JP2012209994A - Charge control device for lithium ion battery pack, control method and lithium ion battery pack system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more appropriately charge a lithium ion secondary battery when the same is used for an assembled battery.SOLUTION: A charge control device for a lithium ion battery pack comprises: voltmeters 4 to monitor charging voltage of each lithium ion cell 2; balance circuits 3 which are installed on each lithium ion cell 2 and individually discharges the same; and a controller 6 which activates, when the charging voltage of one portion of the lithium ion cells 2 is lower than a lower limit voltage of an appropriate charging voltage range and the charging voltage of the other portion of the lithium ion cells 2 continues to be in a state higher than the lower limit voltage for a predetermined period, the balance circuits 3 for a portion of the other lithium ion cells 2.

Description

  The present invention relates to a lithium ion assembled battery charge control device that controls charging of a plurality of lithium ion secondary batteries connected in series, a control method, and a lithium ion assembled battery system including the device.

  Lithium ion secondary batteries have advantages such as high energy density and low self-discharge, and are widely used as storage batteries for automobiles, 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, a battery pack may be configured and used by connecting a plurality of single-cell lithium ion cells. On the other hand, in the lithium ion secondary battery, abnormal heat generation occurs due to overcharge or the like, and furthermore, an ignition accident may occur because the electrolytic solution is an organic solvent.

  For this reason, when using as an assembled battery, in order to charge each lithium ion cell appropriately, the technique which provided the bypass circuit is known (for example, refer patent document 1). In this technique, a plurality of lithium ion cells are connected in series to form a battery circuit array, and a plurality of battery circuit arrays are connected in parallel. In addition, each lithium ion cell is provided with a bypass circuit, and when each lithium ion cell exceeds the upper limit of the appropriate charging voltage range (allowable charging voltage range), the charging current is bypassed with the corresponding bypass circuit, When all the lithium ion cells in the same battery circuit row reach the charge completion voltage, the battery circuit row is disconnected from the charging circuit. This prevents overcharging of the lithium ion cell.

JP 2006-318843 A

  By the way, the present inventor configures an assembled battery by connecting a plurality of lithium ion cells in series, and the following event occurs when the assembled battery is used / operated in a float charge (floating charge) state. Found and confirmed that there is. That is, as a first event, as shown in FIG. 4, due to variations in manufacturing, storage conditions before operation, and the like, there is a variation in the state of charge when operated for a long time, and the specific lithium ion cell 2- Only 1 does not reach the proper charging voltage range (average value ± 20 mV in the figure), and the charging voltages of the other lithium ion cell groups 2-2 are stable within the appropriate charging voltage range. is there.

  As a second event, for example, when a defective lithium ion cell exists in the assembled battery, it is replaced 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 a partially charged state (not fully charged) in consideration of safety, and is incorporated into the assembled battery. In such a case, as shown in FIG. 5, the replaced new lithium ion cell 2-1 does not reach the proper charging voltage range, and the charging voltage of the other lithium ion cell group 2-2 is set to the appropriate charging voltage. It is stable within the voltage range.

  When such an event occurs, the conventional technology provided with a bypass circuit cannot charge a lithium ion cell with a low charging voltage to an appropriate charging voltage range. That is, in the conventional technology, the lithium ion cell that exceeds the upper limit of the appropriate charging voltage range is bypassed or discharged, thereby preventing overcharging of the cell and charging state. It is intended to promote charging of a lithium ion cell having a low level. Therefore, when there is no lithium ion cell exceeding the upper limit, that is, when cells other than the lithium ion cell having a low charging voltage are stable within an appropriate charging voltage range, bypassing and discharging are not performed. For this reason, the charge of the lithium ion cell with a low charge state is accelerated, and it cannot be charged to an appropriate charge voltage range.

  If such an improper charging state continues, the discharge capacity of the assembled battery as a whole is limited by the discharge capacity of the lithium ion cell with a low charging state (when the cell reaches a predetermined voltage, the assembled battery In order to terminate the overall discharge), there is a high possibility that a predetermined discharge time as designed cannot be secured at the time of backup when the commercial power supply fails.

  Accordingly, the present invention provides a lithium ion assembled battery charge control device, a control method, and a lithium ion assembled battery system that enable more appropriate charging when a plurality of lithium ion secondary batteries are used as an assembled battery. For the purpose.

  In order to achieve the above object, the invention described in claim 1 is a lithium ion assembled battery charge control device for controlling charging of a plurality of lithium ion secondary batteries connected in series. Monitoring means for monitoring the charging voltage of the lithium ion secondary battery; individual discharge means provided in each lithium ion secondary battery for individually discharging the lithium ion secondary battery; and some lithium ion secondary batteries When the charging voltage of the other lithium ion secondary battery is lower than the lower limit voltage of the appropriate charging voltage range and the charging voltage of the other lithium ion secondary battery is equal to or higher than the lower limit voltage for a predetermined time, the other lithium ion secondary battery And a processing means for operating the individual discharge means for a part thereof.

  According to the present invention, the monitoring means monitors the charging voltage of each lithium ion secondary battery, the charging voltage of some of the lithium ion secondary batteries is lower than the lower limit voltage of the appropriate charging voltage range, When the state where the charging voltage of the lithium ion secondary battery is equal to or higher than the lower limit voltage of the appropriate charging voltage range continues for a predetermined time, the individual discharging means operates for some of the other lithium ion secondary batteries by the processing means. Is done. That is, a part of the lithium ion secondary battery having an appropriate charging voltage is discharged, thereby promoting the charging of the lithium ion secondary battery having a low charging voltage.

  According to a second aspect of the present invention, in the lithium ion assembled battery charge control device according to the first aspect, the processing means is a lithium ion secondary battery having the highest charging voltage among the other lithium ion secondary batteries. The individual discharge means is operated with respect to the battery.

  The invention according to claim 3 is a lithium ion battery charge control method for controlling charging of a plurality of lithium ion secondary batteries connected in series, the charging of each lithium ion secondary battery. The voltage is monitored, and the state in which the charging voltage of some lithium ion secondary batteries is lower than the lower limit voltage of the appropriate charging voltage range and the charging voltage of other lithium ion secondary batteries is equal to or higher than the lower limit voltage for a predetermined time. When it continues, it discharges with respect to a part of said other lithium ion secondary battery, It is characterized by the above-mentioned.

  The invention according to claim 4 is a lithium ion battery pack system in which a plurality of lithium ion secondary batteries are connected in series, the monitoring means for monitoring the charging voltage of each lithium ion secondary battery, and each lithium ion Provided in the ion secondary battery, the individual discharge means for individually discharging the lithium ion secondary battery, the charging voltage of some lithium ion secondary batteries is lower than the lower limit voltage of the appropriate charging voltage range, Processing means for operating the individual discharge means for a part of the other lithium ion secondary batteries when a state where the charging voltage of the lithium ion secondary battery is equal to or higher than the lower limit voltage continues for a predetermined time; It is characterized by providing.

  According to the invention described in claims 1, 3 and 4, as in the first event and the second event, the charging voltage of some of the lithium ion secondary batteries is lower than the appropriate charging voltage, Some lithium-ion secondary batteries with the correct charging voltage even when the charging voltage of other lithium-ion secondary batteries is within the appropriate charging voltage range (inappropriate charging state) continues for the specified time In contrast, discharge is performed. For this reason, charging of the lithium ion secondary battery having a low charging voltage is promoted, and the entire lithium ion assembled battery can be charged more appropriately.

  In addition, when the improper charging state continues for a predetermined time, the lithium ion secondary battery having an appropriate charging voltage is discharged. In other words, if an improper charge state occurs temporarily, no discharge is performed, so unnecessary discharge is avoided and the charge state of the lithium ion secondary battery with an appropriate charge voltage is maintained appropriately. Is possible. In addition, by discharging when the improper charging state continues for a predetermined time, the lithium ion secondary battery is prevented from being overcharged or undercharged due to the improper charging state being continued for a long time. It becomes possible to charge the entire ion assembled battery appropriately and quickly.

  According to invention of Claim 2, in order to discharge with respect to a lithium ion secondary battery with the highest charge voltage among the lithium ion secondary batteries with appropriate charge voltage, even if it discharges, It becomes possible to maintain the charging voltage of the lithium ion secondary battery within an appropriate charging voltage range. In addition, since the lithium ion secondary battery with the highest charging voltage has good charge acceptance, even if the charging voltage becomes lower than the lower limit voltage of the appropriate charging voltage range, it can be quickly charged to the appropriate charging voltage range. Therefore, it becomes possible to charge the entire lithium ion assembled battery appropriately and quickly.

It is a schematic block diagram which shows the state which applied the lithium ion assembled battery system which concerns on embodiment of this invention to the rectifier. It is a figure which shows the control flow in the float charge state of the system of FIG. FIG. 3 is a diagram showing a continuation of FIG. 2. It is a figure which shows the phenomenon where only the voltage of a specific lithium ion cell falls from the appropriate charge voltage range at the time of the float charge of a lithium ion assembled battery. When a lithium ion cell in a lithium ion assembled battery is replaced, only the voltage of the replaced new lithium ion cell is a diagram illustrating an event that does not reach an appropriate charging voltage range.

  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 lithium ion assembled battery system 1 according to an embodiment of the present invention is applied to a rectifier. In this lithium ion assembled battery system 1, a plurality of lithium ion cells (lithium ion secondary batteries) 2, which are single cells, are connected in series to form a lithium ion assembled battery 20, and charging of such a lithium ion assembled battery 20 is performed. A lithium ion battery charge control device (hereinafter simply referred to as “control device”).

  This control device mainly includes a balance circuit (individual discharge means) 3 and a voltmeter (monitoring means) 4 provided in each lithium ion cell 2, a single main switch 5, and a controller (processing means) 6. ing. Each balance circuit 3, each voltmeter 4 and the main switch 5 are connected to the controller 6 so as to be able to communicate (data transmission).

  The balance 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 balance circuit 3 and the discharge switch 32 are on, both the discharge current and the charge current flow through the discharge resistor 31.

  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. As will be described later, the main switch 5 is normally turned on (closed), and is turned off (opened) in response to an opening command from the controller 6.

  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 balance circuit 3 and the main switch 5 based on the measurement result from each voltmeter 4. As the control, in the float charge state, the charge voltage of some lithium ion cells 2 is lower than the lower limit voltage of the proper charge voltage range, and the charge voltage of other lithium ion cells 2 is equal to or higher than the lower limit voltage (non- The control includes operating the balance circuit 3 for a part of the lithium ion cell 2 having an appropriate charging voltage when the appropriate charging state is continued for a predetermined time.

Specifically, as shown in FIGS. 2 and 3, it is first determined whether or not the operation of the control circuit is normal (step S1). If not normal, an alarm is generated from an alarm unit (not shown), the main switch 5 is turned off to stop charging, and all the balance circuits 3 are turned off (step S2). On the other hand, if the operation of the control circuit is normal, it is determined whether or not the charging current is zero or more (step S3). If the charging current is not zero or more, the process proceeds to a discharge mode to be described later. In this case, it is determined whether or not the total voltage of the assembled battery 20 is equal to or higher than the allowable lower limit total charging voltage VT _min (step S4).

As a result, if it is not the allowable limit total charge voltage VT _min or more, to generate an alarm from the alarm unit (step S5), and in the case of more than the allowable lower limit total charge voltage VT _min is allowable upper limit is the total voltage of the assembled battery 20 The total charging voltage VT _max or lower (step S6), the temperatures of all lithium ion cells 2 are lower than the allowable upper limit temperature Th ° C. (step S7), and the charging current is lower than the allowable maximum charging current Ic (step S8). Judge whether there is. When these requirements are not satisfied, the charging of the assembled battery 20 is stopped, the balance circuit 3 is released, etc., in the same manner as in step S2 (step S9).

On the other hand, when these requirements are satisfied, it is determined whether or not the voltage of each lithium ion cell 2 is equal to or lower than the allowable upper limit cell distribution voltage VA _max (step S10). Here, the allowable upper limit cell distribution voltage VA _max is an upper limit of the allowable variation when the charging voltage of each cell 2 varies in the actual charge state, that is, in the actual total voltage of the assembled battery 20. The voltage (the upper limit voltage with respect to the average voltage), for example, is calculated as follows.
VA _max = total voltage of battery pack 20 / number of cells 2 + allowable error voltage (for example, 20 mV)

If the voltage of any one of the lithium ion cells 2 is not equal to or lower than the allowable upper limit cell distribution voltage VA _max (in the case of “N” in step S10), the bypass circuit 3 of the cell 2 is turned on to perform a bypass discharge ( Step S11). At this time, if the bypass circuit 3 is already on, the on state is maintained.

Next, when such a bypass discharge state continues for the first predetermined time T1 in the same cell 2 (in the case of “Y” in step S12), the assembled battery is performed in the same manner as in step S2. 20 is stopped and the balance circuit 3 is released (step S20). On the other hand, when the predetermined time T1 is not continued (in the case of “N” in step S12), it is determined whether or not the voltage of the cell 2 is equal to or higher than the abnormal upper limit cell voltage VE _max (step S13). Here, the abnormal upper limit cell voltage VE _max is a voltage threshold that may cause an internal abnormality in the cell 2 when the charging voltage of each cell 2 varies in the actual charging state. Is calculated as follows.
VE _max = total voltage of battery pack 20 / number of cells 2 + abnormal voltage difference (for example, 80 mV)

As a result, when the above abnormality upper cell voltage _{VE max} performs the processing of step S20, if not abnormal upper cell voltage _{VE max} or more, the process proceeds to step S14. Here, the first predetermined time T1 in step S12 is, for example, an internal abnormality in the cell 2 or an abnormality in the connection between the cells 2 when the state where the allowable upper limit cell distribution voltage VA _max does not become lower than the allowable upper limit cell distribution voltage VA _max continues even when the bypass discharge is performed. This is a time estimated to have a risk of overheating, or a time during which overcharge can be avoided, and is set according to the characteristics and capacity of the cell 2.

Next, when the voltage of the cell 2 is not equal to or higher than the abnormal upper limit cell voltage VE _max (when “N” in step S13), and when the voltage of any cell 2 is equal to or lower than the allowable upper limit cell distribution voltage VA _max (step S10). In the case of “Y”, the following control is performed. First, for the cell 2 that has been subjected to the bypass discharge due to overvoltage, the bypass circuit 3 is turned off to stop the bypass discharge (step S14). That is, the bypass circuit 3 is turned off when the voltage of the cell 2 that has been subjected to bypass discharge because the charge voltage is higher than the allowable upper limit cell distribution voltage VA _max falls below the voltage VA _max .

Subsequently, it is determined whether or not the voltage of each lithium ion cell 2 is equal to or higher than the allowable lower limit cell distribution voltage VA _min (step S15). Here, the allowable lower limit cell distribution voltage VA _min is a lower limit voltage (lower limit voltage with respect to the average voltage) in which the variation is allowed in the actual charging state when the charging voltage of each cell 2 varies. Yes, for example, it is calculated as follows.
VA _min = total voltage of battery pack 20 / number of cells 2−allowable error voltage (for example, 20 mV)
Thus, in this embodiment, the “appropriate charging voltage range” is the allowable lower limit cell distribution voltage VA _min or more and the allowable upper limit cell distribution voltage VA _max or less, and “the total voltage of the assembled battery 20 ÷ the number of cells 2”. "Is an average charging voltage (" average value "in FIGS. 4 and 5). In addition, the allowable lower limit cell distribution voltage VA _min becomes the “lower limit voltage of an appropriate charging voltage range”.

When the allowable lower limit cell distribution voltage VA _{min is} higher than or equal to the allowable lower limit cell distribution voltage VA _min , if the other cell (selected cell) 2 is subjected to bypass discharge due to low voltage, the bypass circuit 3 is turned off to perform bypass discharge. Stop (step S16). That is, as will be described later, when the charging voltage of the cell 2 is lower than the allowable lower limit cell distribution voltage VA _min , the selected cell 2 is bypass-discharged. When the voltage rises to VA _min or higher, the bypass circuit 3 of the selected cell 2 is turned off.

On the other hand, if the charge voltage of any cell 2 is not equal to or higher than the allowable lower limit cell distribution voltage VA _min , it is determined whether or not such a low voltage state continues for the second predetermined time T2 in the same cell 2. Judgment is made (step S17). Here, the second predetermined time T2 is a time during which the voltage of the cell 2 in the low voltage state can be increased if bypass discharge of the selected cell 2 described later is performed, and unnecessary bypass discharge can be avoided. This is a time during which the overcharged state or the low charged state of the cell 2 can be prevented, and is set according to the characteristics and capacity of the cell 2.

As a result, when the second predetermined time T2 is continued, the bypass circuit 3 of the selected cell 2 is turned on to cause a bypass discharge (step S18). Here, the selected cell 2 is the cell 2 having the highest charging voltage among the cells 2 whose charging voltage is within an appropriate charging voltage range. When the cell 2 is already undergoing bypass discharge, The cell 2 has a high charging voltage. In this way, the bypass discharge is sequentially performed from the cell 2 having a high charging voltage. In addition, a plurality of cells 2 may be bypass-discharged at the same time as the selected cells 2 in accordance with the number of cells 2 in a low voltage state and their charging voltages. Further, in this embodiment, when the charging voltage of the selected cell 2 during the bypass discharge is lower than a predetermined voltage (for example, the allowable lower limit cell distribution voltage VA _min ), the bypass discharge is stopped at that time. Then, bypass discharge is performed on another selected cell 2. That is, bypass discharge of the selected cell 2 is performed within an appropriate charging voltage range.

  Subsequently, it is determined whether or not the bypass discharge of the selected cell 2 is continued for the third predetermined time T3 for the same cell 2 (step S19). Here, the third predetermined time T3 may cause an internal abnormality of the cell 2 or a connection abnormality between the cells 2 when the voltage of the cell 2 in the low voltage state does not increase even if the bypass discharge of the selected cell 2 is performed. This is a time estimated to be present, or a time during which excessive bypass discharge can be avoided, and is set according to the characteristics and capacity of the cell 2. When the third predetermined time T3 is continued, the charging of the assembled battery 20 is stopped, the balance circuit 3 is released, etc., in the same manner as in step S2 (step S20).

  On the other hand, if the third predetermined time T3 is not continued, or if the second predetermined time T2 is not continued in step S17, and after step S16, the process returns to step S3 to repeat the same processing. That is, the processing after step S3 is periodically performed cyclically, and charging voltage abnormality determination and adjustment are performed for all the cells 2 of the assembled battery 20.

In addition, the control by the controller 6 includes initial charge control, recovery charge control, discharge control (discharge mode), and the like. The initial charge control is control when charging (initial charge) the assembled battery 20 at the start of operation of the assembled battery 20, and the recovery charge control is charging (recovery charging) the assembled battery 20 after the assembled battery 20 is discharged. Both control is performed to determine whether the total voltage and charging current of the assembled battery 20 are appropriate, bypass discharge of the cell 2 having a voltage higher than the allowable upper limit cell distribution voltage VA _max , and the like. Then, the control of the float charge state is a control to be transferred when it is determined that the total voltage and the charge current of the assembled battery 20 are appropriate in the initial charge control and the recovery charge control.

  The discharge control is control when the assembled battery 20 is discharged. That is, when the power supply from the commercial power supply 100 is stopped, the assembled battery 20 starts discharging, and power is supplied from the assembled battery 20 to the load facility 102 via the bypass diode 7 and power is supplied to the controller 6. Supplied. In such a discharge mode, it is determined whether or not the charging current is zero or more. If the charging current is zero or more, the process proceeds to the recovery charging control. If the charging current is not zero or more, the following three requirements are satisfied. Judge whether to meet or not. That is, it is determined whether the temperature of all the lithium ion cells 2 is lower than the upper limit temperature Th ° C., whether the discharge current is lower than the allowable maximum discharge current Id, or whether the voltage of each cell 2 is higher than the discharge end voltage VL1. To do. Here, the end-of-discharge voltage VL1 is a voltage on the specification for ending and stopping the discharge, and is set according to the specified capacity of the lithium ion cell 2, the discharge current, and the like. And when satisfy | filling all these requirements, discharge of the assembled battery 20 is continued, and when not satisfy | filling, discharge is stopped.

  Next, the operation of the lithium ion assembled battery system 1 having such a configuration, the lithium ion assembled battery charging control method by the control device, and the like will be described.

First, at the time of float charging, the main switch 5 is turned on, the power from the commercial power source 100 is supplied to the lithium ion assembled battery 20, and the voltage of each lithium ion cell 2 is constantly measured by the voltmeter 4. Is transmitted to the controller 6 in real time. When the charge voltage of any cell 2 is higher than the appropriate charge voltage range (allowable upper limit cell distribution voltage VA _max ), a close command is transmitted from the controller 6 to the balance circuit 3 of the cell 2. Then, the balance circuit 3 is turned on to perform bypass discharge. As a result, the charging voltage of the cell 2 decreases and falls within an appropriate charging voltage range.

On the other hand, at the time of float charging, the state where the charging voltage of any cell 2 is lower than the appropriate charging voltage range (allowable lower limit cell distribution voltage VA _min ) (unsuitable charging state) continues for the second predetermined time T2. In this case, the bypass circuit 3 of the selected cell 2 as described above is turned on, and bypass discharge is performed. As a result, a charging current further flows to the cells 2 other than the selected cell 2, that is, the cells 2 in the low voltage state, and the charging of the cells 2 in the low voltage state is promoted. As a result, the charging voltage of the cell 2 that has been in the low voltage state rises within an appropriate charging voltage range, and then the bypass discharge for the selected cell 2 is stopped. Here, the improper charge state includes a case where bypass discharge is performed on the cell 2 having a charge voltage higher than the proper charge voltage range (allowable upper limit cell distribution voltage VA _max ). That is, bypass discharge for promoting the charging of the cell 2 in the low voltage state is performed regardless of the presence or absence of the cell 2 whose charging voltage is higher than the appropriate charging voltage range.

  As described above, according to the lithium ion assembled battery system 1, the control device, and the charge control method, the charging voltage of some cells 2 is appropriately charged as in the first event and the second event. When the voltage is lower than the lower limit voltage of the voltage range, bypass discharge is performed on the specific selected cell 2 regardless of the presence or absence of the cell 2 whose charging voltage is higher than the appropriate charging voltage range. For this reason, charging of the cell 2 in the low voltage state is promoted, and the entire lithium ion assembled battery 20 can be charged more appropriately. As a result, the discharge capacity of the assembled battery 20 as a whole becomes appropriate, and a predetermined discharge time as designed can be ensured at the time of backup when the commercial power supply 100 fails.

  In addition, when the low voltage state (inappropriate charge state) continues for the second predetermined time T2, bypass discharge is performed on the cell 2 having the proper charge voltage. That is, when a low voltage state occurs temporarily, bypass discharge is not performed, so unnecessary discharge can be avoided and the charge state of the cell 2 with the proper charge voltage can be properly maintained. Become. In addition, by discharging when the low voltage state continues for the second predetermined time T2, the overcharge state or the low charge state of the cell 2 due to the low voltage state continuing for a long time can be avoided, so that the lithium ion It becomes possible to charge the entire assembled battery 20 appropriately and quickly.

  In addition, since the cell 2 having the proper charge voltage is bypass-discharged in order from the cell 2 having the highest charge voltage, the charge voltage of the cell 2 is maintained within the proper charge voltage range even when the bypass discharge is performed. It is possible to do more. Further, since the cell 2 having the highest charging voltage has good charge acceptability, even if the charging voltage is close to the appropriate charging voltage range, the cell 2 is charged to the appropriate charging voltage range at an early stage, and the lithium ion assembled battery 20 It becomes possible to charge the whole properly and quickly.

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, the cell 2 in which the charging voltage is within the appropriate charging voltage range is bypass-discharged as the selected cell 2, but from the appropriate charging voltage range (allowable upper limit cell distribution voltage VA _max ). However, when the cell 2 having a high charging voltage is not bypass-discharged, the cell may be bypass-discharged as the selected cell 2. Moreover, although the system which has one set of lithium ion assembled battery 20 was demonstrated, it is applicable also to the system which connected the assembled battery 20 with two or more. In this case, the control device as described above is provided for each assembled battery 20. Furthermore, although the case where the lithium ion assembled battery system 1 is applied to a rectifier has been described, it can be applied to an uninterruptible power supply (UPS), an automobile storage battery, and the like, and in addition to float charging Can also be applied. That is, the present invention can be applied to all cases in which a state in which the charging voltage of some cells 2 is lower than the lower limit voltage of the appropriate charging voltage range continues for a predetermined time.

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

Claims (4)

A lithium ion assembled battery charge control device for controlling charging of a plurality of lithium ion secondary batteries connected in series,
Monitoring means for monitoring the charging voltage of each of the lithium ion secondary batteries;
Provided in each of the lithium ion secondary batteries, individual discharge means for individually discharging the lithium ion secondary battery,
When the charging voltage of some lithium ion secondary batteries is lower than the lower limit voltage of the appropriate charging voltage range and the state where the charging voltage of other lithium ion secondary batteries is equal to or higher than the lower limit voltage, continues for a predetermined time, Processing means for operating the individual discharge means for a part of the other lithium ion secondary battery;
A lithium ion battery pack charge control device comprising:   2. The lithium according to claim 1, wherein the processing unit operates the individual discharge unit with respect to a lithium ion secondary battery having the highest charging voltage among the other lithium ion secondary batteries. Ion battery pack charge control device. A lithium ion assembled battery charge control method for controlling charging of a plurality of lithium ion secondary batteries connected in series,
Monitoring the charging voltage of each lithium ion secondary battery,
When the charging voltage of some lithium ion secondary batteries is lower than the lower limit voltage of the appropriate charging voltage range and the state where the charging voltage of other lithium ion secondary batteries is equal to or higher than the lower limit voltage, continues for a predetermined time, Discharging a part of the other lithium ion secondary battery,
A method for controlling charging of a lithium ion assembled battery. A lithium ion assembled battery system in which a plurality of lithium ion secondary batteries are connected in series,
Monitoring means for monitoring the charging voltage of each of the lithium ion secondary batteries;
Provided in each of the lithium ion secondary batteries, individual discharge means for individually discharging the lithium ion secondary battery,
When the charging voltage of some lithium ion secondary batteries is lower than the lower limit voltage of the appropriate charging voltage range and the state where the charging voltage of other lithium ion secondary batteries is equal to or higher than the lower limit voltage, continues for a predetermined time, Processing means for operating the individual discharge means for a part of the other lithium ion secondary battery;
A lithium ion assembled battery system comprising:

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