is a high-change region AH in which the OCV changes abruptly with respect to the amount of change in the remaining capacity C. Further, the middle charge (middle discharge) in which the SOC is 35% to less than 95% is a low change region AL in which the OCV with respect to the remaining capacity C is small.

The low change region AL has a first plateau region AL1, an intermediate region AL2, and a second plateau region AL3. The first plateau region AL1 and the second plateau region AL3 are located on both sides of the intermediate region AL2. The plateau regions (flat regions) AL1 and AL3 are regions in which the OCV is substantially constant with respect to the remaining capacity C. Specifically, it is a region in which the amount of change in OCV with respect to the amount of change in the remaining capacity C is 0.5 [mV / Ah] or less.

FIG. 7 is a diagram showing the correlation characteristics of the residual capacity-OCV of the iron phosphate-based lithium ion secondary battery B. Lo shown by the solid line is a new product, and L1 to L3 shown by the broken line are deteriorated products. The capacity retention rates of the lithium ion secondary batteries B of L1 to L3 are Y1 to Y3, and Y3 <Y2 <Y1.

Y = Cot / Co1 ... (2)
Co1 is the initial value of the full charge capacity (new), and Cot is the current value of the full charge capacity (deterioration).

Comparing the correlation characteristics L1 to L3 of the residual capacity-OCV of the deteriorated product with the correlation characteristics L0 of the residual capacity-OCV of the new product, the rising portion K of the high change region AH at the end of charging is on the low residual capacity side (FIG. 7). It is moving horizontally to the left side). K0 to K3 indicate rising portions of the respective correlation characteristics L0 to L3.

In the correlation characteristic L1 to L3 of the residual capacity of the deteriorated product-OCV, the region having a lower residual capacity than the rising portions K1 to K3 of the high change region AH coincides with the correlation characteristic L0 of the residual capacity-OCV at the time of new product. , The invariant regions F1 to F3 in which the correlation characteristic of the residual capacity −OCV does not change before and after deterioration. "The correlation characteristic does not change" means that the graphs are completely matched or almost matched (a deviation of about a measurement error is allowed) before and after deterioration.

The following can be considered as the reason why the invariant region F is generated.
FIG. 8 is a graph showing the positive electrode potential (potential of lithium iron phosphate) of the new lithium secondary battery B, and FIG. 9 is a graph showing the negative electrode potential (potential of graphite) of the new lithium secondary battery B. 10 is a graph showing the correlation characteristics of OCV-residual capacity of a new lithium ion secondary battery B. In FIGS. 8 to 10, P1 indicates the potential and OCV at the time of full charge. P2 indicates the potential at the time of discharge and OCV.

The OCV of the lithium ion secondary battery B is the difference between the positive electrode potential and the negative electrode potential. The change in the end of charging of OCV (curve in the graph) is almost dependent on the change in the end of charging of the positive electrode potential (G1 in FIGS. 8 and 10). Further, the change in the mid-charge of OCV is almost dependent on the change in the mid-charge of the negative electrode potential (G2 in FIGS. 9 and 10).

Lithium iron phosphate, which is a positive electrode material, has almost no irreversible capacity, but graphite, which is a negative electrode material, has an irreversible capacity U1.

The graphite on the negative electrode can be discharged until the lithium is almost empty. On the other hand, the positive electrode lithium iron phosphate cannot be used because the portion corresponding to the irreversible capacity U1 of graphite cannot be discharged.

FIG. 11 is a graph showing the positive electrode potential (potential of lithium iron phosphate) of the lithium ion secondary battery B during charging after capacity deterioration due to the negative electrode coating, and FIG. 12 is lithium during charging after capacity deterioration due to the negative electrode coating. The graph showing the negative electrode potential (potential of graphite) of the ion secondary battery B, FIG. 13 is a graph showing the correlation characteristic of the OCV-residual capacity of the lithium ion secondary battery B after the capacity deterioration due to the negative electrode coating. In FIGS. 11 to 13, P3 indicates the potential and OCV at the time of full charge.

After the capacity deterioration due to the negative electrode coating, the lithium iron phosphate of the positive electrode has almost no capacity deterioration. On the other hand, in the graphite of the negative electrode, the capacity of the film deterioration consumption U2 is added to the initial irreversible capacity U1. Therefore, the lithium ion secondary battery B is charged shallowly by the capacity of the film deterioration consumption U2.

From the above, as the capacity deteriorates, the rising portion K of the high change region AH at the end of charging moves along the curve to the low remaining capacity side (left side in FIG. 13) as shown in FIG. It is estimated that an invariant region F occurs.

By the way, when the deterioration becomes large, the battery performance deteriorates. Therefore, the range of use of the lithium ion secondary battery B is usually determined. That is, the usage range of the capacity retention rate Y is defined, and when the capacity retention rate Y deviates from the usage range (100% to 70% as an example), it is not used.

Therefore, if the invariant region F corresponding to the most deteriorated lithium ion secondary battery B is selected within the usage range, the correlation characteristic of the remaining capacity-OCV does not always change as long as the usage is within the usage range. It will be. For example, when the capacity retention rate Y2 is the limit value of the usage range (70% in the above example), the correlation characteristic of the remaining capacity-OCV always changes in the invariant region F2 as long as it is used within the usage range. do not.

As shown in FIG. 7, the battery 20 defines two points Pa and Pb in the invariant region F2 as measurement points. Specifically, the measurement point on the high capacity side is set as the first measurement point Pa, and the measurement point on the low capacity side is set as the second measurement point Pb. As shown in FIG. 6, the first measurement point Pa is the end point of the first plateau region AL1. Further, the second measurement point Pb is an end point of the second plateau region AL3.

For the measurement points Pa and Pb, it is desirable to select a point (point having a slope or a large slope) in which the OCV change is larger than a predetermined value with respect to the capacitance change so that the measurement point Pa and Pb can be easily detected.

As described below, the battery 20 requires the arrival time required for each lithium ion secondary battery B1 to B4 to reach from the first measurement point Pa to the second measurement point Pb by discharge (mainly self-discharge). Measure T1 to T4. Then, based on the acquired arrival times T1 to T4, the abnormality determination and equalization processing of the lithium ion secondary batteries B1 to B4 are executed.

3. 3. Abnormality determination and equalization processing of the lithium ion secondary battery FIG. 14 is a flowchart of the battery monitoring processing. As shown in FIG. 14, the battery monitoring process is composed of S10 to S100. The CPU 51 of the management device 50 determines whether the parking of the vehicle 1 is detected in S10.

Parking can be detected by communication between the management device 50 and the vehicle ECU 100. That is, when the vehicle is running or stopped, communication is frequently performed between the vehicle ECU 100 and the management device 50 at a predetermined cycle.

On the other hand, when the vehicle is parked, the vehicle ECU 100 is stopped and communication is also stopped. Therefore, when the communication with the vehicle ECU 100 is interrupted for a predetermined period, it can be determined that the vehicle 1 is parked. If it is not parked, the process ends (S10: NO).

When the parking of the vehicle 1 is detected (S10: YES), the CPU 51 of the management device 50 acquires the current I of the battery 20 from the output of the current sensor 41, and each lithium ion secondary battery B1 is obtained from the output of the voltage detection unit 45. ~ B4 battery voltages V1 to V4 are acquired.

Next, the CPU 51 of the management device 50 determines whether the battery 20 is in a state where it can be regarded as no current or no current (S30).

Specifically, the current I of the battery 20 is compared with the first predetermined value, and if the current I is smaller than the first predetermined value, it is determined that the battery 20 is in a state where it can be regarded as no current or no current. The first predetermined value is, for example, about several tens of mA.

When it is determined that the battery 20 can be regarded as no current or no current (S30: YES), the CPU 51 of the management device 50 sets the voltages V1 to V4 of the lithium ion secondary batteries B1 to B4 at the first measurement point Pa. Compare with the first voltage Va. If there is a voltage lower than the first voltage Va, the process ends (S40: NO).

When the voltages V1 to V4 are all higher than the first voltage Va, the management device 50 measures the arrival times T1 to T4 for each of the lithium ion secondary batteries B1 to B4 (S50).

Specifically, the voltages V1 to V4 of the lithium ion secondary batteries B1 to B4 decrease with the passage of time due to the self-discharge of the batteries.

Therefore, the CPU 51 of the management device 50 monitors the voltages of the voltages V1 to V4 of the lithium ion secondary batteries B1 to B4 based on the output of the voltage detection unit 45, and uses the measuring unit 55 to monitor each lithium ion secondary battery. The secondary batteries B1 to B4 measure the arrival times T1 to T4 from the first voltage Va at the first measurement point Pa to the second voltage Vb at the second measurement point Pb.

The measurement of the arrival times T1 to T4 is performed only when the lithium ion secondary batteries B1 to B4 are in a state where they can be regarded as no current or no current.

When the measurement of the arrival times T1 to T4 is completed, the CPU 51 of the management device 50 determines whether the arrival times T1 to T4 are longer than the threshold value Ts (S60), as shown in FIG.

Since the arrival time T is inversely proportional to the self-discharge amount Q [A] of the secondary battery B, the larger the self-discharge amount Q is, the shorter it is. The threshold value Ts is a boundary value between a normal value and an abnormal value of the arrival time T, and when the arrival time T is longer than the threshold value Ts, the lithium ion secondary batteries B1 to B4 can be determined to be normal.

When the arrival times T1 to T4 are all longer than the threshold value Ts, the CPU 51 of the management device 50 calculates the self-discharge amounts Q1 to Q4 of the lithium ion secondary batteries B1 to B4 from the following equation (3) (S70). ..

Q = ΔCab / T ... (3)
ΔCab is the difference between the remaining capacity Ca of the first measurement point Pa and the remaining capacity Cb of the second measurement point Pb, and is a constant value.

Since the self-discharge amount Q is inversely proportional to the arrival time T as described above, as shown in FIG. 16, the shorter the arrival time T, the larger the self-discharge amount Q.

Next, the CPU 51 of the management device 50 determines from the current I of the battery 20 whether charging to the battery 20 has started. Specifically, it is determined based on whether or not the current value of the battery 20 is equal to or higher than the current value (second predetermined value of about several tens of A) flowing during charging.

When the external charger 200 is connected to the battery 20 mounted on the parked vehicle 1 and charging is started, a current of a second predetermined value or more flows through the battery 20, so that the CPU 51 of the management device 50 is used. , Detects the start of charging (S80: YES).

When the CPU 51 of the management device 50 detects the start of charging, it executes an equalization process for equalizing the remaining capacities C of the lithium ion secondary batteries B1 to B4 (S90).

Specifically, as shown in FIG. 16, the self-discharge amount of the other lithium ion secondary batteries B1, B2, and B4 is based on the lithium ion secondary battery B3 having the largest self-discharge amount Q [A]. The remaining capacity difference ΔCq is obtained from the difference ΔQ of Q from the following equation (4), and discharged by each equalization circuit 70 of the lithium ion secondary batteries B1 to B4.

ΔCq = ΔQ × W ... (4)
W is an elapsed time (parking time) from the time when parking is detected in S10 to the start of the equalization process in S90. W is the same time for all lithium ion secondary batteries B1 to B4.

In this configuration, due to the difference in the self-discharge amount Q, the residual capacity difference ΔCq of the lithium ion secondary batteries B1 to B4, which expands during the parking period, can be reduced at the start of charging.

Therefore, since the voltage of each lithium ion secondary battery B1 to B4 rises evenly during charging, it is possible to prevent the lithium ion secondary batteries B1 to B4 from being charged to the overcharge region. The equalization means that the difference in the remaining capacities C of the lithium ion secondary batteries B1 to B4 is made smaller than that in the state before the treatment of S90.

In the above, the case where the external charger 200 is connected and the charging is started has been described as an example, but when the engine is driven and the charging is started by the alternator 150 of the vehicle, the same equalization process (S90) is performed. Is executed.

Therefore, even when charging is started by the alternator 150 of the vehicle, the voltage of each lithium ion secondary battery B1 to B4 rises evenly during charging, so that the lithium ion secondary batteries B1 to B4 are in the overcharge region. It is possible to suppress charging up to.

Further, when the CPU 51 of the management device 50 has one of the lithium ion secondary batteries B1 to B4 whose arrival time T1 to T4 is shorter than the threshold value Ts (S60: NO), the CPU 51 causes an abnormality to the outside. Perform the notification process (S100).

This is because it is considered that the self-discharge amount Q is larger than usual and the possibility of internal short circuit is high. As the abnormality notification mode, lighting of the warning lamp 80 and the like can be exemplified. Further, it is possible to exemplify the abnormality notification to the vehicle ECU 100 after the communication is restored.

It is preferable that the battery monitoring process shown in FIG. 14 is executed every time the parking of the vehicle is detected. Further, if the self-discharge amounts Q1 to Q4 of the lithium ion secondary batteries B1 to B4 are calculated for the first time, the data may be stored in the memory 53 for use thereafter.

4. Explanation of effect The arrival time T1 to T4 until each lithium ion secondary battery B1 to B4 changes from the first voltage Va at the first measurement point Pa to the second voltage Vb at the second measurement point Pb is each lithium ion secondary. There is a correlation with the self-discharge amount Q of the batteries B1 to B4. Therefore, by performing the equalization treatment based on the arrival times T1 to T4, it is possible to eliminate the generation of the residual capacity difference between the lithium ion secondary batteries B1 to B4 due to the variation in self-discharge.

Moreover, since the first measurement point Pa and the second measurement point Pb are points in the invariant region F2 in which the correlation characteristics do not change before and after deterioration, the relationship between the arrival time T and the self-discharge amount Q regardless of the presence or absence of deterioration. Gender is kept constant. That is, if the self-discharge amount Q is the same, the arrival time T is the same regardless of the presence or absence of deterioration. Therefore, the self-discharge amount Q can be accurately detected from the arrival time T regardless of the presence or absence of deterioration, and the remaining capacity C of each lithium ion secondary batteries B1 to B4 can be accurately equalized.

The iron phosphate-based lithium ion secondary batteries B1 to B4 have plateau regions AL1 and AL3 in which the OCV is substantially constant with respect to the residual capacity C in the correlation characteristic of the residual capacity −OCV. In the plateau regions AL1 and AL3, it is difficult to detect the OCV difference of the lithium ion secondary battery, and there is a problem that the method of detecting and equalizing the difference in the remaining capacity from the OCV difference cannot be applied. In this configuration, the arrival time T is measured by using two points with voltage changes such as the end points of the plateau regions AL1 and AL3 as measurement points Pa and Pb, and the difference in residual capacity due to the self-discharge Q is detected from the arrival time T. It is possible to eliminate the occurrence of the remaining capacity difference between the lithium ion secondary batteries B1 to B4.

In this configuration, since charging can be performed with a small difference in remaining capacity, it is possible to suppress a sudden rise in the voltage of some of the lithium ion secondary batteries B1 to B4 during charging. Therefore, it is possible to prevent the lithium ion secondary batteries B1 to B4 from being charged in the overcharged region.

In particular, the external charger 200 may not have a function of monitoring the voltages V1 to V4 of the lithium ion secondary batteries B1 to B4, and even when such an inexpensive external charger 200 is used, the lithium ion secondary battery 200 is used. It is possible to prevent the batteries B1 to B4 from being charged in the overcharged area.

In this configuration, it is possible to determine the presence or absence of an internal short circuit of the lithium ion secondary batteries B1 to B4. Therefore, it is possible to suppress the continuation of the use of the lithium ion secondary battery B causing an internal short circuit, and thus the safety is enhanced.

In this configuration, the arrival times T1 to T4 are measured when the battery 20 is in a state where it can be regarded as no current or no current. Therefore, it is possible to obtain the arrival times T1 to T4 due to the self-discharge of the lithium ion secondary batteries B1 to B4.

Therefore, since the self-discharge amounts Q1 to Q4 can be accurately detected, the remaining capacity C of the lithium ion secondary batteries B1 to B4 can be accurately equalized. Further, the presence or absence of an internal short circuit of the lithium ion secondary batteries B1 to B4 can be accurately determined.

<Other embodiments>
The present invention is not limited to the embodiments described above and the drawings, and for example, the following embodiments are also included in the technical scope of the present invention.

(1) In the first embodiment, an iron phosphate-based lithium ion secondary battery B is exemplified as an example of the power storage element. The power storage element may be a battery having an invariant region F in which the correlation characteristic does not change before and after deterioration in the correlation characteristic of the remaining capacity −OCV, and may be a lithium ion secondary battery other than the iron phosphate type. The power storage element may be another secondary battery, a capacitor, or the like.

Further, the use of the battery 20 is not limited to the vehicle, and may be other uses such as UPS and a power storage unit of a photovoltaic power generation system. Further, in the first embodiment, parking is detected from the state of communication with the vehicle ECU 100, but it can also be determined from the engine stop time and the current value flowing through the battery 20.

(2) The first embodiment illustrates a configuration in which the management device 50 and the equalization circuit 70 are provided inside the battery 20. The management device 50 and the equalization circuit 70 do not necessarily have to be installed inside the battery 20, and may be installed outside the battery 20 as long as they are mounted on the vehicle. That is, the battery 20 is composed of only the sensors that measure the voltage and current of the secondary batteries B1 to B4 and the secondary batteries B1 to B4, and the management device 50 provided outside the battery monitors the output from the sensors. Then, a process of equalizing the secondary batteries B1 to B4 and a process of determining the presence or absence of an abnormality may be executed.

(3) In the first embodiment, the equalization treatment (S90) for equalizing the remaining capacity C of the lithium ion secondary batteries B1 to B4 was performed at the start of charging. The execution timing of the equalization process is not limited to the start of charging, and may be performed before the start of charging, such as immediately after the measurement of the arrival time T. It may also be performed during charging.

(4) In the first embodiment, the presence or absence of an internal short circuit of the power storage element is determined as an example of the process of estimating the internal state of the power storage element based on the arrival time T. In addition to this, the variation in the self-discharge amount Q of the power storage element (an example of the internal state) may be estimated based on the arrival time T.

(5) In the first embodiment, for each of the lithium ion secondary batteries B1 to B4, the remaining capacity difference ΔCq obtained from the difference ΔQ of the self-discharge amount Q is discharged by the equalization circuit 70 to equalize the remaining capacity C. It became. How to determine the discharge amount of each lithium ion secondary battery B1 to B4 in equalizing the remaining capacity C is not limited to the example of the first embodiment.

For example, in the case of FIG. 15, the discharge amount of the lithium ion secondary battery B3 having the shortest arrival time T is used as a reference, and the discharge amounts of the other lithium ion secondary batteries B1, B2, and B4 reach the shortest arrival time T3. Any method may be used as long as it is based on the arrival time T, such as being determined by the ratio of the times T1, T2, and T4.

(6) In the first embodiment, the arrival time T is measured when the battery 20 is in a state where it can be regarded as no current or no current. In addition to this, the arrival time T may be measured during charging or discharging. When measuring during charging or discharging, it is preferable that the current is constant at a low rate.

Further, in the first embodiment, the arrival time T is measured in a state where the battery 20 is regarded as having no current or no current. When a predetermined current is flowing through the lithium ion secondary battery B, the residual capacity-voltage correlation characteristics La and Lb have internal resistance with respect to the residual capacity-OCV correlation characteristic L0, as shown in FIG. The shape of the graph itself is the same, although there is a difference in the amount of voltage change due to.

Therefore, the residual capacity-voltage correlation characteristics La and Lb also have an invariant region F in which the correlation characteristics do not change before and after deterioration, similar to the residual capacity-OCV correlation characteristic L0, when a predetermined current is flowing. .. Therefore, when the arrival time T is measured in a state where a predetermined current (current that cannot be regarded as no current) is flowing, instead of the correlation characteristic L0 of the residual capacity −OCV, the current value is changed. It is preferable to use the residual capacity-voltage correlation characteristics La and Lb. The same applies when a minute current such as several tens of mA is flowing.

Further, when the arrival time T is measured while the current is flowing, the arrival time T is shorter than that in the case of only self-discharge. However, even in a state where a current is flowing, it is the same that the arrival time T can be different due to the difference in self-discharge. Therefore, it is possible to detect the difference in the amount of self-discharge from the difference in the arrival time T. In addition, "La" shown in FIG. 17 shows the correlation characteristic of the residual capacity-voltage during charging, and "Lb" shows the correlation characteristic of the residual capacity-voltage during discharging.

(7) The techniques disclosed in the first and second embodiments include an equalization program for equalizing the remaining capacity of the power storage element, an estimation program for estimating the internal state of the power storage element, and a recording medium on which these programs are recorded. It can be realized by the embodiment.

It is an equalization program that equalizes the remaining capacity of a plurality of storage elements connected in series, and the plurality of storage elements have an invariant region in which the correlation characteristic does not change before and after deterioration in the residual capacity-voltage correlation characteristic. A process (S50) of measuring the arrival time of a plurality of the power storage elements from the first voltage of the first measurement point to the second voltage of the second measurement point in the invariant region. An equalization program for executing an equalization process (S90) for equalizing the remaining capacities of a plurality of the power storage elements based on the measured arrival time.

An estimation program for estimating the internal state of a power storage element, wherein the power storage element has an invariant region in which the correlation characteristic does not change before and after deterioration in the residual capacity-voltage correlation characteristic. Based on the process (S50) of measuring the arrival time from the first voltage of the first measurement point to the second voltage of the second measurement point in the invariant region and the measured arrival time, the power storage element An estimation program that executes an estimation process (S60) that estimates the internal state.

20 ... Battery (corresponding to the "storage system" of the present invention)
22P, 22N ... Positive electrode side terminal part, Negative electrode side terminal part 30 ... Assembly battery 41 ... Current sensor 45 ... Voltage detection unit 50 ... Management device 70 ... Equalization circuit 100 .. .Vehicle ECU
AL1, AL3 ... Plateau area B1 to B4 ... Lithium ion secondary battery F1 to F3 ... Invariant area Pa ... First measurement point Pb ... Second measurement point T ... Reached time

Claims (9)

It is a management device for multiple power storage elements connected in series.
The plurality of storage elements have an invariant region in which the correlation characteristic of the residual capacity-voltage does not change before and after deterioration.
For the plurality of the storage elements, the arrival time until the change from the first voltage of the first measurement point to the second voltage of the second measurement point in the invariant region is measured.
A management device that performs equalization processing for equalizing the remaining capacities of a plurality of the power storage elements based on the measured arrival time. The management device according to claim 1.
A management device that performs the equalization process before or at the start of charging. It is a management device for multiple power storage elements connected in series.
The plurality of storage elements have an invariant region in which the correlation characteristic of the residual capacity-voltage does not change before and after deterioration.
For the plurality of the storage elements, the arrival time until the change from the first voltage of the first measurement point to the second voltage of the second measurement point in the invariant region is measured.
A management device that estimates the internal state of a plurality of the power storage elements based on the measured arrival time. The management device according to claim 3.
A management device that determines that the power storage element is abnormal due to an internal short circuit when the arrival time is shorter than the threshold value. The management device according to any one of claims 1 to 4.
Reaching time when the storage element discharges from the first voltage of the first measurement point to the second voltage of the second measurement point in the invariant region when the plurality of storage elements can be regarded as no current or no current. A management device that measures. The management device according to any one of claims 1 to 5.
The power storage element is a management device, which is a lithium ion secondary battery in which the positive electrode material is lithium iron phosphate and the negative electrode material is graphite. It ’s a power storage system.
With multiple power storage elements connected in series,
A power storage system including the management device according to any one of claims 1 to 6. It is a method of equalizing the remaining capacity of a plurality of power storage elements connected in series.
The plurality of storage elements have an invariant region in which the correlation characteristic of the residual capacity-voltage does not change before and after deterioration.
For the plurality of power storage elements, the arrival time until the change from the first voltage of the first measurement point to the second voltage of the second measurement point in the invariant region is measured.
A method of equalizing the remaining capacities of a plurality of the power storage elements based on the measured arrival time. It is a method of estimating the internal state of the power storage element.
The power storage element has an invariant region in which the correlation characteristic of residual capacity-voltage does not change before and after deterioration.
With respect to the power storage element, the arrival time from the first voltage of the first measurement point to the second voltage of the second measurement point in the invariant region is measured.
A method of estimating the internal state of the power storage element based on the measured arrival time.

Images