JP2020078227A - Charge control device, power storage device, and charge control method - Google Patents

Abstract

To suppress vibration of a current command value while suppressing the occurrence of electrodeposition.SOLUTION: A charge control device for a power storage element includes a calculation unit that calculates a current command value for a charge current of the power storage element such that the current command value does not exceed a current limit value defined by the current limit characteristic. The current limit characteristic has a constant current limit value in a first region in which the voltage of the power storage element is a first voltage or less, which is lower than a CV voltage at the time of CV charging, and has a decreased current limit value as the voltage is higher in a second region in which the voltage of the power storage element is from the first voltage to the CV voltage. The calculation unit calculates the current command value in the second region as a value having a delay with respect to the current limit value on the basis of the current limit value defined by the current limit characteristic and the past current command value.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a method of charging a storage element.

  There is CCCV charging as a method of charging 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 reduced between CC charging and CV charging for the purpose of accurately matching the voltage of the storage element with the CV voltage. It is described that an area is provided for charging while charging.

Japanese Patent No. 5525862

  In a storage element such as a lithium ion secondary battery, electrodeposition may occur 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 negative electrode potential decreases.

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

  The charge control device for the storage element includes a calculator that calculates a current command value of the charging current of the storage element so as not to exceed a current limit value defined by the current limit characteristic, and the current limit characteristic is the storage In the first region in which the voltage of the element 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 element is the first voltage from the first voltage to the CV voltage. In the second region, the higher the voltage is, the lower the current limit value is, and the calculation unit sets the current command value of the second region to the current limit value defined by the current limit characteristic and the past current command value. Based on this, a value having a delay with respect to the current limit value is calculated.

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

A block diagram showing an electrical configuration of a battery and a charging device according to the first embodiment. Exploded perspective view of the battery Plan view of secondary battery Sectional view taken along the line AA of FIG. 3A Current and voltage waveforms during CCCV charging Figure showing current limiting characteristics The figure which shows the correlation of SOC-OCV Figure showing current limiting characteristics Flowchart of current command value calculation processing Diagram showing the charging characteristics of the battery Flowchart of current command value calculation processing The figure which shows a current limiting characteristic about other embodiment.

  The charge control device for the storage element includes a calculator that calculates a current command value of the charging current of the storage element so as not to exceed a current limit value defined by the current limit characteristic, and the current limit characteristic is the storage In the first region in which the voltage of the element 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 element is the first voltage from the first voltage to the CV voltage. In the second region, the higher the voltage is, the lower the current limit value is, and the calculation unit sets the current command value of the second region to the current limit value defined by the current limit characteristic and the past current command 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 decreases in the second region, the charging current decreases during charging while the storage element rises from the first voltage to the CV voltage. Therefore, electrodeposition of the storage element can be suppressed. In this method, the current command value in the second region is set to a value delayed from the current limit value, so that the change in the current command value can be relaxed. Therefore, the vibration of the current command value can be suppressed in the second region. Further, by suppressing the vibration of the current command value, it is possible to suppress the generation of current noise during charging. By suppressing the current noise, the occurrence of electrodeposition can be suppressed. Further, 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 the current value and the power value, it is possible to suppress the vibration of the display value and make it easier for the end user to check the display value.

  In the second region, the current limit value may change in a straight line. With this method, the current command value can be calculated more easily than when the current limit value changes along a curve. Further, compared to the case where the current limit value changes with a curve, the change of the current command value calculated to be a value delayed from the current limit value can be brought close to a constant value, so that the vibration of the current command value can be suppressed. ..

  The calculating unit may determine the current command value of the charging current for the power storage element by weighting and adding the current limit value and the past current command value using a ratio. With this method, the current command value can gently follow the current limit value from the first voltage to the CV voltage.

  The ratio may be different depending on the size of the voltage band curve corresponding to the second region in the OCV curve indicating the OCV-SOC correlation of the power storage element. The vibration of the current command value has a correlation with the size of the OCV curve. In this method, since the ratio varies depending on the size of the OCV curve, it is possible to further suppress the vibration of the current command value.

  The current limiting characteristic may be provided for each temperature of the power storage element. By using the current limiting characteristic according to the temperature of the power storage element, electrodeposition can be suppressed regardless of the temperature of the power storage element.

<Embodiment 1>
1. Description of Battery 50 and Charging Device 10 FIG. 1 is a block diagram showing an electrical configuration of the battery 50 and the charging device 10. The battery 50 includes a current interruption 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 power 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 55P is a power line that connects the positive electrode external terminal 51 and the positive electrode of the assembled battery 60. The power line 55N 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 located on the positive electrode side of the battery pack 60 and are provided on the positive power line 55P.

  The current interruption device 53 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 of the battery 50 can be interrupted by opening the current interrupt device 53.

  The current measuring resistor 54 generates a voltage according to the current I [A] of the battery pack 60. Discharge and charge can be discriminated from the polarity (positive or negative) of the voltage across the current measuring resistor 54. The temperature sensor 115 is a contact type or a non-contact type, and measures the temperature T [° C.] of the battery pack 60.

  The management device 100 is provided in the circuit board unit 65. The management device 100 includes a voltage detection circuit 110, a processing unit 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 a signal line, 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 plurality of lithium-ion secondary batteries 62 connected in series.

  The processing unit 120 includes a CPU 121 having an arithmetic function and a memory 123 that is a storage unit. The processing unit 120 determines the current I of the battery pack 60, the voltage V of each lithium-ion secondary battery 62, the total voltage of the battery pack 60, and the temperature T from the outputs of the current measurement resistor 54, the voltage detection circuit 110, and the temperature sensor 115. Monitor. The processing unit 120 has a charge control function of the battery 50, and performs a calculation process of calculating the current command value Io of the charging current in the current reduction region H2 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 “charge control device” of the present invention.

  The memory 123 is a non-volatile storage medium such as a flash memory or an 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 and past current command values shown in FIG. 5). 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 the external terminals 51 and 52 of the battery 50. The CPU 15 controls the magnitude of the charging current via the charging circuit 13. The current detection resistor 11 is provided to detect the charging current.

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

  The housing 71 houses the battery pack 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 74. The lid 74 has a protrusion 79 that is substantially T-shaped in a plan view. A positive external terminal 51 is fixed to one corner of the front portion of the lid 74, and a negative external terminal 52 is fixed to the other corner.

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

  Although not shown in detail, the electrode body 83 has a porous structure between a negative electrode element in which a base material made of copper foil is coated with an active material and a positive electrode element in which a base material made of aluminum foil is coated with the active material. A separator made of a resin film is arranged. These are all band-shaped, and are wound in a flat shape so that they can be accommodated in the case main body 84 in a state where the negative electrode element and the positive electrode element are displaced from each other on the opposite sides in the width direction with respect to the separator. ..

  A positive electrode terminal 87 is connected to the positive electrode element via a positive electrode current collector 86, and a negative electrode terminal 89 is connected to the negative electrode element via a negative electrode current collector 88. Each of the positive electrode current collector 86 and the negative electrode current collector 88 includes a pedestal portion 90 having a flat plate shape and a leg portion 91 extending from the pedestal portion 90. Through holes are formed in the pedestal portion 90. The leg portion 91 is connected to the positive electrode element or the negative electrode element. Each of the positive electrode terminal 87 and the negative electrode terminal 89 includes a terminal main body portion 92 and a shaft portion 93 protruding downward from a central 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 main body 92 is made of aluminum and the shaft 93 is made of copper, and these are assembled. The terminal main body portions 92 of the positive electrode terminal 87 and the negative electrode 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 from the gaskets 94.

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

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

  At the end of the CC region (the region immediately before the transition to the CV region) F, since the voltage is high and the charging current is large, electrodeposition is likely to occur on the lithium ion secondary battery 62. Electrodeposition is a phenomenon in which lithium metal is deposited on the negative electrode during charging, and is known to occur when the negative electrode potential decreases.

  FIG. 5 is a current limiting characteristic showing the relationship between the maximum cell voltage and the current limiting value. The current limiting characteristic is provided with three regions, that is, a CC region H1, a current reducing region H2, and a CV region H3, and a current limiting value is set for each of the regions H1 to H3. The maximum cell voltage is the maximum voltage of the plurality of lithium-ion secondary batteries 62 connected in series. The data of the current limiting characteristic shown in FIG. 5 is stored in the memory 123.

  The CC region H1 is a region where the maximum cell voltage of the lithium-ion secondary battery 62 is Vo to Vs. The CC area H1 is an area where 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 reducing the charging current as the cell voltage increases. The CV region H3 is a region where the maximum cell voltage is Vc or higher. The CV region H3 is a region where 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 larger than Vo and smaller 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 limiting 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 in the three regions H1 to H3 during charging. You can

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

  When the charging of the battery 50 is started, the processing unit 120 reads the data of the current limiting value Imax defined by the current limiting characteristic of FIG. 5 from the memory 123 and sends it to the charging device 10. The charging device 10 determines the current command value Io of the charging current based on the constraint of the output power of the charging device 10 or the like within a range that does not exceed the current limit value Imax transmitted from the processing unit 120, and CCs the battery 50. 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.

  When the maximum cell voltage of the lithium ion secondary battery 62 rises to the first voltage Vs due to the charging in the CC region H1, the current reduction region H2 is entered.

  In the current reduction region H2, the current limit value is defined by the downward sloping straight line M2 connecting the 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 present 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, the processing unit 120 transmits the calculated current command value Io to the charging device 10. The charging device 10 outputs a charging current based on the current command value Io transmitted from the processing unit 120 to charge the battery 50.

  In the current reduction region H2, the current limit value is decreased as the maximum cell voltage increases, 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 suppressed.

  When the maximum cell voltage of the lithium ion secondary battery 62 rises to the CV voltage Vc due to the charging in the current reduction region H2, the CV region H3 is entered. The CV area H3 corresponds to the “third area” of the present invention.

  As shown in FIG. 5, the current limit value in the 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]. After shifting to the CV area H3, the charging device 10 suspends charging of the battery 50. When the charging is stopped, the voltage increase due to the internal resistance disappears, so that the maximum cell voltage of the lithium ion secondary battery 62 decreases 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 in the control cycle tn with the current limit value determined by the straight line M2 as the upper limit. Then, the charging device 10 outputs the charging current to the battery 50 based on the current command value Io transmitted from the processing unit 120 to charge the battery 50. When the maximum cell voltage of the lithium-ion secondary battery 62 reaches the CV voltage Vc, the current reduction region H2 shifts to the CV region H3.

  In this way, by repeating charging in the current reduction region H2 and stopping charging in the CV region H3, it is possible to charge the battery 50 at a constant voltage (CV charging) while maintaining the maximum cell voltage at the CV voltage Vc. .. Further, as the maximum cell voltage is higher (closer to the CV voltage Vc), the current is charged with a lower current, so that the occurrence of electrodeposition during CV charging can be suppressed.

  As the battery 50 approaches the 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 the charging is terminated when the charging current becomes 0.2 A or less. Further, when the battery 50 is close to full charge, the maximum cell voltage hardly drops from the CV voltage Vc even if charging is stopped, and the charging stopped state continues, so the charging stopped state continues for a predetermined time. This may be the charging end condition.

(B) Vibration Suppression 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 actual capacity (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 located approximately in the range of 31% to 97% SOC. A region where the SOC is 31% or less and a region where the SOC is 97% or more are high change regions in which the amount of change in OCV with respect to the amount of change in SOC is larger than that in the plateau region.

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

  The voltage increase 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 within the current reduction region H2, if the current command value Io of the charging current is lowered from I1 to I2, The voltage rise due to resistance is reduced. 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, when the current command value Io of the charging current I is decreased with the increase of the maximum cell voltage, the increase and decrease of the maximum cell voltage are repeated, so that the current command value Io may oscillate.

  In the current reduction region H2, the processing unit 120 calculates the current command value Io_n at a predetermined control cycle n according to the following equation (2).

Io_n = (1−m) × Io_n _-1 + m × 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 the current limit characteristic. m is a ratio that determines the magnitude of the delay of Io_n with respect to I_limit (m <1).

  An example of calculation of the current command value Io_n is shown. The previous value of the current command value is I1, the current value of the maximum cell voltage is V2, and the current limit value corresponding to the maximum cell voltage V2 defined by the current limit characteristic is I2. When the ratio m is 0.5, the current command value Io_n becomes (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.

The calculation formula of (2) calculates the current command value Io_n by adding both values while weighting the previous value Io_n _-1 of the current command value and the current limit value I_limit according to the ratio m. ing. The obtained current command value Io_n has a delay with respect to the current limit value defined by the current limit characteristic of FIG. The delay is that the current command value does not change up to the current limit value defined by the current limit characteristic, 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 mitigate a steep change in the current command value Io_n and suppress the vibration of the current command value Io.

  The vibration of the current command value Io becomes more significant as the curve of the OCV curve becomes steeper. Therefore, it is advisable to change the ratio m according to the curve (size of the 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 having 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 having a gentle OCV curve and a small inclination, it is preferable to increase the ratio m (close to 1).

  FIG. 8 is a flowchart of the calculation process of the current command value. The calculation process of the current command value Io is composed of 7 steps of S10 to S70, and is repeatedly executed in the current reduction region H2 at a predetermined control cycle tn. The control cycle tn is, for example, 1 [sec].

  In S10, the processing unit 120 uses the outputs of the voltage detection circuit 110, the current measurement resistor 54, and the temperature sensor 115 to determine 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 assembly. The measurement data of the temperature T of the battery 60 is acquired.

  In S20, the processing unit 120 determines whether the measurement data has an abnormality. If the measurement data is abnormal (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 that charging be stopped.

  When the measurement data is normal (S20: NO), the process proceeds to S40, and the processing unit 120 determines whether the control cycle tn has elapsed from the previous process.

  When the control cycle tn has elapsed from the previous process (S40: YES), the process proceeds to S50, and the processing unit 120 performs a process of reading the data of the current limiting characteristic shown in FIG.

After reading the current limiting characteristic, the process proceeds to S60, and the processing unit 120 determines the current command value based on the previous value Io_n _-1 and the current limiting value I_limit corresponding to the maximum cell voltage defined by the current limiting characteristic. The current command value Io_n is calculated from the above equation (2).

  After that, the process proceeds to S70, 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 at the control cycle tn, and the current command value Io_n is transmitted from the management device 100 to the charging device 10 at each control cycle tn. Then, the charging device 10 controls the charging current of 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, where the left vertical axis is the cell voltage, the right vertical axis is the current, and the horizontal axis is the time. Y1 represents the waveform of the current command value after delay according to the equation (2), Y2 represents the waveform of the charging current output from the charging device 10, and Y3 represents 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, since the current command value Io is delayed from the current limit value defined by the current limit characteristic, the change in the current command value Io can be relaxed. Therefore, the vibration of the current command value Io can be suppressed in the current reduction region H2. Further, by suppressing the vibration of the current command value, it is possible to suppress the generation of current noise during charging. By suppressing the current noise, the occurrence of electrodeposition can be suppressed. Further, 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 the current value and the power value, it is possible to suppress the vibration of the display value, and it becomes easier for the end user to check the display value.

  In the current reduction region H2, the current limit value is defined by the straight line M2. By defining the current limit value with the straight line M2, the current command value Io can be calculated more easily and the charging speed is faster than when the current limit value is defined by a curve such as a quadratic curve. Further, the following effects are obtained as compared with the case where the current limit value is defined by a curve such as a quadratic curve. The current command value Io is calculated as a value delayed from the current limit value according to the control characteristics such as the curve of the OCV curve. By defining the current limit value with the straight line M2, the change of the current command value Io can be brought close to a constant value, so that the vibration of the current command value Io can be suppressed.

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

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

  In S10, the processing unit 120 uses the outputs of the voltage detection circuit 110, the current measurement resistor 54, and the temperature sensor 115 to determine the cell voltage V of each secondary battery 62, the total voltage of the assembled battery 60, the charging current I, and the assembled battery 60. The measurement data of the temperature T of is acquired.

  In S20, the processing unit 120 determines whether the measurement data has an abnormality. When the measurement data is normal (S20: NO), the process proceeds to S40, and the processing unit 120 determines whether the control cycle tn has elapsed from the previous process.

  When the control cycle tn has elapsed from the previous process (S40: YES), the processing unit 120 proceeds to S55, and the processing unit 120 stores the current limiting characteristic data corresponding to the temperature T of the assembled battery 60 acquired in S10 in the memory 123. The process of reading from is performed.

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

  After that, the process proceeds to S70, and the processing unit 120 transmits the calculated current command value Io_n to the charging device 10.

  Since the processes of S10 to S70 are repeated at the control cycle tn, when the temperature of the battery pack 60 changes, the current limiting characteristic according to the changed temperature is read. Then, the current command value Io_n is calculated based on the read current limiting characteristic.

  It is known that the lithium-ion secondary battery 62 has a large internal resistance at low temperature, and during charging at low temperature, the potential of the negative electrode decreases and electrodeposition is likely to occur. In the second embodiment, the current limiting characteristic is 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 described above and the 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 illustrated as an example of the power storage element. The power storage element may be another secondary battery such as a lead storage battery, a nickel hydrogen battery, or a lithium air battery. The power storage element is not limited to the case where a plurality of power storage elements are connected in series or series-parallel, and may have a single cell configuration.

  (2) In the first embodiment, an example in which charging is controlled by the maximum cell voltage of the secondary battery 62 is shown, but charging may be controlled by the total voltage of the assembled battery 60.

  (3) In the first embodiment, the current limit value of the current reduction region H2 is defined by one straight line M2. However, if the current limit value decreases with an increase in voltage, it is defined by a curve or a plurality of straight lines. May be.

  (4) In the first embodiment, the current command value Io is calculated by the processing unit 120 of the battery 50. Alternatively, the charging device 10 may calculate the current command value Io. That is, the CPU 15 of the charging device 10 may be the charging control device. In this case, the data of the current limiting characteristic is stored in the internal memory of the charging device 10, and the current command value such as the data of the cell voltage of each secondary battery 62 or the temperature T of the assembled battery is stored in the charging device 10 from the processing unit 120. It is advisable to send the data required to calculate Io.

  (5) In the first embodiment, the current command value Io is calculated based on the equation (2). If the current command value Io is a value that has a delay with respect to the current limit value based on the current limit value defined by the current limit characteristic and the previous value of the current command value, (2 ) May be used for calculation. In the first embodiment, the previous value of the current command value is used as an example of the past current command value, but a value other than the previous value, such as the value of the previous two times, may be used. Further, both the previous value and the two-preceding value 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 that connects the point A corresponding to the maximum allowable current Imax and the point B corresponding to 0 [A]. As shown in FIG. 11, a straight line M2 that defines the current limit value of the current reduction region H2 includes a point A corresponding to the maximum allowable current Imax and a point C corresponding to a predetermined current value Ia larger than 0 [A]. , May be defined by a straight line M3 connecting. In this case, when the CV charging is performed by repeating the current reduction region H2 and the CV region H3, the battery 50 is charged with the charging current of the predetermined current value Ia or more. Further, the predetermined current value Ia may be set to a current value smaller than the current value (0.2 A in the first embodiment) applied to the charging termination determination condition. If the predetermined current value Ia is made larger than the current value applied to the charging end determination condition, the charging current is controlled to be equal to or more than the current value applied to the determination condition, so that the charging end determination condition cannot be detected. By setting the predetermined current value Ia to be equal to or less than the current value applied to the charge termination determination condition, the charge termination determination condition can be detected.

  (7) In the first embodiment, the current limit value is set for the three regions, that is, the CC region H1, the current reduction region H2, and the CV region H3. When the charging is stopped in the CV region H3, if the current command value Io is controlled to 0 [A] in the processing unit 120 in the CV region H3, the setting as the current limit value is unnecessary, As the current limiting characteristic, at least only 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. In addition to this, the battery 50 may be CV-charged in the CV region H3 while controlling the charging current so as to maintain the CV voltage Vc. In this case, the current limit value in the CV region H3 may be set so that electrodeposition does not occur during CV charging in the CV region.

  (9) The battery 50 according to the first and second embodiments can be widely applied regardless of applications such as a power storage device of a solar power generation system, an industrial application such as UPS (uninterruptible power supply), and a vehicle.

  (10) The present technology can be applied to a charge control program for a power storage device. The charge control program for the power storage device is a program that causes a computer to execute a calculation process for calculating a current command value of the charge current of the power storage element so as not to exceed the current limit value defined by the current limit characteristic. In the current limiting characteristic, the current limiting value is constant in the first region in which 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 the first voltage. In the second region from the voltage to the CV voltage, the higher the voltage, the smaller the current limit value. In the calculation process, in the second region, a current command value of a charging current for the storage element is set to the current limit value based on a current limit value defined by the current limit characteristic and a past current command value. On the other hand, a value having a delay is calculated. The present technology can be applied to a recording medium recording a charge control program for a power storage device. The computer is, for example, the processing unit 120.

10 ... Charging device 50 ... Battery (electric storage device)
60 ... Battery pack 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 (3rd area)

Claims (7)

A charge control device for a storage element,
A calculation unit that calculates a current command value of the charging current of the storage element so as not to exceed the current limit value specified by the current limit characteristic,
The current limiting characteristic is
In the first region in which 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, the current limit value is constant,
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 smaller the current limit value,
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 a current limit value defined by the current limit characteristic and a past current command value. Charge control device. The charge control device according to claim 1, wherein
In the second region, the charge control device, wherein the current limit value changes linearly. The charge control device according to claim 1 or 2, wherein
The charge control device, wherein the calculator determines the current command value of the charging current for the power storage element by weighting and adding the current limit value and the past current command value using a ratio. The charge control device according to claim 3,
The charge control device, wherein the ratio varies depending on the size of the curve of the voltage band corresponding to the second region in the OCV curve indicating the OCV-SOC correlation of the power storage element. The charge control device according to any one of claims 1 to 4,
The charge 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 charge control device according to claim 1. A method for controlling charging of a storage element, comprising:
A calculation step of calculating a current command value of the charging current of the storage element so as not to exceed the current limit value defined by the current limit characteristic,
The current limiting characteristic is
In the first region in which 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, the current limit value is constant,
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 smaller the current limit value,
In the calculating step, the current command value of the second region is calculated to be a value having a delay with respect to the current limit value based on the current limit value defined by the current limiting characteristic and the past current command value. Yes, charge control method.

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