JP2011034784A - Secondary battery device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent misdetection of tab disconnection of parallel units, in a pack battery which includes a secondary battery group formed, by serially connecting a plurality of the parallel units having a plurality of parallel-connected secondary battery cells. <P>SOLUTION: The secondary battery device includes the secondary battery group, formed by serially connecting the plurality of the parallel units having the plurality of the parallel-connected secondary battery cells; an abnormality detecting means to detect tab disconnection of each parallel unit in the secondary battery group; and an abnormality detection control means to stop the detection of the tab disconnection by the abnormality detecting means, until reaching a fixed period of time, after starting or stopping charge of the secondary battery group, and until the frequency of charge cycles for the secondary battery group reaches a prescribed frequency. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention provides a secondary battery comprising tab detachment determining means capable of accurately detecting tab detachment of the parallel unit in a group of secondary batteries in which a plurality of parallel units in which a plurality of secondary battery cells are connected in parallel are connected in series. Relates to the device.

  Secondary battery devices that are mounted on various electronic devices and used as a power source for the electronic devices are generally secondary battery groups in which a plurality of parallel units in which a plurality of secondary battery cells are connected in parallel are connected in series, The battery pack is configured as a so-called pack battery including a control / arithmetic unit that controls charging / discharging of the secondary battery group. Incidentally, the control / calculation unit includes a current detection unit that detects a charge / discharge current of the secondary battery group and a voltage detection unit that detects a terminal voltage of each parallel unit in the secondary battery group. The control / arithmetic unit controls the charging and discharging of the secondary battery group based on the detected current / voltage, and protects the secondary battery group from overcharge and overdischarge. Abnormality detection processing such as tab detachment or internal short circuit of the battery group is executed.

  As for abnormality detection processing such as tab detachment or internal short circuit of the secondary battery group in the secondary battery device (pack battery), for example, the terminal voltage of each parallel unit in the secondary battery group is obtained, and the maximum voltage and This is performed by determining a difference from the minimum voltage or a ratio between the maximum voltage and the minimum voltage (see, for example, Patent Document 1). In addition, for secondary battery groups in which an abnormality has been detected, measures such as fusing a thermal fuse inserted in series in the charge / discharge path of the secondary battery group, thereby prohibiting use of the battery pack itself, etc. (See, for example, Patent Document 2).

JP 2007-240234 A JP 2009-76280 A

  By the way, in the case of a secondary battery device (pack battery) using a lithium ion battery as a secondary battery cell, in the conventional general tab deviation detection method disclosed in Patent Document 1, tab deviation rarely occurs. In spite of this, it may be erroneously detected that tab removal has occurred. In addition, even when the terminal voltage of each parallel unit changes greatly due to variations in the temperature characteristics of the secondary battery cells, it may be erroneously detected that the tab is detached. Such erroneous detection of tab detachment is a factor involuntarily disposing of a battery pack with no tab detachment abnormality.

  Such erroneous detection of tab detachment tends to occur particularly in a battery pack using a so-called high voltage type lithium ion battery (secondary battery cell) in which the electrode material and the electrolytic solution are improved to improve performance. Incidentally, a conventional lithium ion battery having a maximum charging voltage of 4.2 V is configured using, for example, lithium cobaltate as a positive electrode material, a carbon material as a negative electrode material, and ethylene carbonate as an electrolytic solution. In contrast, high voltage type lithium ion batteries with improved battery performance use, for example, a mixture of lithium cobaltate and lithium cobalt nickel manganate composite oxide as the positive electrode material, and fluoroethylene carbonate as the electrolyte. The maximum charging voltage is increased to 4.3V.

  The present invention was made to solve the above-described problem of erroneous detection of tab detachment, and the object thereof is to reliably and accurately detect tab detachment in a plurality of parallel units connected in series, It is an object of the present invention to provide a secondary battery device capable of preventing unintentional disposal of a battery pack in which tab separation does not occur.

  The present invention is based on various experiments, and the above-described erroneous detection that tab removal has occurred is likely to occur exclusively at the initial stage of charging / discharging the battery pack (secondary battery group), and tab removal has occurred. Even if not, due to the variation in the temperature characteristics of the secondary battery cells, it has been made paying attention to the result of verification that a large difference may occur in the terminal voltages of the plurality of parallel units at the time of charging / discharging. .

  For example, in the above-described high voltage type lithium ion battery, in general, the surface state of the negative electrode material is unstable, and when the solid electrolyte film is not formed on the surface of the negative electrode material, the charge / discharge is accompanied. Thus, the electrolytic solution reacts on the surface of the negative electrode material and a lithium metal-containing compound is easily formed on the surface of the negative electrode material. And it is thought that this lithium metal containing compound affects the charging / discharging of this lithium ion battery. Specifically, the voltage change of the secondary battery cell (lithium ion battery) due to charging / discharging becomes temporarily irregular due to the presence of the above-described lithium metal-containing compound, resulting in each terminal of a plurality of parallel units. It is considered that the voltage varies greatly.

  In particular, the variation in the terminal voltage of each parallel unit due to the above-described charging / discharging is noticeably generated when the battery pack is charged in a low temperature environment (eg, 5 ° C.) outside the normal operating temperature range (20 ° C. to 50 ° C.). . It has also been found that the above-described terminal voltage variation is almost eliminated even when the battery is left for a certain period of time after charging is stopped or when charging and discharging are repeated. This is considered to be because the solid electrolyte film is sufficiently formed on the surface of the negative electrode material, the surface state of the negative electrode material is stabilized, and the aforementioned lithium metal-containing compound is hardly formed.

  In addition, the variation in the terminal voltage of each parallel unit due to the above-described charging / discharging also occurs due to the variation in the temperature characteristics of the secondary battery cells. Therefore, even if the solid electrolyte film is sufficiently formed on the surface of the negative electrode material, the tab There is a risk of erroneous detection of detachment. However, when the temperature of the secondary battery stabilizes to a substantially constant level after the charge / discharge is stopped, there is almost no variation in the terminal voltage of each parallel unit unless tab disconnection occurs. That is, after charging / discharging is stopped, there is basically no difference in the terminal voltage of each secondary battery cell, so-called open terminal voltage.

The present invention is made to solve the above-mentioned problems based on such verification results.
That is, the secondary battery device according to the present invention includes a secondary battery group in which a plurality of parallel units each having a plurality of secondary battery cells connected in parallel are connected in series, and a current for detecting a charge / discharge current of the secondary battery group. Based on the detection means, the voltage detection means for detecting the terminal voltage of each parallel unit in the secondary battery group, the detection result by the current detection means and the detection result by the voltage detection means, An anomaly detecting means for detecting tab disengagement in each parallel unit;
In particular, the present invention is characterized by comprising an abnormality detection control means for stopping the detection of tab detachment by the abnormality detection means for a predetermined time after starting or stopping charging of the secondary battery group.

  Incidentally, when the abnormality detection control means stops the detection process of tab detachment, a predetermined time after starting charging or stopping charging of the secondary battery group is accompanied by charging of the secondary battery group. It is set as the time required for the surface of the negative electrode constituting the secondary battery cell to react with the electrolyte and stabilize. Specifically, the predetermined time is set as, for example, 10 hours after the start or stop of charging, although it depends on the specifications of the secondary battery group (secondary battery cell).

Further, another secondary battery device according to the present invention detects a secondary battery group in which a plurality of parallel units each having a plurality of secondary battery cells connected in parallel are connected in series, and a charge / discharge current of the secondary battery group. Based on the current detection means, the voltage detection means for detecting the terminal voltage of each parallel unit in the secondary battery group, the detection result by the current detection means and the detection result by the voltage detection means, the secondary battery group An abnormality detecting means for detecting a tab disengagement in each parallel unit in
In particular, the present invention is characterized by comprising an abnormality detection control means for stopping the detection process of tab detachment by the abnormality detection means until the number of charge / discharge cycles for the secondary battery group reaches a predetermined fixed number of times.

  Incidentally, the predetermined number of charge / discharge cycles when the abnormality detection control means stops the detection of tab detachment is determined by repeating the charge / discharge of the secondary battery group. Is set as the number of charge / discharge cycles in which the surface of the negative electrode constituting the material reacts and stabilizes with the electrolytic solution. Specifically, the fixed number of charge / discharge cycles is set to, for example, about 20 cycles although it depends on the specifications of the secondary battery group (secondary battery cells).

The abnormality detection means preferably obtains the terminal voltage of each parallel unit at the time of charging / discharging of the secondary battery group, and the difference or ratio between the maximum terminal voltage and the minimum terminal voltage, or each parallel unit. First tab detachment determining means for detecting the presence or absence of tab detachment by determining a difference or ratio between a maximum value and a minimum value of a fluctuation range per unit time of the terminal voltage of
When the tab detachment is detected by the first tab detachment determining means, the terminal voltage (open terminal voltage) of each parallel unit after stopping the charging / discharging of the secondary battery group is obtained, and the maximum open terminal voltage is obtained. The difference or ratio between the terminal voltage and the minimum open terminal voltage, or the difference or ratio between the maximum value and the minimum value of the fluctuation range per unit time of the terminal voltage of each parallel unit is checked to confirm the occurrence of the tab deviation. 2 tab disengagement judging means.

  According to the secondary battery device of the present invention, after the start or stop of the charging of the secondary battery group, a predetermined constant time (for example, 10 hours) or a predetermined number of charge / discharge cycles is constant. Until the number of times (for example, 20 times) is reached, the detection of tab detachment by the abnormality detection unit is stopped, so that the terminal voltage of the parallel unit may vary due to the surface state of the negative electrode material. It is possible to prevent erroneous detection of tab deviation. Therefore, the secondary battery device (pack battery) in which tab separation does not occur is not discarded as a defective product.

  In the tab removal detection process, not only the terminal voltage of each parallel unit is monitored during charging / discharging to detect tab removal, but also each parallel unit after the secondary battery group has stopped charging / discharging. The terminal voltage, that is, the open terminal voltage, is obtained to check the occurrence of tab detachment, so that the tab detachment in the parallel unit can be accurately and reliably performed without being affected by the temperature distribution and temperature characteristics of the secondary battery cells. Can be detected.

  Therefore, according to the present invention, it is possible to prevent erroneous detection of tab disengagement in an unstable state when the secondary battery device is in an initial stage of use and a solid electrolyte film is not sufficiently formed on the surface of the negative electrode material. In addition, it is possible to prevent erroneous detection of tab detachment due to variations in temperature characteristics of secondary battery cells, so erroneous detection of variations in terminal voltage of parallel units due to characteristics of secondary battery cells as detachment of tabs. Disappears.

The schematic block diagram of the secondary battery apparatus (pack battery) which concerns on one Embodiment of this invention. The figure which shows an example of the tab deviation detection processing procedure which concerns on this invention. The figure which shows the change characteristic of the terminal voltage at the time of discharge in the use initial stage of a lithium ion battery. The figure which expands and shows the irregular shape part in the change characteristic of the terminal voltage shown in FIG. The figure which shows the terminal voltage change characteristic at the time of the discharge changed with the leaving time of the charged lithium ion battery. The figure which shows the terminal voltage change characteristic at the time of the discharge changed by repetition of charging / discharging of a lithium ion battery. The figure which shows the modification of the secondary battery apparatus (pack battery) which concerns on this invention.

Hereinafter, a secondary battery device (pack battery) according to an embodiment of the present invention will be described.
FIG. 1 is a schematic configuration diagram of a main part of a secondary battery device (pack battery) 10 according to the present invention. The battery pack 10 is basically mounted on an electronic device 30 such as a mobile phone terminal or a notebook personal computer, and is connected to and charged by a control / power supply unit (charger) 31 built in the electronic device 30. The secondary battery 1 is provided.

  A commercial power supply is supplied to the control / power supply unit (charger) 31 of the electronic device 30, and the secondary battery 1 is charged with energy obtained from the commercial power supply. The battery pack 10 is used as a power source for the electronic device 30 when the electronic device 30 does not use a commercial power source. That is, the battery pack 10 supplies the power energy accumulated in the secondary battery 1 by charging to the load 32 such as a CPU or a memory that is the main body of the electronic device 30 via the control / power supply unit 31. Configured as follows.

  The battery pack basically has a secondary battery group (secondary battery 1) in which a plurality of parallel units each having a plurality of secondary battery cells connected in parallel are connected in series, and the charge / discharge current of the secondary battery group. A current detecting means for detecting, a voltage detecting means for detecting a terminal voltage of each parallel unit in the secondary battery group, and charging / discharging to the secondary battery group based on the detected current / voltage, and a secondary A control / arithmetic unit is provided that prevents the battery group from being overcharged and overdischarged (protection function), and further performs an abnormality detection process such as tab removal or internal short circuit of the secondary battery group.

  Incidentally, the secondary battery 1 is composed of a lithium ion battery, a nickel hydrogen battery, or the like, and is realized as a battery group in which a plurality of battery cells 2 are connected in series and parallel to ensure a predetermined battery voltage and battery capacity. Specifically, when the secondary battery 1 uses a battery cell 2 that is 4.3 V in a fully charged state, such as the high voltage type lithium ion battery described above, the battery cell 2 is arranged in three stages in series. By connecting, it is realized as having a battery voltage of 12.9 V in a fully charged state as a whole. Further, the battery cells 2 at each stage are connected in parallel by three battery cells 2 to form a parallel unit, so that a necessary electric capacity (amount of current) is secured as 8400 mAh, for example.

  The parallel connection and series connection of the plurality of battery cells 2 are performed using connection tabs made of, for example, a metal plate or lead wires. The secondary battery 1 is realized as a package in which a plurality of parallel units 3 each having a plurality of battery cells 2 connected in parallel are connected in series. In addition, about the parallel connection number of the battery cell 2 which comprises the parallel unit 3, and the stage number of the parallel unit 3 connected in series, according to the specification (battery voltage and battery capacity) requested | required of the secondary battery 1 according to the load 32. Needless to say, the battery is not limited to the secondary battery 1 having a three-parallel / three-stage series configuration illustrated in FIG. Also, in such a secondary battery 1, a temperature sensor 4 such as a thermistor for detecting the battery temperature T is integrally incorporated.

  On the other hand, the battery pack 10 includes a current detection unit (current detection means) 5 that is provided in the charge / discharge path of the secondary battery 1 and detects the charge / discharge current I of the secondary battery 1. The current detection unit 5 includes, for example, a shunt resistor inserted in series in the charge / discharge path, and a sensing amplifier that detects the charge / discharge current I of the secondary battery 1 from the voltage generated between both ends of the shunt resistor. Consists of. Whether the current flowing in the charge / discharge path of the secondary battery 1 is a charge current or a discharge current is determined from the polarity of the voltage generated across the shunt resistor depending on the direction of the current. Needless to say.

  The charging / discharging path of the secondary battery 1 includes a charge control switch (charge prohibiting means) 6 for preventing overcharge of the secondary battery 1 and a discharge for preventing overdischarge of the secondary battery 1. A control switch (discharge prohibiting means) 7 is provided. These control switches 6, 7 are composed of, for example, two P-channel MOS-FETs inserted in series in the charge / discharge path. The operation of these control switches (FETs) 6 and 7 is controlled by a control / arithmetic unit 20 which will be described later. For example, the control switches (FET) 6 and 7 are cut off when a high level (H) control signal is applied to their gates. (Off) Operates to cut off the charging current or discharging current for the secondary battery 1 respectively. That is, the control switches (FETs) 6 and 7 serve as charge / discharge prohibiting means for prohibiting charging and discharging of the secondary battery 1. Of course, N-channel type MOS-FETs can be used as the control switches 6 and 7.

  The control / calculation unit 20 described above is realized by a microprocessor, for example. The control / arithmetic unit 20 basically detects the terminal voltage Vbat of the secondary battery 1 and the terminal voltage Vcell of each battery cell 2 (parallel unit 3) constituting the secondary battery 1. Means. This voltage detection means is realized as a voltage detection function provided in the microprocessor. The control / calculation unit 20 inputs the battery temperature T detected by the temperature detection unit (temperature detection means) 8 using the temperature sensor 4, and the secondary battery 1 detected by the current detection unit 5. Charging and discharging the secondary battery 1 by inputting the charge / discharge current I and the terminal voltage Vbat of the secondary battery 1 detected by the voltage detection means and the terminal voltage Vcell of each battery cell 2 (parallel unit 3), respectively. Control each discharge.

  Incidentally, the control / arithmetic unit 20 illustrated in FIG. 1 includes voltages V1, V2, V3 and a negative voltage V0 on the positive side in a plurality of battery cells 2 (parallel units 3) connected in series in three stages, and the temperature. The voltage Vt indicating the battery temperature T detected by the detection unit 8 is selectively input via the multiplexer 21 and is digitally converted via the A / D converter 22 and captured. In addition, the control / calculation unit 20 takes in the charge / discharge current I detected by the current detection unit 4 through digital conversion via the A / D converter 23. The voltages V1, V2, V3, V0 and the temperature information T are input cyclically in a predetermined cycle in synchronization with the sampling cycle of the multiplexer 21 and the A / D converter 22. The control / calculation unit 20 calculates the terminal voltage Vbat (= V1-V0) of the secondary battery 1 described above from the positive voltages V1, V2, V3 and the negative voltage V0 of the plurality of battery cells 2, and The terminal voltages Vcell1 (= V1-V2), Vcell2 (= V2-V3), and Vcell3 (= V3-V0) of each battery cell 2 (parallel unit 3) are detected.

  The control / calculation unit 20 for detecting the terminal voltages Vbat, Vcell and the charge / discharge current I of the secondary battery 1 in this way is basically provided in the electronic device 30 described above via the communication processing unit 24. The operation of the control / power supply unit 30 is controlled to control the charging of the secondary battery 1 (full charge control), and the above-described charging control switch 6 is turned off to prevent the secondary battery 1 from being overcharged. (Overcharge protection) and further, the discharge control switch 7 is controlled to be turned off to prevent overcharge of the secondary battery 1 (overdischarge protection). Further, the control / calculation unit 20 monitors the remaining charge capacity associated with charging / discharging of the secondary battery 1 as described later, determines the degree of performance degradation (life), and if performance degradation is detected, Outputs the effect. Furthermore, the control / calculation unit 20 detects an abnormality such as an internal short circuit or tab disconnection of the secondary battery 1 and prompts the user of the electronic device 30 to which the battery pack 10 is attached to replace the A function for prohibiting use of the battery pack 10 is provided.

  In the above-described full charge control for the secondary battery 1, in a nickel metal hydride battery or the like, for example, when the secondary battery 1 is charged, the terminal voltage Vbat of the secondary battery 1 gradually increases, and the terminal is fully charged. After the voltage Vbat reaches the peak, the state of full charge (100% charge) is determined using the phenomenon that the voltage Vbat decreases by a constant voltage (ΔV) (−ΔV method), and the charging of the secondary battery 1 is stopped. Done. Also, in constant current / constant voltage charging where the current value is limited to a predetermined value or less and the voltage value is limited to a predetermined value or less as in charging a lithium ion battery, during constant voltage charging after constant current charging When the charging current value becomes a predetermined value or less, it is determined by determining that this is a full charge. In addition, it goes without saying that various charge control methods conventionally proposed, such as detecting a fully charged state from a change in the battery temperature T and a change in the charging current I, can be adopted as appropriate. Further, since the present invention is not directly related to the full charge control itself of the secondary battery 1, further description of the full charge control is omitted.

  Further, the overcharge protection described above is performed when, for example, the terminal voltage Vbat of the secondary battery 1 exceeds a preset overcharge protection voltage as the secondary battery 1 or a plurality of battery cells 2 constituting the secondary battery 1. When the individual terminal voltage Vcell of the (parallel unit 3) exceeds the overcharge protection voltage specific to each battery cell 2, the charge control switch 6 described above is operated to forcibly cut off the charging path, It plays a role to prevent further charging (overcharge). Note that the terminal voltage (charge voltage) Vbat of the secondary battery 1 is managed by the full charge voltage in the above-described charge control in this embodiment, so that overcharge prevention by the operation of the charge control switch 6 is exclusively performed. When the terminal voltage Vcell of each battery cell 2 (parallel unit 3) exceeds its overcharge protection voltage, the battery cell 2 (parallel unit 3) operates.

  Further, overdischarge protection is performed, for example, when the terminal voltage Vbat of the secondary battery 1 approaches a preset overdischarge protection voltage as the secondary battery 1 or individual terminals of the battery cells 2 (parallel units 3) in a plurality of stages. When the voltage Vcell approaches the overdischarge protection voltage unique to each battery cell 2 (parallel unit 3) or reaches the overdischarge protection voltage, the discharge control switch 7 described above is activated to force the charging path. It plays a role of preventing the secondary battery 1 from being deeply discharged (overdischarge). In addition to such a protection function, the control / calculation unit 20 may be used when, for example, an abnormal (excessive) charge / discharge current for the secondary battery 1 is detected from the charge / discharge current I, or by the temperature detection unit 8. When the detected battery temperature is abnormally high, such as exceeding 60 ° C., the charge control switch 6 and / or the discharge control switch 7 is operated to cut off the charge / discharge path, and only the secondary battery 1 In addition, a function for protecting the load 32 and the like is provided.

  Basically, in the secondary battery device (pack battery) configured as described above, the present invention is characterized by the tabs in the plurality of parallel units 3 described above as an abnormality determination function provided in the control / calculation unit 20. It has a means (function) for accurately detecting a deviation. The abnormality determination function for detecting the tab detachment basically obtains the terminal voltage Vcell of each parallel unit 3 at the time of charging / discharging of the secondary battery (secondary battery group) 1 and calculates the maximum terminal voltage Vmax. First tab detachment determining means 20a for detecting the presence or absence of tab detachment by determining the difference (Vmax−Vmin) from the minimum terminal voltage Vmin or the ratio (Vmax / Vmin) between the maximum terminal voltage Vmax and the minimum terminal voltage Vmin. Is provided.

  The first tab deviation determining means 20a detects the fluctuation width ΔVcell per unit time of the terminal voltage Vcell of each parallel unit 3, and the difference (ΔVmax) between the maximum fluctuation width ΔVmax and the minimum fluctuation width ΔVmin. -ΔVmin), or the ratio (ΔVmax / ΔVmin) between the maximum fluctuation range ΔVmax and the minimum fluctuation range ΔVmin may be determined to detect the presence or absence of tab deviation.

  Further, the abnormality determining function for detecting the tab detachment is configured so that each of the secondary batteries (secondary battery group) 1 after the charge / discharge stop when the detachment of the tab is detected by the first tab detachment determination unit 20a. The open terminal voltage OCVcell of the parallel unit 3 is obtained, and the difference between the maximum open terminal voltage OCVmax and the minimum open terminal voltage OCVmin (OCVmax−OCVmin), or the ratio (OCVmax) between the maximum open terminal voltage OCVmax and the minimum open terminal voltage OCVmin. / OCVmin) and second tab disengagement determining means 20b for confirming the occurrence of tab disengagement.

  The second tab deviation determining means 20b detects the variation width ΔVcell per unit time of the open terminal voltage OCVcell of each parallel unit 3, and the difference between the maximum variation width ΔVmax and the minimum variation width ΔVmin ( ΔVmax−ΔVmin) or a ratio (ΔVmax / ΔVmin) between the maximum fluctuation width ΔVmax and the minimum fluctuation width ΔVmin may be determined to detect the presence or absence of the tab deviation. The specific tab detachment determination processing and the role of these first and second tab detachment determination means 20a and 20b will be described later.

  In addition to the first and second tab detachment determination means 20a and 20b, which are such a tab detachment abnormality detection means, the abnormality determination function further includes the start of charging of the secondary battery (secondary battery group) 1 or After the charging is stopped, the first abnormality detection control means 20c that stops the detection of tab detachment by the abnormality detection means for a predetermined time, and charging / discharging of the secondary battery (secondary battery group) 1 And a second abnormality detection control unit 20d for stopping the detection of tab detachment by the abnormality detection unit until the number of cycles reaches a predetermined number of times. About these 1st and 2nd abnormality detection control means 20c, 20d, you may make it provide only one of them, or you may make it selectively use only one of them.

  Note that the charge / discharge cycle described above, for example, pays attention to the charging of the secondary battery 1 from the initial state when the secondary battery 1 starts to be used or from the state where the secondary battery 1 is discharged to the recharge capacity. The process is defined as one cycle until charging to a charged state. The charging capacity of the secondary battery 1 is obtained as a multiplication value of the charging current value and the charging time, and this is obtained as one cycle every time the charging capacity reaches the full charging capacity value of the secondary battery 1. Is possible. When attention is paid to the discharge of the secondary battery 1, for example, when the secondary battery 1 charged to full charge discharges more than a preset capacity along with the discharge or complete discharge, this is one cycle. As long as you ask. Since the secondary battery 1 that has been discharged for one cycle is again charged, this discharge cycle has the same meaning as the above-described charging cycle. Therefore, the number of charge / discharge cycles (number of cycle counts) required as the charge cycle or the discharge cycle has a meaning as the number of recharges of the secondary battery 1 repeatedly. Such management of the number of charge / discharge cycles is executed under the charge / discharge management program (management means) in the control / arithmetic unit 20 described above.

  FIG. 2 includes the above-described tab detachment abnormality detection means (first and second tab detachment determination means 20a, 20b) and its control means (first and second abnormality detection control means 20c, 20d). 6 shows an example of an abnormality determination processing procedure for tab deviation that is executed by the control / calculation unit 20. The abnormality determination process for detachment from the tab is started by first determining whether or not a predetermined time, for example, 10 hours has elapsed after the start or stop of charging of the secondary battery (secondary battery group) 1. <Step S1>.

  Note that, instead of determining whether the predetermined time has elapsed, it may be determined whether or not the number of charge / discharge cycles has reached a predetermined fixed number, for example, 20 times (step S1). When 10 hours have not elapsed since the start or stop of charging of the secondary battery (secondary battery group) 1 or when the number of charge / discharge cycles has not reached 20, the tab removal described below will occur. Cancels the judgment process. In other words, the tab described below only when 10 hours have elapsed since the start or stop of charging of the secondary battery (secondary battery group) 1 or when the number of charge / discharge cycles has reached 20 times. A judgment process of detachment is executed.

  That is, in the case of a high voltage type lithium ion battery, the terminal voltage when the lithium ion battery is charged and discharged in the initial state is unstable with a two-stage curve as illustrated in FIG. To change. In particular, as shown in FIG. 3 surrounded by a broken line, the voltage drop when the terminal voltage Vcell drops from about 4.0 V to about 3.7 V is unstable, and variations among individual lithium ion batteries are large. The variation of the terminal voltage in the unstable portion of the voltage drop, the so-called irregular shape portion, reaches about 80 mV at the maximum as shown in FIG. This is a factor that erroneously determines that a detachment has occurred. In particular, such irregular shapes remarkably occur when a high voltage type lithium ion battery is charged at a low temperature of 5 ° C., for example, outside its normal use temperature range (10 ° C. to 45 ° C.).

  However, when the irregular shape described above is discharged after a predetermined time has elapsed since the first charge, the irregular shape gradually decreases as the standing time until the discharge becomes longer. In addition, when charging / discharging is repeated for a certain number of cycles, the irregular shape gradually decreases. And when the elapsed time until the discharge after the charging described above is long, or when charging and discharging are repeated, a solid electrolyte film is formed on the surface of the negative electrode material of the lithium ion battery as described later, and the surface state of the negative electrode material As a result, it is considered that there is no irregular shape.

  That is, in the case of the above-described high voltage type lithium ion battery, for example, a mixed material of lithium cobaltate and lithium cobalt nickel manganate composite oxide is used as the positive electrode material, and fluoroethylene carbonate is used as the electrolyte. Yes. For this reason, as the lithium ion battery is charged and discharged, the carbon material, which is the negative electrode material, reacts with the electrolytic solution to form a lithium metal-containing compound on the surface of the negative electrode material. This is thought to affect the charge / discharge of the lithium ion battery. However, when the above-described lithium metal-containing compound is stabilized by repeated charging or discharging or after a predetermined time has elapsed since charging, and the solid electrolyte film is formed on the surface of the negative electrode material, the carbon material associated with charging and discharging described above It is considered that the irregular shape described above is eliminated along with this.

  Incidentally, according to the experiments by the present inventors, in the case of the above-described high voltage type lithium ion battery, the change in the terminal voltage when discharged after leaving the first charged state as it is is shown in FIG. As shown, the longer the standing time after charging, the smaller the irregular shape, and almost no irregular shape was seen after standing for about 10 hours. In addition, when charging / discharging is repeated, as shown in FIG. 6, the irregular sharpness gradually decreases as the charging / discharging cycle repeats, and when it is repeated about 20 times, irregular shapes hardly appear. Was confirmed.

  Based on the experimental results, in the secondary battery device according to the present invention, as described above, an initial period in which it can be considered that an irregular shape has occurred is determined <Step S1>. By discontinuing the tab removal detection process, variations in terminal voltage due to irregular shapes are prevented from being erroneously detected as tab removal has occurred. Then, after the above-described initial period, the terminal voltage variation is determined to detect a tab detachment abnormality.

Now, as described above, when the initial period for charging / discharging the secondary battery (secondary battery group) 1 has elapsed, the tab removal detection process is started as shown in FIG. In this tab detachment detection process, first, in the first tab detachment determination means 20a, first, the terminal voltage Vcell at the time of charging / discharging of each parallel unit 32 in the secondary battery (secondary battery group) 1 is detected. <Step S2>. In this case, for example, from the ratio between the maximum value Vmax and the minimum value Vmin of the terminal voltage, for example, Vmax> 1.4 × Vmin.
Then, it is determined that the variation in the terminal voltage Vcell of the plurality of parallel units 3 is increased due to tab disengagement <step S3>.

Focusing on the fluctuation of the terminal voltage Vcell during charging / discharging of each parallel unit 32, from the ratio of the maximum fluctuation width ΔVmax and the minimum fluctuation width ΔVmin of the terminal voltage Vcell per unit time of each parallel unit 32, for example, ΔVmax> 1 .4 x ΔVmin
In this case, it may be determined that the variation in the terminal voltages Vcell of the plurality of parallel units 3 is increased due to tab disengagement <step S3>. If a tab removal is detected, the control flag F is set to [1] <step S4>. On the other hand, if a tab removal is not detected, the control flag F is set to [0] <step S5>. In other words, even if tab removal is detected, it is not determined at this stage that tab removal has occurred.

  Thereafter, when the control flag F is [1] <step S6>, the second tab detachment determination unit 20b described above is activated to verify whether or not a tab detachment has really occurred. In this confirmation process, it is first confirmed whether charging / discharging of the secondary battery 1 is completed by determining whether the charging / discharging current is zero [0] <step S7>. If the charging / discharging of the secondary battery 1 is completed, for example, it is determined whether or not 30 minutes have elapsed from the completion of charging / discharging and the internal state of the secondary battery 1 is stabilized <step S8>. If these conditions are not satisfied, a tab off verification process is awaited until the conditions are satisfied.

When the above conditions are satisfied, the terminal voltage of each parallel unit 3, that is, the open terminal voltage OCVcell is detected <step S9>. The difference between the maximum value OCVmax of the open terminal voltage OCVcell and the minimum value OCVmin is, for example, OCVmax−OCVmin ≧ 100 mV.
<Step S10>, and if there is a voltage difference of 100 mV or more, it is determined that a true tab deviation has occurred <Step S11>. However, in the case where a voltage difference of 100 mV or more is not recognized, the variation in the terminal voltage that led to the detection result of the tab deviation based on the voltage ratio described above is mainly due to the variation in the temperature distribution and temperature characteristics of the secondary battery cell 2. The control flag is set to [0] because it is attributed and not attributed to tab removal <step S12>.

  Incidentally, when the secondary battery 1 in the battery pack has a temperature distribution and there is a temperature difference between the plurality of secondary battery cells 2, there is a difference in the internal resistance of each secondary battery cell 2 due to the temperature difference. Arise. Then, in the terminal voltage measurement in a state where current flows, the difference in the terminal voltage of each battery cell 2 becomes large. However, since the open terminal voltage of each battery cell 2 is measured in the above-described step, a voltage difference due to the internal resistance does not occur, and therefore it is possible to accurately detect tab disengagement.

  Thus, according to the present apparatus for detecting and verifying the tab detachment of the parallel unit (battery cell) 2 as described above, voltage variations caused by irregular shapes occurring at the initial use time, and the battery cell 2 itself The variation in the voltage due to the variation in the temperature characteristic is not erroneously detected as a tab deviation. Moreover, it is possible to simply and effectively prevent erroneous detection of tab disengagement. Therefore, a normal secondary battery device (pack battery) without tab disconnection is not unnecessarily discarded, and it is possible to effectively use energy resources.

  In addition, about the secondary battery apparatus (pack battery) by which tab removal was detected, since the safety standard on use is not satisfy | filled, it is preferable to make it unusable. In this case, the above-described discharge control switch 7 may be forcibly turned off. For example, as shown in FIG. 7, a resistance heating type fuse 26 is inserted in series in the charge / discharge path of the secondary battery 1, It is useful to disconnect the secondary battery 1 itself in a circuit by fusing the resistance heating type fuse 26 and thereby set the battery pack to be permanently disabled. Incidentally, it is desirable to perform the process of prohibiting use of the battery pack by fusing the resistance heating type fuse 26 or controlling the discharge control switch 7 to be turned off on the condition that the secondary battery 1 is not discharged.

  The present invention is not limited to the embodiment described above. Here, a case where a high voltage type lithium ion battery is used has been described as an example. However, when a conventional general 4.2 V type lithium ion battery is used or when a lithium ion battery with further improved performance is used. In addition, the present invention can be similarly applied. Needless to say, the magnetization at which the detection of tab detachment at the initial stage of use and the number of charge / discharge cycles are stopped may be determined in accordance with the characteristics of the battery cell to be used. Moreover, it is sufficient to set the voltage difference and the voltage ratio that define the detection condition of the tab detachment according to the characteristics of the battery cell to be used. In short, the present invention can be implemented with various modifications without departing from the spirit of the present invention.

1 Secondary battery (secondary battery group)
2 battery cell 3 parallel unit 5 current detector 6 charge control switch (charge prohibition means)
7 Discharge control switch (Discharge prohibition means)
8 Temperature detector 20 Control / calculation unit (microprocessor)
20a 1st tab detachment determination means 20b 2nd tab detachment determination means 20c 1st abnormality detection control means 20d 2nd abnormality detection control means 21 Multiplexer (voltage detection part)
26 Resistance heating type fuse

Claims (6)

A secondary battery group in which a plurality of parallel units each having a plurality of secondary battery cells connected in parallel are connected in series;
Current detection means for detecting the charge / discharge current of the secondary battery group;
Voltage detection means for detecting the terminal voltage of each parallel unit in the secondary battery group;
An anomaly detection means for detecting tab disengagement in each parallel unit in the secondary battery group based on the detection result by the current detection means and the detection result by the voltage detection means;
An abnormality detection control means for stopping detection of tab detachment by the abnormality detection means for a predetermined time after starting or stopping charging of the secondary battery group. Battery device.   The predetermined period of time is set as a time required for the surface of the negative electrode constituting the secondary battery cell to react with the electrolyte and stabilize as the secondary battery group is charged. Item 2. The secondary battery device according to Item 1. A secondary battery group in which a plurality of parallel units each having a plurality of secondary battery cells connected in parallel are connected in series;
Current detection means for detecting the charge / discharge current of the secondary battery group;
Voltage detection means for detecting the terminal voltage of each parallel unit in the secondary battery group;
Abnormality detecting means for detecting tab detachment in each parallel unit in the secondary battery group based on the detection result by the current detection means and the detection result by the voltage detection means;
An abnormality detection control means for stopping the detection of tab detachment by the abnormality detection means until the number of charge / discharge cycles for the secondary battery group reaches a predetermined fixed number of times. Battery device.   The predetermined number of times is set as the number of times that the surface of the negative electrode constituting the secondary battery cell reacts with the electrolyte and stabilizes as the secondary battery group is repeatedly charged and discharged. The secondary battery device according to claim 3.   The abnormality detection means obtains the terminal voltage of each parallel unit at the time of charging / discharging of the secondary battery group, and the difference or ratio between the maximum terminal voltage and the minimum terminal voltage or the terminal voltage of each parallel unit. A first tab detachment determining means for detecting the presence or absence of tab detachment by determining a difference or ratio between the maximum value and the minimum value of the fluctuation range per unit time, and tab detachment by the first tab detachment determining means. When detected, the terminal voltage of each parallel unit after stopping the charge and discharge of the secondary battery group, respectively, the difference or ratio between the maximum terminal voltage and the minimum terminal voltage, or the terminal voltage of each parallel unit 4. The secondary battery according to claim 1, further comprising: a second tab detachment determining unit that determines a difference or ratio between a maximum value and a minimum value of a fluctuation range per unit time and confirms the occurrence of the tab detachment. 5. Location.   The secondary battery device according to claim 1, wherein the plurality of secondary battery cells are high-voltage type lithium ion batteries.

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