JP5673422B2 - Secondary battery charging system - Google Patents

Description

  The present invention relates to a charging system for a secondary battery (hereinafter also simply referred to as a battery) mounted on a vehicle.

In recent years, a chargeable / dischargeable battery has been used as a driving power source for vehicles such as hybrid vehicles and electric vehicles, and portable electronic devices such as notebook computers and video camcorders. Among such batteries, as charging to batteries mounted on vehicles such as electric vehicles and plug-in hybrid vehicles, in addition to charging regenerative power from motors and charging with in-vehicle engines, after vehicles are used, External charging using an external power source outside the vehicle can be mentioned.
As an apparatus or a system for charging such a battery, for example, Patent Document 1 discloses that an electric motor can be externally charged from a non-vehicle charger, in addition to being able to be charged by regeneration from an electric motor for driving driving. There is disclosed an electric traveling drive device for a vehicle that includes a battery (battery) that can be discharged to drive the vehicle. The electric travel drive device for a vehicle includes a charging process storage unit that stores a charging process mode when the battery is charged, and a discharge process storage unit that stores a history of battery discharge with respect to the electric motor.
Patent Document 2 discloses a required charging power calculation unit that calculates the necessary charging power necessary to acquire the SOC of the power storage unit (battery) and to set the power storage unit to a predetermined charging state based on the SOC. An electric power system including a charging current determination unit is disclosed. Among these, the charging current determination unit determines the charging current based on the required charging power from the required charging power calculation unit and the chargeable time of the power storage unit acquired in advance by the chargeable time acquisition unit.

JP 2007-252061 A JP 2009-22061 A

  Specifically, the charge processing storage unit of Patent Document 1 corresponds to the amount of charge stored in the battery before the start of external charging, obtained based on the discharge history of the battery (battery) stored in the discharge processing storage unit. Mode is selected. Moreover, in the electric power system of patent document 2, a charging current is determined based on SOC of the battery before the start of external charging. In other words, in the technologies disclosed in Patent Documents 1 and 2, the magnitude of the charging current (the value of the external charging current) in the external charging is determined by the state of the battery (SOC) at the time of starting the external charging. Not too much.

  However, depending on the usage status of the battery when using the vehicle before external charging (for example, the magnitude of the discharging current (or charging current) during driving or the length of time during which charging or discharging is performed) It has been found that if the magnitude of the charging current is set to an appropriate value, the battery characteristics can be affected, for example, deterioration (increase) in the internal resistance of the battery can be suppressed.

  The present invention has been made based on such knowledge, and an object of the present invention is to provide a charging system for a secondary battery that can be charged under a charging condition of external charging in accordance with the usage status of the battery when the vehicle is used. .

One aspect of the present invention is a charging system for a secondary battery mounted on a vehicle, the secondary battery, a current detection device that detects a current value of a current flowing through the secondary battery, and an external device outside the vehicle. A charging device that externally charges the secondary battery using a power source, and a period from the previous external charging to a start of a new external charging at each time point in the period obtained by the current detection device. Using the current value, the secondary battery was charged from a power source other than the external power source from the average discharge current value obtained by dividing the total amount of discharged electricity discharged from the secondary battery by the total discharge time during which this discharge was performed. An acquisition means for obtaining an average discharge current value after subtraction for the period obtained by subtracting an average charge current value obtained by dividing the total charge electricity amount by the total charge time for performing the charge, and based on the average discharge current value after subtraction In the new external charging Determining means for determining the proper use or charging current value of the external charging techniques is charged condition, a secondary battery charging system comprising a.

The battery charging system described above is based on the acquisition means for acquiring the average discharge current value after subtraction for the period from the previous external charge until a new external charge is performed, and the battery based on the average discharge current value after subtraction. And determining means for determining the charging method for properly using the external charging method which is the charging condition in the new external charging. For this reason, according to this system, it can charge on the charge conditions of the external charge according to the use condition of the battery at the time of vehicle use.

In addition, as a method of external charging of the battery, for example, constant current charging (CC charging) for charging at a constant current value or constant current value until the battery voltage (terminal voltage) becomes a predetermined voltage. Examples include constant current-constant voltage charging (CC-CV charging) in which charging is performed by gradually decreasing the current value while maintaining the above-described predetermined voltage after charging. In addition, constant power charging (CP charging) in which charging is performed with a voltage and current at a constant power, or charging with a voltage and current at a constant power value until the battery voltage reaches a predetermined voltage, and then the above-mentioned predetermined power. Constant power-constant voltage charging (CP-CV charging) in which charging is performed by gradually decreasing the current value while maintaining the voltage of the above. Also, CC charging and CP charging can be combined.
Further, in the battery charging system technique, as a technique for determining the charging condition by the determining means, a method of determining the charging condition in advance before starting charging the battery, or each charging the battery There is a method of determining a charging condition (for example, a charging current value) at each time.

In addition to the current sensor for detecting the magnitude of the current, the current detection device includes, in addition to a circuit for driving the current sensor, an acquisition unit (for example, a microcomputer) that controls them and captures the output of the current sensor. ).
Moreover, as a charging device, it is an apparatus which controls the electric power supplied from the external power supply so that a battery can be charged, and charges a battery, for example, a converter and a constant power-constant voltage power supply are mentioned.

  Furthermore, in the above-described secondary battery charging system, the determination unit is configured to increase the voltage of the secondary battery by the external charging and reach a charging upper limit voltage among the charging conditions in the new external charging. If the charging condition during the voltage increase period of the secondary battery is determined to be a charging condition in which the current value of the external charging is within a range of 0.2 to 5.0 times the average discharge current value after the subtraction, good.

  According to the study by the present inventors, the charging condition during the voltage increase period described above is a charging in which the current value of external charging is a value within the range of 0.2 to 5.0 times the average discharge current value after subtraction. It has been found that a battery that is repeatedly charged as a condition can suppress an increase in battery resistance as compared with a battery that is repeatedly charged at an external charging current value outside the above range.

  In the battery charging system described above, the determining means determines the charging condition during the voltage increase period as a charging condition in which the current value of external charging is within a range of 0.2 to 5.0 times the average discharge current value after subtraction. To do. For this reason, a system that suppresses an increase in battery resistance as compared with a battery that repeats charging at a value less than 0.2 times the average discharge current value after subtraction that is outside this range, or a value greater than 5.0 times. It becomes.

  For example, when external charging is performed by CC charging, the voltage increasing period corresponds to the entire charging period from when the battery voltage (inter-terminal voltage) increases to reach the charging upper limit voltage due to the CC charging. Further, for example, when external charging is performed by CC-CV charging, a period from the charging period to the time when the battery voltage rises and reaches the charging upper limit voltage due to the CC charging performed earlier corresponds. In addition, for example, when external charging is performed by CP charging, this CP charging corresponds to the entire charging period from when the voltage increases to the charging upper limit voltage. Further, for example, when external charging is performed by CP-CV charging, a period from the charging period to the time when the battery voltage rises and reaches the charging upper limit voltage due to the CP charging performed earlier corresponds.

It is explanatory drawing of the vehicle concerning embodiment and modification. It is a perspective view of the battery used by embodiment and a modification. It is a flowchart which shows the process in the period after the last external charge by the battery charging system until the start of a new external charge concerning embodiment and modification. It is a flowchart which shows the process of the external charge by the battery charging system concerning embodiment. It is explanatory drawing which shows the relationship with last external charge, new external charge, and period TM in embodiment and modification. It is a graph which shows the time change of the voltage and charging current value of an assembled battery when it assumes that CP-CV charge was started at the time t1 concerning embodiment and modification. In embodiment, it is a graph which shows the change of the voltage of a battery pack and the charging current value obtained by the charging conditions selected in the 1st case. In embodiment, it is a graph which shows the change of the voltage obtained by the charging condition selected by the 2nd case, and a charging current value. In embodiment, it is a graph which shows the change of the voltage obtained by the charging condition selected by the 3rd case, and a charging current value. In embodiment, it is a graph which shows the change of the voltage obtained by the charging condition selected by the 4th case, and a charging current value. In embodiment, it is a graph which shows the change of the voltage obtained by the charging condition selected by the 5th case, and a charging current value. In embodiment, it is a graph which shows the change of the voltage obtained by the charging condition selected by the 6th case, and a charging current value. It is a flowchart which shows the process of a charging condition determination subroutine among the flowcharts of the process of the external charge by the battery charging system concerning embodiment. It is a graph which shows the charging / discharging pattern used for a charging / discharging test. It is a graph which shows the relationship between a current value magnification and internal resistance initial ratio. It is a flowchart which shows the process of external charging by a battery charging system according to a modified embodiment.

(Embodiment)
Next, embodiments of the present invention will be described with reference to the drawings.
First, the vehicle 100 according to the present embodiment will be described. FIG. 1 shows a perspective view of the vehicle 100.
The vehicle 100 includes a plurality of batteries 1 and 1 forming an assembled battery 110, a current sensor 130 that detects a current value I of a current flowing through the assembled battery 110 (battery 1), and an external power source disposed outside the vehicle 100. A plug-in hybrid electric vehicle including a converter 140 that charges the assembled battery 110 (battery 1) using XV. In addition to these, a plug-in hybrid vehicle control device (hereinafter also referred to as a PHV control device) 120, an engine 150, a cable 160, an inverter 170, a front motor 181, a rear motor 182, a vehicle body 190, and a plug 195P are provided at the tip. A cable 195 with a plug is provided. Among these, the assembled battery 110 (battery 1), the PHV control device 120, the current sensor 130, the converter 140, the cable 160, and the cable with plug 195 constitute the external charging system CS1.

  The vehicle 100 can travel using the front motor 181 and the rear motor 182, and can travel using the engine 150, the front motor 181 and the rear motor 182 in combination. On the other hand, while the vehicle is stopped, the plug 195P of the cable with plug 195 is inserted into the external power source XV installed outside the vehicle 100, and the plurality of batteries 1 and 1 in the assembled battery 110 are charged using the external charging system CS1. can do.

  The PHV control device 120 of the vehicle 100 has a CPU, a ROM, and a RAM, and includes a microcomputer (not shown) that operates according to a predetermined program. The PHV control device 120 can communicate with the current sensor 130, the converter 140, the engine 150, the inverter 170, the front motor 181 and the rear motor 182, and performs various controls according to the status of each part. For example, the combination of the driving force of the engine 150 and the driving force of the front motor 181 and the rear motor 182 according to the traveling state of the vehicle 100 is controlled, or the assembled battery 110 is supplied from the external power source XV through the cable with plug 195 and the converter 140. Charge control when charging (battery 1) is performed.

  In the assembled battery 110, 100 batteries 1 and 1 are arranged in an assembled battery case 110A. The battery 1 constituting the assembled battery 110 is a wound lithium ion secondary battery including an electrode body 20 and an electrolyte (not shown) in a rectangular box-shaped battery case 10 (see FIG. 2). The plurality of batteries 1 and 1 are connected in series with each other by bolt fastening with a bus bar (not shown).

The electrolytic solution of the battery 1 is an organic electrolytic solution in which LiPF ₆ is added as a solute to a mixed organic solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) so that lithium ions have a concentration of 1 mol / l. The electrode body 20 is formed by winding a belt-like positive electrode plate 21 and a negative electrode plate 22 into a flat shape via a belt-like separator (not shown) made of polyethylene (see FIG. 2).

The positive electrode plate 21 has a strip-shaped aluminum foil (not shown) made of aluminum, and a positive electrode active material layer (not shown) disposed on both surfaces of the aluminum foil. Among these, the positive electrode active material layer includes positive electrode active material particles, a conductive material, and a binder.
Moreover, the negative electrode plate 22 has copper strip-shaped copper foil (not shown) and the negative electrode active material layer (not shown) arrange | positioned on both surfaces of this copper foil. Among these, the negative electrode active material layer contains graphite and a binder.

  Moreover, the current sensor 130 which is a known DC current sensor detects the magnitude (current value I) of the DC current flowing through the battery 1 (the assembled battery 110). The current value I detected by the current sensor 130 is taken into the PHV control device 120.

  In addition, a converter 140 including a known rectifier is connected to an external power source XV including a 100 V commercial power source disposed outside the vehicle 100 through a cable 195 with a plug. Converter 140 converts the electric power of external power supply XV into a direct current and charges battery 1 (assembled battery 110). The converter 140 is controlled by the PHV control device 120 for its output voltage, output current, or output voltage.

Next, external charging using the above-described external charging system CS1 will be described with reference to the flowchart of FIG. 4 (second routine R2). With this external charging, the battery 1 is charged through the converter 140 while the battery 1 (the assembled battery 110) is mounted on the vehicle using the external power source XV outside the vehicle 100. Of the external charging, the new external charging procedure this time will be described below with reference to the flowchart of FIG.
Also, FIG. 3 shows that the vehicle 100 is in operation during a period TM (see FIG. 5) from the previous external charge performed before the new external charge to the start of the new external charge. 6 shows a flowchart (first routine R1) executed during a certain period.

First, the first routine R1 shown in FIG. 3 will be described. In addition, this 1st routine R1 repeats step S2-S8 mentioned below with cycle period TJ (0.1 second in this embodiment).
In step S1, it is determined whether or not the operation of the vehicle 100 is started (key-on). Here, if NO, that is, if the key is not turned on, step S1 is repeated. If YES, that is, if the key is turned on, the process proceeds to step S2, and the current value I of battery 1 (battery 110) is detected using current sensor 130. Measure.

In step S3, it is determined whether or not the measured current value I is the value of the charging current of the battery 1 (the assembled battery 110).
If YES, that is, if the current value I is the value of the charging current, the process proceeds to step S4, and the total charge electricity amount QC and the total charge time TC at this timing (time) are acquired. Of these, the total amount of charged electricity QC is the charge charged in the battery 1 (the assembled battery 110) from a power source other than the external power source XV (for example, the front motor 181 and the rear motor 182 that generate regenerative power) within the period TM described above. This is the total amount of electricity. The total charging time TC is the total time during which charging is performed with a power source other than the external power source XV within the period TM.
On the other hand, NO, that is, the current value I is not the value of the charging current (that is, the current value I is the value of the discharge current of the battery 1 (the assembled battery 110) or the current is flowing through the battery 1 (the assembled battery 110). If not, the process proceeds to step S5.

  In step S4, the current total charge amount QC and the total charge time TC are obtained. Specifically, since the last external charge, the total charge electricity amount QC stored in the RAM (not shown) is charged to the charge electricity amount ΔQC charged for one cycle time TJ (0.1 second). Are added to obtain a new total charge amount QC (QC = QC + ΔQC) at this timing. The amount of charge ΔQC is the product (= I × 0.1) of the measured current value I and the cycle time TJ (= 0.1 seconds).

  Also, after the previous external charging, the cycle time TJ (= 0.1 seconds) is added to the total charge time TC stored in the RAM to obtain a new total charge time TC at this timing (TC = TC + 0. 1). Thereafter, the process proceeds to step S7, and the obtained total charge electricity amount QC and the total charge time TC are stored in the RAM.

In Step S5, it is determined whether or not the measured current value I is the value of the discharge current of the battery 1 (the assembled battery 110).
If YES, that is, if the current value I is the value of the discharge current, the process proceeds to step S6, and the total discharge electricity amount QD and the total discharge time TD at this timing (time) are acquired. Among these, the total amount of discharged electricity QD is the total amount of discharged electricity discharged from the battery 1 (the assembled battery 110) during the above-described period TM. The total discharge time TD is the total time during which the battery 1 (the assembled battery 110) is discharged within the period TM.
On the other hand, if NO, that is, if the current value I is not the value of the discharge current (that is, no current flows through the battery 1 (the assembled battery 110)), the process proceeds to step S8.

  In step S6, the current total discharge quantity QD and total discharge time TD are obtained. Specifically, since the last external charge, the total amount of discharged electricity QD stored in the RAM was discharged from the battery 1 (the assembled battery 110) during one cycle time TJ (0.1 second). The discharge electric quantity ΔQD is added to obtain a new total discharge electric quantity QD at this timing (QD = QD + ΔQD). The discharge electric quantity ΔQD is the product (= I × 0.1) of the measured current value I and the cycle time TJ (= 0.1 seconds).

Further, after the previous charge X1, the cycle time TJ (= 0.1 seconds) is added to the total discharge time TD stored in the RAM to obtain the total discharge time TD at this timing (TD = TD + 0.1). Thereafter, the process proceeds to step S7, and the obtained total discharge electricity amount QD and the total discharge time TD are stored in the RAM.
In step S8, it is determined whether or not the operation of the vehicle 100 is finished (key-off). Here, if NO, the process returns to step S2 and repeats steps S2 to S8, while if YES, the first routine R1 is terminated.

  As described above, the PHV control device 120 of the vehicle 100 performs the above-described total discharge electricity in the period TM (after the previous external charging and until the new external charging shown in the second routine R2 described below is reached). The quantity QD, total discharge time TD, total charge electricity QC, and total charge time TC are acquired and stored in advance.

Next, this new external charging will be described with reference to the second routine R2 of FIG.
First, in step S11, it is determined whether or not the plug 195P of the cable with plug 195 of the vehicle 100 has been inserted into the external power source XV. If NO, that is, if the plug 195P is not inserted into the external power source XV, step S11 is repeated. If YES, ie, if the plug 195P is inserted into the external power source XV, the process proceeds to step S12.

In step S12, the average discharge current value ID and the average charge current value IC of the battery 1 (the assembled battery 110) in the period TM are acquired. Among these, the average discharge current value ID is a value (ID = QD / TD) obtained by dividing the total discharge quantity QD by the total discharge time TD. Specifically, the average discharge current value ID is calculated using the total discharge quantity QD and the total discharge time TD stored in the RAM.
The average charging current value IC is a value (IC = QC / TC) obtained by dividing the total charge electricity QC by the total charge time TC. Specifically, the average charge current value IC is calculated using the total charge amount QC and the total charge time TC stored in the RAM.

  Next, an average discharge current value IF after subtraction for the battery 1 (the assembled battery 110) is acquired (step S13). Specifically, the average discharge current value IF after subtraction is obtained by subtracting the average charge current value IC from the average discharge current value ID of the battery 1 (the assembled battery 110) obtained in step S12 (IF = ID-IC). ).

Next, in the charging condition determination subroutine in step S20, the use of the external charging method, which is the charging condition for the new external charging this time, is determined based on the above-described average discharge current value IF after subtraction. Specifically, the voltage increase period until the voltage V (t) of the battery 1 (the assembled battery 110) rises from the charging start voltage VS at the beginning of charging and reaches the charging upper limit voltage VM due to the new external charging this time. In the TV, the charging condition is determined so that the external charging current value (charging current value IX (t)) is in the range of 0.2 to 5.0 times the average discharge current value IF after subtraction.
In this embodiment, as a method of external charging of the battery 1 (the assembled battery 110), constant power-constant voltage charging (CP-CV charging) is basically performed. However, in the external charging in the voltage rising period TV prior to the latter half CV charging, the charging current value IX (t) is set within a range of 0.2 to 5.0 times the average discharge current value IF after subtraction. Therefore, constant current charging (CC charging) may be performed instead of CP charging. That is, the charging condition determining subroutine in step S20 determines a charging condition in which the charging current value IX (t) in the voltage rising period TV is within the range of 0.2 to 5.0 times the average discharge current value IF after subtraction. Based on this, external charging is performed.

First, when the battery 1 (the assembled battery 110) is charged by CP-CV charging, the voltage V (t) and the charging current value IX (t) of the battery 1 (the assembled battery 110) change with time (the charging time elapses). FIG. 6 shows a graph of the accompanying change.
CP charging is started at the first time t1, and the battery 1 (the assembled battery 110) is charged with a constant power P. Then, as the charging of the battery 1 (the assembled battery 110) proceeds, the voltage V (t) of the battery 1 (the assembled battery 110) gradually rises from the charging start voltage VS, and charging is performed to keep the power P constant. The current value IX (t) gradually decreases. In this CP charging, if the time t when the charging upper limit voltage (target voltage) VM is reached is the second time t2, the period from the first time t1 to the second time t2 corresponds to the voltage rising period TV (VM = V (t2)).
In this voltage rise period TV, the charging current value IX (t) monotonously decreases from the first current value IP1 (= IX (t1)) to the second current value IP2 (= IX (t2)). The product of the first current value IP1 and the charging start voltage VS and the product of the second current value IP2 and the charging upper limit voltage VM are the same power P (VS · IP1 = VM · IP2 = P). .

  In the present embodiment, the charging current value IX (t) in the voltage rising period TV described above is set in the charging condition determination subroutine S20 before starting the new external charging this time (step S14 of the second routine R2). The charging condition is determined to be in the range of 0.2 to 5.0 times the average discharge current value IF after subtraction. Specifically, assuming that charging is performed by CP charging, the first current value IP1 and the second current value IP2 respectively determined by the charging start voltage VS and the charging upper limit voltage VM, and the above-described average electric discharge current value IF after subtraction. Is determined based on a magnitude relationship with a value obtained by multiplying 0.2 to 5.0 times, specifically, charging conditions in charging prior to CV charging (specifically, separate use of CP charging and CC charging).

Therefore, if the charging start voltage VS of the battery 1 (the assembled battery 110) when starting the new external charging this time is the same, the values of the first current value IP1 and the second current value IP2 are also set. It will be the same again. However, since the average discharge current value IF after subtraction changes depending on the usage state of the vehicle 100 in the above-described period TM, the first current value IP1 and the second current value IP2 are 0.2 of the average discharge current value IF after subtraction. The relationship with the range of ˜5.0 times depends on the magnitude of the average discharge current value IF after subtraction.
Therefore, a plurality of cases (first to sixth cases) will be described in detail below.

(First case)
First, the first current value IP1 is a value equal to or less than 5.0 times the average discharge current value IF after subtraction (IP1 ≦ 5.0 × IF), and the second current value IP2 is the average discharge current value IF after subtraction. A case where the value is 0.2 times or more (IP2 ≧ 0.2 × IF) will be described with reference to FIG.
In this case, as shown in the graph of FIG. 7, CP charging with constant power P is performed during the entire voltage rising period TV. Thereby, in the whole period of voltage rising period TV, the charging current value IX (t) flowing through the battery 1 (the assembled battery 110) is within a range of 0.2 to 5.0 times the average discharge current value IF after subtraction. Because it fits. Thus, as will be described in detail later, as compared with a battery that has been externally charged with a charging current value IX (t) that is outside the range of 0.2 to 5.0 times the average discharge current value IF after subtraction. In addition, an increase in battery resistance in the battery 1 (the assembled battery 110) can be suppressed.

(Second case)
Next, the first current value IP1 is within the range of not more than 5.0 times the subtracted average discharge current value IF and not less than 0.2 times (0.2 × IF ≦ IP1 ≦ 5.0 × IF). The case where the second current value IP2 is a value smaller than 0.2 times the subtracted average discharge current value IF (IP2 <0.2 × IF) will be described with reference to FIG. In this case, when the battery 1 (the assembled battery 110) is charged by CP charging with the constant power P, the charging current value IX (t) is initially 0.2 to 5.0 of the average discharge current value IF after subtraction. Within the double range. However, when the voltage V (t) of the battery 1 (the assembled battery 110) increases thereafter, the charging current value IX (t) falls below the above range before the voltage V (t) reaches the charging upper limit voltage VM. (IX (t) <0.2 × IF) (see FIG. 8).
Therefore, in this case, initially, the battery 1 (the assembled battery 110) is charged by CP charging at a constant power P, but the charging current value IX (t) is 0.2 times the average discharge current value IF after subtraction. At the third time t3 when the magnitude of (IX (t) = 0.2 × IF) is reached, switching to constant current charging (CC charging) with constant current (= 0.2 × IF) (solid line in FIG. 8) portion). If charging is performed under such charging conditions, the charging current value IX (t) may fall within the range of 0.2 to 5.0 times the average discharge current value IF after subtraction over the entire voltage rising period TV. it can. Thereby, compared with the battery which externally charged with the charging current value IX (t) having a value outside the range of 0.2 to 5.0 times the average discharge current value IF after subtraction, the battery 1 (assembled battery) 110), an increase in battery resistance can be suppressed.

(Third case)
Next, in addition to the second current value IP2, the first current value IP1 is 0.2 times or less the subtracted average discharge current value IF (IP2 <IP1 ≦ 0.2 × IF). Will be described. In this case, if the battery 1 (the assembled battery 110) is to be charged by CP charging with a constant power P, the charging current value IX (t) is 0.2 to 5 of the average discharge current value IF after subtraction from the beginning. It will be outside (below) 0 times the range (see FIG. 9).
Therefore, in this case, CC charging with a constant current (= 0.2 × IF) is performed from the beginning (first CC charging indicated by a solid line portion in FIG. 9). If charging is performed under such charging conditions, the charging current value IX (t) may fall within the range of 0.2 to 5.0 times the average discharge current value IF after subtraction over the entire voltage rising period TV. it can. Accordingly, an increase in battery resistance in battery 1 (assembled battery 110) can be suppressed as compared with a battery that is externally charged with a charging current value IX (t) that is outside this range.

(Fourth case)
Next, the first current value IP1 is a value larger than 5.0 times the subtracted average discharge current value IF (IP1> 5.0 × IF), and the second current value IP2 is the subtracted average discharge current value IF. A case where the value is smaller than 0.2 times (IP2 <0.2 × IF) will be described with reference to FIG. In this case, if the battery 1 (the assembled battery 110) is to be charged by CP charging with a constant power P, the charging current value IX (t) is the average discharge current value IF after subtraction at the beginning of charging and at the end of charging. This is outside the range of 0.2 to 5.0 times (see FIG. 10).
Therefore, in this case, for example, as shown in the graph of FIG. 10, CC charging with a constant current (= 5.0 × IF) is performed from the beginning until the voltage V (t) reaches the charging upper limit voltage VM ( 2nd CC charge shown with the continuous line part in FIG. 10). If charging is performed under such charging conditions, the charging current value IX (t) may fall within the range of 0.2 to 5.0 times the average discharge current value IF after subtraction over the entire voltage rising period TV. it can. Accordingly, an increase in battery resistance in battery 1 (assembled battery 110) can be suppressed as compared with a battery that is externally charged with a charging current value IX (t) that is outside this range.

  In this case, for example, CC charging is initially performed with a constant current (= 5.0 × IF), and after the time when the product of the voltage V (t) and the charging current value IX (t) becomes the power P. Then, CP charging with a constant power P is performed within a range where the charging current value IX (t) is 0.2 to 5.0 times the average discharge current value IF after subtraction. Furthermore, after the time when the charging current value IX (t) becomes 0.2 times the average discharge current value IF after subtraction (IX (t) = 0.2 × IF), the constant current (= 0.2 It is also possible to take a method of performing CC charging by (IF) (charging method indicated by a two-dot chain line in FIG. 10).

(Fifth case)
Next, the first current value IP1 is a value (IP1> 5.0 × IF) larger than 5.0 times the average discharge current value IF after subtraction, but the second current value IP2 is the average discharge current value IF after subtraction. A case of 0.2 times to 5.0 times (0.2 × IF ≦ IP2 ≦ 5.0 × IF) will be described with reference to FIG. In this case, when the battery 1 (the assembled battery 110) is to be charged by CP charging with a constant power P, the charging current value IX (t) is 0.2 to the average discharge current value IF after subtraction at the beginning of charging. It will deviate (exceed) the range of 5.0 times (see FIG. 11).
Therefore, in this case, as shown in the graph of FIG. 11, for example, CC charging with constant current (= 5.0 × IF) is performed until the voltage V (t) reaches the charging upper limit voltage VM from the beginning ( Solid line portion in FIG. 11). If charging is performed under such charging conditions, the charging current value IX (t) may fall within the range of 0.2 to 5.0 times the average discharge current value IF after subtraction over the entire voltage rising period TV. it can. Accordingly, an increase in battery resistance in battery 1 (assembled battery 110) can be suppressed as compared with a battery that is externally charged with a charging current value IX (t) that is outside this range.
In this case, for example, CC charging is initially performed with a constant current (= 5.0 × IF), and after the time when the product of the voltage V (t) and the charging current value IX (t) becomes the power P. A method of performing CP charging with a constant power P can also be taken (charging method indicated by a two-dot chain line in FIG. 11).

(Sixth case)
Next, in addition to the first current value IP1, the second current value IP2 is a value larger than 5.0 times the average discharge current value IF after subtraction (IP1>IP2> 5.0 × IF). Will be described. Also in this case, if the battery 1 (the assembled battery 110) is charged by CP charging with the constant power P, the charging current value IX (t) is 0.2 to 5 of the average discharge current value IF after subtraction from the beginning. It will be outside (exceeding) the 0.times. Range (see FIG. 12).
Therefore, in this case as well, CC charging with a constant current (= 5.0 × IF) is performed from the beginning until the voltage V (t) reaches the charging upper limit voltage VM (solid line portion in FIG. 12). If charging is performed under such charging conditions, the charging current value IX (t) may fall within the range of 0.2 to 5.0 times the average discharge current value IF after subtraction over the entire voltage rising period TV. it can. Accordingly, an increase in battery resistance in battery 1 (assembled battery 110) can be suppressed as compared with a battery that is externally charged with a charging current value IX (t) that is outside this range.

In the present embodiment, based on the first to sixth cases described above, the charging condition determination subroutine in step S20 will be described with reference to FIG.
Specifically, first, in step S21, the voltage VS at the start of charging is detected from the voltage V (t) of the assembled battery 110 (battery 1). Specifically, the total voltage of 100 batteries 1 and 1 is measured using a voltage sensor (not shown), and is set as a charging start voltage VS.

  Next, in step S22, the first current value IP1 and the second current value IP2 described above are calculated. The first current value IP1 and the second current value IP2 are charging current values at the charging start voltage VS and the charging upper limit voltage VM when charging by CP charging with a constant power P. Specifically, the first current value IP1 is obtained from IP1 = P / VS, and the second current value IP2 is obtained from IP2 = P / VM.

In step S23, the first current value IP1 is compared with a value 0.2 times the subtracted average discharge current value IF (0.2 × IF) and a value 5.0 times (5.0 × IF). Do.
Here, when the first current value IP1 is smaller than 0.2 times the subtracted average discharge current value IF (IP1 <0.2 × IF), the process proceeds to step S24, and external charging in the voltage rising period TV is performed. The CC charging (first CC charging) by the constant current (= 0.2 × IF) shown in the third case (see FIG. 9) is determined.
When the first current value IP1 and the average discharge current value IF after subtraction are in the above-described relationship, as shown in the third case, if charging is performed by the first CC charging shown as the third case, the voltage rises. Over the entire period TV, the charging current value IX (t) flowing through the assembled battery 110 (battery 1) can be within the range of 0.2 to 5.0 times the average discharge current value IF after subtraction.
After step S24, the process returns to the second routine R2.

On the other hand, in step S23, the first current value IP1 is in the range of 5.0 times or less and 0.2 times or more of the average discharge current value IF after subtraction (0.2 × IF ≦ IP1 ≦ 5.0 × IF). If there is, the process proceeds to step S25, and it is determined whether or not the second current value IP2 is 0.2 times (0.2 × IF) or more of the average discharge current value IF after subtraction.
Here, if YES, that is, if the second current value IP2 is a value equal to or greater than 0.2 times the average discharge current value IF after subtraction (IP2 ≧ 0.2 × IF), the process proceeds to step S26, where the voltage rise period TV is External charging is determined as CP charging with constant power P.
When the second current value IP2 and the average discharge current value IF after subtraction are in the above-described relationship, as shown in the first case (see FIG. 7), if charging is performed by CP charging, the voltage rise period In the entire TV period, the charging current value IX (t) can be within a range of 0.2 to 5.0 times the average discharge current value IF after subtraction.
After step S26, the process returns to the second routine R2.

On the other hand, if NO in step S25, that is, if the second current value IP2 is smaller than 0.2 times the average discharge current value IF after subtraction (IP2 <0.2 × IF), the process proceeds to step S27. The external charging during the voltage rising period TV is determined to be the CP-CC charging shown in the second case (see FIG. 8). That is, initially, the assembled battery 110 is charged by CP charging with a constant power P, but the charging current value IX (t) is 0.2 times the average discharge current value IF after subtraction (IP (t) = 0.2). After the time when the size of (× IF) is reached (the above-mentioned second time t2), the charging is determined to be performed by CC charging with a constant current (= 0.2 × IF).
When the first current value IP1, the second current value IP2, and the average discharge current value IF after subtraction are in the above-described relationship, if the charging is performed by CP-CC charging shown in the second case, Over the period, the charging current value IX (t) can be within a range of 0.2 to 5.0 times the average discharge current value IF after subtraction.
After step S27, the process returns to the second routine R2.

On the other hand, when the first current value IP1 is larger than 5.0 times the average discharge current value IF after subtraction (IP1> 5.0 × IF) in step S23, the process proceeds to step S28, and the voltage increase period TV is set. External charging is determined to be CC charging (second CC charging) with a constant current (= 5.0 × IF) shown in the fourth, fifth, and sixth cases (see FIGS. 10, 11, and 12).
As shown in the fourth to sixth cases, when the first current value IP1 and the average discharge current value IF after subtraction are in the above relationship, the second current value IP2 and 5.0 × IF, and 0 Regardless of the magnitude relationship with 2 × IF, if charging is performed with the second CC charge, the charging current value IX (t) is subtracted from 0.2 to 5 of the average discharge current value IF after subtraction over the entire period of the voltage rising period TV. It can be within the range of .0 times.
After step S25, the process returns to the second routine R2.

In this embodiment, the external charging methods in the fourth to sixth cases where the first current value IP1 is IP1 <0.2 × IF are all based on a constant current (= 5.0 × IF). The second CC charge was assumed. That is, in these cases, regardless of the magnitude relationship between the second current value IP2 and 5.0 × IF and 0.2 × IF, the external charging condition during the voltage rising period TV is determined to be the second CC charging. However, in the fourth to sixth cases, different external charging methods may be employed. In this case, the magnitude relationship between the second current value IP2 and 5.0 × IF and 0.2 × IF is changed. Based on this specification, it is preferable to determine the appropriate use of the external charging method, which is the charging condition for external charging in the voltage rise period TV.

  Specifically, when the second current value IP2 is smaller than 0.2 times the average discharge current value IF after subtraction (IP2 <0.2 × IF) (corresponding to the fourth case), the voltage rise period For example, as shown by a two-dot chain line in FIG. 10, external charging in the TV is initially charged with a constant current (= 5.0 × IF), but the voltage V (t) is the power P / (5 ... 0 × IF) and after that, CP charging is performed with a constant power P, and the charging current value IX (t) becomes IX (t) = 0.2 × IF. Thereafter, a charging method for charging with a constant current (= 0.2 × IF) may be determined. Further, when the second current value IP2 is within the range of 5.0 times or less and 0.2 times or more of the average discharge current value IF after subtraction (0.2 × IF ≦ IP2 ≦ 5.0 × IF) (first In this case, the external charging in the voltage rising period TV is initially charged with a constant current (= 5.0 × IF) as indicated by a two-dot chain line in FIG. Further, after the time when the voltage V (t) becomes the magnitude of the power P / (5.0 × IF), it is possible to determine the charging method for performing the CP charging with the constant power P.

  In step S14 of the second routine R2, the assembled battery 110 (battery 1) is charged. Specifically, for the assembled battery 110 (battery 1), first, during the voltage increase period TV, the above-described CP charging, CP-CC charging, first CC charging, or second CC determined in the charging condition determination subroutine S20 described above. Charge and then CV charge.

  After the above-described charging, in step S15, the total discharge electricity amount QD, the total discharge time TD, the total charge electricity amount QC, and the total charge time TC stored in the RAM are reset. Thereby, the total discharge electricity amount QD, the total discharge time TD, the total charge electricity amount QC, and the total charge time TC in the period from the new external charge to the next new external charge are newly stored in the RAM. Can do.

  In the present embodiment, the PHV control device 120 that executes step S13 is used as the acquisition unit, the PHV control device 120 that executes the charging condition determination subroutine S20 is used as the determination unit, and the PHV control device 120 and the converter 140 are used as the charging device. Each corresponds.

By the way, the present inventors investigated the characteristics (change in internal resistance) of the battery 1 by changing the external charging method for the battery 1 (the assembled battery 110) mounted on the vehicle.
First, 100 new (initial) batteries 1 and 1 that have just been manufactured are accommodated in an assembled battery case 110A while being connected in series using a bus bar (not shown). did. Then, the total + electrode and the total − electrode of the assembled battery 110 were connected to an external power supply device (not shown), and the internal resistance of the assembled battery 110 was measured.
Specifically, the assembled battery 110 with SOC 60% was subjected to a constant current discharge of 30 C using an external power supply, and the voltage at the time when 10 seconds had elapsed from the start of discharge was measured. Then, the value of the internal resistance of the battery pack 110 was calculated by dividing the voltage change due to the constant current discharge by the current value (30C) of the constant current discharge. Note that the value of the internal resistance at this time is the “initial internal resistance value R0” of the battery pack 110.

Next, for the assembled battery 110, the charge / discharge test and the external charge were repeated alternately (hereinafter referred to as Example 1).
Among these, the charging / discharging test performed charging / discharging about the assembled battery 110 using the charging / discharging apparatus which is not illustrated. Specifically, the charging / discharging device was controlled so as to execute a charging / discharging pattern for 420 seconds continuously as shown in FIG. 14 (the vertical axis of the charging / discharging pattern shown in FIG. 14 represents the current value I of the battery pack 110). Where the + side represents the charging current and the-side represents the discharging current). This charge / discharge pattern is a pattern in which pulse discharge of about 70 A at maximum and pulse charge of about 40 A at maximum are alternately repeated. A test value IFT corresponding to an average discharge current value IF after subtraction in this charge / discharge pattern is obtained in advance.
In the external charging, the assembled battery 110 was charged by CC charging at a constant charging current value IT up to the charging upper limit voltage VM using an external power supply device. The charging current value IT is equal to the test value IFT in the charge / discharge test described above (IT = IFT). That is, the current value magnification IJ (= IT / IFT) obtained by dividing the charging current value IT by the test value IFT is 1.0.

After the charge / discharge test and external charge described above were alternately repeated 100 times, the value of the internal resistance of the assembled battery 110 was measured again in the same manner as described above. The value of the internal resistance at this time is defined as “post-test internal resistance value R1” of the assembled battery 110.
And about this assembled battery 110, internal resistance initial stage ratio HR before and behind a test was computed. Specifically, the internal resistance initial ratio HR is obtained by dividing the internal resistance value R1 after the test by the initial internal resistance value R0 (HR = R1 / R0).

In addition, the present inventors prepared a plurality of new assembled batteries 110, and for these assembled batteries 110, the charge / discharge test and the external charge were alternately repeated, and the internal resistance initial ratio HR before and after the test was calculated. .
However, it differs from the above-mentioned Example 1 in that the magnitude of the charging current value IT is changed and the assembled battery 110 is externally charged.
Specifically, the charge current value IT was set to 0.12 times the test value IFT, and the charge / discharge test and the external charge were alternately repeated 100 times (Comparative Example 1). Further, the charge current value IT was set to 0.2 times the test IFT, and the charge / discharge test and the external charge were alternately repeated (Example 2). Similarly, the charging current value IT is 0.32 times the value of the test IFT (Example 3), 3.0 times the value (Example 4), 5.0 times the value (Example 5), and 8. The charge / discharge test and external charging were alternately repeated with the value 0 times (Comparative Example 2). That is, the current value magnifications IJ (= IT / IFT) of Example 2, Example 3, Example 4, Example 5, Comparative Example 1 and Comparative Example 2 are 0.2, 0.32, and 3.0, respectively. , 5.0, 0.12 and 8.0.
And each charge / discharge test was done about each assembled battery 110 which performed each Example 2-5 and Comparative Examples 1 and 2, and internal resistance initial stage ratio HR before and behind a test was computed, respectively.

FIG. 15 shows the relationship between the current value magnification IJ and the internal resistance initial ratio HR in each of the assembled batteries 110 of Examples 1 to 5 and Comparative Examples 1 and 2.
According to FIG. 15, when the current value magnification IJ is in the range of 0.2 to 5.0, each internal resistance initial ratio HR is equal to IJ <0.2 or IJ> 5. It can be seen that it is smaller than the internal resistance initial ratio HR when 0 is set.
In view of this, in the case of external charging, the charging condition is such that the charging current value IX (t) is a value within the range of 0.2 to 5.0 times the average discharge current value IF after subtraction. As can be seen, when external charging of the assembled battery 110 is repeated, an increase in battery resistance can be suppressed as compared to the assembled battery 110 in which external charging is repeated at a charging current value IX (t) outside this range. .

  As described above, the external charging system CS1 according to the present embodiment executes the acquisition unit (step S13) that acquires the average discharge current value IF after subtraction for the period TM until the new external charging is performed after the previous external charging. PHV control device 120), and determination means for determining a charging condition in the new external charging of the battery 1 based on the average discharge current value IF after subtraction (PHV control device 120 executing the charging condition determining subroutine S20) Is provided. Thereby, based on the average discharge current value IF after subtraction, the charging condition in the external charging according to the usage state of the battery 1 (assembled battery 110) when the vehicle 100 is used is appropriately set, and the battery 1 (assembled battery 110). Can be charged.

  In the external charging system CS1, the determining means (PHV control device 120 that executes the charging condition determining subroutine S20) determines the charging conditions in the voltage rising period TV, and the average discharge after the charging current value IX (t) of external charging is subtracted. The charging condition is determined within the range of 0.2 to 5.0 times the current value IF. For this reason, according to this system, compared with a battery that repeats charging with a value less than 0.2 times the average discharge current value IF after subtraction, or a value more than 5.0 times, which is outside this range, the battery An increase in resistance can be suppressed.

(Deformation)
Next, modifications of the present invention will be described with reference to the drawings.
It should be noted that the external charging system CS2 according to the present modified embodiment is different from the above-described embodiment in that the charging condition (charging current value) is determined each time the assembled battery 110 (battery 1) is charged. Is different.
Therefore, the differences from the embodiment will be mainly described, and the description of the same parts as the embodiment will be omitted or simplified. In addition, the same effect is produced about the part similar to embodiment. In addition, the same contents are described with the same numbers.

  Similar to the external charging system CS1 of the embodiment, the external charging system CS2 according to the present modified embodiment includes a battery pack 110 (battery 1), a PHV control device 220, a current sensor 130, a converter 140, a cable 160, and a cable 195 with a plug. (See FIG. 1).

External charging using the external charging system CS2 will be described with reference to the flowchart (third routine R3) of FIG. Note that, in the present modification, as in the embodiment, constant power-constant voltage charging (CP-CV charging) is basically performed as a method for external charging of the battery 1 (the assembled battery 110). However, in the external charging in the voltage rising period TV prior to the latter half CV charging, the charging current value IX (t) is set within a range of 0.2 to 5.0 times the average discharge current value IF after subtraction. Therefore, in order to determine the charging current value IX (t) every cycle time TJ (0.1 seconds in this modification), the use of the external charging method, which is the charging condition , is determined in advance before charging. Different from the embodiment.

First, steps S11 to S13 are performed in the same manner as the second routine R2 of the above-described embodiment.
Next, in step S31, the voltage V (t) of the assembled battery 110 (battery 1) is detected using a voltage sensor (not shown).

Subsequently, it is determined whether or not the measured voltage V (t) has reached the charging upper limit voltage VM.
If NO, that is, if the voltage V (t) has not reached the charging upper limit voltage VM, the process proceeds to step S33. On the other hand, if YES, that is, if the voltage V (t) reaches the charging upper limit voltage VM, the process proceeds to step S39, and the assembled battery 110 (battery 1) is further charged by CV charging.

  In step S33, a temporary charging current value IY (t) to be flowed when CP charging with a constant power P is performed is calculated from the measured voltage V (t). Specifically, the temporary charging current value IY (t) is a quotient obtained by dividing the power P by the voltage V (t) measured in step S31 (IY (t) = P / V (t)).

Subsequently, in step S34, the calculated temporary charging current value IY (t), a value 0.2 times the subtracted average discharge current value IF (0.2 × IF), and a value 5.0 times (5. 0 × IF).
Here, if the temporary charging current value IY (t) is smaller than 0.2 times the subtracted average discharge current value IF (IY (t) <0.2 × IF), the process proceeds to step S35. 2 × IF is determined as a charging current value IX (t) (IX (t) = 0.2 × IF).
After step S35, the process proceeds to step S38.

On the other hand, the temporary charging current value IY (t) is within the range of 5.0 times or less and 0.2 times or more of the average discharge current value IF after subtraction (0.2 × IF ≦ IY (t) ≦ 5.0 × IF). In step S36, the temporary charging current value IY (t) is determined as the charging current value IX (t) (IX (t) = IY (t)).
After step S36, the process proceeds to step S38.

On the other hand, when the temporary charging current value IY (t) is larger than 5.0 times the average discharge current value IF after subtraction (IY (t)> 5.0 × IF), the process proceeds to step S37, where 5.0 × IF Is determined as a charging current value IX (t) (IX (t) = 5.0 × IF).
After step S37, the process proceeds to step S38.

  Thus, in any case of steps S35 to S37, during the current cycle time TJ, the charging current value IX (t) flowing through the assembled battery 110 (battery 1) is subtracted from 0.2 to 5 of the average discharge current value IF after subtraction. It can be within the range of .0 times.

  In step S38, during the current cycle time TJ, the assembled battery 110 (battery 1) is charged with the charging current value IX (t) determined in step S35, S36 or S37 described above, and the process returns to step S31. The voltage V (t) of the assembled battery 110 (battery 1) is measured again.

  Further, after the CV charging in step S39, step S15 is executed as in the above-described embodiment, and the third routine R3 is terminated.

  In this modification, the PHV control device 220 that executes step S13 corresponds to an acquisition unit, and the PHV control device 220 that executes steps S35, S36, and S37 corresponds to a determination unit.

  As described above, the external charging system CS2 according to the present modification obtains the subtracted average discharge current value IF for the period TM from the previous external charging until the new external charging is performed (executes step S13). PHV control device 220) and determination means for determining a charging condition (charging current value IX (t)) in the new external charging of battery 1 based on this average discharge current value IF after subtraction (steps S35, S36, PHV control device 220) that executes S37. Thereby, based on the average discharge current value IF after subtraction, the charging condition in the external charging according to the usage state of the battery 1 (assembled battery 110) when the vehicle 100 is used is appropriately set, and the battery 1 (assembled battery 110). Can be charged.

  In the external charging system CS2, the determining means (PHV control device 220 that executes steps S35, S36, and S37) determines the charging conditions during the voltage rising period TV, and the average after the charging current value IX (t) of external charging is subtracted. The charging condition is determined to be in the range of 0.2 to 5.0 times the discharge current value IF. For this reason, according to this system, compared with a battery that repeats charging with a value less than 0.2 times the average discharge current value IF after subtraction, or a value more than 5.0 times, which is outside this range, the battery An increase in resistance can be suppressed.

In the above, the present invention has been described with reference to the embodiments and modifications. However, the present invention is not limited to the above-described embodiments and the like, and it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof. Yes.
For example, in the embodiment, as a method of external charging of the battery 1 (the assembled battery 110), CP-CV charging is basically performed. However, for example, CC charging for charging at a constant current value, or after charging at a constant current value until the battery voltage (voltage between terminals) reaches a predetermined voltage, the current value is maintained while maintaining the above-mentioned predetermined voltage. Alternatively, CC-CV charging may be performed in which charging is performed by gradually decreasing the voltage. In this case as well, the charging current value IX (t) may be set within the range of (0.2 × IF) to (5.0 × IF).
As a specific example of CC charging, a temporary charging current value IZ is set prior to the start of charging. When this temporary charging current value IZ is 0.2 × IF ≦ IZ ≦ 5.0 × IF, The charging current value IZ is set as a charging current value IX (t) (IX (t) = IZ). On the other hand, when IZ <0.2 × IF, IX (t) = 0.2 × IF. On the other hand, when IZ> 5.0 × IF, there may be mentioned IX (t) = 5.0 × IF.

1 battery (secondary battery)
100 Vehicle 120, 220 Plug-in hybrid vehicle control device (acquisition means, determination means)
130 Current sensor (current detector)
140 Converter (charging device)
150 engine (power supply other than external power supply)
181 Front motor (Power supply other than external power supply)
182 Rear motor (power supply other than external power supply)
CS1, CS2 External charging system (charging system for secondary battery)
I Current value IC Average charging current value ID Average discharging current value IF Average subtracting discharge current value IX (t) Charging current value (current value of external charging)
QC Total charge electricity QD Total discharge electricity TC Total charge time TD Total discharge time TM Period TV Voltage rise period (period)
V (t) Voltage VM Charge upper limit voltage XV External power supply

Claims (2)

A charging system for a secondary battery mounted on a vehicle,
A secondary battery,
A current detection device for detecting a current value of a current flowing through the secondary battery;
A charging device for externally charging the secondary battery using an external power source outside the vehicle;
In the period from the last external charge to the start of a new external charge,
Using the current value at each time point in the period obtained by the current detection device,
From the average discharge current value obtained by dividing the total amount of discharged electricity discharged from the secondary battery by the total discharge time during which this discharge was performed, the total amount of charged electricity charged to the secondary battery from a power source other than the external power source is calculated as follows. Subtract the average charging current value divided by the total charging time when charging,
Acquisition means for acquiring an average discharge current value after subtraction for the period;
A charging system for a secondary battery, comprising: an external charging method that is a charging condition in the new external charging, or a determination unit that determines a charging current value based on the average discharge current value after subtraction. A rechargeable battery charging system according to claim 1,
The determining means includes
Among the charging conditions in the new external charging, the charging conditions in the voltage increase period from when the voltage of the secondary battery increases due to the external charging to reach the charging upper limit voltage, the current value of the external charging after the subtraction A charging system for a secondary battery, which is determined to have a charging condition within a range of 0.2 to 5.0 times the average discharge current value.

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