JP2013115912A - Charge control system and charge control method for battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve more appropriate charging in using a plurality of secondary cells as a battery pack.SOLUTION: The present invention comprises a volt meter 4 that monitors a charging voltage of each lithium ion cell 2; a bypass circuit 3 that is provided for each cell 2 and individually discharges the cells 2; and a controller 6 that operates the bypass circuit 3 for all the cells 2 other than a part of the cells 2 when a state where charging voltages of a part of the cells 2 are lower than a predetermined voltage continues for a predetermined time.

Description

  The present invention relates to an assembled battery charge control system and a charge control method for controlling charging of an assembled battery in which a plurality of secondary batteries are connected in series.

  For example, lithium ion secondary batteries have advantages such as high energy density and low self-discharge amount, and are widely used as automobile storage batteries, storage batteries for electric / electronic devices, and the like. In addition, in order to obtain a voltage and capacity according to the purpose of use, there are cases where a plurality of lithium ion cells, which are single cells, are connected in series to form a battery pack. Thus, when using as an assembled battery, the charge state of each lithium ion cell may vary at the time of charge. That is, the charge voltage of some lithium ion cells is high and the battery is overcharged, and the charge voltages of some other lithium ion cells are low and may be in a subcharged state (a state that does not reach full charge).

  For this reason, when using a lithium ion secondary battery as an assembled battery, in order to charge each lithium ion cell appropriately without variation, a technique provided with a bypass circuit (resistance) is known (for example, (See Patent Document 1). In this technique, a plurality of lithium ion cells are connected in series, and each lithium ion cell is provided with a bypass circuit. When the voltage of a certain lithium ion cell exceeds the upper limit of an appropriate charging voltage range (allowable charging voltage range) during charging, the lithium ion cell is discharged (bypass discharge) by a bypass circuit corresponding to this cell. By reducing the charging voltage, the charging of the lithium ion cell having a low voltage is promoted.

Japanese Patent Application Laid-Open No. 2002-064947

  By the way, this inventor confirmed that even if it provided the above bypass circuits, charge of the lithium ion cell with a low voltage may not be accelerated | stimulated. For example, when a defective lithium ion cell exists in the assembled battery, it is necessary to replace it with a new lithium ion cell. In this case, the new lithium-ion cell is usually shipped from the factory in a discharged state or partially charged state (not fully charged) in consideration of safety, and is incorporated into the assembled battery as it is, and is fully charged in the same series. It will be mixed with the lithium ion cell.

  However, after that, bypass discharge operates, but the new lithium ion cell that has been replaced does not reach the proper charge voltage range, and the charge voltage of other lithium ion cells is stable within the proper charge voltage range. It was confirmed. That is, even if there is a cell with a low charge voltage, if there is no cell that exceeds the upper limit of the allowable charge voltage range, that is, cells other than the lithium ion cell with a low charge voltage are stable within the proper charge voltage range. If it is, bypass discharge is not performed. Or even if bypass discharge is performed, a cell with a low charging voltage may not reach an appropriate charging voltage range.

  As a result, a cell having a low charging voltage does not reach an appropriate charging voltage range. When such a cell having a low charging voltage exists, the discharge capacity of the assembled battery as a whole is limited by the discharge capacity of the cell having a low charging state because of the series connection (the cell reaches a predetermined voltage). Then, the discharge of the entire assembled battery is terminated), and there is a possibility that a predetermined discharge time as designed cannot be secured.

  Accordingly, an object of the present invention is to provide an assembled battery charge control system and a charge control method that enable more appropriate charging when a plurality of secondary batteries are used as an assembled battery.

  In order to achieve the above object, the invention according to claim 1 is an assembled battery charge control system for controlling charging of an assembled battery in which a plurality of secondary batteries are connected in series, wherein each of the secondary batteries Monitoring means for monitoring the charging voltage, individual discharging means provided in each of the secondary batteries for individually discharging the secondary batteries, and charging voltages of some of the secondary batteries are lower than the first predetermined voltage Control means for operating the individual discharge means for all secondary batteries other than the partial secondary batteries when the state continues for a predetermined time.

  According to this invention, the charging voltage of each secondary battery is monitored by the monitoring means, and when the state where the charging voltage of some of the secondary batteries is lower than the first predetermined voltage continues for a predetermined time, the control means The individual discharge means is operated for all the secondary batteries except for some of the secondary batteries. That is, a large number of secondary batteries excluding some secondary batteries are discharged, and this facilitates charging of secondary batteries having a low charging voltage.

  According to a second aspect of the present invention, in the charge control system according to the first aspect, the control means is configured such that a charge voltage of the partial secondary batteries is the first predetermined voltage during the operation of the individual discharge means. When the voltage reaches a second predetermined voltage higher than the voltage, the operation of the individual discharge means for all the secondary batteries is stopped.

  According to a third aspect of the present invention, in the charge control system according to the first or second aspect, even if the control means operates the individual discharge means for a predetermined time, the charge voltage of the partial secondary battery is An alarm is output when the second predetermined voltage higher than the first predetermined voltage is not reached.

  According to a fourth aspect of the present invention, in the charge control system according to the first to third aspects, the control means is configured such that the charging voltage of the secondary battery in which the individual discharge means is operating is higher than a third predetermined voltage. When it becomes low, the operation of the individual discharge means for the secondary battery is stopped.

  The invention according to claim 5 is an assembled battery charge control method for controlling charging of an assembled battery in which a plurality of secondary batteries are connected in series, wherein the charging voltage of each of the secondary batteries is monitored. All the secondary batteries other than the part of the secondary batteries are individually discharged when a state in which the charging voltage of the secondary battery is lower than the first predetermined voltage continues for a predetermined time. .

  According to this invention, the charging voltage of each secondary battery is monitored, and when a state where the charging voltage of some of the secondary batteries is lower than the first predetermined voltage continues for a predetermined time, Discharge is performed separately for all the secondary batteries. That is, a large number of secondary batteries excluding some secondary batteries are discharged, and this facilitates charging of secondary batteries having a low charging voltage.

  According to a sixth aspect of the present invention, in the charge control method according to the fifth aspect, during the individual discharge, a charge voltage of the some secondary batteries is higher than the first predetermined voltage. When the voltage reaches a voltage or higher, the individual discharge for all the secondary batteries is stopped.

  According to the first and fifth aspects of the present invention, when a state in which the charging voltage of some of the secondary batteries is low (inappropriate charging state) continues for a predetermined time, a large number of secondary batteries excluding the some secondary batteries The battery is discharged. That is, even if the charging voltage of a secondary battery other than a secondary battery with a low charging voltage is within the appropriate charging voltage range, these secondary batteries are discharged, so charging of a secondary battery with a low charging voltage is possible. Can be promoted.

  In addition, since all the secondary batteries other than the secondary battery having a low charging voltage are discharged, the majority of the secondary batteries are discharged, and the charging of the secondary batteries having a low charging voltage can be further promoted. . As a result, the entire assembled battery can be more appropriately charged, the discharge capacity of the entire assembled battery becomes appropriate, and a predetermined discharge time as designed can be secured.

  Further, when the improper charging state continues for a predetermined time, the other secondary batteries are discharged. That is, when an improper charge state occurs temporarily, no discharge is performed, so unnecessary discharge can be avoided and the charge state of the secondary battery with the proper charge voltage can be properly maintained. It becomes. In addition, by discharging when the improper charging state continues for a predetermined time, avoiding the overcharged state or low charging state of the secondary battery due to the improper charging state lasting for a long time, the entire assembled battery Can be appropriately and quickly charged.

  According to the second and sixth aspects of the invention, since the condition for stopping the individual discharge for all the secondary batteries is set to the second predetermined voltage higher than the first predetermined voltage, the start of the individual discharge is started. And the frequency of repeating the stop can be reduced, and charging of a secondary battery having a low voltage can be surely and sufficiently performed.

  According to the third aspect of the present invention, if a secondary battery other than the low voltage is discharged for a predetermined time and the charging voltage of the secondary battery having a low charging voltage does not reach the predetermined voltage or higher, an alarm is output. Therefore, it is possible to respond promptly and appropriately. That is, in such a case, there is a possibility that there is an abnormality such as an internal short circuit or poor connection in a secondary battery with a low charging voltage, and an alarm is output, so that quick and proper charging stop or replacement can be performed. This makes it possible to avoid unnecessary discharge with respect to other normal secondary batteries.

  According to the fourth aspect of the present invention, when the charging voltage of the secondary battery during the individual discharge becomes lower than the third predetermined voltage, the individual discharge is stopped, so the secondary battery is overdischarged. Can be prevented, and the state of charge of the entire assembled battery can be properly maintained.

It is a schematic block diagram which shows the state which applied the charge control system of the lithium ion assembled battery which concerns on embodiment of this invention to the rectifier. It is a figure which shows the control flow of the controller of the system of FIG. FIG. 3 is a diagram showing a continuation of FIG. 2.

  The present invention will be described below based on the illustrated embodiments.

  FIG. 1 is a schematic configuration diagram showing a state in which a charging control system (hereinafter simply referred to as “charging control system”) 1 for a lithium ion battery pack according to an embodiment of the present invention is applied to a DC power supply system. This charging control system 1 is a system that controls charging of a lithium ion battery pack 20 in which a plurality of lithium ion cells (lithium ion secondary batteries) 2 that are single cells are connected in series.

  This charging control system 1 mainly includes a bypass circuit (individual discharge means) 3 and a voltmeter (monitoring means) 4 provided in each lithium ion cell 2, a single main switch 5, a controller (control means) 6, It has. Each bypass circuit 3 and each voltmeter 4 are connected to a controller 6 so as to be able to communicate (data transmission).

  The bypass circuit 3 is a circuit that bypasses the charging current to the corresponding lithium ion cell 2 and discharges the lithium ion cell 2 to lower the voltage. Specifically, the discharge resistor 31 and the discharge switch 32 are connected in series, and are connected in parallel with the lithium ion cell 2. As will be described later, during normal charging, the discharge switch 32 is turned off (opened) in response to a close command from the controller 6 while the discharge switch 32 is turned off (opened). Thereby, the charging current is bypassed to the discharging resistor 31 side, and the lithium ion cell 2 is discharged by the discharging resistor 31 as a load, and the voltage is lowered. Therefore, when the bypass circuit 3 and the discharge switch 32 are on, the discharging resistor 31 consumes a part of the charging current input to the assembled battery 20.

  The voltmeter 4 is connected in parallel to the corresponding lithium ion cell 2, and always measures and monitors the voltage of the lithium ion cell 2 not only during charging or discharging, and transmits the measurement result to the controller 6 in real time. It is. Although not shown in the figure, each has a measuring device for measuring the total voltage, charging current, discharging current, and temperature of each lithium ion cell 2 of the lithium ion assembled battery 20, and the measurement results from these measuring devices are It is transmitted to the controller 6 in real time.

  The main switch 5 is a switch that controls a charging current to the lithium ion assembled battery 20, and is provided in a charging circuit that supplies power to the lithium ion assembled battery 20. That is, it is connected between the AC / DC converter 101 and the lithium ion assembled battery 20 (charging circuit), the electric power from the commercial power source 100 is converted into DC by the AC / DC converter 101, and the lithium ion is passed through the main switch 5. It is supplied to the assembled battery 20. The main switch 5 is in an on (closed) state in normal times.

  A bypass diode 7 is connected in parallel with the main switch 5. The bypass diode 7 has a function of allowing only a current flow from the lithium ion assembled battery 20 and prevents a current from flowing to the lithium ion assembled battery 20. Thereby, the discharge from the lithium ion assembled battery 20 is always possible, and power is supplied from the lithium ion assembled battery 20 to the load facility 102 via the bypass diode 7. Here, the AC / DC converter 101 and the load facility 102 are connected, and in normal times, the power from the commercial power supply 100 is converted into direct current by the AC / DC converter 101 and supplied to the load facility 102. It has become.

The controller 6 is a device that controls each bypass circuit 3 based on the measurement result from each voltmeter 4. As a control for this, when a state in which the charging voltage of some of the lithium ion cells 2 is lower than a predetermined voltage (inappropriate charging state) continues for a predetermined time, mainly in the float charging state, other than this part of the lithium ion cells 2 Control for operating the bypass circuit 3 for all the lithium ion cells 2 is included. Here, the float charge state is a state in which the total charge voltage of the assembled battery 20 reaches a predetermined voltage and is charged at a constant pressure. Further, in this embodiment, a ± allowable error voltage (for example, ± 20 mV) of the average charging voltage _VA obtained by dividing the total charging voltage by the number of cells 2 is set as an appropriate charging voltage range, and each cell is included in this voltage range. 2 charging voltage is accommodated.

Specifically, as shown in FIGS. 2 and 3, first, when any of the voltages of the lithium ion cell 2 is higher than the bypass voltage V _B, the bypass discharge to turn on the bypass circuit 3 of the cell 2 (Step S1). At this time, if the bypass circuit 3 is already on, the on state is maintained. Here, the bypass voltage V _B is a reference voltage for performing bypass discharge in order to eliminate the variation in the charging voltage generated between the cells 2 and is calculated as follows, for example.
V _B = average charge voltage V _A +10 mV

Next, when the voltage of the lithium ion cell 2 that has been performing the bypass discharge as described above becomes equal to or lower than the average charge voltage _VA , the bypass circuit 3 of the cell 2 is turned off to stop the bypass discharge. (Step S2).

Subsequently, it is determined whether or not there is a lithium ion cell 2 whose charge voltage is lower than the allowable lower limit voltage V _min (first predetermined voltage) (step S3). Here, the allowable lower limit voltage V _min is a lower limit value of an appropriate charging voltage range, and is calculated as follows.
V _min = average charge voltage V _A −20 mV

If there is no lithium ion cell 2 lower than the allowable lower limit voltage _Vmin , the timer on the memory is reset (step S4), and if present, the timer is incremented and added (step S5). In this embodiment, a timer is provided for each cell 2 lower than the allowable lower limit voltage _Vmin , and the timer is counted for each cell 2. That is, it is monitored whether or not the low voltage state continues in the same cell 2. When the timer is less than the preset first predetermined time T1 (in the case of “N” in step S6), the process returns to step S1 to repeat the same processing, and the timer is equal to or longer than the first predetermined time T1. In the case of (“Y” in step S6), the process proceeds to step S7 and subsequent steps. Here, the first predetermined time T1 is a time during which it is determined that the voltage of the low voltage cell 2 does not increase even if the current state of the bypass discharge in steps S1 and S2 is continued further, or will be described later. This time is sufficient to obtain the effect of the bypass discharge in step S7, and is set according to the characteristics, capacity, etc. of the cell 2. For example, it is set to 24 hours.

In the processing after step S7, first, the bypass circuit 3 is turned on to perform a bypass discharge for all the lithium ion cells 2 other than the specific cell 2 (a part of the cells 2) (step S7). Here, the specific cell 2, cell 2 timer has elapsed the first predetermined time T1 or more, i.e., it is the cell 2 is lower than the allowable lower limit voltage V _min condition continues the first predetermined time T1 or more . Next, when the voltage of the lithium ion cell 2 during the bypass discharge becomes lower than the average charge voltage V _A (third predetermined voltage), the bypass circuit 3 of the cell 2 is turned off to stop the bypass discharge. (Step S8).

Subsequently, after a predetermined time (processing cycle time), it is determined whether or not the charging voltage of the specific cell 2 is equal to or higher than the average charging voltage V _A (second predetermined voltage) (step S9). Thus, what is determined by the high average charging voltage V _A than the allowable lower limit voltage V _min, when determining the allowable lower limit voltage V _min, early bypass discharge is finished (return to step S1 as described below This is because the frequency of repeating the processing after step S7 again increases. In other words, this is for surely and sufficiently promoting the charging of the cell 2 having a low voltage. In this embodiment, the average charging voltage V _A is set as the second predetermined voltage, but other voltages, for example, a voltage 10 mV lower than the average charging voltage V _A may be set as the second predetermined voltage.

When the charging voltage of the specific cell 2 is less than the average charging voltage _VA , it is determined whether or not such a bypass discharge state continues for a second predetermined time T2 or more (step S10). Here, the second predetermined time T2 may cause an internal abnormality of the cell 2 or a connection abnormality between the cells 2 when the voltage of the low voltage cell 2 does not increase even if the bypass discharge of step S7 is performed. Or a time during which excessive bypass discharge can be avoided, and is set according to the characteristics and capacity of the cell 2. For example, it is set as 100 hours.

  If the second predetermined time T2 is not continued, the process returns to step S8 and the same processing is repeated. If the second predetermined time T2 is continued, an alarm is output and the bypass discharge of all the cells 2 is stopped. (Step S11), the process is terminated. Here, the alarm is output by turning on the alarm lamp of the controller 6 or notifying the computer of the management center.

On the other hand, when the charging voltage of the specific cell 2 is equal to or higher than the average charging voltage _VA (“Y” in step S9), the bypass circuits 3 of all the cells 2 that are performing the bypass discharge are turned off to stop the bypass discharge. (Step S12). Then, the timer is reset (step S13), and the process returns to step S1 to repeat the same processing. The control according to FIGS. 2 and 3 is based on the premise that charging is in progress. When the AC / DC converter 101 fails and the assembled battery 20 starts discharging, all bypass discharges are stopped. To finish the control.

  Next, the operation of the charge control system 1 having such a configuration, a charge control method by the charge control system 1 and the like will be described. Here, when one cell 2 in the assembled battery 20 is replaced with a new cell (hereinafter referred to as “exchange cell”) 2, the voltage / charge state (SOC: State Of Charge) of the exchange cell 2 is The case where the value is low will be described as an example.

First, power from the commercial power supply 100 is supplied to the lithium ion assembled battery 20, the voltage of each lithium ion cell 2 is constantly monitored by the voltmeter 4, and the measurement result is transmitted to the controller 6 in real time. Then, the charging voltage of any cell 2 is higher than the bypass voltage V _B, the cell 2 is bypassed discharged (step S1).

On the other hand, when the charging voltage of the exchange cell 2 is lower than the allowable lower limit voltage V _min (“Y” in step S3), the timer is incremented (step S5) and the process returns to step S1. Then, the voltage of the predetermined time (processing cycle time) after exchange cell 2 if it becomes more than the allowable lower limit voltage V _min, the timer is reset (step S4). On the other hand, if less than the voltage of the exchange cell 2 is still allowable lower limit voltage V _min, the timer is incremented (step S5), and if such a state continues first predetermined time T1 or more (in step S6 "Y" ) Bypass discharge (multiple bypass discharge) is performed on all the lithium ion cells 2 other than the exchange cell 2 (specific cell 2) (step S7).

Subsequently, when the charge voltage of the exchange cell 2 is lower than the average charge voltage _VA (“N” in step S9) and the state of multiple bypass discharge has not continued for the second predetermined time T2 or longer (“ N "), many bypass discharges are continued. On the other hand, when the charging voltage of the exchange cell 2 becomes equal to or higher than the average charging voltage _VA (“Y” in step S9), bypass discharge of all the cells 2 is stopped (step S12), and the normal mode (step S1) is restored. The same processing is performed. On the other hand, if the charge voltage of the exchange cell 2 is lower than the average charge voltage _VA even if the multiple bypass discharge is continued for the second predetermined time T2 or more (in the case of “Y” in step S10), that is, the exchange cell 2 When the voltage does not increase, the above alarm is output and the bypass discharge of all the cells 2 is stopped (step S11).

As described above, according to the charge control system 1 and the charge control method, the state in which the charge voltages of some of the cells 2 (specific cells 2) are lower than the allowable lower limit voltage _Vmin (unsuitable charge state) is the first. For a predetermined time T1 or longer, all cells 2 other than the specific cell 2 are subjected to bypass discharge. That is, regardless of the presence or absence of the cell 2 having a higher charging voltage than the bypass voltage V _B , the cells 2 other than the specific cell 2 (the cell 2 that always exists) are bypass-discharged. Can be promoted.

  In addition, since all the cells 2 other than the specific cell 2 are bypass-discharged, the majority of the cells 2 are bypass-discharged, and the charging of the specific cell 2 having a low charging voltage can be further promoted. As a result, the entire lithium ion assembled battery 20 can be more appropriately charged, the discharge capacity of the entire assembled battery 20 becomes appropriate, and a predetermined discharge time as designed can be secured.

  Further, when the inappropriate charge state of the specific cell 2 continues for the first predetermined time T1, bypass discharge is performed on the cells 2 other than the specific cell 2. That is, when an improper charge state occurs temporarily, bypass discharge is not performed, so unnecessary bypass discharge can be avoided, and the charge state of the cell 2 with an appropriate charge voltage can be properly maintained. It becomes possible. Also, bypass discharge is performed when the improper charging state continues for the first predetermined time T1, thereby avoiding an overcharged state or a low charged state of the cell 2 due to the improper charging state continuing for a long time. Thus, the entire assembled battery 20 can be appropriately and quickly charged.

On the other hand, even if all the cells 2 other than the specific cell 2 are bypass-discharged for a predetermined time, if the charging voltage of the specific cell 2 does not reach the predetermined voltage or higher, an alarm is output, so that a prompt and appropriate response can be made. It becomes possible. That is, in such a case, there is a possibility that an abnormality such as an internal short circuit or a connection failure may exist in the specific cell 2, and an alarm is output, so that quick and proper charge stop or cell replacement can be performed. At the same time, it is possible to avoid unnecessary discharge to other normal cells 2. Further, when the voltage of the cell 2 during the bypass discharge becomes less than the average charge voltage _VA , the bypass discharge of the cell 2 is stopped, so that the cell 2 is prevented from being overdischarged. It becomes possible to maintain the charge state of the whole battery 20 appropriately.

  Although the embodiment of the present invention has been described above, the specific configuration is not limited to the above embodiment, and even if there is a design change or the like without departing from the gist of the present invention, Included in the invention. For example, in the above embodiment, since the timer is counted for each cell 2, when the voltage of the plurality of cells 2 is low, when the first predetermined time T1 elapses in each cell 2, Although many bypass discharges are performed, the timers of all the cells 2 may be cleared at the time of performing many bypass discharges. As a result, frequent bypass discharge can be prevented and voltage stabilization of the entire assembled battery 20 can be achieved.

Furthermore, the cell 2 whose charging voltage is lower than the allowable lower limit voltage _Vmin at the time of performing the multiple bypass discharge may be the specific cell 2 and excluded from the multiple bypass discharge.

Further, it is possible to count with one timer without providing a timer for each cell 2. That is, the allowable lower limit voltage V starts counting at the time of the occurrence is low cell 2 than _min, the voltage of the cell 2 is allowable lower limit voltage V _min is also equal to or higher than the voltage of the other cells 2 is allowable lower limit voltage V _min If it is lower, continue counting. Thus, the same count may be continued until all the cells 2 become equal to or higher than the allowable lower limit voltage _Vmin . As a result, the time to reach the first predetermined time T1 is accelerated, and even when the voltage is low in the plurality of cells 2 or the voltage is frequently low (not stable) in one cell 2, it is early. Many bypass discharges can be performed to accelerate the charging of the cell 2 having a low voltage at an early stage.

In the above embodiment, the alarm output and the bypass discharge are stopped when the voltage of the low-voltage cell 2 does not increase even after a large number of bypass discharges are performed for a predetermined time. As long as charging is not stopped or an abnormality such as a rise in the temperature of the cell 2 is not detected, many bypass discharges may be performed permanently. Further, after the bypass discharge is stopped in step S8, when the voltage of the cell 2 becomes equal to or higher than the average charge voltage _VA again, the bypass discharge may be started again.

  In the above embodiment, the bypass circuit 3 is constituted by the discharge resistor 31 and the discharge switch 32. However, the present invention is not limited to this, and any circuit that can bypass a predetermined current by a command from the controller 6 can be used. .

  On the other hand, the case of having one set of lithium ion assembled battery 20 has been described, but the present invention can also be applied when a plurality of assembled batteries 20 are connected. In this case, the charge control system 1 as described above is provided for each assembled battery 20. Moreover, not only the lithium ion cell 2, but in order to eliminate the charge state variation between series cells, it can be widely applied to secondary batteries in general. Furthermore, although the case where the charge control system 1 is applied to a DC power supply system has been described, it can also be applied to an uninterruptible power supply (UPS), a storage battery for automobiles, and the like. Can be applied. That is, the present invention can be applied to all cases in which a state where the charge voltage of some of the cells 2 is low continues for a predetermined time.

1 Lithium ion battery charge control system 2 Lithium ion cell (lithium ion secondary battery)
20 Lithium ion battery 3 Bypass circuit (individual discharge means)
4 Voltmeter (monitoring means)
5 Main switch 6 Controller (control means)
7 Bypass diode

Claims (6)

A charge control system for an assembled battery that controls charging of the assembled battery in which a plurality of secondary batteries are connected in series,
Monitoring means for monitoring the charging voltage of each secondary battery;
An individual discharge means provided in each of the secondary batteries, for discharging the secondary battery individually;
When the state where the charging voltage of some of the secondary batteries is lower than the first predetermined voltage continues for a predetermined time, the individual discharge means is operated for all the secondary batteries other than the some secondary batteries. Control means;
A battery pack charge control system comprising:   When the charging voltage of the secondary batteries reaches a second predetermined voltage higher than the first predetermined voltage during the operation of the individual discharging means, the control means applies to all the secondary batteries. 2. The assembled battery charge control system according to claim 1, wherein the operation of the individual discharge means is stopped.   The control means issues an alarm when the charge voltage of the secondary batteries does not reach a second predetermined voltage higher than the first predetermined voltage even after operating the individual discharge means for a predetermined time. The assembled battery charge control system according to claim 1, wherein the battery pack is output.   The control means stops the operation of the individual discharge means for the secondary battery when the charging voltage of the secondary battery in which the individual discharge means is operating is lower than a third predetermined voltage. The assembled battery charging control system according to any one of claims 1 to 3. A battery pack charge control method for controlling charging of a battery pack in which a plurality of secondary batteries are connected in series,
Monitoring the charging voltage of each secondary battery,
When a state in which the charging voltage of some of the secondary batteries is lower than the first predetermined voltage continues for a predetermined time, all the secondary batteries other than the some secondary batteries are individually discharged.
A charge control method for an assembled battery. During the individual discharge, when the charging voltage of the some secondary batteries reaches a second predetermined voltage higher than the first predetermined voltage, the individual discharge for all the secondary batteries is stopped. The charge control method for an assembled battery according to claim 5.

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