JP2015029389A - Battery pack, electric power tool, and charger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery pack in which reduction of the discharge capacity of a secondary battery is minimized during discharge.SOLUTION: A battery pack includes a secondary battery consisting of a plurality of battery cells, storage means for storing the history information about the history of a plurality of battery cells, and setting means for setting an overdischarge threshold on the basis of the history information. If the voltage of any one battery cell, out of the plurality of battery cells, dropped down to the overdischarge threshold in the past, the setting means sets a second threshold larger than a first threshold when the voltage of any one battery cell has not dropped down to the overdischarge threshold.

Description

  The present invention relates to a charging device for charging a secondary battery used as a power source for a cordless electric tool or the like.

  Conventionally, lithium ion batteries have been used as secondary batteries for cordless power tools. In the method of charging a lithium ion battery described in Patent Document 1, a charging voltage value is set, and when the lithium ion battery reaches the charging voltage value, charging is performed so as to reduce the charging current.

JP 2008-187790 A

  By the way, the lithium ion battery has a plurality of battery cells connected in series. When the battery cell is overdischarged below a predetermined voltage value, the battery cell is deteriorated. Once the battery cell is deteriorated, the battery cell is accelerated and deteriorated when the battery cell again becomes a predetermined voltage value or less. However, when the entire lithium ion battery is viewed, there are battery cells that have deteriorated in this way, while there are battery cells that have not progressed so much.

  Moreover, even if the battery cell is overcharged with a predetermined voltage value or more, the battery cell is deteriorated. In recent years, the capacity of lithium ion batteries has been increased, but the life of lithium ion batteries with higher capacity is shorter (deteriorates quickly and overcharges).

  As described above, each battery cell of the lithium ion battery is deteriorated by repeated charging and discharging, but the degree of deterioration varies from cell to cell. In addition, battery cells that have deteriorated more easily become overdischarged and overcharged.

  FIG. 15 is a graph showing the relationship between the number of times of charging (cycle number, horizontal axis) and discharge capacity (vertical axis) of a conventional battery. When overcharge is detected in one specific battery cell for the first time in the charge of the number of cycles C1, the charge stops at that time. However, even if a specific battery cell deteriorates in this way (the degree of deterioration is large) and overcharge is detected, the deterioration of the battery cells varies, so the remaining battery cells have a low degree of deterioration. It can happen. However, since it is necessary to stop charging when one battery cell is overcharged, even if there is a battery cell with a small degree of deterioration, it is not possible to charge the battery cell any further. Therefore, there is a problem that the discharge capacity of the entire secondary battery is remarkably reduced with the cycle number C1 as a boundary.

  In view of this situation, the present invention intends to provide a battery pack that suppresses a decrease in discharge capacity of a secondary battery during discharge.

  The present invention has a secondary battery composed of a plurality of battery cells, storage means for storing history information relating to the history of the plurality of battery cells, and setting means for setting an overdischarge threshold based on the history information. The setting means is a first in the case where the voltage of any one of the plurality of battery cells has decreased to the overdischarge threshold in the past, and has not decreased the overdischarge threshold. A charging device is provided that is set to a second threshold value that is greater than the threshold value.

  According to such a charging device, it is possible to appropriately charge the secondary battery according to the deterioration of the secondary battery. Thereby, the further deterioration of a secondary battery can be suppressed.

  The setting means sets the overdischarge threshold to the first threshold until a predetermined period elapses after the secondary battery starts discharging even if the battery cell has been overdischarged in the past. It is preferable to set.

    Voltage detection means for detecting the voltage of the secondary battery is provided, and the voltage detection means does not detect the voltage of the secondary battery until a predetermined period elapses after the secondary battery starts discharging. It is preferable.

    The history information preferably includes overdischarge information indicating whether a voltage of at least one battery cell of the plurality of battery cells is equal to or lower than the overdischarge threshold.

  The charging condition includes a current value of a current supplied to the secondary battery until the secondary battery reaches a target voltage, and the charging control unit is configured to supply the current until the secondary battery reaches the charging target voltage. It is preferable to charge by value.

    The history information includes an overdischarge number indicating the number of times that the battery cell has become an overdischarge state, and the setting means sets the overdischarge threshold as the first threshold when the overdischarge number is less than a predetermined number. Preferably, the overdischarge threshold is set to a second threshold greater than the first threshold when the number of overdischarges is equal to or greater than a predetermined number.

  The setting means sets the overdischarge threshold as a first threshold when a predetermined period has not elapsed since the secondary battery started discharging even if the number of overdischarges is a predetermined number or more. It is preferable to do.

  According to another aspect of the present invention, the battery pack according to any one of the above is detachable, and includes a motor supplied with power from the battery pack, and a switching element that controls rotation of the motor. Provide tools.

  Preferably, the battery pack includes a discharge prohibiting unit that stops discharging when the battery cell is overdischarged, and the switching element is blocked by an output from the discharge prohibiting unit.

  Further, the present invention is a charging device for charging the battery pack according to any one of the above, wherein information acquisition means for acquiring history information relating to the history of the secondary battery, and charging conditions are set based on the history information Setting means for charging, and charging control means for charging the secondary battery based on the charging condition, wherein the setting means has a voltage of any one of the plurality of battery cells in the past. In the case where the discharge threshold has been lowered, at least one of the charging voltage and the charging current is set smaller than that in the case where the discharge voltage has not been lowered to the overdischarge threshold.

  According to the charging device of the present invention, it is possible to appropriately charge the secondary battery according to the deterioration of the secondary battery. Thereby, the further deterioration of a secondary battery can be suppressed.

The circuit diagram of the charging device of a 1st embodiment. The table which showed the relationship between the battery cell charging voltage of 1st Embodiment, and charging current. The flowchart which shows the charge process of 1st Embodiment. The graph which showed the relationship between the voltage value and time of the battery cell at the time of charge in 1st Embodiment, and the relationship between charging current and time. The graph which showed the relationship between the voltage value and time of the battery cell at the time of charge in 1st Embodiment, and the relationship between charging current and time. The graph which showed the relationship between the voltage value and time of the battery cell at the time of charge in 1st Embodiment, and the relationship between charging current and time. The graph which showed the relationship between the voltage value of a battery cell and time, and the relationship between charging current and time when overcharge is detected during charging in the first embodiment. The graph which showed transition of the discharge capacity of the battery pack at the time of repeating the charging process in 1st Embodiment. The circuit diagram of the battery pack and electric tool in 1st Embodiment. The graph which showed the relationship between the time at the time of discharge when the battery cell in 1st Embodiment has not deteriorated, and a voltage. The graph which showed the relationship between the time at the time of discharge when the battery cell in 1st Embodiment deteriorated, and a voltage. The flowchart which showed the process at the time of discharge of the battery pack in 1st Embodiment. The graph which showed the relationship between the cycle number of a battery cell and discharge capacity in 1st Embodiment. The flowchart which shows the charge process in 2nd Embodiment. The graph which showed transition of the discharge capacity of the battery pack at the time of repeating the conventional charge process.

(First embodiment)
Hereinafter, a charging device 1 according to a first embodiment of the present invention and a battery pack 2 attached to the charging device 1 will be described with reference to the accompanying drawings. FIG. 1 is a circuit diagram showing a state where a battery pack 2 is attached to the charging device 1. The battery pack 2 is used as a power source for a cordless tool (not shown).

  First, the battery pack 2 to be charged will be described. As shown in FIG. 1, the battery pack 2 includes a battery set formed by connecting a plurality of battery cells 2a (in this embodiment, 10 cells as an example) in series, a protection IC 2b, a power supply circuit 2c, and a memory 2e. And a microcomputer 2d, a communication terminal 2f, a tool terminal 2i, a shunt resistor 2g, and a current detection circuit 2h. The battery cell type to be charged is not particularly limited and can be any secondary battery. In the present embodiment, a battery pack 2 incorporating a lithium ion battery will be described as an example. The protection IC 2b monitors the voltage of each battery cell 2a and prevents any one of them from becoming a normal state due to overcharge or overdischarge. Is output to the microcomputer 2d. When receiving these signals, the microcomputer 2d sends a charge stop signal for instructing the microcomputer 50 of the charging apparatus 1 to stop charging via the communication terminal 2f.

  The power supply circuit 2c transforms the voltages of the plurality of battery cells 2a and supplies the power to the microcomputer 2d.

  The memory 2e has overcharge information indicating that the battery cell 2a has been overcharged in the past, and overcharge cell number information indicating the number of overcharge cells that have been overcharged in the past. Is remembered. There is no overcharge information in the initial stage (the state where the deteriorated battery is not charged), the number of overcharged cells is 0, and if any cell is overcharged by repeated charging, the microcomputer 2d Overcharge information (information indicating that overcharge has occurred) is stored, or the number of overcharge cells is added.

  Moreover, the memory 2e memorize | stores the overdischarge information which shows the overdischarge frequency | count that the said battery cell 2a became the overdischarge state in the past for every battery cell 2a. In the initial stage, the number of overdischarges is zero, and if any cell is overdischarged during discharge, the microcomputer 2d adds the number of overdischarges.

  The history information of the present invention is information relating to the state of the battery cell 2a during charging and discharging, and corresponds to overcharge information or overdischarge information in the present embodiment.

  The memory 2e further stores the rated voltage, the rated capacity, and the number of battery cells 2a connected in series as battery type information. The battery type information may be stored in a ROM built in the microcomputer 2d instead of the memory 2e.

  The current detection circuit 2h detects a current value from the voltage drop of the shunt resistor 2g, and inputs the detection signal to the microcomputer 2d.

  The battery pack 2 has terminals corresponding to a positive terminal and a negative terminal for charging provided in the charging device 1. When the battery pack 2 is attached to the charging device 1, the corresponding terminals are connected to each other. .

  Next, the charging device 1 will be described. The charging device 1 includes a power supply unit, a microcomputer 50, various detection units connected to an input port of the microcomputer 50, a controlled unit connected to an output port of the microcomputer 50, and the like.

  The power supply unit includes a main power supply for supplying charging power and an auxiliary power supply for supplying a drive voltage to the microcomputer 50 and the like. The main power source is a power source for charging the battery pack 2, and includes a first rectifying / smoothing circuit 10, a switching circuit 20, and a second rectifying / smoothing circuit 30.

  The first rectifying / smoothing circuit 10 includes a full-wave rectifying circuit 11 and a smoothing capacitor 12. The AC voltage supplied from the AC power supply 205 is full-wave rectified by the full-wave rectifying circuit 11 and smoothed by the smoothing capacitor 12. Output a DC voltage. The AC power source 205 is an external power source such as a commercial power source.

  The switching circuit 20 is connected to the output side of the first rectifying / smoothing circuit 10 and includes a high-frequency transformer 21, a MOSFET 22, and a PWM control IC 23. The PWM control IC 23 changes the drive pulse width of the MOSFET 22, the MOSFET 22 performs switching according to the drive pulse width, and the DC output from the first rectifying and smoothing circuit 10 is used as the voltage of the pulse train waveform. The voltage of the pulse train waveform is applied to the primary side winding of the high-frequency transformer 21, boosted (or stepped down) by the high-frequency transformer 21, and output to the second rectifying and smoothing circuit 30.

  The second rectifying / smoothing circuit 30 includes a diode 31, a smoothing capacitor 32, and a discharging resistor 33. The second rectifying / smoothing circuit 30 rectifies and smoothes the output voltage obtained from the secondary side of the high-frequency transformer 21 to generate a DC voltage, The DC voltage is output from the positive terminal and the negative terminal of the charging device 1.

  The auxiliary power supply 40 is connected to the first rectifying / smoothing circuit 10 and the switching circuit 20 and supplied with power, and is a constant voltage power supply for supplying a stabilized reference voltage Vcc to various circuits such as the microcomputer 50 and operational amplifiers 61 and 65 described later. Circuit. The auxiliary power supply 40 includes transformers 41a and 41b, a switching element 42, a control element 43, a rectifier diode 44, a three-terminal regulator 46, oscillation preventing capacitors 45 and 47, a reset IC 48, and the like. The reset IC 48 is an IC that outputs a reset signal to the microcomputer 50 and resets the microcomputer 50.

  The rectifying / smoothing circuit 6 is a rectifying / smoothing circuit that is connected to the auxiliary power supply 40, the switching circuit 20, and the like and serves as a power supply for the PWM control IC 23. The rectifying / smoothing circuit 6 includes a secondary coil 6a, a rectifier diode 6b, and a smoothing capacitor 6c of the transformer 41a. .

  The microcomputer 50 includes a first output port 51a, a second output port 51b, an A / D input port 52, an information port 53, a reset port 54, and the like. The microcomputer 50 processes various signals input to the A / D input port 52, and outputs various signals based on the results from the first output port 51a and the second output port 51b to various controlled units. The operation of the charging device 1 is controlled.

  The second output port 51 b has a plurality of ports, one of which is connected to the charging current setting circuit 70.

  The charging current setting circuit 70 includes resistors 71, 72, 73, and 74 connected between the reference voltage Vcc and the ground, and is a circuit for setting the charging current to a predetermined current value. A connection point between the resistor 71 and the resistor 72 is connected to a non-inverting input terminal of an operational amplifier 66 constituting the charging current control circuit 60. One ends of the resistors 73 and 74 are individually connected to corresponding ports of the output port 51b. The other ends of the resistors 73 and 74 are connected to a connection point of the resistors 71 and 72.

  In the present embodiment, the charging current setting circuit 70 selectively sets three types of current values I1, I2, and I3 as setting currents for charging. Here, I1, I2, and I3 satisfy the relationship of I1> I2> I3. Specifically, no signal is output from each of the output ports 51b connected to the resistors 73 and 74, and the value obtained by dividing the reference voltage Vcc by the resistors 71 and 72 is the set current as the current value I1. It becomes a reference value when setting as. In the present embodiment, the charging current value I1 is 7.5A as an example.

  Further, the port connected to the resistor 73 in the second output port 51b outputs a low signal, and the port connected to the resistor 74 in the second output port 51b does not output a signal, thereby causing the resistor 71 and A value obtained by dividing the reference voltage Vcc by the combined resistances of the resistors 72 and 73 becomes a reference value when the set current is set as the current value I2. The charging current I2 is smaller than the charging current I1, and is 5A as an example in the present embodiment.

  Further, the second output port 51b does not output from the port connected to the resistor 73, and the port connected to the resistor 74 outputs a low signal, whereby the reference voltage Vcc is set to the resistor 71 and the resistor 72. , 74 is a reference value for setting the set current as the current value I3. The charging current I3 is smaller than the charging current I2, and is 3.5 A as an example in the present embodiment.

  The current values I1, I2, and I3 may be set to different values depending on the type of the battery pack 2 (rated voltage, that is, the number of cells, the capacity, the number of parallel cells, etc.). That is, if the type of the battery pack 2 is different, the combinations of the current values I1, I2, and I3 may be different. For example, the connection form of the battery cells 2a of the battery pack 2, specifically, the first connection form in which a plurality of battery cells 2a are connected in series, and the plurality of battery cells 2a are connected in series, and the cell set is connected in series In accordance with the second connection form in which the battery cells 2a are connected in parallel and the third connection form in which the battery cells 2a are connected in parallel (two battery cells are connected in parallel) and a plurality of cell sets are connected in series. The value may be changed. In the case of the second and third connection configurations, the current value of the first connection configuration is doubled. Even in this case, the type (battery voltage and capacity) of the battery pack 2 may be read by the information port 54 and the output of the port connected to the resistors 73 and 74 may be changed according to the information.

  As described above, the charging current control circuit 60 is connected to the charging current setting circuit 70 and controls the charging current based on the setting by the charging current setting circuit 70. The charging current control circuit 60 includes operational amplifiers 61 and 65, resistors 62, 63, 64, 66 and 67, and a diode 68. The A / D input port 52 has a plurality of ports, one of which is connected to the output side of the operational amplifier 61.

  The current detection resistor 203 is connected between the second rectifying / smoothing circuit 30 and the charging voltage control circuit 100 and detects a charging current flowing through the battery pack 2.

  The A / D input port 52 of the microcomputer 50 has a plurality of ports, and each is connected to the charging current control circuit 60 and the battery voltage detection circuit 90.

  The battery voltage detection circuit 90 includes resistors 91 and 92, and is connected to a plus terminal of the battery set when the battery pack 2 is mounted on the charging device 1. The voltage supplied to the battery pack 2, that is, the voltage of the battery pack 2 is divided by the resistors 91 and 92, and the value is input to one of the A / D input ports 52 of the microcomputer 50 as battery voltage information. When power is not supplied to the battery pack 2, information indicating the voltage of the battery pack 2 is input as battery voltage information to one of the A / D input ports 52 via the battery voltage detection circuit 90. The

  The first output port 51a of the microcomputer 50 has a plurality of ports, which are connected to the charge control signal transmission unit 4 and the display unit 130, respectively. A charging voltage control circuit 100 and a charging current setting circuit 70 are connected to the second output port 51 b of the microcomputer 50. The auxiliary power circuit 40 is connected to the reset port 54. The information port 53 is connected to the communication terminal 2f.

  The charging control signal transmission unit 4 is connected to the switching circuit 20 and the microcomputer 50, and is connected to a photocoupler that transmits a signal for controlling on / off of the PWM control circuit 23, and a light emitting element side that constitutes the photocoupler. It comprises an FET 4a for controlling on / off of the light emitting element. Here, the first output port 51a has a plurality of ports, one of which is connected to the gate of the FET 4a. When a port connected to the FET 4a in the output port 51a outputs a high signal, the FET 4a is turned on, and the photocoupler of the charge control signal transmission unit 4 is turned on. As a result, the PWM control circuit 23 is activated and charging is started. When the port connected to the FET 4a in the output port 51a outputs a low signal, the FET 4a is turned off, and the photocoupler of the charge control signal transmission unit 4 is turned off. As a result, the PWM control circuit 23 is stopped and charging is stopped (terminated).

  The charging current signal transmission unit 5 includes a photocoupler or the like, and feeds back the charging voltage and charging current signals from the charging voltage control circuit 100 and the charging current control circuit 60 to the PWM control IC 23.

  The display unit 130 is a circuit for displaying the state of charge, and includes an LED 131 and resistors 132 and 133. When the port connected to the resistor 132 in the first output port 51a outputs a high signal, the LED 131 lights red, and when the port connected to the resistor 133 in the first output port 51a outputs a high signal, the LED 131 is turned on. Lights up in green, and when a high signal is output from both ports, the LED 131 lights up in orange. In the present embodiment, the microcomputer 50 turns on the red LED 131 in a state before charging, such as when the battery pack 2 is not connected or in a standby state, and turns on orange by simultaneously lighting two LEDs 131 during charging. After the charging is finished, the green LED 131 is turned on.

  The charging voltage control circuit 100 is connected to the second rectifying / smoothing circuit 30 and controls the charging voltage. The charging voltage control circuit 100 includes resistors 101, 103, 105, 106, 107, 108, 110, 111, 112, 114, 115, 116, 118, 121, a potentiometer 102, FETs 109, 113, 117, 122, a capacitor 104, It consists of a shunt regulator 120, a diode 119, and the like. Resistors 108, 112, and 116 are connected to each of the plurality of ports of the second output port 51b. The gate of the FET 122 is connected to one of the corresponding second output ports 51b.

  The charging voltage is set by switching on and off the FETs 109, 113, 117, and 122 by a signal from the second output port 51b of the microcomputer 50. In the following description, the combined resistance determined by the resistors 101 and 121 and the potentiometer 102 is R1, and the combined resistance determined by the resistors 105, 106, 110, and 114 is R2.

  That is, the combined resistance R <b> 1 changes depending on whether the FET 122 is on or off. When the FET 122 is off, the combined resistance R1 is a series resistance of the resistance 101 and the potentiometer 102. When the FET 122 is on, the resistor R1 is a series resistance of the combined resistance of the resistor 101 and the resistor 121 and the potentiometer 102.

  The resistor R2 changes depending on the on / off state of the FETs 109, 113, and 117, and is a combined resistance of the resistor 105 and the resistor in which the corresponding FETs 109, 113, and 117 among the resistors 106, 110, and 114 are turned on.

  The charging voltage increases substantially in proportion to the resistor R1, and increases in proportion to the reciprocal of the resistor R2. In the present embodiment, the microcomputer 50 switches the charging voltage by switching the FETs 122, 109, 113, 117 on and off. The charging voltage indicates a voltage value applied to the battery pack 2.

  The microcomputer 50 determines the charging voltage based on the type (rated voltage, capacity, number of parallel connection of battery cells) of the battery pack 2 that is mounted, and overcharge information. In the present embodiment, for each type of battery pack 2, first, a charging voltage of the battery pack 2 (in other words, a charging voltage per battery cell 2a (hereinafter referred to as a battery cell charging voltage)) is set. Here, the battery cell charging voltage is a value obtained by dividing the charging voltage of the battery pack 2 by the number of cells connected in series. Specifically, one of three voltage values V1, V2, and V3 is set as the battery cell charging voltage. Here, in the same type of battery cell 2a, the voltage values V1, V2, and V3 are constant voltage values, and have a relationship of V1> V2> V3. As the voltage value V1, the rated voltage (charge voltage) of the battery cell 2a is set. When the rated voltage of the battery cell 2a is 4.2V, for example, V1 is 4.2V, V2 is 4.1V, and V3 is 3.9V. In the voltage of the battery pack 2, V1 is 4.2V × number of cells, V2 is 4.1V × number of cells, and V3 is 3.9V × number of cells.

  Further, if the type of the battery pack 2 is different, the combination of the battery cell charging voltages V1, V2, and V3 is also different. However, in the combination of each battery pack 2, V1, V2, and V3 have a relationship of V1> V2> V3. Here, the type of battery pack includes a battery pack including a battery cell that has been overcharged in the past and a battery pack not including the battery cell. As shown in the table of FIG. 2, the battery cell charging voltages V1, V2, and V3 are communicated from the microcomputer 2d of the battery pack 2 for each type of the battery pack 2 along with the values of the charging currents I1, I2, and I3. The microcomputer 50 of the charging device 1 is selected by the information, and the microcomputer 50 controls the charging current control circuit 60 and the charging voltage control circuit 100 so that the charging current and the charging voltage become the selected values. As will be described later, in the present embodiment, the battery cell charging voltage and the charging current are set depending on whether or not there is an overcharged battery cell 2a (deteriorated cell) or the number of the deteriorated cells. Therefore, in the table of FIG. 2, the presence / absence of the deteriorated cells, the number of deteriorated cells, the battery cell charging voltage, and the charging current are stored in association with each other. In FIG. 2, only the table of one battery pack 2 is stored, but actually a plurality of such tables may be stored according to the type of the battery pack 2. In this case, as described above, the charging currents I1, I2, and I3 may be changed for each type of the battery pack 2. The table is stored in a ROM (not shown) in the microcomputer 50.

  Or it is good also as battery cell charging voltage V1, V2, V3 according to the rated voltage of the battery cell 2a of the battery pack 2. FIG. For example, when the battery cell 2a includes a rated 4.2V battery (first battery cell) and a rated 4.35V battery (second battery cell), in the case of the first battery cell, V1 is 4.2V, V2 Is 4.1V, V3 is 3.9V, and in the case of the second battery cell, V1 may be 4.35V, V2 may be 4.2V, and V3 may be 4.0V. When the charging voltage is changed to three types as described above, the three charging voltages V1 to V3 can be switched by providing the resistor 123 and the FET 124 in parallel with the resistor 121 and the FET 122 as shown in FIG.

  Next, the microcomputer 50 sets a charging voltage (hereinafter, battery pack charging voltage) to be applied to the battery pack 2. A battery cell charging voltage (any one of V1, V2, and V3) is set by dividing the battery pack charging voltage by the number of battery cells 2a connected in series (10 in the present embodiment). Specifically, the FETs 122, 109, 113, and 117 of the charging voltage control circuit 100 are switched on and off so that the voltage applied to the battery pack 2 is set to the battery pack charging voltage. Specifically, when the charging voltage is set to V1, if the number of battery cells is 4 (4.2V × 4 cells), the FETs 109, 113, and 117 are all turned off. When the number of battery cells is 5, the FET 109 is turned on and the FETs 113 and 117 are turned off. Similarly, in the case of seven cells, the FET 113 is turned on and the FETs 109 and 117 are turned off. In the case of 10 cells, the FET 117 is turned on and the FETs 109 and 113 are turned off. When setting the charging voltages V2 and V3, in FIG. 16, the FETs 109, 113, and 117 are in the same state as described above. If the charging voltage is V2, the FET 122 is turned on, the FET 124 is turned off, and the charging voltage V3 is set. For example, the FET 124 may be turned on and the FET 122 may be turned off. That is, when not deteriorated (deterioration degree is small), V1 (4.2V × number of cells as the charge voltage of the battery pack), and when deterioration degree is medium, V2 (also 4.1V × cell number), When the degree of deterioration is large, V3 (3.9 V × number of cells) is set.

  With reference to FIG. 3, the charging process of the battery pack 2 performed by the charging device 1 will be described. In step 201, the microcomputer 50 controls the display of the LED 131. That is, when the battery pack 2 is not attached to the charging device 1, the LED 131 is lit red as a pre-charge display.

  In step 202, the microcomputer 50 determines whether or not the battery pack 2 is attached to the charging device 1. That is, when the predetermined information from the microcomputer 2d is received via the information port 53, it is determined that the battery pack 2 is attached. When the information port 53 does not receive a signal, the microcomputer 2d Judge that it is not installed. Alternatively, when the signal input from the battery voltage detection circuit 90 to the A / D port 52 is changed, it is determined that the battery pack 2 is attached.

  In step 203, the microcomputer 50 receives battery type information from the microcomputer 2 d via the information port 53. Specifically, first, the microcomputer 2d reads out battery type information from the memory 2e and transmits it to the microcomputer 50. The microcomputer 50 receives the battery type information via the information port 53, and determines the type (rated voltage, that is, the number of cells, capacity, etc.) of the battery pack 2 that is installed.

  In step 205, the microcomputer 50 receives the charging history of the battery pack 2 (information on whether or not it has been overcharged in the past, information on the number of overcharged cells) from the microcomputer 2d via the information port 53. That is, at the time of the previous charging, information on whether or not the charging of the battery pack 2 has been terminated because at least one battery cell 2a has been overcharged is received from the memory 2e of the battery pack 2.

  The microcomputer 2d reads overcharged cell number information from the memory 2e and transmits it to the microcomputer 50.

  Thereafter, in step 206 to step 212, the battery cell charging voltage, the battery pack charging voltage, and the charging current are set. When the battery cell charging voltage is set, the microcomputer 50 transmits the set value to the microcomputer 2d via the information port 53. As described above, the battery pack charging voltage is set by switching on / off of the FETs 122, 107, 113, 117 as described above, and the charging current is set by the resistor 73 in the second output port 51b. , 74 by changing the output of the port connected.

  In step 206, the microcomputer 50 determines whether there is a battery cell that has been overcharged in the past, in other words, whether the number of overcharged cells is other than zero or zero.

  If a negative determination is made in step 206 (the number of overcharged cells is 0) (step 206: NO), in step 207, the microcomputer 50 determines the battery cell charge voltage (battery pack) from the battery pack charge voltage based on the table of FIG. The voltage obtained by dividing the charging voltage by the number of cells is calculated and set as V1 when the degree of deterioration is small. In step 208, the microcomputer 50 sets the charging current to the current value I1 based on the table of FIG.

  In step 206b, the microcomputer 50 determines whether or not the number of overcharged battery cells received in step 205 is greater than or equal to a predetermined number. The number of overcharges may be used instead of the number of cells.

  If a negative determination is made in step 206b (step 206b: NO), in step 209, the microcomputer 50 determines that the battery cell charge voltage is deteriorated from the battery pack charge voltage based on the table of FIG. Calculate and set as In step 210, the microcomputer 50 sets the charging current to the current value I2 based on the table of FIG.

  If an affirmative determination is made in step 206b (step 206b: YES), in step 211, the microcomputer 50 calculates the battery cell charging voltage from the battery pack charging voltage as V3 when the degree of deterioration is large based on the table of FIG. Set. In step 210, the microcomputer 50 sets the charging current to the current value I3 based on the table of FIG.

  In step 213, the microcomputer 50 controls the PWM control IC 23 via the photocoupler of the charge control signal transmission unit 4 to start charging. Charging is performed by constant voltage and constant current control. That is, charging is performed with the set charging current, and when at least one voltage of the battery cell 2a reaches the charging voltage, the voltage of the battery cell 2ac is changed to the battery cell charging voltage by gradually decreasing the charging current. Maintained.

  In step 214, the microcomputer 50 lights the LED 131 in orange indicating charging. In step 215, the microcomputer 50 determines whether overcharge is detected in at least one battery cell 2a among the plurality of battery cells 2a during charging. That is, in the battery pack 2, when the protection IC 2b detects that any one of the battery cells 2a is overcharged, it transmits an overcharge detection signal to the microcomputer 2d. When receiving the overcharge detection signal, the microcomputer 2d sends a charge stop signal to the microcomputer 50. If the microcomputer 50 receives the charge stop signal, it determines that at least one battery cell 2a is overcharged (step 215: YES). When there are battery cells 2 a that are simultaneously overcharged, the microcomputer 2 d may also send the number of battery cells 2 a that are simultaneously overcharged to the microcomputer 50. Next, in step 217, the microcomputer 50 updates the overcharge information in the memory 2e to the microcomputer 2d, and adds the number of overcharge cells or the number of overcharges by the number of battery cells in the overcharge state detected this time. To instruct. Even if the microcomputer 50 does not send an instruction to the microcomputer 2d, when the microcomputer 2d receives the overcharge detection signal, the microcomputer 2d may automatically update the overcharge information.

  If a negative determination is made in step 215 (step 215: NO), it is determined in step 216 whether or not full charge is detected. Specifically, the microcomputer 50 detects the voltage of the battery pack 2 via the battery voltage detection circuit 90, and the voltage reaches the battery pack charging voltage (battery cell voltage set in steps 207, 209, and 211). Then, when it is determined that the current value detected by the current detection circuit 203 (the output of the operational amplifier 61 of the charging current control circuit 60) has dropped to a predetermined value, it is determined that the battery is fully charged. If a negative determination is made in step 216 (step 216: NO), the process returns to step 215.

  When an affirmative determination is made in step 216 (step 216: YES), or after execution of step 217, in step 218, the microcomputer 50 controls the PWM control IC 23 via the photocoupler of the charge control signal transmission unit 4. Then, charging is terminated by interrupting the supply of power to the battery pack 2.

  In step 219, the microcomputer 50 turns on the LED 131 in green and notifies that the charging is finished. In step 220, the microcomputer 50 determines whether or not the battery pack 2 has been removed from the charging device 1. When the battery pack 2 has been removed from the charging device 1 (step 220: YES), the process returns to step 201 and repeats step 220 to enter a standby state, and the battery pack has not been removed from the charging device. (Step 220: NO), the process enters a standby state by repeating Step 220.

  FIG. 4-6 shows the voltage (vertical axis) and time (time) of the battery cell 2a when the charging voltage is set to V1, V2, and V3 and the battery is fully charged by executing the above charging process. The horizontal axis) and the relationship between charging current (vertical axis) and time (horizontal axis) are shown. As shown in FIG. 4-6, charging is performed at each set charging current (I1 to I3), and when the voltage of the battery cell 2a reaches the charging voltage (V1, V2, V3), the battery cell 2a is charged. The charging current is continuously decreased so that the voltage is maintained, and charging is terminated when the voltage is decreased to a predetermined current value.

  FIG. 7 shows a case where overcharge is detected in one cell when the charging voltage V1 and the current value of the charging current are set to I1. The voltage value indicated by the dotted line indicates the battery cell 2a that has deteriorated, and the voltage value indicated by the solid line indicates the battery cell that has not deteriorated. Since the battery cell 2a that has deteriorated has a high internal resistance, the voltage value increases faster than the other battery cells 2a. If the charging is continued, the voltage of the battery cell 2a, which has been deteriorated, rapidly rises and exceeds the charging voltage V1, reaches an overvoltage value higher than the charging voltage V1, is determined to be in an overcharged state, and charging ends. Since the battery cells 2a are connected in series, in this case, charging of the battery cells 2a that have not deteriorated is also terminated. On the other hand, as shown in FIGS. 5 and 6, when charging the battery pack 2 including the battery cells that have been overcharged in the past, the charging voltage and charging current are reduced, so the voltage value of the deteriorated cell ( The dotted line) does not reach the overvoltage value (> constant voltage value), and charging can be continued until the end (full charge) without stopping charging during charging.

  FIG. 8 is a graph showing the relationship between the discharge capacity (vertical axis) and the number of cycles (number of times of charging) when the charging process according to the present embodiment is repeated. As shown in FIG. 8, even if overcharge is detected for the first time in the number of cycles C1, even if there is an undegraded battery cell 2a as shown in FIG. The cycle life can be improved without the discharge capacity being significantly reduced at the cycle number C1.

  According to the present embodiment, the next charging is performed with the battery cell charging voltage V2 and the charging current I2 as shown in FIG. That is, since charging is performed over time at a battery cell charging voltage and charging current lower than the previous time, the battery cell 2a determined to be overcharged the previous time is not determined to be overcharged. Therefore, it becomes possible to charge the battery so that the discharge capacity becomes larger than the time point of the cycle number C1.

  When charging is repeated by the method of FIG. 5, it is conceivable that the battery cell 2a deteriorates and the battery cell 2a is determined to be in an overcharged state. When the number of such battery cells 2a is counted a predetermined number of times, the battery cell charging voltage is set to V3 and the charging current is set to I3 to perform charging as shown in FIG. Alternatively, when the overcharge state is determined by the method of FIG. 5 (charging voltage V2 and charging current I2) regardless of the number of cells determined to be deteriorated cells, the set values (charging voltage V3 and charging current I3) shown in FIG. ) May be charged.

  As described above, when any of the battery cells 2a is recognized as being in an overcharged state (the cell voltage has reached the overvoltage value), charging ends. However, by switching to the charging method of FIG. It becomes possible to increase the discharge capacity (number of cycles) of the battery pack 2 as compared with the case where charging is continued by the method. That is, when the battery is overcharged even once in the past charge, the deterioration of the battery cell 2a can be suppressed by using a shallow charge.

  The following modifications may be made to the above charging method. For example, the battery cell charging voltage is set from three types (V1, V2, V3), but is not limited to three types, and may be set from a plurality of types.

  The charging current is also set from three types (I1, I2, and I3), but may be set from a plurality of types.

  In the above embodiment, both the battery cell charging voltage (battery pack charging voltage) and the charging current are set and changed based on the overcharged cell information, but only one of them is overcharged cell information. Can be set and changed, and the remaining one may use a fixed value regardless of the overcharged cell information.

  Further, the battery cell charging voltage and the charging current were determined by the determination in step 206 and the determination in step 206b. That is, the battery cell charging voltage and the charging current were set based on the same range of the number of overcharged cells. However, the battery cell charging voltage and the charging current may be determined based on different standards. For example, the battery cell charging voltage is set to V1 when the number of overcharged cells is less than a first predetermined value, and the battery cell charging voltage is set to V2 when the number is over a first predetermined value and less than a second predetermined value. Set to V3 when greater than or equal to the second predetermined value. On the other hand, when the number of overcharged cells is less than a third predetermined value that is different from the first predetermined value, the charging current I1 is set to be equal to or greater than the third predetermined value and different from the second predetermined value. The charging current I2 may be set when it is less than a predetermined value of 4, and the charging current I3 may be set when it is equal to or more than a fourth predetermined value.

  In step 206, if there is at least one battery cell that has been overcharged during past charging, the battery cell charging voltage has been set to a value other than V1 (V2 or V3). The battery cell charging voltage may be set to a value other than V1 in the overcharged state.

  The overcharged cell number information may store the number of overcharges for each battery cell 2a, instead of simply storing the number of overcharged battery cells 2a. In this case, in steps 206 and 206b, determination may be performed based on the number of overcharges for each battery cell. For example, the number of times that each battery cell 2a is overcharged may be summed, and it may be determined whether the total value is equal to or greater than a threshold value. The maximum value and the threshold value may be compared. In this case, in step 217, the battery cell 2a that has been overcharged in step 215 is specified, and the number of times that the battery cell 2a has been overcharged is updated.

  Next, processing during discharging of the battery pack 2 will be described. FIG. 9 is a circuit diagram when the battery pack 2 is attached to the electric power tool 200. The electric tool 200 includes a motor 201, a main switch 202, an FET 204, and a connection terminal 203. The motor 201 is rotated by the electric power supplied from the battery pack 2 when the operator turns on the main switch 202.

  When the microcomputer 2d outputs a discharge stop signal from the tool terminal 2i, the power tool 200 receives the discharge stop signal from the connection terminal 203. The FET 204 is turned off by the discharge reception signal. Thereby, the power supply line from the battery pack 2 is interrupted, and the rotation of the motor 201 is stopped.

  With reference to FIGS. 10 and 11, the relationship between the voltage of battery cell 2a during discharge and time will be described. FIG. 10 shows a state at the time of discharging in a state where the battery cell 2a is not deteriorated. When the discharge is started, the voltage of the battery cell 2a gradually decreases, and when the threshold value a is reached, the microcomputer 2d outputs a discharge stop signal. Thereby, the discharge of the battery pack 2 is stopped.

  FIG. 11 is a graph showing a state during discharging when the battery cell 2a is deteriorated. The voltage of the battery cell 2a that has deteriorated is indicated by a dotted line, and the voltage of the battery cell 2a that has not deteriorated is indicated by a solid line. When charging / discharging of the battery pack 2 is repeated, the battery cell 2a deteriorates. If the discharge to the threshold value a is continued in a state where the battery cell 2a is deteriorated, the progress of the deterioration is further accelerated. Therefore, in this embodiment, as shown in FIG. 11, when it is determined that the battery cell 2 a has deteriorated, that is, when the battery cell 2 a is overdischarged once in the past discharge, the threshold value is larger than a. Change to By doing in this way, discharge of the battery cell 2a which has progressed deterioration can be kept within a reasonable range, and further battery deterioration can be suppressed.

  With reference to FIG. 12, the processing of the microcomputer 2d at the time of discharging will be described. In the following description, the case where the battery pack 2 is attached to the electric tool 200 as shown in FIG. 9 will be described. In step 401, the microcomputer 2d determines whether or not the discharge of the battery cell 2a has been started. When the operator turns on the power tool 202, electric power is supplied from the battery pack 2. At this time, the microcomputer 2d determines that the discharge is started by the detection signal from the current detection circuit 2h.

  In step 402, the microcomputer 2d selects and sets the voltage value a (threshold value a) as the overdischarge threshold value. The overdischarge threshold is a value indicating the lower limit value of the voltage of the battery cell 2a. As will be described later, when the microcomputer 2d determines that at least one of the plurality of battery cells 2a has reached the overdischarge threshold, the discharge is stopped. Send a signal.

  In step 403, the microcomputer 2d receives the overdischarge cell information from the memory 2e, and determines whether the overdischarge frequency of any battery cell 2a is equal to or greater than a predetermined value. That is, it is determined whether or not an overdischarge state has occurred during the past discharge. If a negative determination is made in step 403 (step 403: NO), the process proceeds to step 408.

  If an affirmative determination is made in step 403 (step 403: YES), in step 404, the microcomputer 2d determines whether a predetermined time has elapsed since the discharge start time. If an affirmative determination is made in step 404 (step 404: YES), in step 407, the overdischarge threshold is changed from a to b. Here, in FIG. 11, the threshold value at the start of discharge is a, and the threshold value is changed to b after a predetermined time has elapsed. A large starting current flows at the start of discharging (when the motor is started), and the voltage of the battery pack 2 is remarkably lowered by this starting current (overcurrent). The threshold value is set to a small value for a predetermined time from the start of discharge so that the voltage drop reaches the discharge threshold value and the discharge does not stop. As another method, the threshold value may be set to b, and the battery voltage may not be detected for a predetermined time from the start of discharge (discharging continues even if the voltage drops below the threshold value).

  In step 408, the microcomputer 2d determines whether the discharge state is detected based on the detection signal from the current detection circuit 2h. If an affirmative determination is made in step 408 (step 408: YES), it is determined in step 409 whether at least one cell has reached the overdischarge threshold. In step 409, b is used as the overdischarge threshold when step 407 is executed, and a is used as the overdischarge threshold when step 407 is not executed. Specifically, the voltage value of each battery cell 2a is detected by the protection IC 2b, and the microcomputer 2d detects the detected voltage based on the set overdischarge threshold, and the voltage value of the battery cell 2a becomes equal to or lower than the overdischarge threshold. Judgment is made. When the microcomputer 2d determines that the voltage value of the battery cell 2a is equal to or lower than the overdischarge threshold, the microcomputer 2d determines that at least one battery cell 2a is overdischarged.

  If a negative determination is made in step 404 (step 404: NO), it is determined in step 405 based on the detection signal from the current detection circuit 2h whether the discharge state is still detected. If a negative determination is made in step 405 (step 405: NO), the process returns to step 401. If an affirmative determination is made in step 405 (step 405: YES), it is determined in step 406 whether at least one battery cell has reached the overdischarge threshold a.

  If an affirmative determination is made in step 406 or an affirmative determination is made in step 409, the process proceeds to step 410, where the microcomputer 2 d outputs a discharge stop signal and turns off the FET 204 of the electric power tool 200. That is, while the predetermined period has not elapsed, in step 406, determination is performed using the overdischarge threshold a.

  In step 411, the number of overdischarges of the battery cell 2a specified as having a voltage value lower than the overdischarge threshold in step 406 or step 409 is added (overdischarge information is updated), and the process returns to step 401. In addition, you may update only the frequency | count of overdischarge as the battery pack 2, without specifying the battery cell 2a.

  In the processing at the time of discharging, when a specific battery cell 2a has exceeded a predetermined value in an overdischarged state (step 403: YES), it is considered that the battery cell 2a has been deteriorated. Therefore, in step 407, by setting the overdischarge threshold value high, it is possible to prevent the battery cell 2a having deteriorated from becoming less than the voltage value b, and to suppress further deterioration of the battery cell 2a. . That is, further deterioration of the battery cell 2a is suppressed by making the discharge voltage threshold shallow. However, the overdischarge threshold value is not set to the threshold value b until a predetermined time has elapsed (until S404: YES). This is because, for example, when the power tool 200 is used in a cold environment and the temperature of the battery cell 2a is reduced at the start of discharge, the internal resistance increases and an overcurrent flows. This is because it is conceivable that the voltage of the battery pack 2 rapidly decreases due to overcurrent, and the voltage of the battery cell 2a decreases to the voltage value b. In the present embodiment, the overdischarge threshold is maintained at a until the discharge period elapses for a predetermined time, and overdischarge is determined (step 406). Since the sudden drop in voltage occurs at the time of starting the motor, the overdischarge threshold is changed to b in step 407 for the first time after the discharge period has continued for a predetermined time, so that the battery cell 2a temperature decreases or the motor 201 starts. It can be avoided that the voltage drop is judged as overdischarge.

  As described above, the microcomputer 2d receives a signal from the protection IC 2b at the time of overcharging during charging, and transmits to the charging apparatus 1 that it is overcharged. Alternatively, a signal from the protection IC 2b is received at the time of overdischarge during discharge, and a message indicating overdischarge is transmitted to the charging device 1. Then, the charging device 1 or the power tool 200 performs a charge stop operation or a discharge stop operation based on the signal. Further, the microcomputer 2d stores the overcharge frequency and overdischarge frequency during charging and discharging in the memory 2e. And charge control is changed according to overcharge frequency at the time of the next charge. Alternatively, the microcomputer 2d transmits the overdischarge frequency during discharging to the charging device 1 before the start of charging, and the charging device 1 performs optimal charging control based on the signal.

  FIG. 13 is a graph showing the relationship between the discharge capacity (vertical axis), the number of cycles, and (horizontal axis) of the battery pack 2 when the discharge process according to the present embodiment is executed. The graph shown by the dotted line shows the transition of the discharge capacity when the processing at the time of discharge according to the present embodiment is executed, and the solid line shows the transition of the discharge capacity by the conventional processing at the time of discharging without changing the overdischarge threshold.

  Since the overdischarge threshold is set to a up to the number of cycles C2, the discharge capacity decreases as the number of cycles increases in the same manner as in the conventional process and the process of the present embodiment. However, since the overdischarge threshold is maintained at “a” in the conventional process, the deterioration of the battery cell 2 a is accelerated as the number of cycles increases. This is because the battery cell 2a is more deteriorated due to a decrease in voltage value as its discharge capacity is reduced. On the other hand, in the present embodiment, the overdischarge threshold is changed to b from the number of cycles C2. Therefore, the battery cell 2a having deteriorated can be prevented from being discharged below the voltage value b, and the battery cell 2a gradually deteriorates. Therefore, a large discharge capacity can be maintained for a long time as the entire battery pack 2 (the number of cycles can be improved).

  In the above embodiment, the overdischarge count is used for each battery cell 2a as an index for determining overdischarge of the battery cell 2a. However, the index for determining overdischarge of the battery cell 2a is limited to the overdischarge count. Not. For example, if any of the battery cells 2a is overdischarged once, the overdischarge threshold at the next discharge may be increased. In this case, in step 403, if an overdischarge state has occurred in the past, the process may proceed to step 404. In addition, the memory 2e stores the total number of overdischarges of the total number of overdischarges of the battery cells 2a in all the battery cells 2a as overcharge information, and can be used as an index for judging the progress of deterioration of the battery cells 2a. Good. In this case, in steps 402 and 407, a threshold value corresponding to the total number of overdischarges is set, and in steps 406 and 409, it is determined whether the total number of overdischarges is equal to or less than the set threshold value.

  Alternatively, the overdischarge threshold may be changed from a to b in consideration of not only the number of overdischarges but also the number of overcharged cells. Alternatively, the overdischarge threshold may be changed based only on the number of overcharges without using the number of overdischarge cells.

Further, the overdischarge threshold is set in two stages of a and b, but is not limited to two stages as long as it is set in a plurality of stages.
(Second Embodiment)

  The charging process of the charging device 1 according to the second embodiment will be described with reference to the flowchart of FIG. The apparatus configuration of the second embodiment is the same as that of the first embodiment.

  Steps 301-303 are the same as steps 201-203 (FIG. 3) in the charging process of the first embodiment. In step 305, the microcomputer 50 receives overdischarge information. In step 306, the microcomputer 50 determines whether or not the number of overdischarges of at least one battery cell 2a is greater than or equal to a predetermined value based on the overdischarge information. Here, the predetermined value is the same as the predetermined value in step 403 in FIG. 12, but may not be the same as the predetermined value in step 403.

  When a negative determination is made at step 306 (step 306: NO), the routine proceeds to step 307, and when an affirmative determination is made at step 306 (step 306: YES), the routine proceeds to step 309. Steps 307, 308, 309, 310, 311, 312, 313, 314-317 are the same as steps 207, 208, 209, 210, 213, 214, 215, 216-220 of FIG. However, if an affirmative determination is made in step 313 (corresponding to step 215), the process proceeds to step 315 without performing step 217.

  According to the charging process of the second embodiment, the battery cell charging voltage, the battery pack charging voltage, and the charging current are set according to whether or not the overdischarge state has been detected a predetermined number of times. That is, the number of times the overdischarge state is detected is used as an index indicating the deterioration of the battery cell 2a. When the deterioration of the battery cell 2a progresses, the charging voltage and the charging current are set low, and the load applied to the battery cell 2a is set. By reducing, it becomes possible to suppress the deterioration of the battery cell 2a and to sufficiently charge the battery cell 2a which has not deteriorated.

  In the second embodiment, the charging voltage is selected from two types of V1 and V2, and the charging current is also selected from two types of I1 and I2. However, the charging voltage to be selected and the type of charging current are selected. As long as there are a plurality of types, the number does not have to be two. For example, if the number of overdischarges is less than a first value, the charging voltage V1 and the charging current I1 are set. If the number of overdischarges is greater than or equal to the first value and less than the second value, the charge voltage V2 and the charge If the current I2 is set and the number of overdischarges is equal to or greater than the second value, the charging voltage V3 and the charging current I3 may be set.

  In the first embodiment, the charging voltage and the charging current are determined based on the overcharge information. On the other hand, in the second embodiment, the charging voltage and the charging current are determined based on the overdischarge information. However, the charging voltage and the charging current are not limited to these as long as the information can determine the degree of deterioration of the battery cell 2a. For example, the degree of deterioration of the battery cell 2a may be determined in consideration of both overcharge information and overdischarge information.

DESCRIPTION OF SYMBOLS 1 Charging device 2 Battery pack 50 Microcomputer 2f Microcomputer 2e Memory 2a Battery cell

Claims (9)

A secondary battery comprising a plurality of battery cells;
Storage means for storing history information regarding the history of a plurality of battery cells;
Setting means for setting an overdischarge threshold based on the history information,
When the voltage of any one of the plurality of battery cells has been lowered to the overdischarge threshold in the past, the setting means is a first when the overdischarge threshold has not been lowered. A battery pack that is set to a second threshold value that is greater than the threshold value.   The setting means sets the overdischarge threshold to the first threshold until a predetermined period elapses after the secondary battery starts discharging even if the battery cell has been overdischarged in the past. The battery pack according to claim 1, wherein the battery pack is set. Voltage detecting means for detecting the voltage of the secondary battery;
2. The battery pack according to claim 1, wherein the voltage detection unit does not detect the voltage of the secondary battery until a predetermined period elapses after the secondary battery starts discharging.   2. The battery pack according to claim 1, wherein the history information includes overdischarge information indicating whether a voltage of at least one battery cell of the plurality of battery cells is equal to or lower than the overdischarge threshold. The history information includes the number of overdischarges indicating the number of times that the battery cell has become overdischarged,
The setting means sets the overdischarge threshold to a first threshold when the number of overdischarges is less than a predetermined number, and sets the overdischarge threshold to a first when the number of overdischarges is a predetermined number or more. The battery pack according to claim 1, wherein the battery pack is set to a second threshold value greater than the threshold value.   The setting means sets the overdischarge threshold as a first threshold when a predetermined period has not elapsed since the secondary battery started discharging even if the number of overdischarges is a predetermined number or more. The battery pack according to claim 5. The battery pack according to any one of claims 1 to 6 is detachable,
A motor powered by the battery pack;
And a switching element for controlling rotation of the motor. The battery pack has discharge prohibiting means for stopping discharge when the battery cell is overdischarged,
The power tool according to claim 7, wherein the switching element is interrupted by an output from the discharge prohibiting unit. A charging device for charging the battery pack according to any one of claims 1 to 6,
Information acquisition means for acquiring history information relating to the history of the secondary battery;
Setting means for setting a charging condition based on the history information;
Charging control means for charging the secondary battery based on the charging condition,
When the voltage of any one of the plurality of battery cells has dropped to the overdischarge threshold in the past, the setting means may reduce at least one of a charging voltage and a charging current to the overdischarge threshold. A charging device, characterized in that it is set smaller than a case where it has never been lowered.

Images