JP7329178B2 - Charging control device, power storage device, charging control method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method of charging an electric storage element.

CCCV charging is available as a charging method for the storage element. CCCV charging is a method of charging with a constant current until the voltage of the storage element reaches the CV voltage, and then charging the secondary battery with a constant voltage. In Patent Document 1 below, when switching from CC charging to CV charging, the charging current is decreased between CC charging and CV charging for the purpose of accurately matching the voltage of the storage element to the CV voltage. It is described that a region is provided in which charging is performed while the battery is being charged.

Japanese Patent No. 5525862

Electricity storage elements such as lithium ion secondary batteries may undergo electrodeposition during charging. Electrodeposition is a phenomenon in which metal ions such as lithium are deposited on the negative electrode, and is known to occur when the potential of the negative electrode decreases.

The present invention has been completed based on the circumstances as described above, and an object of the present invention is to suppress the fluctuation of the current command value while suppressing the occurrence of electrodeposition.

A charging control device for a power storage element includes a calculator that calculates a current command value for a charging current of the power storage element so as not to exceed a current limit value defined by a current limit characteristic, wherein the current limit characteristic is defined by the power storage element. In a first region where the voltage of the device is lower than the CV voltage during CV charging and is equal to or lower than the first voltage, the current limit value is constant, and the voltage of the storage device is the first voltage between the first voltage and the CV voltage. In the second region, the higher the voltage, the lower the current limit value. Based on this, a value having a delay with respect to the current limit value is calculated.

It is possible to suppress oscillation of the current command value while suppressing the occurrence of electrodeposition.

FIG. 2 is a block diagram showing the electrical configuration of the battery and charging device for the first embodiment; Battery exploded perspective view Plan view of secondary battery AA line sectional view of FIG. 3A Current waveform and voltage waveform during CCCV charging Diagram showing current limit characteristics Diagram showing SOC-OCV correlation Diagram showing current limit characteristics Flowchart of current command value calculation processing Diagram showing the charging characteristics of a battery Flowchart of current command value calculation processing FIG. 10 is a diagram showing current limiting characteristics of another embodiment;

A charging control device for a power storage element includes a calculator that calculates a current command value for a charging current of the power storage element so as not to exceed a current limit value defined by a current limit characteristic, wherein the current limit characteristic is defined by the power storage element. In a first region where the voltage of the device is lower than the CV voltage during CV charging and is equal to or lower than the first voltage, the current limit value is constant, and the voltage of the storage device is the first voltage between the first voltage and the CV voltage. In the second region, the higher the voltage, the lower the current limit value. Based on this, a value having a delay with respect to the current limit value is calculated.

In this method, since the current limit value is decreased in the second region, the charging current is decreased while the storage element rises from the first voltage to the CV voltage during charging. Therefore, the electrodeposition of the storage element can be suppressed. In this method, the current command value in the second region is set to a value that is delayed with respect to the current limit value, so changes in the current command value can be mitigated. Therefore, in the second region, oscillation of the current command value can be suppressed. Also, by suppressing the oscillation of the current command value, it is possible to suppress the occurrence of current noise during charging. By suppressing the current noise, it is possible to suppress the occurrence of electrodeposition. Furthermore, since the peak of the charging current can be suppressed, the load on the charging device can be suppressed. When the charging device displays information such as a current value and a power value, vibration of the displayed value can be suppressed, making it easier for the end user to check the displayed value.

In the second region, the current limit value may vary linearly. In this method, the current command value can be calculated more easily than when the current limit value changes along a curve. In addition, compared to the case where the current limit value changes along a curve, the fluctuation of the current command value can be suppressed because the change in the current command value, which is calculated to be delayed with respect to the current limit value, can be made close to constant. .

The calculation unit may determine the current command value of the charging current for the storage element by weighting the current limit value and the past current command value using a ratio and adding them. This method allows the current command value to gently follow the current limit value from the first voltage to the CV voltage.

The ratio may differ depending on the magnitude of the curve of the voltage band corresponding to the second region in the OCV curve showing the OCV-SOC correlation of the storage element. The oscillation of the current command value has a correlation with the magnitude of the curve of the OCV curve. In this method, the ratio varies depending on the size of the curve of the OCV curve, so the oscillation of the current command value can be further suppressed.

The current limiting characteristic may be provided for each temperature of the storage element. Electrodeposition can be suppressed regardless of the temperature of the storage element by using the current limiting characteristic according to the temperature of the storage element.

<Embodiment 1>
1. Description of Battery 50 and Charging Device 10 FIG. 1 is a block diagram showing the electrical configuration of the battery 50 and charging device 10 . The battery 50 includes a current interrupting device 53 , an assembled battery 60 including a plurality of secondary batteries 62 , a current measuring resistor 54 , a management device 100 and a temperature sensor 115 . The secondary battery 62 is an example of a storage element. The secondary battery 62 is, for example, a lithium ion secondary battery.

The current interrupting device 53, the current measuring resistor 54 and the assembled battery 60 are connected in series via power lines 55P and 55N. The power line 55</b>P is a power line that connects the positive external terminal 51 and the positive electrode of the assembled battery 60 . The power line 55</b>N is a power line that connects the negative external terminal 52 and the negative electrode of the assembled battery 60 . The current interrupting device 53 and the current measuring resistor 54 are positioned on the positive electrode side of the assembled battery 60 and provided on the power line 55P on the positive electrode side.

The current interrupting device 53 can be composed of a contact switch (mechanical type) such as a relay, or a semiconductor switch such as an FET or a transistor. By opening the current interrupting device 53, the current of the battery 50 can be interrupted.

The current measuring resistor 54 generates a voltage corresponding to the current I[A] of the assembled battery 60 . Discharging and charging can be determined from the polarity (positive/negative) of the voltage across the current measuring resistor 54 . The temperature sensor 115 measures the temperature T [° C.] of the assembled battery 60 by contact or non-contact.

The management device 100 is provided in the circuit board unit 65 . The management device 100 includes a voltage detection circuit 110 , a processing section 120 and a power supply circuit 130 . The voltage detection circuit 110 is connected to both ends of each lithium ion secondary battery 62 by signal lines, and measures the cell voltage V of each lithium ion secondary battery 62 and the total voltage of the assembled battery 60 . The total voltage of the assembled battery 60 is the total voltage of the multiple lithium ion secondary batteries 62 connected in series.

The processing unit 120 includes a CPU 121 having an arithmetic function and a memory 123 as a storage unit. The processing unit 120 calculates the current I of the assembled battery 60, the voltage V of each lithium ion secondary battery 62, the total voltage and temperature T of the assembled battery 60 from the outputs of the current measuring resistor 54, the voltage detection circuit 110, and the temperature sensor 115. Monitor. The processing unit 120 has a charging control function for the battery 50, and performs calculation processing for calculating a current command value Io of the charging current in a current reduction region H2, which will be described later. The processing unit 120 is an example of the "calculation unit" of the present invention, and the management device is an example of the "charging control apparatus" of the present invention.

The memory 123 is a non-volatile storage medium such as flash memory or EEPROM. The memory 123 stores a monitoring program for monitoring the state of the assembled battery 60 and data necessary for executing the monitoring program.

The memory 123 stores a calculation program for calculating the current command value Io of the charging current and data necessary for executing the calculation program (current limiting characteristics shown in FIG. 5, past current command values, etc.). The calculation program can be written in a recording medium such as a CD-ROM.

The charging device 10 includes a current detection resistor 11 , a charging circuit 13 and a CPU 15 and is connected to external terminals 51 and 52 of the battery 50 . The CPU 15 controls the magnitude of charging current via the charging circuit 13 . A current detection resistor 11 is provided to detect the charging current.

The battery 50 has a container 71 as shown in FIG. The container 71 includes a main body 73 and a lid 74 made of synthetic resin material. The main body 73 is cylindrical with a bottom. The main body 73 has a bottom portion 75 and four side portions 76 . An upper opening 77 is formed at the upper end portion by the four side portions 76 .

The housing body 71 houses the assembled battery 60 and the circuit board unit 65 . The assembled battery 60 has a plurality of lithium ion secondary batteries 62 . The circuit board unit 65 is arranged above the assembled battery 60 .

The lid 74 closes the upper opening 77 of the main body 73 . An outer peripheral wall 78 is provided around the lid body 74 . The lid 74 has a projecting portion 79 that is substantially T-shaped in plan view. A positive electrode external terminal 51 is fixed to one corner of the front portion of the lid 74 , and a negative electrode external terminal 52 is fixed to the other corner.

As shown in FIGS. 3A and 3B, the lithium-ion secondary battery 62 includes an electrode body 83 and a non-aqueous electrolyte housed in a rectangular parallelepiped case 82 . The case 82 has a case main body 84 and a lid 85 that closes the upper opening.

The electrode body 83, although not shown in detail, is provided between a negative electrode element in which an active material is applied to a base material made of copper foil and a positive electrode element in which an active material is applied to a base material made of aluminum foil. A separator made of a resin film is arranged. Each of these is strip-shaped, and is wound flat so as to be accommodated in the case main body 84 with the negative electrode element and the positive electrode element shifted to opposite sides in the width direction with respect to the separator. .

A positive terminal 87 is connected to the positive element through a positive current collector 86, and a negative terminal 89 is connected to the negative element through a negative current collector 88, respectively. The positive electrode current collector 86 and the negative electrode current collector 88 are composed of a flat plate-shaped pedestal portion 90 and leg portions 91 extending from the pedestal portion 90 . A through hole is formed in the base portion 90 . Leg 91 is connected to the positive or negative element. The positive electrode terminal 87 and the negative electrode terminal 89 are composed of a terminal main body portion 92 and a shaft portion 93 projecting downward from the center portion of the lower surface thereof. Among them, the terminal body portion 92 and the shaft portion 93 of the positive electrode terminal 87 are integrally formed of aluminum (single material). In the negative electrode terminal 89, the terminal body portion 92 is made of aluminum and the shaft portion 93 is made of copper, and these are assembled together. The terminal bodies 92 of the positive terminal 87 and the negative terminal 89 are arranged at both ends of the lid 85 via gaskets 94 made of an insulating material, and are exposed to the outside through the gaskets 94 .

The lid 85 has a pressure relief valve 95 . Pressure relief valve 95 is located between positive terminal 87 and negative terminal 89 as shown in FIG. 3A. The pressure release valve 95 opens to reduce the internal pressure of the case 82 when the internal pressure of the case 82 exceeds the limit value.

2. Battery Charging Control (A) Current Limiting Characteristics and Suppression of Electrodeposition FIG. 4 shows current waveforms I and V of the lithium ion secondary battery 62 during CCCV charging. CCCV charging is a method of charging the lithium ion secondary battery 62 with a constant current until it reaches the CV voltage (CC charging), and then charging the secondary battery 62 with the CV voltage at a constant voltage (CV charging).

At the end of the CC region (the region just before the transition to the CV region) F, the lithium ion secondary battery 62 is prone to electrodeposition because the voltage is high and the charging current is large. Electrodeposition is a phenomenon in which lithium metal deposits on the negative electrode during charging, and is known to occur due to a decrease in negative electrode potential.

FIG. 5 shows current limit characteristics showing the relationship between the maximum cell voltage and the current limit value. The current limiting characteristic has three regions, a CC region H1, a current reduction region H2, and a CV region H3, and a current limiting value is defined for each of the regions H1 to H3. The maximum cell voltage is the maximum voltage of the multiple lithium ion secondary batteries 62 connected in series. Data of the current limiting characteristics shown in FIG. 5 are stored in the memory 123 .

The CC region H1 is a region in which the maximum cell voltage of the lithium ion secondary battery 62 is Vo to Vs. The CC region H1 is a region in which the battery 50 is charged with constant current (CC charging). The current reduction region H2 is a region where the maximum cell voltage of the lithium ion secondary battery 62 is Vs to Vc. The current reduction region H2 is a region where the battery 50 is charged while the charging current is reduced as the cell voltage rises. The CV region H3 is a region where the maximum cell voltage is Vc or higher. The CV region H3 is a region in which charging is temporarily stopped when the maximum cell voltage becomes equal to or higher than the CV voltage.

Vo is the minimum voltage of the lithium ion secondary battery 62 . Vs is a first voltage greater than Vo and less than Vc. Vc is a control target voltage (CV voltage) of the maximum cell voltage of the lithium ion secondary battery 62 during constant voltage charging (during CV charging) by repeating the current limit region H2 and the CV region H3. The processing unit 120 compares the measured value (maximum cell voltage) of the voltage detection circuit 110 with Vs and Vc to determine where the battery 50 is located among the three regions H1 to H3 during charging. can do

In CC region H1, the current limit value is defined by a horizontal straight line M1. The current limit value is constant regardless of the maximum cell voltage, and its value is the maximum allowable current (rated current) Imax of the lithium ion secondary battery 62 . CC region H1 corresponds to the "first region" of the present invention.

At the start of charging of battery 50 , processing unit 120 reads data of current limit value Imax defined by the current limit characteristics of FIG. The charging device 10 determines the current command value Io of the charging current within a range not exceeding the current limit value Imax transmitted from the processing unit 120, based on restrictions on the output power of the charging device 10, etc., and sets the battery 50 to CC. to charge.

In this example, the current command value Io in the CC region H1 is determined by the charging device 10, but may be determined by the management device 100 and notified to the charging device 10. FIG.

When the maximum cell voltage of the lithium-ion secondary battery 62 rises to the first voltage Vs by charging in the CC region H1, it shifts to the current reduction region H2.

In the current reduction region H2, the current limit value is defined by a right-sloping straight line M2 connecting points A and B in FIG. The current limit value linearly decreases from the maximum allowable current Imax to 0 while the maximum cell voltage of the lithium ion secondary battery 62 changes from Vs to Vc. The current reduction region H2 corresponds to the "second region" of the invention.

In the current reduction region H2, the processing unit 120 calculates the current command value Io of the charging current at the control cycle tn with the current limit value determined by the straight line M2 as the upper limit. Then, processing unit 120 transmits the calculated current command value Io to charging device 10 . The charging device 10 outputs charging current based on the current command value Io transmitted from the processing unit 120 to charge the battery 50 .

Within the current reduction region H2, the higher the maximum cell voltage is, the more the current limit value is decreased, so that when the cell voltage of the lithium ion secondary battery 62 rises to near the CV voltage Vc due to charging, electrodeposition occurs. can be restrained from doing

When the maximum cell voltage of the lithium ion secondary battery 62 rises to the CV voltage Vc due to charging in the current reduction region H2, it shifts to the CV region H3. The CV region H3 corresponds to the "third region" of the present invention.

As shown in FIG. 5, the current limit value in CV region H3 is 0 [A]. Therefore, after shifting to the CV region H3, the processing unit 120 notifies the charging device 10 that the current command value is 0 [A]. The charging device 10 temporarily stops charging the battery 50 after the transition to the CV region H3. When charging stops, the voltage rise due to the internal resistance disappears, so the maximum cell voltage of the lithium ion secondary battery 62 drops from the CV voltage Vc and returns to the current reduction region H2.

When returning to the current reduction region H2, as described above, the processing unit 120 calculates the current command value Io at the control cycle tn with the current limit value determined by the straight line M2 as the upper limit. Then, charging device 10 outputs charging current to battery 50 based on current command value Io transmitted from processing unit 120 to charge battery 50 . When the maximum cell voltage of the lithium ion secondary battery 62 reaches the CV voltage Vc, it shifts from the current reduction region H2 to the CV region H3.

By repeating charging in the current reduction region H2 and stopping charging in the CV region H3 in this manner, the battery 50 can be charged at a constant voltage (CV charging) while maintaining the maximum cell voltage at the CV voltage Vc. . Also, the higher the maximum cell voltage (the closer it is to the CV voltage Vc), the lower the charging current, so the occurrence of electrodeposition during CV charging can be suppressed.

As the battery 50 approaches full charge, the charging current of the battery 50 gradually decreases. In this example, the charging termination determination condition is set to 0.2 A as an example, and charging is terminated when the charging current becomes 0.2 A or less. Further, when the battery 50 approaches full charge, even if charging is stopped, the maximum cell voltage hardly drops from the CV voltage Vc, and the charging stop state continues, so the charging stop state continues for a predetermined time. may be used as the charging end condition.

(B) Suppression of Vibration of Current Command Value FIG. 6 is an OCV curve of the lithium-ion secondary battery 62 . The SOC (state of charge) is the ratio of the remaining capacity Cr to the available capacity Ca of the secondary battery 62, as shown in (1) below. OCV (open circuit voltage) is the open circuit voltage of the secondary battery 62 .

SOC=(Cr/Ca)×100 (1)

The OCV curve X1 has a plateau region in which the amount of change in OCV with respect to the amount of change in SOC is substantially flat. The plateau region is a region in which the amount of change in OCV with respect to the amount of change in SOC is 2 [mV/%] or less. The plateau region is generally located between 31% and 97% SOC. The region where the SOC is 31% or less and the region where the SOC is 97% or more are high change regions where the amount of change in OCV with respect to the amount of change in SOC is larger than the plateau region.

X2 indicated by a dashed line in FIG. 6 is a charge curve showing voltage changes of the lithium ion secondary battery 62 when charged at a predetermined rate. The charging curve X2 is shifted upward with respect to the OCV curve X1, and has a higher voltage value even if the SOC value is the same. This voltage difference ΔV is the amount of voltage increase due to the internal resistance of the lithium ion secondary battery 62, and depends on the magnitude of the charging current.

The voltage rise due to the internal resistance of the lithium-ion secondary battery 62 decreases as the charging current decreases. As shown in FIG. 7, when the maximum cell voltage of the lithium ion secondary battery 62 rises from V1 to V2 in the current reduction region H2, if the current command value Io of the charging current is lowered from I1 to I2, the internal Voltage rise due to resistance becomes smaller. Therefore, the maximum cell voltage of the secondary battery 62 drops from V2 to V3. When the maximum cell voltage drops to V3, the current command value Io of the charging current is raised from I2 to I3.

As described above, if the current command value Io of the charging current I is decreased as the maximum cell voltage increases, the maximum cell voltage is repeatedly increased and decreased, so the current command value Io may oscillate.

The processing unit 120 calculates the current command value Io_n at a predetermined control cycle n in accordance with the following (2) arithmetic expression within the current reduction region H2.

Io_n = (1-m) x Io_n _-1 + m x I_limit (2)
Io_n _-1 is the previous value of the current command value. I_limit is a current limit value corresponding to the maximum cell voltage defined by current limit characteristics. m is the ratio that determines the magnitude of the delay of Io_n to I_limit (m<1).

A calculation example of the current command value Io_n is shown. Let I1 be the previous value of the current command value, V2 be the current value of the maximum cell voltage, and I2 be the current limit value corresponding to the maximum cell voltage V2 defined by the current limit characteristics. When the ratio m is 0.5, the current command value Io_n is (I1+I2)/0.5, which is an intermediate value between the previous value I1 of the current command value and the current limit value I2.

In the formula (2), the previous value Io_n _-1 of the current command value and the current limit value I_limit are weighted according to the ratio m, and the current command value Io_n is obtained by adding both values. ing. The obtained current command value Io_n has a delay with respect to the current limit value defined by the current limit characteristics of FIG. The lag is that the current command value does not change up to the current limit value defined by the current limit characteristics, and the current command value has a difference Δ with respect to the current limit value. The smaller the ratio m, the larger the delay, and the closer the ratio m is to 1, the smaller the delay.

By having such a delay, it is possible to moderate abrupt changes in the current command value Io_n and suppress oscillation of the current command value Io.

The steeper the OCV curve, the more noticeable the oscillation of the current command value Io. Therefore, it is preferable to vary the ratio m according to the curve (magnitude of inclination) of the OCV curve. That is, in the voltage band (Vs to Vc) of the current reduction region H2, when charging a secondary battery with a steep OCV curve and a large slope, it is preferable to reduce the ratio m. In the voltage band (Vs to Vc) of the current reduction region H2, when charging a secondary battery with a gentle OCV curve and a small slope, it is preferable to increase the ratio m (close to 1).

FIG. 8 is a flowchart of a current command value calculation process. The calculation process of the current command value Io is composed of seven steps S10 to S70, and is repeatedly executed at a predetermined control cycle tn in the current reduction region H2. The control cycle tn is, for example, 1 [sec].

In S10, the processing unit 120 determines the cell voltage V of each lithium ion secondary battery 62, the total voltage of the assembled battery 60, the charging current I, and the Measured data of the temperature T of the battery 60 is acquired.

In S20, the processing unit 120 determines whether there is an abnormality in the measurement data. If there is an abnormality in the measurement data (S20: YES), error processing is performed. The error process is, for example, a process of notifying the charging device 10 of an abnormality and requesting suspension of charging.

If the measurement data is normal (S20: NO), the processing unit 120 proceeds to S40 and determines whether the control cycle tn has passed since the previous processing.

If the control cycle tn has passed since the previous process (S40: YES), the processing unit 120 proceeds to S50, and the processing unit 120 reads the current limiting characteristic data shown in FIG.

After reading out the current limit characteristics, the processing unit 120 proceeds to S60, and the processing unit 120 determines the current limit value I_limit corresponding to the maximum cell voltage defined by the current command value _{Io_n-1} and the current limit value defined by the current limit characteristics. , the current command value Io_n is calculated from the above equation (2).

After that, the process proceeds to S<b>70 , and the processing unit 120 transmits the calculated current command value Io_n to the charging device 10 .

The processing of S10 to S70 is repeated in control cycle tn, and current command value Io_n is transmitted from management device 100 to charging device 10 in each control cycle tn. Then, the charging device 10 controls the charging current in the current reduction region H2 based on the transmitted current command value Io_n.

FIG. 9 is a graph showing the charging characteristics of the battery 50, with the cell voltage on the left vertical axis, the current on the right vertical axis, and the time on the horizontal axis. Y1 indicates the waveform of the current command value after the delay according to formula (2), Y2 indicates the waveform of the charging current output from the charging device 10, and Y3 indicates the waveform of the maximum cell voltage.

3. Effect In this method, the current reduction region H2 is provided between the CC region H1 and the CV region H3, and the charging current decreases as the secondary battery 62 increases to the CV voltage Vc during charging. Therefore, the electrodeposition of the lithium ion secondary battery 62 can be suppressed. In this method, the current command value Io is set to a value that is delayed with respect to the current limit value defined by the current limit characteristics, so changes in the current command value Io can be moderated. Therefore, oscillation of the current command value Io can be suppressed in the current reduction region H2. Also, by suppressing the oscillation of the current command value, it is possible to suppress the occurrence of current noise during charging. By suppressing the current noise, it is possible to suppress the occurrence of electrodeposition. Furthermore, since the peak of the charging current can be suppressed, the load on the charging device 10 can be suppressed. When the charging device 10 displays information such as a current value and a power value, vibration of the displayed value can be suppressed, making it easier for the end user to check the displayed value.

The current reduction region H2 defines the current limit value with a straight line M2. By specifying the current limit value by the straight line M2, the current command value Io can be easily calculated and the charging speed is increased compared to the case where the current limit value is specified by a curve such as a quadratic curve. Moreover, compared with the case where the current limit value is defined by a curve such as a quadratic curve, the following effects are obtained. The current command value Io is calculated as a value delayed with respect to the current limit value according to control characteristics such as the curve of the OCV curve. By defining the current limit value by the straight line M2, the change in the current command value Io can be brought close to constant, so that the oscillation of the current command value Io can be suppressed.

<Embodiment 2>
In the second embodiment, current limiting characteristics are provided according to the temperature T of the assembled battery 60 . As for the current limiting characteristic, the lower the temperature T, the smaller the maximum allowable current Imax.

FIG. 10 is a flow chart of a current command value calculation process. The current command value calculation process of FIG. 10 differs from the calculation process of FIG. 8 in the process of S55.

In S10, the processing unit 120 determines the cell voltage V of each secondary battery 62, the total voltage of the assembled battery 60, the charging current I, and the Measured data of the temperature T of is acquired.

In S20, the processing unit 120 determines whether there is an abnormality in the measurement data. If the measurement data is normal (S20: NO), the processing unit 120 proceeds to S40 and determines whether the control cycle tn has passed since the previous processing.

If the control cycle tn has passed since the previous process (S40: YES), the processing unit 120 moves to S55, and the processing unit 120 stores the data of the current limiting characteristics corresponding to the temperature T of the assembled battery 60 acquired in S10 in the memory 123. Perform processing to read from

After reading out the current limit characteristics, the processing unit 120 proceeds to S60, based on the previous current command value Io_n _-1 and the current limit value I_limit defined by the current limit characteristics, the above equation (2) Then, the current command value Io_n is calculated.

After that, the process proceeds to S<b>70 , and the processing unit 120 transmits the calculated current command value Io_n to the charging device 10 .

Since the processing of S10 to S70 is repeated at the control cycle tn, when the temperature of the assembled battery 60 changes, the current limiting characteristic corresponding to the temperature after the change is read. Then, the current command value Io_n is calculated based on the read current limit characteristics.

The lithium-ion secondary battery 62 is known to have a large internal resistance at low temperatures, and during charging at low temperatures, the potential of the negative electrode decreases and electrodeposition is likely to occur. In Embodiment 2, current limiting characteristics are provided for each temperature of the assembled battery 60, and the lower the temperature, the smaller the maximum allowable current Imax. Therefore, it is possible to suppress the occurrence of electrodeposition during charging at a low temperature.

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

(1) In the first embodiment, the lithium-ion secondary battery 62 is exemplified as an example of the storage element. The storage element may be a lead-acid battery, a nickel-metal hydride battery, a lithium-air battery, or another secondary battery. The power storage device is not limited to connecting a plurality of devices in series or series-parallel, and may be configured as a single cell.

(2) In the first embodiment, the charging is controlled by the maximum cell voltage of the secondary battery 62, but the total voltage of the assembled battery 60 may be used to control charging.

(3) In the first embodiment, the current limit value of the current reduction region H2 is defined by one straight line M2. may

(4) In the first embodiment, the processing unit 120 of the battery 50 calculates the current command value Io. Alternatively, the charging device 10 may calculate the current command value Io. That is, the CPU 15 of the charging device 10 may be used as the charging control device. In this case, the internal memory of the charging device 10 holds the data of the current limiting characteristics, and the processing unit 120 sends the charging device 10 the current command value such as the cell voltage of each secondary battery 62 and the temperature T of the assembled battery. Data necessary for calculating Io may be transmitted.

(5) In the first embodiment, the current command value Io is calculated based on the formula (2). If the current command value Io obtains a value with a delay with respect to the current limit value based on the current limit value defined by the current limit characteristics and the previous value of the current command value, then (2 ) may be calculated using a formula other than the formula. In the first embodiment, the previous value of the current command value is used as an example of the past current command value. Also, both the previous value and the value before last may be used as the past current command value.

(6) In the first embodiment, the current limit value of the current reduction region H2 is defined by the straight line M2 connecting the point A corresponding to the maximum allowable current Imax and the point B corresponding to 0[A]. As shown in FIG. 11, the straight line M2 that defines the current limit value of the current reduction region H2 has a point A corresponding to the maximum allowable current Imax and a point C corresponding to a predetermined current value Ia greater than 0 [A]. , may be defined by a straight line M3 connecting . In this case, the battery 50 is charged with a charging current equal to or greater than the predetermined current value Ia during CV charging by repeating the current reduction region H2 and the CV region H3. Further, the predetermined current value Ia is preferably set to a current value smaller than the current value (0.2 A in the first embodiment) applied to the charging end determination condition. If the predetermined current value Ia is made larger than the current value applied to the charging termination determination condition, the charging current is controlled to be equal to or higher than the current value applied to the charging termination determination condition, so the charging termination determination condition cannot be detected. By making the predetermined current value Ia equal to or less than the current value applied to the charging termination determination condition, the charging termination determination condition can be detected.

(7) In Embodiment 1, the current limit values are set for the three regions of CC region H1, current reduction region H2, and CV region H3. When charging is stopped in the CV region H3, if the processing unit 120 controls the current command value Io to 0 [A] in the CV region H3, it is not necessary to set the current limit value. As for the current limiting characteristics, at least the CC region H1 and the current reduction region H2 may be set.

(8) In the first embodiment, the battery 50 is CV charged at the CV voltage Vc by repeating charging in the current reduction region H2 and stopping charging in the CV region H3. Alternatively, in the CV region H3, the battery 50 may be CV charged while controlling the charging current so as to maintain the CV voltage Vc. In this case, it is preferable to set the current limit value in the CV region H3 so that electrodeposition does not occur during CV charging in the CV region.

(9) The battery 50 of Embodiments 1 and 2 can be widely applied regardless of industrial use such as a power storage device of a photovoltaic power generation system, UPS (uninterruptible power supply), and vehicle use.

(10) The present technology can be applied to a charging control program for a power storage device. The charging control program for the power storage device is a program that causes the computer to execute calculation processing for calculating a current command value for the charging current of the power storage element so as not to exceed the current limit value defined by the current limit characteristics. In the current limit characteristic, the current limit value is constant in a first region where the voltage of the storage element is lower than the CV voltage during CV charging and is equal to or lower than the first voltage, and the voltage of the storage element is set to the first voltage. In the second region from voltage to the CV voltage, the higher the voltage, the lower the current limit. In the calculation process, in the second region, the current command value of the charging current for the storage element is set to the current limit value based on the current limit value defined by the current limit characteristic and the past current command value. It is calculated to a value that has a delay with respect to The present technology can be applied to a recording medium recording a charging control program for a power storage device. The computer is the processing unit 120 as an example.

10... Charging device 50... Battery (power storage device)
60... Assembled battery 62... Lithium ion secondary battery (storage element)
100... Management device (charging control device)
120 ... processing unit (calculation unit)
H1...CC area (first area)
H2... Current reduction area (second area)
H3...CV area (third area)

Claims (7)

A charging control device for a power storage element,
a calculation unit that calculates a current command value for the charging current of the storage element so as not to exceed a current limit value defined by current limit characteristics;
The current limiting characteristic is
The current limit value is constant in a first region where the voltage of the storage element is lower than the CV voltage during CV charging and is equal to or lower than the first voltage,
In the second region where the voltage of the storage element is from the first voltage to the CV voltage, the higher the voltage, the more the current limit value decreases,
The calculation unit calculates the current command value of the second region to a value having a delay with respect to the current limit value based on the current limit value defined by the current limit characteristic and the past current command value. charge controller. The charging control device according to claim 1,
The charging control device, wherein the current limit value linearly changes in the second region. The charging control device according to claim 1 or 2,
The charging control device, wherein the calculation unit determines a current command value of a charging current for the storage element by weighting the current limit value and a past current command value using a ratio and adding them. The charging control device according to claim 3,
The charging control device, wherein the ratio varies depending on the magnitude of a curve of a voltage band corresponding to the second region in an OCV curve showing the OCV-SOC correlation of the storage element. The charging control device according to any one of claims 1 to 4,
The charging control device, wherein the current limiting characteristic is provided for each temperature of the storage element. a storage element;
A power storage device comprising the charging control device according to any one of claims 1 to 5. A charging control method for a power storage element, comprising:
a calculating step of calculating a current command value for the charging current of the storage element so as not to exceed a current limit value defined by current limit characteristics;
The current limiting characteristic is
The current limit value is constant in a first region where the voltage of the storage element is lower than the CV voltage during CV charging and is equal to or lower than the first voltage,
In the second region where the voltage of the storage element is from the first voltage to the CV voltage, the higher the voltage, the more the current limit value decreases,
In the calculating step, the current command value of the second region is calculated to have a delay with respect to the current limit value based on the current limit value defined by the current limit characteristic and the past current command value. charge control method.

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