JP2007110877A - Battery pack and its charger, and charging method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To securely prevent an abnormal large current from flowing through a secondary battery in a battery pack constituted to suppress damage caused by the charging of an overdischarged battery, by performing trickle charging to charge the secondary battery while causing a trickle charge circuit to limit a charging current from a charger at least at an initial time of charging. <P>SOLUTION: A charging control determination portion 21 supervises the charging current performing the trickle charging by a current-detecting resistor 16. When the current becomes a predetermined value or higher, the determination portion determines that abnormalities occur in the trickle charging circuit 25 and the charger 2, or that an inappropriate charger which is not a standard commodity is connected, then the determination portion turns off FETs 13, 27 intervened at a charging path 11 to the packed batteries 14 from the charger 2. By such constitution, the flowing of an abnormal large current through packed batteries 14 is securely prevented. Moreover, the inappropriate charger is excluded. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a battery pack, a charger for the battery pack, and a charging method, and more particularly, to a battery pack that performs trickle charging suitable for charging an overdischarge battery.

  The overdischarge (deep discharge) battery in which the battery voltage is extremely lowered due to leaving it for a long period of time, etc., when the battery is rapidly charged from the initial stage of charging, the metal is eluted from the positive electrode or the metal is deposited at the negative electrode. Or the separator is clogged or the electrolytic solution is decomposed. FIG. 4 schematically shows the mechanism of the deterioration, and FIG. 5 shows the change in the terminal voltage of the secondary battery during rapid charging. 4 and 5 illustrate a lithium ion battery as an example.

  FIG. 4A shows a state in which normal charging / discharging is performed, and Li ions can be inserted into and removed from the negative electrode through the separator. On the other hand, FIG. 4B shows an initial state of deterioration after the rapid discharge of the overdischarge battery, and decomposition of the electrolytic solution starts on the positive electrode surface and the positive electrode metal Mn is eluted. Further, in the negative electrode, metal Li is deposited, and the separator is clogged.

  FIG. 4 (c) shows a state in which rapid charging is repeated in the above-described overdischarge and the deterioration progresses. Metal Li is deposited on the negative electrode film to inhibit the diffusion of Li ions. Also, electrons are taken from Li in the negative electrode, and Mn metal is deposited, and the decomposition of the electrolytic solution proceeds to generate gas.

Therefore, the trickle charging, which performs charging with a current smaller than usual at the beginning of charging, has been conventionally performed. In Patent Document 1, the terminal voltage of a secondary battery to be charged is detected, and if it is equal to or lower than the deep discharge voltage, trickle charging is performed for a predetermined period, and the terminal voltage is detected again after charging and is increased. If it is determined that it is deep discharge, the charging is switched to rapid charging, and if it does not increase, a decrease in the terminal voltage is determined as a cause other than deep discharge (such as failure), and a charging device that stops charging is shown. Yes.
Japanese Patent Laid-Open No. 11-262197

  However, the above-described conventional technology focuses only on the abnormality of the secondary battery. For this reason, there is a problem that an abnormality of the trickle charging circuit cannot be dealt with. Specifically, even if the charging path is switched to the trickle charging circuit including a current limiting resistor, the current limiting resistor is short-circuited, or the FET for switching to the normal rapid charging charging path is short-circuited. If a current close to rapid charging flows, even if the secondary battery has deteriorated, the terminal voltage will rise, and the battery will be mistakenly determined to be normal and continue to be charged. Or serious problems such as leakage.

  On the other hand, in some regions, improper chargers that are not genuine products are available at low cost, and if such a charger matches the battery pack and the terminal, it may be possible to charge the battery pack. . In this case, even if the current limiting resistance of the trickle charging circuit is functioning normally, an abnormal high voltage is output from the charging current supply circuit of the charger, and the desired trickle charging cannot be performed. There is also a problem.

  The objective of this invention is providing the battery pack which can prevent that an abnormal charging current flows at the time of trickle charge, its charger, and the charging method.

  The battery pack of the present invention includes a secondary battery, a trickle charging circuit, and a charging control unit, and the charging control unit causes the trickle charging circuit to limit a charging current from a charger to charge the secondary battery. In the battery pack capable of being charged, the battery pack has a detecting means for detecting a current flowing in the secondary battery, and the charging control means has a charging current equal to or higher than a value predetermined by the detecting means during the trickle charging. When detected, the charging path from the charger to the secondary battery is cut off.

  The charging method of the present invention is a trickle for charging a secondary battery by limiting a charging current from the charger in a method for a battery pack to charge a built-in secondary battery with a charging current from a charger. Charging is performed, and when a charging current exceeding a predetermined value is detected during trickle charging, the charging path from the charger to the secondary battery is cut off.

  According to the above configuration, the charge control unit performs trickle charging in which the trickle charging circuit limits the charging current from the charger and charges the secondary battery, thereby suppressing damage due to charging of the overdischarge battery. In the battery pack and the charging method as described above, the charging current during trickle charging is monitored by the detecting means, and if the charging current exceeds a predetermined value, the charging control means causes an abnormality in the trickle charging circuit such as a short circuit of a current limiting resistor. The charging current cannot be limited, the charging control means and the switching element for switching the current path are abnormal, the charging current cannot be switched to the trickle charging circuit, the charger is abnormal, or the Something abnormal has occurred, such as an improper charger that is not a product connected, causing the charging voltage to increase undesirably. Determined that, in such turning OFF the FET interposed charging path to the secondary battery from the charger and blocks the charging path.

  Therefore, when the battery pack performs self-diagnosis and trickle charging abnormality is detected, charging is stopped, so that an abnormal large current can be prevented from flowing through the secondary battery.

  Furthermore, in the battery pack of the present invention, the charging control means stops charging current to the charging control means on the charger side via the communication means in conjunction with the interruption of the charging path to the secondary battery. A signal to be transmitted is transmitted.

  According to the above configuration, the charging current is cut off on the battery pack side as well as the charging current cut off operation on the battery pack side as described above. Even when an abnormality has occurred and the charging current cannot be cut off, the charging current can be cut off.

  In the battery pack of the present invention, the charge control means causes the trickle charge to be performed at least in the initial stage of charge.

  According to the above configuration, trickle charging may be performed at the time of supplementary charging, but the effect of preventing a large current according to the present invention is effective when the secondary battery is performed at the initial stage of charging where there is a possibility of deep discharge. Is.

  Furthermore, in the battery pack of the present invention, a fast charging FET and a discharging FET are provided in series in a charging path from the charger to the secondary battery, and the trickle charging circuit includes the trickle charging FET. And a current limiting resistor, which is provided in parallel with the fast charging FET.

  According to the above configuration, fast charge and trickle charge are realized by reciprocally controlling the corresponding FETs, and a current limiting resistor is interposed in series with the charge path and short-circuited by the fast charge FET. The safety against the ON failure of the current limiting resistance can be improved as compared with the configuration to be performed.

  In addition, the charger of the present invention includes a charging current supply circuit, a trickle charging circuit, and a charging control means, and the charging control means restricts the charging current from the charging current supply circuit to the trickle charging circuit and performs secondary operation. In a charger configured to perform trickle charging for charging a battery, the charger has detection means for detecting the charging current, and the charging control means is a charging current greater than or equal to a value predetermined by the detection means during the trickle charging. Is detected, the charging path from the trickle charging circuit to the secondary battery is cut off.

  According to the above configuration, the charging control means performs trickle charging in which the trickle charging circuit limits the charging current from the charging current supply circuit and charges the secondary battery, thereby causing damage to the overdischarge battery due to charging. In the charger, the charger current during trickle charging is monitored by the detection means, and when the charge current exceeds a predetermined value, the charge control means causes an abnormality in the trickle charging circuit such as a short circuit of a current limiting resistor. The charging current cannot be limited, the charging control means and the switching element for switching the current path are abnormal, and the charging current cannot be switched to the trickle charging circuit, or the charging current supply circuit is abnormal. It is judged that some kind of abnormality has occurred, and the FET interposed in the charging path from the trickle charging circuit to the secondary battery is turned off. And Runado, blocking the the charging path.

  Therefore, since charging is stopped when abnormality in trickle charging is detected, it is possible to prevent an abnormal large current from flowing through the secondary battery.

  In the battery pack and the charging method of the present invention, as described above, the charge control means performs trickle charging in which the trickle charging circuit restricts the charging current from the charger to charge the secondary battery, thereby overcharging the battery. In the battery pack and the charging method for suppressing damage due to charging to the battery, the charging current during trickle charging is monitored by the detection means. The charge current cannot be limited due to an abnormality in the trickle charge circuit, or the charge current cannot be switched to the trickle charge circuit due to an abnormality in the charging control means or the switching element that switches the current path. The charging voltage becomes undesirably high due to an abnormality in the charger, or an inappropriate charger that is not genuine. Determines that some abnormality has occurred, such as by OFF the FET interposed charging path to the secondary battery from the charger and blocks the charging path.

  Therefore, when the battery pack performs self-diagnosis and an abnormality in trickle charging is detected, charging is stopped, so that an abnormal large current can be prevented from flowing through the secondary battery.

  In the charger according to the present invention, as described above, the charge control means performs trickle charging in which the trickle charging circuit limits the charging current from the charging current supply circuit to charge the secondary battery, thereby overdischarge. In the charger that suppresses damage due to charging of the battery, the charger current during trickle charging is monitored by the detection means, and when the charge current exceeds a predetermined value, the charge control means The charging current cannot be limited due to an abnormality in the trickle charging circuit, or the charging current cannot be switched to the trickle charging circuit due to an abnormality in the charging control means or the switching element that switches the current path. It is determined that some abnormality such as an abnormality has occurred in the supply circuit, and is interposed in the charging path from the trickle charging circuit to the secondary battery. Such as by OFF the FET that, to cut off the said charging path.

  Therefore, charging is stopped when abnormality in trickle charging is detected, so that an abnormal large current can be prevented from flowing through the secondary battery.

[Embodiment 1]
FIG. 1 is a block diagram showing an electrical configuration of a charging system according to an embodiment of the present invention. The charging system includes a battery pack 1 and a charger 2 that charges the battery pack 1. However, an electronic device system may be configured to further include a load device (not shown) that receives power from the battery pack 1. . In that case, although the battery pack 1 is charged from the charger 2 in FIG. 1, the battery pack 1 may be attached to the load device and charged through the load device. The battery pack 1 and the charger 2 are connected to each other by DC high-side terminals T11 and T21 that supply power, communication signal terminals T12 and T22, and GND terminals T13 and T23 for power supply and communication signals. . Similar terminals are also provided when the load device is provided.

  In the battery pack 1, the DC high-side charging path 11 extending from the terminal T11 includes FETs 12 and 13 having different conductivity types for charging and discharging, and the charging path 11 Is connected to the high-side terminal of the battery pack 14. The low side terminal of the assembled battery 14 is connected to the GND terminal T13 via the DC low side charging path 15, and the charging path 15 converts the charging current and the discharging current into voltage values. A current detection resistor 16 is interposed.

  The assembled battery 14 includes a plurality of secondary battery cells connected in series and parallel, and the temperature of the cells is detected by a temperature sensor 17 and input to an analog / digital converter 19 in a control IC 18. The voltage between the terminals of each cell is read by the voltage detection circuit 20 and input to the analog / digital converter 19 in the control IC 18. Furthermore, the current value detected by the current detection resistor 16 is also input to the analog / digital converter 19 in the control IC 18. The analog / digital converter 19 converts each input value into a digital value and outputs the digital value to the charge control determination unit 21.

  The charge control determination unit 21 includes a microcomputer and its peripheral circuits, etc., and in response to each input value from the analog / digital converter 19, a charge current for requesting an output from the charger 2. The voltage value, current value, and pulse width (duty) are calculated and transmitted from the communication unit 22 to the charger 2 via the terminals T12 and T22; T13 and T23. In addition, the charging control determination unit 21 detects an abnormality outside the battery pack 1 such as a short circuit between the terminals T11 and T13 or an abnormal current from the charger 2 from each input value from the analog / digital converter 19. A protection operation such as blocking the FETs 12 and 13 is performed against an abnormal temperature rise of the assembled battery 14.

  The charge control determination unit 21 constitutes a charge control means together with the FETs 12 and 13, and when charging and discharging are normally performed, the FETs 12 and 13 are turned on to enable charging and discharging, and an abnormality is detected. Turn off to disable charging / discharging. The charging control determination unit 21 is also connected with a timer 23 for detecting an abnormality of the assembled battery 14 as described later.

  In the charger 2, the request is received by the communication unit 32 of the control IC 30, and the charging control unit 31 controls the charging current supply circuit 33 to calculate the charging current with the voltage value, the current value, and the pulse width. Supply. The charging current supply circuit 33 is composed of an AC-DC converter, a DC-DC converter, etc., and converts an input voltage into a voltage value, a current value, and a pulse width instructed by the charging control unit 31, and a terminal T21, T11: Supply to charging paths 11 and 15 via T23 and T13. The charge control unit 31 and the charge current supply circuit 33 constitute charge control means.

  In the battery pack 1, a trickle charging circuit 25 is provided in the DC high-side charging path 11 in parallel with the normal (rapid) charging FET 12. The trickle charging circuit 25 includes a series circuit of a current limiting resistor 26 and an FET 27, and the charge control determination unit 21 sets the discharging FET 13 at the initial stage of charging and when performing auxiliary charging near full charge. The FET 12 for rapid charging is turned OFF while the FET 12 is ON, and the trickle charging FET 27 is turned ON to perform trickle charging. During normal charging and discharging, the FET 12 is turned ON while the FET 13 remains ON. Is turned off, and charging / discharging with normal current is performed. Whether or not trickle charging is performed at the initial stage of the charging is determined from whether or not the voltage between terminals of each cell detected by the voltage detection circuit 20 is 2.5 V or less in the case of a lithium ion battery, for example. If the voltage exceeds 2.5 V, trickle charging is not performed, and rapid charging is performed from the beginning.

  In the battery pack 1 configured as described above, it should be noted that the charging control determination unit 21 monitors the charging current by the current detection resistor 16 during trickle charging, and becomes a predetermined value, for example, 100 mA or more. The trickle charging circuit 25 such as a short circuit of the current limiting resistor 26 has an abnormality and the charging current cannot be limited, or the charging control determination unit 21 or the FET 12 has an abnormality. Cannot be switched over, or the charger 2 is abnormal, or the charger voltage is undesirably high due to an improper charger being connected. The FET 13 interposed in the charging path 11 is turned off.

  FIG. 2 is a flowchart for explaining the operation of the charging control determination unit 21 as described above. In the normal state, as shown in step S1, the quick charge FET 12 and the discharge FET 13 are turned on, the trickle charge FET 27 is turned off, and charging / discharging is possible. When the charger 2 is connected to the battery pack 1 or power feeding is started from the connected charger 2 or load device, the charging operation is started and the process proceeds to step S2.

  In step S2, each input value from the analog / digital converter 19 is taken, and in step S3, it is determined whether an abnormal state such as the overvoltage, overcurrent, or overheat has occurred from the input value. In the abnormal state, the trickle charge FET 27 remains OFF in step S4, and the quick charge FET 12 and the discharge FET 13 are turned OFF. In step S5, a signal for stopping the charging current is sent to the charger 2. Send and finish the process.

  If it is not abnormal in step S3, the process proceeds to step S6, where it is determined whether the voltage between terminals of each cell is 2.5 V or less. If it is determined that the voltage has not been reached, trickle charging is not performed. In step S7, rapid charging is performed from the beginning. Then, in step S8, when the voltage between the terminals of each cell reaches 4.2V, the process is terminated.

  On the other hand, if the voltage between the terminals of each cell is 2.5 V or less in step S6, it is determined that the battery is overdischarged and the trickle charge is started. In step S11, the timer 23 is started, In S12, the trickle charge FET 27 is turned on while the discharge FET 13 is turned on, and the quick charge FET 12 is turned off. Subsequently, in step S13, it is determined whether or not the charging current by the current detection resistor 16 is 100 mA or more, and if it is 100 mA or more, some abnormality has occurred in the trickle charging circuit 25 or the charger 2. In step S14, the trickle charge FET 27 and the discharge FET 13 are turned OFF while the quick charge FET 12 is turned OFF, and the process proceeds to step S5.

  On the other hand, if the charging current is less than 100 mA in step S13, it is determined that no abnormality has occurred in the trickle charging circuit 25 or the charger 2, and the voltage between the terminals of each cell is again determined in step S15. It is determined whether or not the voltage has reached 2.5V. If the voltage has reached, it is determined that the assembled battery 14 is normal and has only been overdischarged, and the charging is switched to the quick charge in step S7. If not, it is determined that an abnormality has occurred in the assembled battery 14, and in step S16, the process returns to step S13 until a predetermined time is counted by the timer 23, and the charging current is monitored while monitoring. The trickle charge is continued until a predetermined time elapses, and when the predetermined time elapses, the operation proceeds to the trickle charge end operation in step S14.

  Therefore, the charging control determination unit 21 not only performs a protection operation against an abnormality outside the battery pack 1 such as a short circuit between the terminals T11 and T13 or an abnormal current from the charger 2, but also trickle charging in the battery pack 1. Since the circuit 25 is self-diagnosed and charging is stopped when an abnormality is detected, it is possible to prevent an abnormal large current from flowing through the assembled battery 14, and charging by an improper (non-regular) charger. Can be prevented.

  In addition, the charging control determination unit 21 transmits a signal for stopping the charging current to the charging control unit 31 on the charger 2 side via the communication units 22 and 32 in conjunction with the interruption of the charging path 11. . Specifically, the voltage value and current value of the charging current that requires the charger 2 to output are set to zero. As a result, the charging current is interrupted on the battery pack 1 side, and the charging current is also interrupted on the charger 2 side, so that the FETs 12, 13, 27 are short-circuited on the battery pack 1 side. Even when an abnormality has occurred and the charging current cannot be interrupted, the charging current can be reliably interrupted.

[Embodiment 2]
FIG. 3 is a block diagram showing an electrical configuration of a charging system according to another embodiment of the present invention. This charging system is similar to the charging system shown in FIG. 1, and corresponding portions are denoted by the same reference numerals, and the description thereof is omitted. It should be noted that in this charging system, the trickle charging circuit 25 is provided in the charger 2a. Therefore, an FET 35 is provided in the charging path 34 from the charging current supply circuit 33 of the charger 2a to the high-side terminal T11, and in parallel with the FET 35, the current limiting resistor 26 and the FET 27 of the trickle charging circuit 25 A series circuit is provided.

  Then, the charging control unit 31a of the control IC 30a reads each cell voltage from the charging control determination unit 21a of the control IC 18a of the battery pack 1a by communication at the initial stage of charging, and performs trickle charging when the voltage is 2.5 V or less. The charging current during that time is read from the current detection resistor 37, which is a detecting means interposed in the low-side charging path 36, through the analog / digital converter 38. When the current becomes 100 mA or more, it is determined as abnormal and the FET 27 is turned off. At the same time, the FETs 12 and 13 on the battery pack 1a side are also turned off by communication. Further, after the trickle charge is performed for a predetermined time counted by the timer 23, when the voltage between the terminals of each cell obtained by communication is 2.5 V or less, an abnormality occurs in the assembled battery 14. And then stop the subsequent charging.

  With this configuration, charging can be stopped when trickle charging abnormality is detected on the charger 2a side.

  In the above description, the trickle charging circuit 25 including the trickle charging FET 27 and the current limiting resistor 26 is provided in parallel with the fast charging FETs 12 and 35 provided in the charging paths 11 and 34. May be provided as a current limiting resistor only, and may be provided in series with the charging paths 11 and 34, and a fast charging FET may be provided so as to bypass the current limiting resistor. However, the current limiting resistor 26 is provided by branching from the charging paths 11 and 34 and the charging paths 11 and 34 and the current limiting resistor 26 are switched by the dedicated FETs 12, 27; 27, 35. It is possible to improve the safety against ON failure.

  In the present invention, at least in the initial stage of charging, trickle charging is performed by limiting the charging current from the charger to the trickle charging circuit to charge the secondary battery, thereby suppressing damage due to charging of the overdischarge battery. In the battery pack, the charging current during trickle charging is monitored by the current detection resistor, and if the charging current exceeds a predetermined value, the charging control determination unit causes an abnormality in the trickle charging circuit or the charger, or is not a genuine product. Since it is judged that an appropriate charger is connected and the FET interposed in the charging path from the charger to the secondary battery is turned off, it is possible to reliably prevent an abnormal large current from flowing through the secondary battery. can do.

It is a block diagram which shows the electric constitution of the charging system which concerns on one Embodiment of this invention. It is a flowchart which shows the main process operation | movement of the battery pack which comprises the said charging system. It is a block diagram which shows the electric constitution of the charging system which concerns on other embodiment of this invention. It is a figure which shows typically the mechanism of deterioration by quick charge in the state which the lithium ion battery was overdischarged. It is a graph which shows the change of the terminal voltage in FIG.

Explanation of symbols

1, 1a Battery pack 2, 2a Charger 11, 15 Charging path 12, 13, 27, 35 FET
14 Battery assembly 16, 37 Current detection resistor 17 Temperature sensor 18, 18a, 30, 30a Control IC
19, 38 Analog / digital converter 20 Voltage detection circuit 21, 21a Charging control determination unit 22, 32 Communication unit 23 Timer 25 Trickle charging circuit 26 Current limiting resistor 31, 31a Charging control unit 33 Charging current supply circuit T11, T21; T12 , T22; T13, T23 terminals

Claims (6)

A battery comprising a secondary battery, a trickle charging circuit and a charging control means, wherein the charging control means can perform trickle charging in which the trickle charging circuit restricts a charging current from a charger to charge the secondary battery. In the pack,
Detecting means for detecting a current flowing in the secondary battery;
The charge control means shuts off a charge path from a charger to a secondary battery when a charge current greater than a predetermined value is detected by the detection means during trickle charge.   The charging control means transmits a signal for stopping the charging current to the charging control means on the charger side via the communication means in conjunction with the interruption of the charging path to the secondary battery. The battery pack according to claim 1.   3. The battery pack according to claim 1, wherein the charge control unit causes the trickle charge to be performed at least at an initial stage of the charge.   A fast charging FET and a discharging FET are provided in series on a charging path from the charger to the secondary battery, and the trickle charging circuit includes a trickle charging FET and a current limiting resistor. The battery pack according to any one of claims 1 to 3, wherein the battery pack is provided in parallel with a field-effect FET. A charge current supply circuit; a trickle charge circuit; and a charge control means, wherein the charge control means performs trickle charge for charging the secondary battery by limiting the charge current from the charge current supply circuit to the trickle charge circuit. In the charger
Detecting means for detecting the charging current;
The charging control unit cuts off a charging path from the trickle charging circuit to the secondary battery when a charging current greater than a predetermined value is detected by the detecting unit during the trickle charging. vessel. In the method for the battery pack to charge the built-in secondary battery with the charging current from the charger,
A trickle charge is performed to charge the secondary battery by limiting a charging current from the charger, and when a charging current exceeding a predetermined value is detected during the trickle charging, A charging method characterized by blocking a charging path.

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