JP2021129487A - Power storage device - Google Patents

Abstract

To equalize the battery charge rate even when the estimation accuracy of the battery charge rate due to an open circuit voltage of the battery is not good in a power storage device including a plurality of batteries connected in series.SOLUTION: A power storage device 1 includes batteries B1 and B2, a cell balance circuit CV that discharges the batteries B1 and B2, a charge rate estimation unit 521 that estimates the charge rate of the batteries B1 and B2 by a current integration method using an integrated value of a current flowing through the batteries B1 and B2, an accuracy determination unit 522 that determines whether the estimation accuracy of the charge rate is good, and a cell balance control unit 523 that controls the operation of the cell balance circuit CV such that the charge rates of the batteries B1 and B2 are equalized when it is determined that the estimation accuracy of the charge rate is good, and does not equalize the charge rates of the batteries B1 and B2 when it is determined that the estimation accuracy of the charge rate is not good.SELECTED DRAWING: Figure 1

Description

The present invention relates to a power storage device including a plurality of batteries connected in series.

As a power storage device, when the amount of change in the open circuit voltage of a battery with respect to the unit change amount of the charge rate of any one of a plurality of batteries connected in series is smaller than a predetermined amount, the amount of change is greater than the predetermined amount. When shifting to a larger case, there is one that equalizes the charge rate of each battery by using the correspondence relationship between the charge rate and the open circuit voltage. Patent Document 1 is a related technique.

By the way, if the charge rates of the batteries are not equalized, the capacity that can be used by the entire battery is limited, and the mileage of the vehicle equipped with the power storage device may be shortened.

Therefore, in the above-mentioned power storage device, a battery estimated by using the correspondence relationship between the charge rate and the open circuit voltage, such as when the change amount of the battery open circuit voltage with respect to the unit change amount of the battery charge rate is smaller than a predetermined amount. If the estimation accuracy of the charge rate of the battery is not good, the charge rate of each battery may not be equalized and the mileage of the vehicle may be shortened.

Japanese Unexamined Patent Publication No. 2015-136268

An object according to one aspect of the present invention is a case where the estimation accuracy of the battery charge rate estimated by using the correspondence between the charge rate and the open circuit voltage is not good in a power storage device including a plurality of batteries connected in series. Even so, it is to equalize the charge rate of each battery.

The power storage device according to the present invention is a power storage device according to a current integration method using a plurality of batteries connected in series, a cell balance circuit for discharging each battery, and an integrated value of the current flowing through each battery. The charge rate estimation unit that estimates the charge rate, the accuracy determination unit that determines whether the charge rate estimation accuracy is good, and the charge rate estimation unit that determines whether the charge rate estimation accuracy is good, equalizes the charge rates of each battery when it is determined that the charge rate estimation accuracy is good. The operation of the cell balance circuit is controlled so as to be performed, and when it is determined that the estimation accuracy of the charge rate is not good, a cell balance control unit that does not equalize the charge rate of each battery is provided.

As a result, even if the estimation accuracy of the battery charge rate estimated using the correspondence between the charge rate and the open circuit voltage is not good, the battery is estimated using the integrated value of the current flowing through the battery. When the estimation accuracy of the charge rate is good, the charge rate of each battery can be equalized.

When the estimation timing comes, the charge rate estimation unit determines the charge rate estimated at the previous estimation timing, the integrated value of the current flowing through each battery between the previous estimation timing and the current estimation timing, and the full charge capacity of each battery. The charge rate of each battery is estimated by the current integration method using, or the charge rate of each battery is estimated by the voltage method using the open circuit voltage of each battery, and the accuracy determination unit determines the detection accuracy of the open circuit voltage. When the index based on at least one of the first index shown, the second index showing the calculation accuracy of the integrated current value, and the third index showing the estimation accuracy of the full charge capacity is higher than the threshold value. It may be configured to determine that the estimation accuracy of the charge rate is good.

As a result, as the number of indexes used increases, the determination accuracy when determining whether or not the estimation accuracy of the charge rate is good can be increased. Further, since the index to be used can be selected from the first to third indexes according to the processing capacity of the accuracy determination unit, the degree of freedom of the processing capacity of the accuracy determination unit can be increased.

According to the present invention, in a power storage device including a plurality of batteries connected in series, even if the estimation accuracy of the battery charge rate estimated by using the correspondence between the charge rate and the open circuit voltage is not good. , The charge rate of each battery can be equalized.

It is a figure which shows an example of the power storage device of an embodiment. It is a figure which shows an example of the information stored in the storage part. It is a figure which shows other example of the information stored in the storage part. It is a flowchart which shows an example of cell balance processing.

Hereinafter, embodiments will be described in detail based on the drawings.

FIG. 1 is a diagram showing an example of a power storage device according to an embodiment.

The power storage device 1 shown in FIG. 1 is mounted on an industrial vehicle such as an electric forklift or a vehicle Ve such as an electric vehicle, and has batteries B1 and B2, a current meter 2, a thermometer 3, switches SW1 and SW3, and a monitoring ECU. It includes (Electronic Control Unit) 4, a cell balance circuit CV, and a battery ECU 5.

In addition to the power storage device 1, the vehicle Ve controls the operation of the motor M for traveling of the vehicle Ve, the inverter circuit Inv for driving the motor M, and the inverter circuit Inv, and the charger Ch provided outside the vehicle Ve. It is provided with a vehicle ECU 6 that communicates with.

The inverter circuit Inv includes a switch, and when the switch is repeatedly turned on and off, the DC power supplied from the batteries B1 and B2 is converted into AC power and supplied to the motor M. Further, the inverter circuit Inv converts the AC power (regenerative power) supplied from the motor M into DC power by repeatedly turning the switch on and off, and supplies the AC power (regenerative power) to the batteries B1 and B2.

The vehicle ECU 6 is configured to include a processor, a storage unit, and the like, and is supplied from the inverter circuit Inv to the batteries B1 and B2 by changing the duty ratio of the control signal that controls the on / off of the switch of the inverter circuit Inv. The electric power or the electric power supplied from the batteries B1 and B2 to the inverter circuit Inv is changed. The function of the vehicle ECU 6 may be included in the function of the battery ECU 5 to integrate the battery ECU 5 and the vehicle ECU 6, and the battery ECU 5 after the integration may be provided in the power storage device 1 or the vehicle Ve.

The batteries B1 and B2 are each composed of one or more secondary batteries such as a lithium ion battery or a nickel hydrogen battery. The negative terminal of the battery B1 is connected to the positive terminal of the battery B2. That is, the batteries B1 and B2 are connected in series with each other. The positive terminal of the battery B1 is connected to the positive input terminal of the inverter circuit Inv. The negative terminal of the battery B2 is connected to the negative input terminal of the inverter circuit Inv via the ammeter 2 and the switches SW1 and SW2. Further, when the charger Ch is connected to the vehicle Ve via a charging cable or the like, the positive terminal of the battery B1 is connected to the positive terminal of the charger Ch, and the negative terminal of the battery B2 is the ammeter 2 and the switch SW1. It is connected to the negative terminal of the charger Ch via SW3. Further, the positive terminal of the battery B1 is connected to the input terminal In1 of the monitoring ECU 4, the connection point between the negative terminal of the battery B1 and the positive terminal of the battery B2 is connected to the input terminal In2 of the monitoring ECU 4, and the negative terminal of the battery B2 is. It is connected to the input terminal In3 of the monitoring ECU 4. When the batteries B1 and B2 are not particularly distinguished, they are simply referred to as batteries B. Further, the number of batteries B connected in series with each other may be three or more.

The ammeter 2 is composed of a shunt resistor or the like, detects the current flowing through the batteries B1 and B2, and sends the detected current to the monitoring ECU 4.

The thermometer 3 is composed of a thermistor or the like, detects the temperatures of the batteries B1 and B2, and sends the detected temperatures to the monitoring ECU 4.

The monitoring ECU 4 is configured to include a processor, a storage unit, and the like, and detects the respective voltages of the batteries B1 and B2. That is, the monitoring ECU 4 detects the voltage applied between the input terminal In2 and the input terminal In3 as the voltage of the battery B2, and subtracts the voltage of the battery B2 from the voltage applied between the input terminal In1 and the input terminal In3. The voltage is detected as the voltage of the battery B1. Further, the monitoring ECU 4 transmits the detected voltage, the current detected by the ammeter 2, and the temperature detected by the thermometer 3 to the battery ECU 5 by using CAN (Controller Area Network) communication or the like.

The switches SW1 to SW3 are each composed of a semiconductor switch (for example, MOSFET (Metal Oxide Semiconductor Field Effect Transistor)), an electromagnetic relay, or the like. The switches SW1 to SW3 may be connected to the positive terminal side of the battery B1.

When the switches SW1 and SW2 are conductive and the switch SW3 is cut off, it becomes possible to supply electric power from the inverter circuit Inv to the batteries B1 and B2, and to supply electric power from the batteries B1 and B2 to the inverter circuit Inv. Becomes possible. Further, when the charger Ch is connected to the vehicle Ve, the switches SW1 and SW3 are electrically connected, and when the switch SW2 is cut off, the charger Ch can supply electric power to the batteries B1 and B2. When power is supplied to the batteries B1 and B2 from the inverter circuit Inv or the charger Ch, the batteries B1 and B2 are charged, and the charge rates of the batteries B1 and B2 (the ratio of the capacity of the battery B to the full charge capacity of the battery B) and When the voltage increases and power is supplied from the batteries B1 and B2 to the inverter circuit Inv, the batteries B1 and B2 are discharged and the charge rate and voltage of the batteries B1 and B2 decrease.

The cell balance circuit CV includes resistors R1 and R2 and switches S1 and S2.

The resistor R1 and the switch S1 are connected in series with each other and are connected in parallel with the battery B1. That is, one terminal of the resistor R1 is connected to the positive terminal of the battery B1, the other terminal of the resistor R1 is connected to one terminal of the switch S1, and the other terminal of the switch S1 is connected to the negative terminal of the battery B1. When the switch S1 is switched from the cutoff state to the conductive state, the battery B1 is discharged by the resistor R1, and the charge rate and the voltage of the battery B1 decrease.

The resistor R2 and the switch S2 are connected in series with each other and are connected in parallel with the battery B2. That is, one terminal of the resistor R2 is connected to the positive terminal of the battery B2, the other terminal of the resistor R2 is connected to one terminal of the switch S2, and the other terminal of the switch S2 is connected to the negative terminal of the battery B2. When the switch S2 is switched from the cutoff state to the conductive state, the battery B2 is discharged by the resistor R2, and the charge rate and the voltage of the battery B2 decrease.

When the resistors R1 and R2 are not particularly distinguished, they are simply referred to as resistors R. Further, when the switches S1 and S2 are not particularly distinguished, it is simply referred to as the switch S. Further, when three or more batteries B are provided in the power storage device 1, the resistors R and the switches S connected in series with each other are connected in parallel to each battery B, and any switch S is switched from the cutoff state to the conductive state. Each battery B is selectively discharged.

The battery ECU 5 includes a storage unit 51 and a processor 52.

The storage unit 51 is composed of a RAM (Random Access Memory), a ROM (Read Only Memory), or the like. Further, the storage unit 51 shows the correspondence relationship between the information D1 indicating the correspondence relationship between the polarization elimination time and the index P1 (first index) and the current integration duration and the index P2 (second index), which will be described later. Information D2, information D3 indicating the correspondence between the elapsed time after manufacturing the device and the index P3 (third index), and information D4 in which the charge rate of the battery B and the open circuit voltage of the battery B are associated with each other (information D3). SOC-OCV characteristics) and the like are stored. The open circuit voltage is a voltage detected by the monitoring ECU 4 when the current detected by the ammeter 2 is zero or substantially zero.

The index P1 indicates the detection accuracy of the open circuit voltage. In the current integration method described later, the open circuit voltage is acquired, and the charge rate is estimated after the current flows through the battery B based on the charge rate corresponding to the open circuit voltage. As the elapsed time (polarization elimination time) after the charging or discharging of the batteries B1 and B2 is completed, the open circuit voltage detected by the monitoring ECU 4 becomes the true battery voltage after the polarization of the battery B is eliminated. As the elapsed time after the charging or discharging of the batteries B1 and B2 is completed increases, the open circuit voltage used in the current integration method approaches the true battery voltage, the detection accuracy becomes higher, and the index P1 becomes higher. It shall be.

Further, the index P2 indicates the calculation accuracy of the integrated value of the currents flowing through the batteries B1 and B2. When the current detected by the ammeter 2 contains an error, the accuracy of calculating the integrated value of the current decreases as the time during which the current detected by the ammeter 2 continues to be integrated (current integration duration) increases. Therefore, it is assumed that the index P2 becomes low.

Further, the index P3 indicates the estimation accuracy of the full charge capacity. The full charge capacity of the batteries B1 and B2 decreases as they deteriorate over time. When the full charge capacity is not estimated, the estimated value of the full charge capacity deviates from the actual full charge capacity. Therefore, as the elapsed time after manufacturing the power storage device 1 (elapsed time after manufacturing the device) increases, the more It is assumed that the estimation accuracy of the full charge capacity becomes low and the index P3 becomes low. When the full charge capacity is estimated, the estimated value of the full charge capacity approaches the actual full charge capacity, so that the estimation accuracy of the full charge capacity is high and the index P3 is high.

FIG. 2A is a diagram showing an example of information D1. The horizontal axis of the two-dimensional coordinates shown in FIG. 2A indicates the polarization elimination time, and the vertical axis indicates the index P1. The solid line shown in FIG. 2A shows the information D1 (information D11) when the temperature of the battery B is the temperature T1, and the broken line shown in FIG. 2A shows the temperature at which the temperature of the battery B is lower than the temperature T1. Information D1 (information D12) when it is T2 is shown.

In the information D11 and D12 shown in FIG. 2A, as described above, as the polarization elimination time increases, the open circuit voltage detected by the monitoring ECU 4 approaches the true battery voltage, so that the polarization elimination time increases. As the number increases, the index P1 approaches the maximum value P1max. That is, in the current integration method described later, when the basic charge rate is obtained from the open circuit voltage, the longer the polarization elimination time of the open circuit voltage, the higher the accuracy of estimating the charge rate by the current integration method. When the polarization of the batteries B1 and B2 is eliminated, the index P1 of the information D11 and D12 becomes the same as the maximum value P1max.

Further, when the time until the batteries B1 and B2 are sufficiently depolarized becomes longer as the temperature is lower, the index P1 of the information D11 at the time t after the lapse of a predetermined time after the charging or discharging of the batteries B1 and B2 is completed. Is larger than the index P1 of the information D12. In this way, since the index P1 changes according to the temperatures of the batteries B1 and B2, the information D11 and the information D12 are used properly according to the temperature detected by the thermometer 3, so that the index P1 regarding the detection accuracy of the open circuit voltage is used properly. Can be made more accurate.

FIG. 2B is a diagram showing an example of information D2. The horizontal axis of the two-dimensional coordinates shown in FIG. 2B indicates the current integration duration, and the vertical axis indicates the index P2. The solid line shown in FIG. 2B shows information D2. Further, when the charge rates of the batteries B1 and B2 are estimated using the open circuit voltage, the current integration duration is reset to zero and the index P2 is reset to the maximum value P2max in the information D2.

In the information D2 shown in FIG. 2B, as described above, as the current integration duration increases, the error included in the current integration value increases. Therefore, as the current integration duration increases, the index P2 becomes smaller. It shall be. That is, in the current integration method described later, as the current integration duration increases, the error included in the current integration value increases, so that the accuracy of estimating the charge rate by the current integration method decreases.

FIG. 2C is a diagram showing an example of information D3. The horizontal axis of the two-dimensional coordinates shown in FIG. 2C indicates the elapsed time after product manufacturing, and the vertical axis indicates the index P3. The solid line shown in FIG. 2C shows information D3. Further, at time t1 and t2, the full charge capacity is updated by using the charge rate of the batteries B1 and B2 before and after charging and the integrated value of the current flowing through the batteries B1 and B2 being charged, so that the index of the information D3 It is assumed that P3 has risen slightly.

In the information D3 shown in FIG. 2C, as described above, when the full charge capacity is not estimated, the estimated value of the full charge capacity deviates from the actual full charge capacity, so that the elapsed time after manufacturing the device increases. It is assumed that the index P3 becomes smaller as the amount is increased. That is, since the error of the full charge capacity used in the current integration method described later increases, the accuracy of estimating the charge rate by the current integration method becomes low.

FIG. 3A is a diagram showing an example of information D4. The horizontal axis of the two-dimensional coordinates shown in FIG. 3A indicates the charge rate [%] of the battery B, and the vertical axis indicates the open circuit voltage (true battery voltage) [V] of the battery B. The solid line shown in FIG. 3A uses batteries B1 and B2 (for example, lithium iron phosphate (LiFePO4) as the positive electrode material and graphite as the negative electrode material) having a flat region in the correspondence between the charge rate and the open circuit voltage. The information D4 when the battery was used is shown. The ratio of the amount of change in the open circuit voltage to the amount of unit change in the charge rate (the slope of the solid line shown in FIG. 3A) is predetermined in the entire range (0 to 100 [%]) of the charge rate of the battery B. When the value is less than or equal to the value, the corresponding area is defined as a flat area, and the area other than the flat area is defined as a non-flat area. Alternatively, of the entire charge rate region of the battery B, the region corresponding to the case where the change amount of the open circuit voltage with respect to the unit change amount of the charge rate is smaller than the detection error of the monitoring ECU 4 is set as a flat region, and the region other than the flat region is defined as a flat region. It is a non-flat area.

In the flat region, the ratio of the change in the open circuit voltage to the unit change in the charge rate is relatively small. Therefore, when the charge rate of the battery B is included in the flat region, it is opened due to an error in the open circuit voltage due to polarization or the like. It may be difficult to uniquely obtain the charge rate from the circuit voltage. Therefore, when the charge rate of the battery B is included in the flat region, the charge rates of the batteries B1 and B2 may not be equalized even if the open circuit voltages of the batteries B1 and B2 are equalized. Therefore, when the charge rate of the battery B is included in the non-flat region, the open circuit voltages of the batteries B1 and B2 are equalized, and when the charge rate of the battery B is included in the flat region, the open circuits of the batteries B1 and B2 are equalized. It is conceivable not to equalize the voltage, but if the flat region of the batteries B1 and B2 is relatively large, the chance of equalizing the charge rates of the batteries B1 and B2 may decrease.

Further, FIG. 3B shows batteries B1 and B2 (for example, for a negative electrode material) in which the correspondence relationship between the charge rate and the open circuit voltage during charging and the correspondence relationship between the charge rate and the open circuit voltage during discharge are different from each other. It is a figure which shows an example of the correspondence relationship between the charge rate and an open circuit voltage in the case of a battery (battery using SiO). The horizontal axis of the two-dimensional coordinates shown in FIG. 3B indicates the charge rate [%] of the battery B, and the vertical axis indicates the open circuit voltage [V] of the battery B. The solid line shown in FIG. 3B shows the correspondence between the charging rate of the batteries B1 and B2 after charging and the open circuit voltage, and the broken line shown in FIG. 3B shows the charging of the batteries B1 and B2 after discharging. The correspondence between the rate and the open circuit voltage is shown.

For example, the charge rate SOC1 corresponding to the open circuit voltage OCV on the solid line is smaller than the charge rate SOC2 corresponding to the open circuit voltage OCV on the broken line.

Therefore, for example, when another battery B1 is connected in parallel to the battery B1 and another battery B2 is connected in parallel to the battery B2, a recirculation current flows between the batteries B1 and recirculates between the batteries B2. When a current flows, it is not known whether the batteries B1 and B2 are in the charged state or the discharged state, respectively, and there is a possibility that the charge rate cannot be uniquely obtained from the open circuit voltage. In such a case, even if the open circuit voltages of the batteries B1 and B2 are equalized, the charge rates of the batteries B1 and B2 may not be equalized.

Therefore, in the power storage device 1 of the embodiment, as will be described later, the charge rate of each battery B is not equalized by equalizing the open circuit voltage of each battery B, but the current flowing through the batteries B1 and B2. When it is determined that the estimation accuracy of the charge rates of the batteries B1 and B2 estimated using the integrated values is good, the charge rates of the batteries B1 and B2 are directly equalized.

The processor 52 shown in FIG. 1 includes a charge rate estimation unit 521, an accuracy determination unit 522, and a cell balance control unit 523. By executing the program stored in the storage unit 51 by the processor 52, the charge rate estimation unit 521, the accuracy determination unit 522, and the cell balance control unit 523 are realized.

When the estimation timing comes, the charge rate estimation unit 521 estimates the charge rates of the batteries B1 and B2 by the voltage method or the current integration method described later. For example, the charge rate estimation unit 521 uses the voltage method as the estimation timing when the current stops flowing through the batteries B1 and B2, such as when the ignition of the vehicle Ve is turned off or when the charging of the batteries B1 and B2 by the charger Ch is completed. , Estimate the charge rate of batteries B1 and B2. Further, the charge rate estimation unit 521 sets a timing at which a certain period of time repeatedly elapses when a current is flowing through the batteries B1 and B2, such as when the ignition of the vehicle Ve is turned on or when the batteries B1 and B2 are charged by the charger Ch. As the estimation timing, the charge rates of the batteries B1 and B2 are estimated by the current integration method.

<Voltage method>
The charge rate estimation unit 521 refers to the information D4 stored in the storage unit 51, and refers to the same open circuit voltage as the voltage transmitted from the monitoring ECU 4 when the current transmitted from the monitoring ECU 4 is zero or substantially zero. Let the charge rate corresponding to be the charge rate of the battery B at the current estimated timing.

<Current integration method>
The charge rate estimation unit 521 indicates that "charge rate [%] = charge rate [%] estimated at the previous estimated timing + (integrated value of the current flowing through the battery B between the previous estimated timing and the current estimated timing). The calculation result of "[Ah] / full charge capacity of battery B [Ah]) x 100" is used as the charge rate of battery B at the current estimated timing.

The accuracy determination unit 522 determines whether or not the estimation accuracy of the charge rate estimated by the current integration method is good. That is, when the index P based on at least one of the indexes P1 to P3 is higher than the threshold value Pth, the accuracy determination unit 522 determines that the estimation accuracy of the charge rate estimated by the current integration method is good, and the index P When is equal to or less than the threshold value Pth, it is determined that the estimation accuracy of the charge rate estimated by the current integration method is not good. For example, index P = index P1 + index P2 + index P3.

In this way, since the parameter used in the current integration method is the "charge rate estimated at the previous estimation timing", the charge rate is estimated by the voltage method at the previous estimation timing, and the previous estimation. When the index P1 is relatively large in the timing, the estimation accuracy of the charge rate estimated by the current integration method is relatively high in the current estimation timing.

Further, as a parameter used in the current integration method, there is a "current integrated value of the current flowing through the battery B between the previous estimation timing and the current estimation timing". Therefore, when the index P2 is relatively small, this time. At the estimation timing, the estimation accuracy of the charge rate estimated by the current integration method becomes relatively low.

Further, since there is "full charge capacity of battery B" as a parameter used in the current integration method, when the index P3 is relatively small, the estimation accuracy of the charge rate estimated by the current integration method is high at the current estimation timing. It will be relatively low.

When the accuracy determination unit 522 determines that the estimation accuracy of the charge rate estimated by the current integration method is good, the cell balance control unit 523 performs cell balance to equalize the charge rate estimated by the current integration method. If the accuracy determination unit 522 determines that the estimation accuracy of the charge rate estimated by the current integration method is not good, the cell balance that equalizes the charge rate estimated by the current integration method is not performed.

For example, the cell balance control unit 523 determines that the estimation accuracy of the charge rate estimated by the current integration method is good, and the charge rate of the battery B1 and the charge rate of the battery B2 estimated by the current integration method. When the charge rate difference ΔSOC, which is the absolute value of the difference, is equal to or greater than the threshold SOCth, and the charge rate of the battery B1 is larger than the charge rate of the battery B2, the integrated current obtained by dividing the voltage of the battery B1 by the resistor R1. The switch S1 is kept conductive and the switch S2 is shut off until the decrease in the charge rate of the battery B1 obtained by dividing the value by the full charge capacity of the battery B1 becomes the same as the charge rate difference ΔSOC. do.

Further, the cell balance control unit 523 determines that the estimation accuracy of the charge rate estimated by the current integration method is good, and the charge rate difference ΔSOC is equal to or greater than the threshold SOCth, and the battery B2. When the charge rate is larger than the charge rate of the battery B1, the amount of decrease in the charge rate of the battery B2 obtained by dividing the integrated value of the current obtained by dividing the voltage of the battery B2 by the resistor R2 by the full charge capacity of the battery B2 is The switch S2 is brought into a conductive state and the switch S1 is put into a cutoff state until the charging rate difference becomes the same as ΔSOC.

When the charge rates of the batteries B1 and B2 are included in the non-flat region, the cell balance control unit 523 equalizes the charge rates of the batteries B1 and B2 by equalizing the open circuit voltages of the batteries B1 and B2. It may be configured to allow.

Further, the charge rate estimation unit 521, the accuracy determination unit 522, and the cell balance control unit 523 execute the cell balance process.

FIG. 4 is a flowchart showing an example of cell balance processing. It is assumed that the ignition of the vehicle Ve is on.

First, when the charge rate estimation unit 521 receives from the vehicle ECU 6 that the ignition of the vehicle Ve has been turned off (step S1: Yes), the battery ECU 5 switches from the normal state to the sleep state (step S2). When the battery ECU 5 is in the normal state, all functions (charge rate estimation unit 521, accuracy determination unit 522, cell balance control unit 523, etc.) operate, and when the battery ECU 5 is in the sleep state, the charge rate is estimated. Functions other than the unit 521 (accuracy determination unit 522, cell balance control unit 523, etc.) are stopped.

Next, when a certain time elapses after the battery ECU 5 is switched to the sleep state (step S3: Yes), the charge rate estimation unit 521 switches the battery ECU 5 from the sleep state to the normal state by activating the battery ECU 5 (step S3: Yes). S4), it is determined whether or not it is possible to correct the charge rates of the batteries B1 and B2 (step S5). For example, in the charge rate estimation unit 521, when the charge rates of the batteries B1 and B2 estimated by the voltage method are included in the non-flat region, and the current detected by the current meter 2 becomes zero, the batteries B1 and B2 If the time (polarization elimination time) until the monitoring ECU 4 detects an open circuit voltage close to the true battery voltage after a lapse of a predetermined time from the start of polarization elimination is equal to or greater than the threshold value Tth, the charge rate can be corrected. If it is judged that it is possible and the charge rates of the batteries B1 and B2 estimated by the voltage method are included in the flat region, or if the polarization elimination time is shorter than the threshold Tth, it is not possible to correct the charge rate. to decide. The threshold value Tth is the time required from when the current detected by the ammeter 2 becomes zero until the polarization of the batteries B1 and B2 is sufficiently eliminated.

Next, when the charge rate estimation unit 521 determines that the charge rates of the batteries B1 and B2 can be corrected (step S5: Yes), the charge rate estimation unit 521 estimates the charge rates of the batteries B1 and B2 by the voltage method. If the charge rates of the batteries B1 and B2 are corrected (step S6) and it is determined that the charge rates of the batteries B1 and B2 cannot be corrected (step S5: No), the charge rates of the batteries B1 and B2 are not corrected.

Next, the accuracy determination unit 522 determines whether or not the estimation accuracy of the charge rate estimated by the current integration method is good (step S7).

Next, the cell balance control unit 523 determines that the estimation accuracy of the charge rate estimated by the current integration method is good (step S7: Yes), and the charge rate difference ΔSOC is equal to or greater than the threshold value SOCth. (Step S8: Yes), the operation of the cell balance circuit CV is controlled so that the charge rates of the batteries B1 and B2 are equalized (step S9). The threshold value SOCth may be obtained based on the relationship between the charge rate difference ΔSOC and the mileage of the vehicle Ve.

On the other hand, the cell balance control unit 523 determines that the estimation accuracy of the charge rate estimated by the current integration method is not good (step S7: No), or the charge rate difference ΔSOC is smaller than the threshold SOCth (step). S8: No), the charge rates of the batteries B1 and B2 are not equalized.

As described above, in the power storage device 1 of the embodiment, when it is determined that the estimation accuracy of the charge rate estimated by the current integration method is good, the charge rates of the batteries B1 and B2 estimated by the current integration method are equalized. When the cell balance is performed and it is determined that the estimation accuracy of the charge rate by the current integration method is not good, the cell balance that equalizes the charge rates of the batteries B1 and B2 estimated by the current integration method is not performed. .. As a result, even if the estimation accuracy of the charge rate estimated by the voltage method is not good, if the estimation accuracy of the charge rate estimated by the current integration method is good, the batteries B1 and B2 estimated by the current integration method The charge rate can be equalized.

Further, in the power storage device 1 of the embodiment, at least one of an index P1 indicating the detection accuracy of the open circuit voltage, an index P2 indicating the calculation accuracy of the integrated current value, and an index P3 indicating the estimation accuracy of the full charge capacity. When the index P based on the above is higher than the threshold value Pth, it is determined that the estimation accuracy of the charge rate is good. As a result, as the number of indexes used increases, the determination accuracy when determining whether or not the estimation accuracy of the charge rate is good can be increased. Further, since the index to be used can be selected from the indexes P1 to P3 according to the processing capacity of the accuracy determination unit 522, the degree of freedom of the processing capacity of the accuracy determination unit 522 can be increased.

<Other operations of processor 52>
When the processor 52 shown in FIG. 1 receives from the vehicle ECU 6 that the ignition is switched from the ignition off to the ignition on by the operation of the ignition switch by the user, the switches SW1 and SW2 are switched from the cutoff state to the conduction state, and the switch SW3 is in the cutoff state. The input power command value Win or the output power command value Wout according to the charge rate of the batteries B1 and B2 is transmitted to the vehicle ECU 6.

Further, when the charge rate of at least one of the charge rates of the batteries B1 and B2 becomes equal to or less than the first lower threshold value, the processor 52 transmits the limited output power command value Wout to the vehicle ECU 6, and the charge rate is changed. When the value exceeds the first upper limit threshold value, the limited input power command value Win is transmitted to the vehicle ECU 6. The vehicle ECU 6 controls the operation of the inverter circuit Inv so that the power corresponding to the output power command value Wout is supplied from the batteries B1 and B2 to the inverter circuit Inv, and the power corresponding to the input power command value Win is supplied to the inverter circuit. The operation of the inverter circuit Inv is controlled so that the Inv supplies the batteries B1 and B2. When the output power command value Wout or the input power command value Win is limited, the vehicle ECU 6 reduces the duty ratio of the control signal for controlling the on / off of the switch of the inverter circuit Inv, thereby causing the inverters from the batteries B1 and B2. The power supplied to the circuit Inv or the power supplied from the inverter circuit Inv to the batteries B1 and B2 is limited.

Further, when the charging rate of at least one of the charging rates of the batteries B1 and B2 becomes equal to or less than the second lower limit threshold value smaller than the first lower limit threshold value, or the charging rate thereof is higher than the first upper limit threshold value. When the value exceeds the large second upper limit threshold value, power is supplied from the batteries B1 and B2 to the inverter circuit Inv by shutting off the switches SW1, SW2, and SW3, and power is supplied from the inverter circuit Inv to the batteries B1 and B2. It is prohibited that the battery B1 and B2 are supplied with electric power from the charger Ch. The second lower threshold is the charge rate of the batteries B1 and B2 immediately before the batteries B1 and B2 are in the overcharged state, and the second upper threshold is the battery immediately before the batteries B1 and B2 are in the overcharged state. Let it be the charge rate of B1 and B2. This makes it possible to prevent the batteries B1 and B2 from being in an overcharged state or an overdischarged state.

Further, when the switch SW1 is conducting the processor 52, when the voltage transmitted from the monitoring ECU 4 exceeds the overvoltage threshold value, or when the current transmitted from the monitoring ECU 4 exceeds the overcurrent threshold value, or the monitoring EUC4 When the temperature transmitted from is equal to or higher than the overtemperature threshold value, it is determined that an abnormality has occurred in the batteries B1 and B2, and that fact is transmitted to the vehicle ECU 6. When the vehicle ECU 6 receives that the batteries B1 and B2 have an abnormality, the vehicle ECU 6 shuts off the switches SW1, SW2, and SW3 to supply electric power from the batteries B1 and B2 to the inverter circuit Inv. It is prohibited that power is supplied to the batteries B1 and B2, and that power is supplied to the batteries B1 and B2 from the charger Ch.

Further, when the processor 52 receives from the vehicle ECU 6 that the ignition is switched from the ignition on to the ignition off by the operation of the ignition switch by the user, the switches SW1 and SW2 are switched from the conductive state to the cutoff state, and the switch SW3 is kept in the cutoff state. do.

Further, when the processor 52 receives a charging start instruction for the batteries B1 and B2 from the vehicle ECU 6 after the charger Ch and the vehicle Ve are connected via the charging cable, the processor 52 conducts the switches SW1 and SW3 and switches SW2. The cutoff state is set, and the current command value corresponding to the charging rate of the batteries B1 and B2 is transmitted to the vehicle ECU 6. The vehicle ECU 6 transmits the current command value to the charger Ch so that the current corresponding to the current command value is supplied from the charger Ch to the batteries B1 and B2.

The present invention is not limited to the above embodiments, and various improvements and changes can be made without departing from the gist of the present invention.

1 Power storage device 2 Ammeter 3 Thermometer 4 Monitoring ECU
5 Battery ECU
6 Vehicle ECU
51 Storage unit 52 Processor 521 Charge rate estimation unit 522 Charge / discharge control unit 523 Accuracy determination unit 524 Cell balance control unit Ve Vehicle Invert Inverter circuit M Motor Ch Charger SW1, SW2, SW3 Switch B1, B2 Battery CV Cell balance circuit

Claims (2)

With multiple batteries connected in series,
A cell balance circuit that discharges each battery and
A charge rate estimation unit that estimates the charge rate of each battery by a current integration method that uses the integrated value of the current flowing through each battery.
An accuracy determination unit that determines whether or not the estimation accuracy of the charge rate is good,
When it is determined that the estimation accuracy of the charge rate is good, the operation of the cell balance circuit is controlled so that the charge rates of the batteries are equalized, and it is determined that the estimation accuracy of the charge rate is not good. , The cell balance control unit that does not equalize the charge rate of each battery,
A power storage device equipped with. The power storage device according to claim 1.
When the estimation timing comes, the charge rate estimation unit includes the charge rate estimated at the previous estimation timing, the integrated value of the current flowing through each battery between the previous estimation timing and the current estimation timing, and the charge rate estimation unit of each battery. The charge rate of each battery is estimated by the current integration method using the full charge capacity, or the charge rate of each battery is estimated by the voltage method using the open circuit voltage of each battery.
The accuracy determination unit includes a first index indicating the detection accuracy of the open circuit voltage, a second index indicating the calculation accuracy of the integrated value of the current, and a third index indicating the estimation accuracy of the full charge capacity. A power storage device characterized in that when an index based on at least one of them is higher than a threshold value, it is determined that the estimation accuracy of the charge rate is good.

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