JP2011155785A - Method and apparatus for managing lithium ion battery pack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To more reliably prevent internal short-circuiting and abnormal heat generation due to overdischarging. <P>SOLUTION: When a battery pack 20 is discharged, the voltage of each lithium ion cell 2 in the end stage of discharge is measured and stored. Before the battery pack 20 is charged, it is determined based on the stored voltages whether or not there is an overdischarged lithium ion cell 2 in the battery pack 20. When there is the overdischarged lithium ion cell 2, the battery pack 20 is not charged. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a lithium ion assembled battery management method and management apparatus for managing an assembled battery configured by connecting a plurality of lithium ion secondary batteries in series.

  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.

  In addition, when the lithium ion secondary battery is overdischarged, the cobalt of the positive electrode is eluted or the copper of the current collector of the cathode (negative electrode) is eluted. May cause fever. Moreover, since the energy density is high, there is a high risk of sudden overheating during a short circuit. For this reason, in order to prevent overdischarge, a technique is known in which when the voltage of any lithium ion secondary battery reaches a predetermined voltage (such as the discharge end voltage), the assembled battery is disconnected from the load and the discharge is terminated. (For example, refer to Patent Documents 1 and 2).

JP 2004-349195 A JP 2007-166747 A

  By the way, for example, when a lithium ion secondary battery is used as a backup power source for communication equipment, control equipment, etc., depending on the importance of the communication equipment, the lithium ion secondary battery is used in order to maintain the function of the communication equipment. In some cases, it is necessary to discharge to a voltage lower than the voltage of. That is, regardless of the techniques of Patent Documents 1 and 2, there are cases where the lithium ion secondary battery has to be overdischarged. In such a case, when the lithium ion secondary battery is recovered and charged, an internal short circuit occurs. Or abnormal heat generation.

  For this reason, for example, it may be possible to measure the open-circuit voltage of each lithium ion secondary battery and determine the presence or absence of an internal short circuit immediately before performing the recovery charge after discharge. The upper voltage may have recovered, and it is difficult to properly determine the presence or absence of an internal short circuit. Furthermore, when multiple lithium ion secondary batteries are connected in series and used as an assembled battery, there is a large variation in the internal resistance of each lithium ion secondary battery, especially when the lithium ion secondary battery has deteriorated over time. The variation is great. For this reason, it is difficult to appropriately determine the presence or absence of an internal short circuit based on the internal resistance of the lithium ion secondary battery.

  Therefore, an object of the present invention is to provide a management method and a management apparatus for a lithium ion assembled battery that can more reliably prevent an internal short circuit or abnormal heat generation due to overdischarge.

  In order to achieve the above object, the invention described in claim 1 is a method for managing a lithium ion battery pack, which manages a battery pack configured by connecting a plurality of lithium ion secondary batteries in series, wherein the battery pack When the battery is discharged, the voltage of each lithium ion secondary battery at the end of discharge is measured and stored, and before charging the assembled battery, the battery is over-discharged based on the stored voltage. It is determined whether there is a certain lithium ion secondary battery, and when there is a lithium ion secondary battery in an overdischarged state, the assembled battery is not charged.

  The invention according to claim 2 is a lithium ion secondary battery in which the assembled battery is temporarily temporarily charged and is in an overdischarged state in the assembled battery based on a voltage rise state of each lithium ion secondary battery. It is characterized by determining whether there exists.

  The invention according to claim 3 is a lithium ion secondary battery in which the assembled battery is temporarily temporarily discharged and is in an overdischarged state in the assembled battery based on a voltage drop situation of each lithium ion secondary battery. It is characterized by determining whether there exists.

  The invention according to claim 4 is a lithium ion assembled battery management device that manages an assembled battery configured by connecting a plurality of lithium ion secondary batteries in series, and discharges when the assembled battery is discharged. Monitoring means for measuring and storing the voltage of each lithium ion secondary battery in the last stage, and before charging the assembled battery, based on the voltage stored by the monitoring means, an overdischarge state is established in the assembled battery. Determining means for determining whether or not there is a certain lithium ion secondary battery, and avoidance of charging of the assembled battery when the determining means determines that there is a lithium ion secondary battery in an overdischarged state And means.

  The invention according to claim 5 is based on temporary charging means for temporarily charging the assembled battery before charging the assembled battery, and voltage rise status of each lithium ion secondary battery during the temporary charging. Determining means for determining whether or not there is a lithium ion secondary battery in an overdischarged state in the assembled battery, and the determination means determines that there is a lithium ion secondary battery in an overdischarged state. In some cases, the lithium-ion battery pack management apparatus includes an avoidance unit that avoids charging of the battery pack.

  The invention according to claim 6 is based on temporary discharge means for temporarily discharging the assembled battery before charging the assembled battery, and a voltage drop state of each lithium ion secondary battery during the temporary discharge. Determining means for determining whether or not there is a lithium ion secondary battery in an overdischarged state in the assembled battery, and the determination means determines that there is a lithium ion secondary battery in an overdischarged state. In some cases, the lithium-ion battery pack management apparatus includes an avoidance unit that avoids charging of the battery pack.

  According to the first and fourth aspects of the present invention, whether or not there is a lithium ion secondary battery in an overdischarged state based on the voltage of each lithium ion secondary battery at the end of discharge when the assembled battery is discharged. Determine. That is, since the determination is made based on the voltage at the time of actual discharge, it is possible to appropriately determine the presence or absence of the lithium ion secondary battery that is in an overdischarged state.

  According to the second and fifth aspects of the present invention, is there a lithium ion secondary battery that is temporarily overcharged and that is in an overdischarged state based on the voltage rise status of each lithium ion secondary battery? Determine whether or not. That is, since the determination is made based on the normality / abnormality of the charging state at the time of temporary charging, it is possible to appropriately determine whether or not there is a lithium ion secondary battery in an overdischarged state.

  According to the invention described in claims 3 and 6, is there a lithium ion secondary battery that is temporarily discharged and temporarily overdischarged based on the voltage drop status of each lithium ion secondary battery? Determine whether or not. That is, since the determination is based on the normality / abnormality of the discharge state at the time of temporary discharge, it is possible to appropriately determine whether or not there is a lithium ion secondary battery in an overdischarged state.

  And if there is a lithium ion secondary battery that is in an overdischarged state based on such a proper determination result, the assembled battery is not charged, so an internal short circuit or abnormal heat generation due to overdischarge is caused. It becomes possible to prevent more reliably.

It is a schematic block diagram which shows the application example of the management apparatus of the lithium ion assembled battery which concerns on Embodiment 1 of this invention. It is a schematic block diagram which shows the application example of the management apparatus of the lithium ion assembled battery which concerns on Embodiment 3 of this invention.

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

(Embodiment 1)
FIG. 1 is a schematic configuration diagram showing a state in which a lithium ion assembled battery unit 1 including a lithium ion assembled battery management device (hereinafter simply referred to as “management device”) according to this embodiment is applied to a rectifier. . In this embodiment, a case will be described in which the lithium ion assembled battery 20 is used as a backup power source for the load facility 100 and is operated by float charging using a rectifier.

  The lithium ion assembled battery 20 is configured by connecting 12 lithium ion cells (lithium ion secondary batteries) 2 in series, and is connected to the power supply system in parallel with the load facility 100. That is, the commercial power supply 31 is connected to the load facility 100 and the lithium ion assembled battery 20 via the rectifier (AC / DC converter) 32, and the electric power from the commercial power supply 31 is rectified (DC converted) by the rectifier 32. It is supplied to the load equipment 100 and the lithium ion assembled battery 20.

  The lithium ion assembled battery 20 is connected to a rectifier 32 via a charge switch (avoidance means) 41. The charging switch 41 is normally turned on (closed), and, as will be described later, when the control device (determination means) 6 controls the opening and closing of the lithium ion cell 2 that is in an overdischarged state. When the determination is made, charging of the lithium ion assembled battery 20 is avoided.

  Further, a bypass diode 42 is connected in parallel with the charge switch 41. The bypass diode 42 has a function of allowing only the flow of current from the lithium ion assembled battery 20 and prevents current from flowing to the lithium ion assembled battery 20. Thereby, the discharge from the lithium ion assembled battery 20 to the load facility 100 is always possible via the bypass diode 42, and in the event of a power failure of the commercial power supply 31 or a failure of the rectifier 32, the lithium ion assembled battery 20 to the load facility 100. Backup power is supplied to the.

  A monitoring device (monitoring means) 5 is attached to the lithium ion assembled battery 20. The monitoring device 5 is a device that measures the voltage of each lithium ion cell 2 and the voltage of the entire lithium ion battery pack 20 and stores it in a memory (not shown). A cell voltmeter connected to measure the voltage of each lithium ion cell 2 and a total voltmeter connected to both terminals of the lithium ion assembled battery 20 to measure the voltage of the entire lithium ion assembled battery 20 are provided. For example, as described later, when the lithium ion assembled battery 20 is discharged, the voltage of the entire lithium ion assembled battery 20 and the lithium ion cells 2 during the entire discharge including the end of discharge is measured and stored (monitored). .

  The control apparatus 6 is connected to such a monitoring apparatus 5 so that communication is possible. The control device 6 controls opening / closing of the charging switch 41 based on the voltage measured and stored by the monitoring device 5. Specifically, before the recharged lithium ion battery pack 20 is recovered and charged, the lithium ion battery pack 20 includes the lithium ion battery cell 2 measured and stored by the monitoring device 5 at the end of discharge. It is determined whether there is a lithium ion cell 2 in an overdischarged state. When it is determined that there is a lithium ion cell 2 in an overdischarged state, an “off (open) command” is transmitted to the charge switch 41.

  Here, the determination as to whether or not each lithium ion cell 2 is in an overdischarge state is made based on whether or not the voltage of each lithium ion cell 2 at the end of discharge has reached a voltage that is recognized as overdischarge. The voltage recognized as overdischarge is set based on the discharge end voltage (voltage at which discharge should be terminated), the aging of the lithium ion battery pack 20, the ambient temperature, or the magnitude of the discharge current.

  The charging switch 41, the bypass diode 42, the monitoring device 5, and the control device 6 as described above constitute a management device that manages the lithium ion assembled battery 20. The management device and the lithium ion assembled battery 20 constitute a lithium ion assembled battery unit 1. In this embodiment, the assembled battery unit 1 is detachably connected to the rectifier 32 and the load facility 100. Yes. The lithium ion assembled battery 20 is detachably connected to the charge switch 41, the bypass diode 42, and the monitoring device 5.

  Next, the operation of the management apparatus having such a configuration, and a management method (hereinafter simply referred to as “management method”) of the lithium ion assembled battery 20 using the management apparatus will be described.

  First, at the time of maintenance charging (float charging), the charging switch 41 is turned on, and power is supplied from the commercial power supply 31 to the entire load facility 100 and the lithium ion assembled battery 20 as described above. The entire 20 is charged. At the time of this charging, the monitoring device 5 measures and stores the voltage of the entire lithium ion assembled battery 20 and each lithium ion cell 2.

  Next, when power supply from the commercial power supply 31 to the load facility 100 is stopped due to a power failure of the commercial power supply 31 or a failure of the rectifier 32, the lithium ion group is instantaneously (without instantaneous interruption) via the bypass diode 42. The battery 20 starts discharging, and power from the lithium ion assembled battery 20 is supplied to the load facility 100. During the discharge, as described above, the voltage of the entire lithium ion assembled battery 20 and each lithium ion cell 2 is measured and stored by the monitoring device 5 until at least the discharge is completed.

  Here, normally, in order to prevent overdischarge, when the total voltage of the entire lithium ion assembled battery 20 reaches a predetermined voltage (total discharge end voltage), or the cell voltage of any lithium ion cell 2 is When a predetermined voltage (cell discharge end voltage) is reached, the discharge is terminated. However, when the load facility 100 is a highly important communication device or the like, it may be necessary to discharge to a voltage lower than the discharge end voltage.

  Subsequently, when power supply from the commercial power supply 31 becomes possible (restored), power is supplied again from the commercial power supply 31 to the load facility 100. At the same time, as described above, the control device 6 determines whether or not there is a lithium ion cell 2 in an overdischarged state in the lithium ion battery pack 20, and if there is a lithium ion cell 2 in an overdischarged state If determined, an “off command” is transmitted to the charging switch 41. Thereby, the charge switch 41 is turned off (opened), and the lithium ion assembled battery 20 is not charged. On the other hand, when it is determined by the control device 6 that there is no lithium ion cell 2 in the overdischarged state, the on state of the charge switch 41 is maintained and the lithium ion assembled battery 20 is charged.

  As described above, according to this management device and management method, there is a lithium ion cell 2 that is in an overdischarged state based on the voltage of each lithium ion cell 2 at the end of discharge when the lithium ion battery pack 20 is discharged. It is determined whether or not. That is, since it determines based on the voltage at the time of actual discharge, it is possible to determine appropriately the presence or absence of the lithium ion cell 2 in an overdischarged state. And based on such an appropriate determination result, when there is the lithium ion cell 2 in an overdischarged state, the lithium ion assembled battery 20 is not charged. For this reason, even if there is a case where it is necessary to discharge to a voltage lower than the discharge end voltage, it is possible to more reliably prevent an internal short circuit or abnormal heat generation due to overdischarge.

(Embodiment 2)
In this embodiment, the method for determining whether or not there is a lithium ion cell 2 in an overdischarged state is different from that in the first embodiment, and other configurations are the same as those in the first embodiment. For this reason, about the structure equivalent to Embodiment 1, the description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  That is, in this embodiment, before the recovery charge (main charge) of the lithium ion assembled battery 20, the lithium ion assembled battery 20 is temporarily provisionally charged, based on the voltage increase status of each lithium ion cell 2, It is determined whether or not there is a lithium ion cell 2 in an overdischarged state in the lithium ion battery pack 20. Specifically, the charging switch 41 is kept in an ON state at the time when the power supply from the rectifier 32 (commercial power supply 31) becomes possible after the lithium ion battery pack 20 is discharged. For this reason, the lithium ion assembled battery 20 is temporarily charged in response to the power supply from the rectifier 32.

  Subsequently, the entire lithium ion assembled battery 20 and the voltage of each lithium ion cell 2 during temporary charging are measured and stored by the monitoring device 5. Then, in the control device 6, a voltage increase amount (ΔV / Δt) per unit time is calculated from the voltage of each lithium ion cell 2 measured and stored by the monitoring device 5, and this voltage increase amount (ΔV / Δt). Whether or not there is a lithium ion cell 2 in an overdischarged state is determined depending on whether or not is smaller than a predetermined value (threshold value). That is, in the overdischarged state, even if charging is performed, the voltage does not increase properly, and the voltage increase amount (ΔV / Δt) is considered to be smaller than a predetermined value. Is.

  When it is determined that there is a lithium ion cell 2 in an overdischarged state, the control device 6 turns off the charging switch 41 and the main charging of the lithium ion assembled battery 20 is not performed. As described above, the commercial power supply 31, the rectifier 32, the monitoring device 5, and the control device 6 constitute temporary charging means for temporarily temporary charging the lithium ion assembled battery 20.

  Here, the temporary charge time (Δt) is a time during which the overdischarge state can be determined based on the voltage increase amount (ΔV / Δt), and even if the lithium ion cell 2 in the overdischarge state is charged, an internal short circuit occurs. Or a time when no abnormal heat generation occurs. Further, the predetermined value (threshold value) of the voltage increase amount (ΔV / Δt) is a value by which the overdischarge state can be determined, and is set based on the charging current value, the aging of the lithium ion assembled battery 20, or the discharge amount. ing.

  As described above, according to this embodiment, the lithium ion assembled battery 20 is temporarily temporarily charged, and there is a lithium ion cell 2 in an overdischarged state based on the voltage rise state of each lithium ion cell 2. It is determined whether or not. That is, since it is determined whether or not the battery is overdischarged depending on whether or not it is properly charged by temporary charging, it is possible to appropriately determine the presence or absence of the lithium ion cell 2 in the overdischarge state. For this reason, as in the first embodiment, it is possible to more reliably prevent an internal short circuit or abnormal heat generation due to overdischarge.

(Embodiment 3)
FIG. 2 is a schematic configuration diagram illustrating a state in which the lithium ion assembled battery unit 1 including the management device according to this embodiment is applied to a rectifier. In this embodiment, the method for determining whether or not there is a lithium ion cell 2 in an overdischarged state is different from that in the first embodiment, and other configurations are the same as those in the first embodiment. For this reason, about the structure equivalent to Embodiment 1, the description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  That is, in this embodiment, when the rectifier 32 and the control device 6 are connected so as to be communicable and power supply from the rectifier 32 can be started, a signal to that effect (restoration signal) is sent to the control device 6. The rectifier 32 is controlled based on a control signal transmitted from the control device 6. And before carrying out recovery charge (main charge) of the lithium ion assembled battery 20, the lithium ion assembled battery 20 is temporarily discharged temporarily, and based on the voltage drop condition of each lithium ion cell 2, the lithium ion assembled battery 20 It is determined whether or not there is a lithium ion cell 2 in an overdischarged state.

  Specifically, when the control device 6 receives the restoration signal from the rectifier 32, a supply stop command is transmitted from the control device 6 to the rectifier 32, and power is not supplied from the rectifier 32. For this reason, the lithium ion assembled battery 20 temporarily discharges temporarily, and power is supplied from the lithium ion assembled battery 20 to the load facility 100.

  Subsequently, the voltage of the entire lithium ion assembled battery 20 and each lithium ion cell 2 during temporary discharge is measured and stored by the monitoring device 5. Then, the control device 6 calculates a voltage drop amount (ΔV / Δt) per unit time from the voltage of each lithium ion cell 2 measured and stored by the monitoring device 5, and this voltage drop amount (ΔV / Δt). It is determined whether or not there is a lithium ion cell 2 in an overdischarged state depending on whether or not is within a predetermined value (threshold). That is, when discharging in an overdischarged state, the voltage does not drop properly (does not discharge properly), and the voltage drop amount (ΔV / Δt) is considered to be smaller or larger than a predetermined value. Such a determination is performed.

  When it is determined that there is a lithium ion cell 2 in an overdischarged state, the control device 6 turns off the charging switch 41 and the main charging of the lithium ion assembled battery 20 is not performed. Further, after the temporary discharge, a supply start command is transmitted from the control device 6 to the rectifier 32, and power is supplied from the rectifier 32 to the load facility 100. At this time, if it is determined that there is no lithium ion cell 2 in an overdischarged state, the charging switch 41 is turned on, so that power is also supplied to the lithium ion assembled battery 20 and main charging is performed. Thus, the rectifier 32, the load facility 100, and the control device 6 constitute temporary discharge means for temporarily discharging the lithium ion assembled battery 20.

  Here, the temporary discharge time (Δt) is a time during which the overdischarge state can be determined based on the voltage drop amount (ΔV / Δt), and even if the lithium ion cell 2 in the overdischarge state is discharged, an internal short circuit occurs. Or a time when no abnormal heat generation occurs. Further, the predetermined value (threshold value) of the voltage drop amount (ΔV / Δt) is a value by which an overdischarge state can be determined, such as the discharge current value, the aging of the lithium ion assembled battery 20, or the voltage value at the start of discharge. Is set based on.

  As described above, according to this embodiment, the lithium ion assembled battery 20 is temporarily temporarily discharged, and there is a lithium ion cell 2 in an overdischarged state based on the voltage drop state of each lithium ion cell 2. It is determined whether or not. That is, whether or not the lithium ion cell 2 is in the overdischarged state can be appropriately determined because it is determined whether or not the overdischarged state is present depending on whether or not the temporary discharge is appropriately performed. For this reason, as in the first and second embodiments, it is possible to more reliably prevent an internal short circuit or abnormal heat generation due to overdischarge.

  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 second embodiment, the commercial power supply 31, the rectifier 32, the monitoring device 5, and the control device 6 constitute the temporary charging means, but a single charger may be used as the temporary charging means. Similarly, in Embodiment 3, the rectifier 32, the load facility 100, and the control device 6 constitute temporary discharge means, but a single discharger may be used as temporary discharge means. Furthermore, in Embodiments 1 to 3, the monitoring device 5 and the control device 6 may be integrated.

  Moreover, although the case where it had one set of lithium ion assembled batteries 20 was demonstrated, it is applicable also when multiple lithium ion assembled batteries 20 are connected in parallel. Furthermore, although the case where the lithium ion assembled battery 20 is applied to a rectifier has been described, it can also be applied to an uninterruptible power supply (UPS), an automobile storage battery, and the like.

1 Lithium ion battery unit 2 Lithium ion cell (lithium ion secondary battery)
20 Lithium ion battery 31 Commercial power supply 32 Rectifier 41 Charge switch (avoidance means)
42 Bypass diode 5 Monitoring device (monitoring means)
6 Control device (determination means)
100 load equipment

Claims (6)

A method of managing a lithium ion assembled battery for managing an assembled battery configured by connecting a plurality of lithium ion secondary batteries in series,
When the assembled battery is discharged, the voltage of each lithium ion secondary battery at the end of discharge is measured and stored,
Before charging the assembled battery, based on the stored voltage, it is determined whether there is a lithium ion secondary battery in the overdischarged state in the assembled battery,
When there is a lithium ion secondary battery in an overdischarged state, the battery pack is not charged.
A method for managing a lithium ion assembled battery. A method of managing a lithium ion assembled battery for managing an assembled battery configured by connecting a plurality of lithium ion secondary batteries in series,
Before charging the battery pack, the battery pack is temporarily temporarily charged, and the lithium ion secondary battery is in an overdischarged state in the battery pack based on the voltage rise state of each lithium ion secondary battery. Whether or not there is
When there is a lithium ion secondary battery in an overdischarged state, the battery pack is not charged.
A method for managing a lithium ion assembled battery. A method of managing a lithium ion assembled battery for managing an assembled battery configured by connecting a plurality of lithium ion secondary batteries in series,
Before charging the battery pack, the battery pack is temporarily temporarily discharged, and the lithium ion secondary battery is in an overdischarged state in the battery pack based on the voltage drop state of each lithium ion secondary battery. Whether or not there is
When there is a lithium ion secondary battery in an overdischarged state, the battery pack is not charged.
A method for managing a lithium ion assembled battery. A lithium-ion battery management device that manages battery packs configured by connecting a plurality of lithium-ion secondary batteries in series,
Monitoring means for measuring and storing the voltage of each lithium ion secondary battery at the end of discharge when the assembled battery is discharged;
Before charging the assembled battery, based on the voltage stored by the monitoring means, determining means for determining whether there is a lithium ion secondary battery in an overdischarged state in the assembled battery;
Avoidance means for avoiding charging of the assembled battery when it is determined by the determination means that there is a lithium ion secondary battery in an overdischarged state;
An apparatus for managing a lithium ion battery pack, comprising: A lithium-ion battery management device that manages battery packs configured by connecting a plurality of lithium-ion secondary batteries in series,
Before charging the battery pack, temporary charging means for temporarily charging the battery pack;
Determination means for determining whether or not there is a lithium ion secondary battery in an overdischarged state in the assembled battery based on a voltage rise situation of each lithium ion secondary battery during the temporary charging;
Avoidance means for avoiding charging of the assembled battery when it is determined by the determination means that there is a lithium ion secondary battery in an overdischarged state;
An apparatus for managing a lithium ion battery pack, comprising: A lithium-ion battery management device that manages battery packs configured by connecting a plurality of lithium-ion secondary batteries in series,
Temporary charging means for temporarily discharging the assembled battery before charging the assembled battery;
Determination means for determining whether there is a lithium ion secondary battery in an overdischarged state in the assembled battery based on a voltage drop situation of each lithium ion secondary battery during the temporary discharge;
Avoidance means for avoiding charging of the assembled battery when it is determined by the determination means that there is a lithium ion secondary battery in an overdischarged state;
An apparatus for managing a lithium ion battery pack, comprising:

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