JP2005245056A - Battery pack and rechargeable electric appliance set - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery pack, which can prevent or suppress the performance deterioration or the life reduction of a battery pack without dropping the convenience of the battery pack or the workability at use by setting a discharge time properly, and also provide a rechargeable electric appliance set. <P>SOLUTION: A charge/discharge controller starts the charge to a battery cell(#2), and a capacity computer 4 judges whether the battery cell is fully charged or not (#3), and when it is fully charged(YES in #3), the charge/discharge controller stops the charge of the battery cell by sending out a charge stop signal to the control circuit of a charger (#4). Next, a timer starts the clocking of the time form the timing of having stopped the above charge (#5), and the charge/discharge controller starts the charge in a second mode by switching off a switching element Q1 and switching on a switching element Q2 (#7), when the clocking time T exceeds a specified time T1 (YES in #6). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention includes a battery pack, a battery pack, a charger that performs a charging operation on the battery pack, and an electric appliance that performs a predetermined operation using power supplied from the battery pack as a power source. The present invention relates to an electric appliance set.

  Conventionally, a battery pack comprising a plurality of battery cells, a charger for charging the battery pack, and an electric appliance main body that performs a predetermined operation using power supplied from the battery pack charged by the charger as a power source are provided. There is a rechargeable electric appliance set. The battery pack employed in this type of rechargeable electric appliance set includes, for example, a nickel cadmium battery, a lead storage battery, a lithium ion battery, or the like. It is known that the preferred state of charge is different when not used (when left for a relatively long time).

  Among them, the lithium ion battery has a property that the capacity deterioration greatly proceeds when left or stored in a fully charged state or a state close thereto. Furthermore, the capacity deterioration of the lithium ion battery is accelerated as the standing time is prolonged, and the battery whose capacity is deteriorated cannot recover the capacity. Therefore, when the battery pack composed of lithium ion batteries is repeatedly used for a relatively long time in a fully charged state, the battery life of the user is reduced at a stage where the number of uses is low. I often feel.

In Patent Document 1 below, when it is detected that the battery pack has entered the storage state, the unit cell (battery cell) is forcibly discharged to charge the unit cell. A technique for reducing the amount to about 50% of full charge is disclosed.
JP 2001-23588 A

  By the way, it is preferable not to perform the above-described discharge in a battery pack that is frequently used after being charged to full charge and then mounted on the main body of the electric appliance in a relatively short time. By discharging as described above, the usable time of the battery pack is shortened, so that the convenience of the battery pack and the workability when used while attached to the main body of the electric appliance are reduced, or the life of the battery pack is reduced. This is because it is possible to make the user misunderstand that the shortage is not shortened.

  In addition, even a battery pack that is often left for a relatively long time in a fully charged state may be used by being attached to the main body of the electric appliance within a relatively short time. In addition, the convenience and workability of the battery pack as described above are reduced.

  Thus, it is considered that the timing for discharging and the necessity of discharging should be set according to how the user uses the battery pack.

  The present invention has been made in view of such circumstances, and by appropriately setting the discharge timing, the battery pack performance deterioration and short-lived without reducing the convenience of the battery pack and workability during use. An object of the present invention is to provide a battery pack and a rechargeable electric appliance set that can be prevented or suppressed.

  In order to achieve the above object, a battery pack according to the first means of the present invention is a lithium ion battery pack comprising a plurality of battery cells charged by a charger, and the electricity stored in the battery cells. Capacitance detection means for detecting the capacity, and when the electric capacity stored in the battery cell exceeds a predetermined value when the charging operation by the charger is stopped, the time from the stop point is measured. Timing means, discharging means for forcibly discharging the charge accumulated in the battery cells, and discharge control means for controlling the discharge operation by the discharging means, the discharge control means being predetermined by the timing means When the time is measured, the discharging operation by the discharging means is started.

  The battery pack according to the second means of the present invention is a lithium ion battery pack comprising a plurality of battery cells charged by a charger, and an electric capacity detection means for detecting the electric capacity accumulated in the battery cells. When the electric capacity accumulated in the battery cell exceeds a predetermined value at the time when the charging operation by the charger is stopped, the standing time from the stop time to the discharge start time of the battery cell is measured. Time measuring means, discharging means for forcibly discharging the electric charge accumulated in the battery cell, and discharge control means for controlling the discharge operation by the discharging means, the discharge control means, when the stop, Based on the past standing time measured by the time measuring means, it is determined whether or not the discharging operation by the discharging means is necessary.

  In the battery pack described above, the discharge means is configured to be able to change a discharge current value, and the discharge control means varies the discharge current value according to the remaining capacity of the battery cell.

  The battery pack further includes a discharge time measurement unit that measures a discharge time of the battery cell by the discharge unit, and the discharge control unit is configured to measure the discharge time when the discharge time measurement unit measures a predetermined time. The discharge operation by the means is stopped.

  The battery pack further includes battery temperature detection means for detecting the temperature of the battery cell, and the discharge control means is configured to detect the battery temperature when the battery temperature detected by the battery temperature detection means is equal to or higher than a predetermined temperature. The discharge current value is increased as compared with the case where the temperature is lower than the predetermined temperature.

  The battery pack further includes an ambient temperature detection unit that detects an ambient temperature of the battery pack, and the discharge control unit is configured to detect the battery temperature when the battery temperature detected by the battery temperature detection unit is equal to or higher than a predetermined temperature. The difference between the battery temperature and the ambient temperature detected by the ambient temperature detection means is calculated, and the discharge current value is varied according to the temperature difference.

  In the battery pack described above, the discharge control means stops the discharge operation by the discharge means when the remaining capacity of the battery cell reaches a predetermined value by the discharge operation by the discharge means.

  The rechargeable electric appliance set according to the third means of the present invention includes a battery pack, a charger that performs a charging operation on the battery pack, and a predetermined operation using power supplied from the battery pack as a power source. A rechargeable electric appliance set including an electric appliance main body to perform, wherein the battery pack is the battery pack according to any one of claims 1 to 7.

  In the battery pack according to the first means of the present invention, when the electric capacity stored in the battery cell exceeds a predetermined value when the charging operation by the charger is stopped, the battery cell is forcibly discharged. Since it is the target, it is possible to prevent or suppress the performance deterioration and shortening of the life of the battery pack.

  In addition, when the predetermined time is set as a standby time for the discharge operation, the battery pack is almost fully charged when the battery pack is used by being attached to the electric appliance main body within a short time after charging until full charge. Can be provided to the user. Therefore, it is possible to prevent or reduce the convenience of the battery pack and the workability when used by being mounted on an electric appliance body, or the misunderstanding of the shortening of the life of the battery pack.

  Furthermore, when the predetermined time is set as a threshold value for determining whether or not discharge is necessary, the discharge may occur in the case of a battery pack that is frequently used by being mounted on the electric appliance body within a short time after full charge. It is possible to prevent or reduce the execution of discharge when it is considered unnecessary.

  In the battery pack according to the second means of the present invention, in the same manner as described above, the battery pack in the case where the battery pack is used by being attached to the main body of the electric appliance within a relatively short time after being fully charged. It is possible to prevent or reduce the convenience and the deterioration of workability when used by being mounted on an electric appliance main body.

  In the rechargeable electric appliance set according to the third means of the present invention, it is possible to prevent or suppress the performance deterioration and shortening of the life of the battery pack without deteriorating the convenience of the battery pack and the workability during use. A rechargeable electric appliance set including a battery pack can be provided.

  Hereinafter, a first embodiment of a rechargeable electric appliance set according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of an external appearance of a charger constituting the rechargeable electric appliance set 1 of the present embodiment and a battery suitable for the charger.

  In FIG. 1, the battery pack 2 to be charged by the charger 4 is, as shown in FIG. 1A, a holding unit 3 in an electric appliance main body 100 (an electric tool is illustrated in FIG. 1A). 1 is used while being attached to the charger 4 as it is after being attached and detached, as shown in FIG. 1 (b). A battery cell 21 (see FIG. 3), which will be described later, built in the battery pack 2 is a lithium ion battery, and the battery voltage may be various, such as 12V, 18V, and 24V.

  The battery pack 2 illustrated in FIG. 1 has a main body 5 that holds battery cells 21 (see FIG. 3), and a connector 6 for establishing electrical connection between the electric appliance main body 100 and the charger 4. doing. The charger 4 is provided with a connector portion 7 having an opening. By attaching the connector portion 6 of the battery pack 2 to the connector portion 7 of the charger 4, the battery pack 2 and the charger 4 are connected to each other. An electrical connection is established.

  More specifically, the battery pack 2 and the charger 4 have an external appearance as shown in FIG. In this example, as shown in FIG. 2A, the connector part 6 of the battery pack 2 has a shape protruding from the main body part 5, and the electrodes 8, 9, 10, and 11 are exposed on the side surfaces. It is arranged. As shown in FIG. 2 (b), the connector portion 7 of the charger 4 has a recess into which the connector portion 6 of the battery pack 2 can be inserted, and the electrodes 8, 9 of the battery pack 2 are formed on the inner surface thereof. , 10 and 11 are provided with electrodes 12, 13, 14, and 15 for electrical connection. For example, the electrodes 9 and 15 are positive charging electrodes, the electrodes 8 and 12 are negative charging electrodes, and the electrodes 10 and 14 are electrodes for transmitting control signals (such as a charging start signal and a charging stop signal) described later. The electrode 11 is an electrode for detecting that the battery pack 2 is attached to the charger 4 or the electric appliance main body 100, and the electrode 13 is an electrode for detecting that the battery pack 2 is attached to the charger 4. It is. If the battery pack 2 is not attached to the charger 4, the charger 4 cannot be charged, and if it is attached, it can be charged. Of the electrode 8, the electrode 8a and the electrode 8b are connected to the electrode 12a and the electrode 12b, respectively. For example, if the battery pack 2 is a battery having a large capacity (the capacity of the battery is expressed in ampere / hour), both the electrode 8a and the electrode 8b are provided, and if the battery pack 2 is a small capacity battery, only the electrode 8a is provided. (Including a form in which the electrode 8b is covered with an insulating member). The electrode 12b can detect whether or not it is in contact with the electrode 8b. The presence or absence of the electrode 8b of the battery pack 2 can be detected, and thereby the battery capacity of the battery pack 2 can be detected. For this reason, it is not necessary to provide a separate charger due to the difference in battery capacity of the battery pack 2, and the charger 4 can be used for charging the battery pack 2 having different battery capacities.

  The battery pack 2 and the charger 4 are provided with, for example, slit-shaped air holes 16 and 17 at positions on the surfaces facing each other when they are combined. The charger 4 incorporates a cooling fan (not shown) so that the air flow created by the cooling fan is also supplied to the battery cells 21 in the battery pack 2 being charged through the vent holes 16 and 17. It has become. In the charger 4, a charging status display unit 18 that displays the charging status of the battery pack 2 is provided on the side of the vent hole 17. The charging status display unit 18 includes a plurality of lamps made of, for example, LEDs arranged in a line, and is attached with “empty” characters indicating that the charging amount is substantially 0 according to the charging amount of the battery pack 2. The lamps are lit in order from the lamps to the lamps marked with “full” indicating that the charge amount is approximately 100%. In the present embodiment, the charging status display unit 18 is provided in the charger 4, but the charging status display unit 18 may be provided in the battery pack 2.

  The charger 4 includes a cable 19 and an outlet 20, and the outlet 4 is connected to a commercial power source, so that the charger 4 is supplied with electric power from the commercial power source via the cable 19 and the outlet 20. The supplied power is converted into power suitable for charging the battery cell 21 by a power supply circuit 41 described later.

  FIG. 3 is a block diagram showing a circuit configuration of the rechargeable electric appliance set 1.

  As shown in FIG. 3, the rechargeable electric appliance set 1 includes an electric appliance main body 100, a charger 4, and a battery pack 2. The electric appliance main body 100, the charger 4 and the battery pack 2 shown in FIG. These correspond to the electric appliance main body 100, the charger 4 and the battery pack 2 shown in FIG. 1 or FIG. When the battery pack 2 is attached to the charger 4 to charge the battery pack 2 with the charger 4, the terminals 8 and 12 (12a and 12b), the terminals 9 and 15, the terminals 10 and 14, and the terminals 11 and 13 are respectively The power is supplied from the charger 4 to the battery pack 2 and control signals (such as a charge start signal and a charge stop signal) are transmitted and received through these terminals. The electric appliance main body 100 includes terminals 104 and 105 and terminals not shown. When the battery pack 2 is mounted on the electric appliance main body 100, the terminals 104 and 9, terminals 105 and 8, and the above-described illustration are omitted. The terminal and the terminal 11 (see FIG. 2) are connected, and power is supplied from the battery pack 2 to the electric appliance main body 100 via these terminals.

  The electric appliance main body 100 includes a driven member 106 (see FIG. 1) to be driven and a load 101 including a motor that drives the driven member 106, a switch 102 that switches on / off of power supply to the load 101, And an input operation unit 103 for performing an input for instructing on / off of the switch 102. The input operation unit 103 is operated by a user of the electric appliance 1, and when the switch 102 is turned on by the input operation unit 103 in a state where the battery pack 2 is attached to the electric appliance main body 100. Electric power is supplied from the battery pack 2 to the load 101.

  The charger 4 includes a power supply circuit 41 and a control circuit 42. Further, the charger 4 includes a capacity display circuit (not shown) that displays a lamp provided in the charging status display unit 18 according to the charging status of the battery pack 2. A capacity display circuit may be provided in the battery pack 2.

  The power supply circuit 41 supplies power to the battery pack 2 after converting power supplied from a commercial power supply (not shown) into power suitable for charging the battery cells 21, for example, a rectifier circuit or a DC− It consists of a DC converter.

  The control circuit 42 controls the supply / stop of power by the power supply circuit 41 based on a signal from the control circuit 25 (to be described later) of the battery pack 2. When the charging start signal is transmitted from the control circuit 25 of the battery pack 2, the control circuit 42 causes the power supply circuit 41 to supply power to the battery pack 2, and a charging stop signal is transmitted from the control circuit 25 of the battery pack 2. Then, the power supply circuit 41 stops the power supply to the battery pack 2.

  The battery pack 2 includes a battery cell 21, a temperature sensor 22, a resistor Rt, a protection circuit 23, a discharge circuit 24, and a control circuit 25.

  The temperature sensor 22 detects the temperature of the battery cell 21 (hereinafter referred to as battery temperature), and is configured to include, for example, a thermistor. The temperature sensor 22 outputs the detected battery temperature information to the control circuit 42.

  The resistor Rt is for detecting the charging current to the battery cell 21 and the discharging current from the battery cell 21. One terminal of the resistor Rt is connected to the control circuit 25, and the control circuit 25 takes in the potential at the connection point F so that the charging current or discharging current, and thus the electric charge stored in the battery cell 21 is stored. Detect capacity indirectly.

  The protection circuit 23 includes an unillustrated switching element and the like, and in order to prevent overcharging and overdischarging of the battery cell 21, the charging current and the discharging current are limited by a predetermined value, or the battery cell 21 is fully charged. Then, the current path is interrupted.

  The discharge circuit 24 is for discharging the electric charge accumulated in the battery cell 21. Here, the reason why the discharging operation by the discharging circuit 24 is performed will be described. In the following description, the state from when the battery pack 2 is stopped to being used until the battery pack 2 is used (power is supplied to the electric appliance main body 100) is referred to as “Left”.

  Here, general properties of the lithium ion battery will be described. FIG. 4A shows that one cycle is a period from when a charged lithium ion battery is mounted on the electric appliance main body 100 and used again until the battery is charged again, and the battery temperature and the lithium ion battery leaving time are constant. FIG. 4B is a graph showing changes in the number of cycles and the deterioration of the capacity of the lithium ion battery (maximum electric capacity that can be charged) when the remaining capacity of the lithium ion battery at the start of leaving is used as a parameter. FIG. 4C is a graph showing changes in the number of cycles and the capacity deterioration of the lithium ion battery when the temperature and the remaining capacity of the lithium ion battery at the start of standing are constant and the standing time is used as a parameter. With the remaining capacity of the lithium ion battery and the leaving time of the lithium ion battery at Is a graph showing changes in capacity deterioration of the cycle number and the lithium ion battery when the.

  As shown in FIGS. 4A to 4C, the capacity deterioration of the lithium ion battery proceeds as the number of cycles increases. As shown in FIG. 4 (a), in a lithium ion battery configured with a lithium ion battery, the capacity deterioration of the lithium ion battery progresses faster as the remaining capacity of the lithium ion battery at the start of leaving is increased. The capacity deterioration of the lithium ion battery is particularly remarkable when the ion battery is left in a fully charged state.

  Further, as shown in FIG. 4B, the capacity deterioration of the lithium ion battery progresses faster as the leaving time of the lithium ion battery becomes longer. Note that “continuous charge / discharge” in FIG. 4B indicates that the standing time is substantially zero. Furthermore, as shown in FIG. 4 (c), the capacity deterioration of the lithium ion battery progresses faster as the battery temperature at the start of leaving is higher.

  As described above, in the lithium ion battery, since the capacity deterioration of the lithium ion battery is accelerated as the remaining capacity of the lithium ion battery at the start of leaving is increased, in the present embodiment, the inside of the battery pack 2 constituted by the lithium ion battery. Is provided with a discharge circuit 24, and the discharge circuit 24 discharges to a remaining capacity that is considered to be able to suppress the capacity deterioration of the battery pack 2.

  The discharge circuit 24 includes a plurality of switching elements Q1 and Q2 made of, for example, FETs (Field-Effect Transistors), and resistors R1 and R2 connected in series to the switching elements Q1 and Q2, respectively. The switching element Q1 and the resistor R1 And the direct circuit of the switching element Q2 and the resistor R2 are connected in parallel to the battery cell 21. The resistors R1 and R2 have different resistance values r1 and r2 (r1> r2). Each gate terminal of the switching elements Q1 and Q2 is connected to the control circuit 25. When a voltage corresponding to an ON signal is supplied from the control circuit 25 to the gate terminal, the switching elements Q1 and Q2 are turned on ( On the other hand, when a voltage corresponding to the off signal is supplied, the switching elements Q1 and Q2 are turned off (opened).

  For example, when the switching element Q1 is turned on and the switching element Q2 is turned off, the charge accumulated in the battery cell 21 flows from the positive electrode to the negative electrode of the battery cell 21 through the resistor R1, the switching element Q1, and the resistor Rt ( Called the first discharge mode). When the switching element Q1 is turned off and the switching element Q2 is turned on, the charge accumulated in the battery cell 21 flows from the positive electrode to the negative electrode of the battery cell 21 through the resistor R2, the switching element Q2, and the resistor Rt ( This is referred to as a second discharge mode). Further, when both of the switching elements Q1 and Q2 are turned on, the electric charge accumulated in the battery cell 21 is divided into a series circuit of the resistor R1 and the switching element Q1 and a series circuit of the resistor R2 and the switching element Q2 from the positive electrode. And flow again to the negative electrode of the battery cell 21 through the resistor Rt (referred to as a third discharge mode).

  As described above, the battery cells 21 are discharged by appropriately turning on and off the switching elements Q1 and Q2. In the discharge circuit 24 shown in FIG. 3, there are three ways to turn on and off the switching elements Q1 and Q2, and since the resistance value is r1> r2, the discharge current is in the case of the first discharge mode. Is minimized, and the second discharge mode is maximized.

  In this embodiment, according to the remaining capacity of the battery cell 21, the on / off combination of the switching elements Q1, Q2 is changed to change the magnitude of the discharge current.

  That is, when the battery cell 21 is fully charged, the battery cell 21 is discharged in the second discharge mode (large discharge current) in order to quickly escape from the fully charged state. In order to prevent or suppress heating of the battery cell 21 due to heat generated by the resistors R1 and R2 in the circuit 24, discharging is performed in the first or third discharge mode (discharge current smaller than the second discharge mode).

  The control circuit 25 controls the overall operation of the battery pack 2. For example, a ROM (Read Only Memory) that stores a control program for controlling the operation of the battery pack 2 and a RAM (temporarily storing data) Random Access Memory) and the like, and a microcomputer for reading out a control program from the ROM and executing it are configured. The control circuit 25 receives power from the power supply circuit 41 of the charger 4 when the battery pack 2 is attached to the charger 4, and the battery when the battery pack 2 is not attached to the charger 4. Power is supplied from the cell 21.

  FIG. 5 is a block diagram showing a configuration of the control circuit 25.

  As shown in FIG. 5, the control circuit 25 controls the on / off operation of the connection detector 251 that detects the connection with the electric appliance body 100 or the charger 4 and the switching elements Q <b> 1 and Q <b> 2 of the discharge circuit 24. Capacity calculation for calculating the remaining capacity of the battery cell 21 by the discharge control unit 252, the timer 253 for measuring the time from the timing when the battery cell 21 is fully charged, and the current (charge current and discharge current) flowing through the resistor Rt The charge / discharge control unit 252 and the like operate as follows.

  FIG. 6 is a flowchart showing the operation of the control circuit 25.

  As shown in FIG. 6, when connection detection unit 251 detects that battery pack 2 is attached to charger 4 (YES in step # 1), charge / discharge control unit 252 controls control circuit 42 of charger 4. To start charging the battery cell 21 (step # 2). Then, the capacity calculation unit 254 determines whether or not the battery cell 21 is fully charged based on the charging current flowing through the resistor Rt (step # 3), and when it is not fully charged, it is fully charged. Until the battery is fully charged (NO in step # 3), the charge / discharge control unit 252 sends a charge stop signal to the control circuit 42 of the charger 4 to send out the battery cell. 21 is stopped (step # 4).

  Next, the timer 253 starts measuring time from the timing when the charging is stopped (timing when the battery cell 21 is fully charged) (step # 5), and the charge / discharge control unit 252 It is determined whether T has exceeded a predetermined time T1 (step # 6). The charge / discharge control unit 252 stands by when the measurement time T does not exceed the predetermined time T1 (NO in step # 6), and when the measurement time T exceeds the predetermined time T1 (YES in step # 6), the switching element Q1 is turned off and switching element Q2 is turned on to start discharging in the second discharge mode (step # 7). The predetermined time T1 is, for example, 0.5 hours, 1 hour, or 1.5 hours.

  As described above, the discharge is started after the elapse of the predetermined time T1 from the timing when the battery cell 21 is fully charged in consideration of the following. That is, when the battery pack 2 is mounted on the electric appliance main body 100 and used relatively soon after the charging is completed, the convenience and workability due to the shortened time that the user can use the battery pack 2 are reduced. This is in order to avoid causing a decrease or misunderstanding that the life has not been shortened but shortened. Further, if the battery cell 21 is left to stand after the predetermined time T1 has elapsed from the timing when the battery cell 21 is fully charged, the life of the battery pack 2 is often adversely affected.

  Returning to FIG. 6, the capacity calculation unit 254 calculates the remaining capacity P of the battery cell 21 based on the discharge current flowing through the resistor Rt, and the charge / discharge control unit 252 determines whether or not the remaining capacity P falls below the threshold value Pth. Determination is made (step # 8). When the remaining capacity P of the battery cell 21 is not less than the threshold value Pth, the charge / discharge control unit 252 continues discharging in that state (NO in step # 8), and the remaining capacity P of the battery cell 21 falls below the threshold value Pth. (YES in step # 8), the charge / discharge control unit 252 switches the switching element Q1 from off to on and the switching element Q2 from on to off (switches to the first discharge mode described above), so that the discharge current is smaller. Is discharged (step # 9).

  Then, the charge / discharge control unit 252 determines whether or not the remaining capacity P of the battery cell 21 has fallen below the target value Pmin (step # 10), and when the remaining capacity P of the battery cell 21 has not fallen below the target value Pmin. In this state, discharging is continued (NO in step # 10), and when the capacity P of the battery cell 21 falls below the target value Pmin (YES in step # 10), discharging is stopped (step # 11). The target value Pmin is, for example, a capacity corresponding to 50% of full charge.

  As described above, since the battery cell 21 does not start discharging immediately after being fully charged, but starts discharging after a predetermined time T1 from the timing when the battery cell 21 is fully charged, It is possible to avoid the convenience of the pack 2 and the deterioration of workability when the electric appliance main body 100 is, for example, an electric tool, or misunderstanding of the shortening of the life.

  Further, since the discharge is stopped when the remaining capacity P of the battery cell 21 is reduced to a predetermined capacity (the target value Pmin), the remaining capacity of the battery cell 21 when the discharge is stopped is appropriately set. Thus, a balance between the usable time of the battery pack 2 and the suppression of the capacity deterioration of the battery cell 21 can be achieved.

  In addition, when the state of the battery cell 21 at the start of discharge is fully charged, the battery cell 21 is discharged with a large discharge current. When the remaining capacity of the battery cell 21 is reduced by the discharge, the battery cell 21 is discharged with a small discharge current. While being able to escape quickly, heating of the battery cell 21 due to heat generated by the resistance in the discharge circuit 24 can be prevented or suppressed.

  The present invention can employ the following modifications (1) to (7) in place of or in addition to the above-described embodiment.

  (1) In the first embodiment, the discharge is started after waiting for a predetermined time T1 from the timing when the battery is fully charged, but at the start of the measurement of the standby time, the battery cell 21 is charged until the battery is fully charged. For example, when the battery pack 2 is removed from the charger 4 and left when the battery cell 21 is charged with an electric capacity of 90% of full charge, the progress of capacity deterioration is greatly increased. It may be set to a timing at which the battery pack 2 starts to be left in a state where a capacity that is considered to be early is accumulated.

  (2) In the first embodiment, the stop timing of the discharge operation by the discharge circuit 24 is set to the timing at which the remaining capacity P of the battery cell 21 reaches a predetermined capacity (the target value Pmin), but is not limited thereto. When the correlation between the discharge time and the remaining capacity P of the battery cell 21 is known in advance, the timer 253 measures the discharge time by the discharge circuit 24, and the measured time has reached a predetermined time. Sometimes, the discharge operation by the discharge circuit 24 may be controlled to stop.

  Further, considering that the battery pack 2 may be used relatively quickly after being fully charged, for example, the battery pack 2 is left after each charge, and the average of the time left is When the battery pack 2 is longer than the predetermined time, it is determined that the battery pack 2 is often left for a long time in a fully charged state. It may be determined that the battery pack 2 is rarely left for a long time in a fully charged state, and control may be performed so as not to discharge after completion of charging.

  FIG. 7 is a flowchart showing the operation of the control circuit 25 combining these controls. Note that steps # 21 to # 24 in the flowchart shown in FIG. 7 are the same as steps # 1 to # 4 in the flowchart shown in FIG. In the first embodiment, when discharging, the magnitude of the discharge current is switched in accordance with the remaining capacity of the battery cell 21, but in this embodiment, such switching is not performed. From the start to the completion of discharge, the switching element Q1 is turned off and the switching element Q2 is turned on to perform a discharge operation with a constant discharge current in the second discharge mode. Further, it is assumed that the average value Tav of the leaving time of the battery pack 2 derived based on the previous discharging operation is calculated in advance.

  As shown in FIG. 7, when the battery cell 21 is fully charged and the charge / discharge control unit 252 stops the charging operation of the battery cell 21, the timer 253 starts measuring time from the charge stop timing (step). # 25). The time measurement started in step # 25 is stopped when the use of the battery pack 2 is started, and the time measured at this time is the average time in the process of step # 26 at the next discharge. Used to calculate Tav.

  Next, the charge / discharge control unit 252 determines whether or not the average time Tav of the measurement time calculated in advance is larger than the predetermined time T2 (step # 26). When the average time Tav is less than or equal to the predetermined time T2 (NO in step # 26), the process is terminated without performing the discharge processes in steps # 28 to # 31.

  On the other hand, when the average time Tav is larger than the predetermined time T2 (YES in step # 26), the switching element Q1 is turned off and the switching element Q2 is turned on to start discharging in the second discharge mode (step # 27). Then, after resetting, the timer 253 starts measuring time from the discharge start timing (step # 28), and the charge / discharge control unit 252 waits until the measurement time T exceeds the predetermined time T3 (step # 28). NO at step # 29).

  Then, when measurement time T exceeds predetermined time T3 (YES in step # 29), charging / discharging control unit 252 stops the discharging operation by discharging circuit 24 by turning off both switching elements Q1 and Q2 (step S29). # 30).

  According to this, the structure which detects the remaining capacity of the battery cell 21 in order to stop discharge like 1st Embodiment becomes unnecessary.

  In addition, since the average value of the battery pack 2 leaving time is set as a parameter for determining the necessity of discharging, the user of the battery pack 2 uses the battery pack 2 in a fully charged state for a relatively long time, for example. For example, when the battery pack 2 is used in a relatively short time, for example, when the battery pack 2 is used in a relatively short period of time, the remaining capacity of the battery cell 21 is reduced by forcibly discharging the battery cell 21. Whether or not to discharge can be determined according to how to use the battery pack 2 such that the fully charged state is maintained without performing the above.

  (3) As described above, the progress of capacity deterioration of the battery pack 2 changes according to the battery temperature at the time of full charge. Therefore, under the condition that the electric capacity and the leaving time of the battery pack 2 when left are the same, the life of the battery pack 2 can be extended by lowering the battery temperature. Therefore, the battery temperature at full charge may be set as a parameter for determining whether or not discharge is necessary, and the magnitude of the discharge current may be changed according to the battery temperature during discharge.

  FIG. 8 is a flowchart showing the operation of the control circuit 42 in the present embodiment. Note that steps # 41 to # 44 in the flowchart shown in FIG. 8 are the same as steps # 1 to # 4 in the flowchart shown in FIG.

  As shown in FIG. 8, when the battery cell 21 is fully charged and the charge / discharge control unit 252 stops the charging operation of the battery cell 21, the timer 253 starts measuring time from the charge stop timing (step S <b> 8). # 45) Charging / discharging control unit 252 waits until measurement time T exceeds predetermined time T1 (NO in step # 46).

  Then, when measurement time T exceeds predetermined time T1 (YES in step # 46), charging / discharging control unit 252 determines whether or not battery temperature K is higher than predetermined temperature K1 based on the battery temperature information from temperature sensor 22. Is determined (step # 47).

  When battery temperature K is higher than predetermined temperature K1 (YES in step # 47), charging / discharging control unit 252 is large when switching element Q1 is turned off and switching element Q2 is turned on (set to the second discharge mode). Discharging is started with the discharging current (step # 48). On the other hand, when battery temperature K is equal to or lower than predetermined temperature K1 (NO in step # 47), switching element Q1 is turned on and switching element Q2 is turned off (set to the first discharge mode) to discharge with a small discharge current. Is started (step # 49).

  Then, the charge / discharge control unit 252 determines whether or not the remaining capacity P of the battery cell 21 has fallen below the target value Pmin by the discharge operation started in step # 48 or # 49 (step # 50). When the remaining capacity P of 21 is not lower than the target value Pmin (NO in step # 50), discharging is continued in the same state, and when the remaining capacity P of the battery cell 21 is lower than the target value Pmin (in step # 50). YES), the discharge is stopped (step # 51).

  According to this, since the battery is discharged with a large discharge current when the battery temperature at the time of full charge is relatively high, it is possible to escape from the full charge state quickly and suppress the capacity deterioration of the battery pack 2.

  (4) The battery temperature is unlikely to decrease when the ambient temperature of the battery pack 2 is relatively high, and is likely to decrease when the ambient temperature is relatively low. As described above, since the battery temperature is also affected by the ambient temperature of the battery pack 2, more preferable discharge control is performed by adding not only the battery temperature but also the ambient temperature as a parameter for determining whether or not discharge is necessary. be able to. That is, when the battery temperature is equal to or higher than a relatively high predetermined temperature, the temperature difference between the ambient temperature and the battery temperature is observed, and control for changing the discharge current of the discharge operation according to the temperature difference is performed.

  In the present embodiment, as shown in FIG. 2A, an ambient temperature sensor 26 is provided at an appropriate position of the main body 5 of the battery pack 2 separately from the temperature sensor 22 that detects the battery temperature. The sensor 26 detects the ambient temperature around this attachment position.

  FIG. 9 is a flowchart showing the operation of the control circuit 42 of the present embodiment. Note that steps # 61 to # 64 in the flowchart shown in FIG. 9 are the same as steps # 1 to # 4 in the flowchart shown in FIG.

  As shown in FIG. 9, when the battery cell 21 is fully charged and the charging / discharging control unit 252 stops the charging operation of the battery cell 21, the timer 253 starts measuring time from the charging stop timing (step # 65) Charging / discharging control unit 252 waits until measurement time T exceeds predetermined time T1 (NO in step # 66). The process of step # 66 is synonymous with the process of step # 6 of the flowchart shown in FIG.

  When measurement time T exceeds predetermined time T1 (YES in step # 66), charge / discharge control unit 252 determines whether or not battery temperature Kd is higher than predetermined temperature K2 based on the battery temperature information from temperature sensor 26. Is determined (step # 67).

  When battery temperature Kd is greater than predetermined temperature K2 (YES in step # 67), charge / discharge control unit 252 calculates difference ΔK between battery temperature Kd and ambient temperature Kt, and whether the temperature difference ΔK is smaller than threshold value ΔKth. It is determined whether or not (step # 68).

  When temperature difference ΔK is smaller than threshold value ΔKth, that is, when ambient temperature Kt is a temperature close to a relatively high battery temperature Kd (YES in step # 68), charging / discharging control unit 252 turns switching element Q1 off and switching Device Q2 is turned on (set to the second discharge mode) to start discharging with a large discharge current (step # 69).

  Charge / discharge control unit 252 also determines that temperature difference ΔK between battery temperature Kd and ambient temperature Kt is greater than or equal to threshold ΔKth when battery temperature Kd is equal to or lower than predetermined temperature K2 in step # 67 (NO in step # 67). If there is (the ambient temperature Kt is relatively low) (NO in step # 68), the switching element Q1 is turned on and the switching element Q2 is turned off (set to the first discharge mode) with a small discharge current. Is started (step # 70).

  When the difference ΔK between the battery temperature Kd and the ambient temperature Kt is relatively large (when the ambient temperature Kt is relatively low), the battery pack 2 (battery cell 21) is discharged with a small discharge current. This is to prevent the cooling from being hindered by the heat generated in the discharge circuit 24 by increasing the discharge current more than necessary.

  Then, the charge / discharge control unit 252 determines whether or not the capacity P of the battery cell 21 has fallen below the target value Pmin by the discharge operation started in step # 69 or # 70 (step # 71). When the capacity P of the battery cell 21 is not lower than the target value Pmin, the discharge is continued in the same state (NO in step # 71). When the capacity P of the battery cell 21 is lower than the target value Pmin (YES in step # 71), the discharge is performed. Is stopped (step # 72).

  Thus, since not only the battery temperature but also the ambient temperature is added as a parameter for determining whether or not discharge is necessary, more appropriate discharge control can be performed.

  (5) The discharge circuit 24 is not limited to the one described above, and, for example, three or more current paths having different resistance values are formed. From these current paths, the remaining capacity of the battery cell 21 being discharged and the battery If the current path of the discharge current is appropriately switched according to the temperature or the like, more accurate discharge control can be performed.

  (6) You may combine discharge control of 1st Embodiment and said other modification (1)-(3) suitably.

  (7) The means for discharging in order to escape from the fully charged state is not limited to the discharge circuit 24 described above. For example, when the battery pack 2 includes the capacity display circuit described above, all the lamps are connected by the capacity display circuit. The power stored in the battery cell 21 may be consumed by lighting.

It is the schematic of the external appearance of the battery suitable for the charger which comprises the rechargeable electric appliance set of this embodiment, and the said charger. It is a figure which shows the external appearance of a battery pack and a charger. It is a block diagram which shows the circuit structure of a rechargeable electric appliance set. It is a graph which shows the general property of a lithium ion battery. It is a block diagram which shows the structure of a control circuit. It is a flowchart which shows operation | movement of a control circuit. It is a flowchart which shows operation | movement of the control circuit in the modification of the rechargeable electric appliance set which concerns on this invention. It is a flowchart which shows operation | movement of the control circuit in the modification of the rechargeable electric appliance set which concerns on this invention. It is a flowchart which shows operation | movement of the control circuit in the modification of the rechargeable electric appliance set which concerns on this invention.

Explanation of symbols

1, 1 'rechargeable electric appliance set 2 battery pack 4 charger 21 battery cell 22 temperature sensor 24 discharge circuit 25 control circuit 251 connection detection unit 252 charge / discharge control unit 253 timer 254 capacity calculation unit 26 ambient temperature sensors Q1, Q2 switching Element R1, R2 resistance

Claims (8)

In a lithium ion battery pack comprising a plurality of battery cells charged by a charger,
A capacitance detecting means for detecting the capacitance stored in the battery cell;
When the electric capacity accumulated in the battery cell at the time when the charging operation by the charger is stopped exceeds a predetermined value, time measuring means for measuring the time from the stop time;
Discharging means for forcibly discharging the charge accumulated in the battery cells;
A discharge control means for controlling a discharge operation by the discharge means,
The battery pack according to claim 1, wherein the discharge control means starts a discharge operation by the discharge means when a predetermined time is measured by the time measuring means. In a lithium ion battery pack comprising a plurality of battery cells charged by a charger,
A capacitance detecting means for detecting the capacitance stored in the battery cell;
When the electric capacity stored in the battery cell exceeds a predetermined value when the charging operation by the charger is stopped, the standing time from the stop time to the discharge start time of the battery cell is measured. Timekeeping means,
Discharging means for forcibly discharging the charge accumulated in the battery cells;
A discharge control means for controlling a discharge operation by the discharge means,
The battery pack according to claim 1, wherein the discharge control unit determines whether or not the discharge operation by the discharge unit is necessary based on a past leaving time measured by the time measuring unit at the time of the stop. The discharging means is configured such that the discharge current value can be changed,
The battery pack according to claim 1, wherein the discharge control unit varies the discharge current value according to a remaining capacity of the battery cell. Discharging time measuring means for measuring the discharging time of the battery cell by the discharging means,
4. The battery pack according to claim 1, wherein the discharge control unit stops the discharge operation by the discharge unit when a predetermined time is measured by the discharge time measurement unit. 5. Battery temperature detecting means for detecting the temperature of the battery cell;
The discharge control means increases the discharge current value when the battery temperature detected by the battery temperature detection means is equal to or higher than a predetermined temperature as compared with a case where the battery temperature is lower than the predetermined temperature. The battery pack according to claim 3. Comprising an ambient temperature detection means for detecting the ambient temperature of the battery pack;
The discharge control means calculates a difference between the battery temperature and the ambient temperature detected by the ambient temperature detection means when the battery temperature detected by the battery temperature detection means is equal to or higher than a predetermined temperature. The battery pack according to claim 5, wherein the discharge current value is changed according to the battery voltage.   The discharge control means stops the discharge operation by the discharge means when the remaining capacity of the battery cell reaches a predetermined value by the discharge operation by the discharge means. Battery pack.   In a rechargeable electric appliance set comprising a battery pack, a charger that performs a charging operation on the battery pack, and an electric appliance main body that performs a predetermined operation using power supplied from the battery pack as a power source, A battery pack is the battery pack according to any one of claims 1 to 7, wherein the battery pack is a rechargeable electric appliance set.

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