JP2015029390A - Charger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charger for charging a secondary battery so that the discharge capacity is not reduced even if charging is repeated, while preventing overcharge of the secondary battery.SOLUTION: A charger includes acquisition means for acquiring the state information indicating the state of a secondary battery, setting means for setting the charging condition depending on the temporal change in the state information, and charging control means for charging the secondary battery under the charging condition. The state information includes the information about the temperature of the secondary battery, and the charging condition is the charging voltage of the secondary battery. If the rate of increase in the temperature of the secondary battery with respect to the time is less than a threshold, the setting means sets the charging voltage to a first voltage, otherwise sets the charging voltage to a second voltage lower than the first voltage. The charging control means controls the charging so that the voltage value of the secondary battery becomes the charging voltage.

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 charging is performed so that the charging current is reduced when the lithium ion battery reaches the charging voltage value.

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 overcharged at a predetermined voltage value or higher, the battery cell is deteriorated. In recent years, the capacity of lithium ion batteries has been increasing. However, the higher the capacity of lithium ion batteries, the shorter the lifespan (deteriorating quickly and overcharging).

  For example, conventionally, the voltage of each battery cell is monitored during charging of a lithium ion battery, and when it is determined that one battery cell is overcharged, charging of the entire lithium ion battery is stopped.

  By the way, although each battery cell of a lithium ion battery deteriorates also by repeating charging / discharging, the degree of deterioration varies for every cell. In addition, battery cells that are more deteriorated are more likely to be overcharged. Therefore, it is possible that the deterioration of a specific battery cell proceeds (the degree of deterioration is large), but the remaining battery cells have a low degree of deterioration. However, in the conventional charging method, even if there is a battery cell with a small degree of deterioration, charging is terminated when one battery cell is overcharged, so that the battery capacity of a battery cell that has not deteriorated is sufficiently increased. I couldn't make the most of my life.

  In view of such circumstances, an object of the present invention is to provide a charging device that charges a secondary battery so that the discharge capacity does not decrease even if charging is repeated while preventing overcharging of the secondary battery.

  The present invention includes an acquisition unit that acquires state information indicating a state of a secondary battery, a setting unit that sets a charging condition in accordance with a time change of the state information, and charging that charges the secondary battery under the charging condition. Control means, wherein the state information includes information on the temperature of the secondary battery, the charging condition is a charging voltage of the secondary battery, and the setting means is the time of the secondary battery with respect to time. If the rate of increase in temperature is less than a threshold, the charging voltage is set to a first voltage, and if the rate of increase in temperature of the secondary battery over time is greater than or equal to a threshold, the charging voltage is set to the first voltage. The charging device is set to a second voltage lower than the voltage, and the charging control means performs charging so that the voltage value of the secondary battery becomes the charging voltage.

  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 charging condition is a charging current of the secondary battery, and the setting means sets the charging current to a first current value if an increase rate of the temperature of the secondary battery with respect to time is less than a threshold value. If the rate of increase of the temperature of the secondary battery with respect to time is equal to or greater than a threshold value, the charging current is set to a second current value lower than the first current value, and the charging control means It is preferable to charge the battery with the charging current.

  The setting unit preferably changes the threshold value according to an initial temperature of the secondary battery.

  Obtaining means for obtaining state information indicating a state of the secondary battery, setting means for setting a charging condition according to a time change of the state information, charging control means for charging the secondary battery with the charging condition, The state information includes information on the voltage of the secondary battery, the charging condition is a charging voltage of the secondary battery, and the setting means increases the voltage of the secondary battery with respect to time. If the rate is less than the threshold, the charging voltage is set to the first voltage, and if the rate of increase of the voltage of the secondary battery with respect to time is equal to or greater than the threshold, the charging voltage is set to be lower than the first voltage. Preferably, the voltage is set to 2 and the charging control means performs charging so that the voltage value of the secondary battery becomes the charging voltage.

  The charging condition is a charging current of the secondary battery, and the setting means sets the charging current to a first current value if an increase rate of the voltage of the secondary battery with respect to time is less than a threshold value. If the rate of increase of the voltage of the secondary battery with respect to time is equal to or greater than a threshold value, the charging current is set to a second current value lower than the first current value, and the charging control means It is preferable to charge the battery with the charging current.

  The setting means can change the threshold according to an initial voltage of the secondary battery.

  The present invention includes an acquisition unit that acquires state information indicating a state of a secondary battery, a setting unit that sets a charging condition according to the state information, and a charging control unit that charges the secondary battery with the charging condition. The state information includes information related to the temperature of the secondary battery before starting charging, the charging condition is a charging voltage of the secondary battery, and the setting means includes the temperature before starting charging. When the temperature is low, a threshold for changing the charging voltage is set larger than when the temperature is high.

  The present invention includes an acquisition unit that acquires state information indicating a state of a secondary battery, a setting unit that sets a charging condition according to the state information, and a charging control unit that charges the secondary battery with the charging condition. The state information includes information on the voltage of the secondary battery before starting charging, the charging condition is a charging voltage of the secondary battery, and the setting means includes the voltage before starting charging. When the battery voltage is low, a threshold for changing the charging voltage is set larger than when the voltage is high.

  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 circuit diagram of the charging device of this Embodiment. The graph explaining the charge process of this Embodiment. The flowchart which shows the charge process of this Embodiment. The table which showed the relationship between the threshold value used by the charge process of this Embodiment, and the initial temperature of a battery cell.

  Hereinafter, a charging device 1 according to an 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, a battery pack 2 includes a battery set formed by connecting a plurality of battery cells 2a (four cells in the present embodiment) in series, a battery type discrimination resistor 7, and a thermistor that is a temperature sensitive element. 8 and a protection IC 2b. 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 battery type discrimination resistor 7 has a specific resistance value corresponding to the type of the battery pack 2 (rated voltage, number of battery cells connected in series, etc.), and is connected in series from the resistance value. It is possible to know the type of battery pack, such as the number of battery cells 2a. The thermistor 8 is disposed in contact with or close to the battery set, and detects the temperature of the battery set. 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 battery pack 2 has terminals corresponding to the positive and negative terminals for charging provided in the charging device 1, and a terminal for connecting the protection IC 2b and the A / D input port 52 (described later), When the battery pack 2 is attached to the charging device 1, these corresponding terminals (or terminals and ports) 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, 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, 74, 75, and 76 connected between the reference voltage Vcc and the ground, and is a circuit for setting the charging current to a predetermined current value. is there. 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 to 76 are individually connected to corresponding ports of the output port 51b. The other ends of the resistors 73 to 76 are connected to connection points of the resistors 71 and 72.

  The current value of the charging current is determined according to the type of battery pack 2 (rated voltage, number of cells, capacity, number of cells in parallel). In the present embodiment, the charging current setting circuit 70 selectively sets three types of current values I1, I2, and I3 according to the type of the battery pack 2 as the setting current at the time of charging. Specifically, no signal is output from the ports connected to the resistors 73, 74, 75, and 76 of the output port 51b, and the value obtained by dividing the reference voltage Vcc by the resistors 71 and 72 is the set current. Becomes a reference value for setting as the current value I1. 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 resistors 74, 75, and 76 in the second output port 51b does not output a signal, so that the resistor A value obtained by dividing the reference voltage Vcc by 71 and the combined resistance of the resistors 72 and 73 is a reference value for setting the set current 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 resistors 73, 75, 76, and the port connected to the resistor 74 outputs a low signal, so that the reference voltage Vcc is connected to the resistor 71, The value divided by the combined resistance of the resistors 72 and 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. In the above description, an example is shown in which the ports connected to the resistors 75 and 76 of the second output port 51b do not always output a signal. However, by outputting a low signal also to these ports, It is also possible to set a current value different from the values I1 to I3.

  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, which are connected to the battery type determination circuit 9, the charging current control circuit 60, the battery temperature detection circuit 80, and the battery voltage detection circuit 90, respectively. Yes. One of the A / D input ports 52 can be connected to the protection IC 2 b of the battery pack 2, and the other one of the A / D input ports 52 can be connected to the battery type discrimination resistor 7 of the battery pack 2. Is possible. When the abnormal signal of the battery cell 2a is received from the port connected to the protection IC 2b among the A / D input ports 52, the microcomputer 50 stops the charging of the battery pack 2. Further, when the microcomputer 50 (A / D port 52) detects from the current signal from the charging current control circuit 60 that the charging current has decreased below a predetermined value in the constant voltage charging section in the constant current / constant voltage charging control. Then, the charging of the battery pack 22 is stopped.

  The battery temperature detection circuit 80 includes resistors 81 and 82 connected in series between the reference voltage Vcc and the ground, and the connection point of the resistors 81 and 82 is connected to the thermistor 8 of the battery pack 2. It is connected to one of the A / D input ports 52a of the microcomputer 50. When the temperature of the battery set 2a of the battery pack 2 changes, the voltage value associated with the temperature change is applied to the corresponding port among the A / D input ports 52a of the microcomputer 50. Thereby, the charging device 1 can grasp the temperature of the battery set 2a.

  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 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.

  The battery type determination circuit 9 includes a resistor 9a, and the microcomputer 50 determines the type (rated voltage or series) of the battery pack 2 connected based on the divided value of the reference voltage Vcc by the resistor 9a and the battery type determination resistor 7. The number of battery cells connected, the number of battery cells connected in parallel, etc.).

  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. One of the A / D input ports 52 is connected to the protection IC 2 b, the other one is connected to the battery type discrimination resistor 7, and the other one is connected to the thermistor 8.

  The charging control signal transmission unit 4 is connected to the switching circuit 20 and the microcomputer 50, and includes a photocoupler that transmits a signal for controlling on / off of the PWM control circuit 23. Here, the first output port 51a has a plurality of ports, one of which is connected to the photocoupler. When the output port 51a is switched between a high state and a low state, the photocoupler is turned on and off. When the photocoupler is turned on, the PWM control circuit 23 is activated and charging is started. On the other hand, when the photocoupler is turned off, 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, 123, potentiometer 102, FETs 109, 113, 117, 122, 124. , Capacitor 104, shunt regulator 120, 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 gates of the FETs 122 and 124 are 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, 122, and 124 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, 121, 123 and the potentiometer 102 is R1, and the combined resistance determined by the resistors 105, 106, 110, 114 is R2.

  That is, the combined resistance R1 changes depending on whether the FETs 122 and 124 are turned on or off. When both the FETs 122 and 124 are off, the combined resistance R1 is a series resistance of the resistance 101 and the potentiometer 102. When the FET 122 is on and the FET 124 is off, the resistor R1 is a series resistance of the combined resistance of the resistor 101 and the resistor 121 and the potentiometer 102. When both the FETs 122 and 124 are on, the resistor R1 is a series resistance of the combined resistance of the resistor 101, the resistor 121, and the resistor 123, 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, 124, 109, 113, 117 on and off. The charging voltage indicates a voltage value applied to the battery pack 2. That is, by switching the FETs 122 and 124, the charging voltages V1, V2, and V3 are switched according to the degree of deterioration of the battery pack 2, and the voltage of the battery pack 2 connected by switching the FETs 109, 113, and 117 (the number of cells connected in series) ) Is switched to the charging voltage according to

  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 attached and the progress of deterioration of the battery cell 2a described later. 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. The voltage value V1 is set to a value lower than the rated voltage of the battery cell 2a. 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.

  Next, the microcomputer 50 calculates a value obtained by multiplying the set battery cell charging voltage (any one of V1, V2, and V3) by the number of battery cells 2a connected in series (4 in the present embodiment). The charging voltage applied to the pack 2 (hereinafter referred to as the battery pack charging voltage) is set. Specifically, the FETs 122, 109, 113, and 117 are turned on and off so that the voltage applied to the battery pack 2 is set to the battery pack charging voltage.

  The charging process of the battery pack 2 performed by the charging device 1 will be described. The charging process of the present embodiment is performed by constant voltage constant current control. That is, charging is performed with the charging current set at the start of charging, and when the voltage of the battery pack 2 reaches the battery pack charging voltage, the voltage of the battery pack 2 is reduced by gradually decreasing the charging current. Maintained. The microcomputer 50 detects the voltage of the battery pack 2 via the battery voltage detection circuit 90. In the present embodiment, the rate of increase of the temperature of the battery pack 2 (battery cell 2a) when a predetermined time has elapsed is calculated, and the charging voltage is set based on the rate of increase.

  FIG. 2 shows the relationship between the voltage of the battery cell 2a (vertical axis), the temperature of the battery cell 2a (vertical axis), and the charging current (vertical axis) with respect to time (horizontal axis) in constant voltage constant current control. It is a graph. 2 (a) -2 (c) corresponds to the conventional constant voltage constant current control, and FIGS. 2 (d) -2 (f) correspond to the constant voltage constant current control of the present embodiment. FIGS. 2A, 2B, and 2C show graphs in the case where the deterioration of the battery cell 2a progresses in the order shown in FIGS. 2D, 2E, and 2C. The graph when the deterioration of the battery cell 2a progresses in the order of f) is shown. In FIG. 2, the charging currents during constant current control are all the same value. As the deterioration of the battery cell 2a proceeds, the rate of increase of the temperature of the battery cell 2a with respect to time (hereinafter referred to as a temperature gradient) increases. This is because when the battery cell 2a deteriorates, its internal resistance increases, so that the amount of heat generated during charging increases. Actually, the temperature gradient is A in FIGS. 2 (a) and 2 (d), but the temperature gradient is B larger than A in FIGS. 2 (b) and 2 (e). 2C and 2F, the temperature gradient is C greater than B. Similarly, when the deterioration of the battery cell 2a progresses, the rate of increase of the voltage of the battery cell 2a with respect to time (hereinafter referred to as voltage gradient) also increases.

  As shown in FIGS. 2 (a) -2 (c), in the conventional constant current / constant voltage control, even if the battery cell 2a deteriorates, the charging voltage of the battery cell 2a (battery pack 2) is always set during the constant voltage control. V1 (V1 × number of cells). On the other hand, in the present embodiment, as shown in FIG. 2 (d), when the battery cell 2a has not deteriorated, the charging voltage is set to V1, but the deterioration is to some extent as shown in FIG. 2 (e). When it has advanced, the charging voltage is set to V2 lower than V1, and when the deterioration further proceeds as shown in FIG. 2 (f), the charging voltage is set to V3 lower than V2. More specifically, the temperature of the battery cell 2a is measured at the start of charging and when a predetermined time has elapsed, and a temperature gradient is calculated. The charging voltage is set to V1 when the temperature gradient is smaller than a predetermined value b described later, and the charging voltage is set to V2 when the temperature gradient is equal to or larger than the predetermined value b and smaller than the predetermined value c. At this time, the charging voltage is set to V3.

  With reference to FIG. 3, the above-described charging process will be described in more detail. 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. Such determination is made by determining whether there is an input to the corresponding ports of the battery temperature detection circuit 80, the battery voltage detection means 90, and the battery type determination circuit 9, and if the input is detected in these circuits, the battery pack It is determined that 1 is attached.

  In step 203, the microcomputer 50 determines the type of the battery pack 2 connected based on the divided voltage value of the battery type discrimination resistor 7 and the resistor 9a (rated voltage, capacity, number of battery cells 2a connected in series, etc.). Is identified.

  In step 204, the microcomputer 50 selects the battery cell charging voltage V1 corresponding to the specified type of the battery pack 2, and multiplies the number of battery cells 2a connected in series to the battery cell charging voltage in step 205. Thus, the battery pack charging voltage is calculated, and the charging voltage of the charging voltage control circuit 100 is set to the calculated battery pack charging voltage. As described above, the battery pack charging voltage is set by switching the FETs 122, 124, 109, 113, 117 on and off.

  In step 206, the microcomputer 50 selects the charging current corresponding to the specified type of the battery pack 2 from any one of the current values I1, I2, and I3, and sets the charging current of the charging current setting circuit 70 to the selected value. Set. The setting of the charging current is performed by not outputting to the port connected to the resistors 73, 74, 75, 76 in the second output port 51b, or by sending a low signal.

  In step 207, the microcomputer 50 detects the temperature of the battery pack 2 before starting charging (hereinafter referred to as initial temperature). Specifically, the microcomputer 50 detects the temperature of the battery pack 2 by the thermistor 8 and the battery temperature detection circuit 80. More specifically, the microcomputer 50 detects a divided voltage value of the combined resistance of the thermistor 8 and the resistor 82 and the resistor 81 from the A / D input port 52, and the battery pack 2 (battery) based on the divided voltage value. The temperature of the cell 2a) is detected.

  In step 208, the microcomputer 50 controls the PWM control IC 23 via the photocoupler of the charging control signal transmission unit 4 to start charging.

  In step 209, the microcomputer 50 turns on the LED 131 in orange indicating charging.

  In step 210, the microcomputer 210 determines whether or not a predetermined time (for example, 3 minutes after the start of charging) has elapsed. If a negative determination is made in step 210 (step 210: NO), in step 211, the microcomputer 50 determines 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 after the detected voltage reaches the battery pack charging voltage, the charging current detected by the charging current control circuit 60 is When it falls to a predetermined value, it is determined that the battery is fully charged.

  If a negative determination is made in step 211 (step 211: NO), the process returns to step 210. If an affirmative determination is made in step 211 (step 211: YES), charging ends in step 217. Specifically, the microcomputer 50 controls the PWM control IC 23 via the photocoupler of the charging control signal transmission unit 4 to stop the supply of power to the battery pack 2 and terminates the charging.

  If an affirmative determination is made in step 210 (step 210: YES), in step 212, the microcomputer 50 detects the temperature of the battery pack 2 from the thermistor 8 and the battery temperature detection circuit 80. Further, by dividing the difference between the temperature detected this time and the initial temperature detected in step 207 by a predetermined time, a rate of temperature increase with respect to time (hereinafter referred to as a temperature gradient) is calculated. Further, it is determined whether or not the temperature gradient is equal to or greater than a predetermined value b. The predetermined value b is selected based on the initial temperature. Specifically, as shown in FIG. 4, when the initial temperature is less than T1, the predetermined value b is set to b1, and when the initial temperature is T1 or more and less than T2, the predetermined value b is set to b2. When the initial temperature is equal to or higher than T2 and lower than T3, the predetermined value b is set to b3. When the initial temperature is abnormal T3, the predetermined value b is set to b4. Here, b1, b2, b3, and b4 satisfy the relationship of b1> b2> b3> b4. T1, T2, and T3 satisfy the relationship of T1 <T2 <T3.

  During charging, the temperature of the battery pack 2 tends to increase more rapidly as the initial temperature is lower. Although the temperature gradient represents the degree of deterioration of the battery cell 2a, if the initial temperature is different, the degree of deterioration of the battery cell 2a cannot be determined only by the temperature gradient. Therefore, the lower the initial temperature, the larger the predetermined value b as the threshold value is set. That is, by changing the threshold value according to the initial temperature, it is possible to cope with the change in the temperature gradient of the battery pack 2 due to the difference in the initial temperature. it can.

  When a negative determination is made in step 212 (step 212: NO), the microcomputer 50 maintains the battery cell charging voltage at V1, that is, maintains the battery pack cell charging voltage at V1 × (the number of series cells). Charging is continued, and the process waits until full charge is detected in step 216. The full charge detection method at this time is the same as in step 211.

  On the other hand, when an affirmative determination is made in step 211 (step 212: YES), in step 213, the microcomputer 50 determines whether or not the temperature gradient is equal to or greater than a predetermined value c. The predetermined value c is also selected based on the initial temperature in the same manner as the predetermined value b. That is, as shown in FIG. 4, when the initial temperature is lower than T1, the predetermined value c is set to c1, and when the initial temperature is equal to or higher than T1 and lower than T2, the predetermined value c is set to c2. Is equal to or greater than T2 and less than T3, the predetermined value c is set to c3, and when the initial temperature is abnormal T3, the predetermined value c is set to c4. Here, c1, c2, c3, and c4 satisfy the relationship of c1> c2> c3> c4.

  As described above, the temperature of the battery pack 2 tends to increase more rapidly as the initial temperature is lower. Although the temperature gradient represents the degree of deterioration of the battery cell 2a, if the initial temperature is different, the degree of deterioration of the battery cell 2a cannot be determined only by the temperature gradient. Therefore, the lower the initial temperature, the larger the predetermined value c as the threshold value is set. That is, by changing the threshold value according to the initial temperature, it is possible to cope with the change in the temperature gradient of the battery pack 2 due to the difference in the initial temperature. it can.

  If a negative determination is made in step 213 (step 213: NO), in step 214, the microcomputer 50 selects the battery cell charging voltage V2 corresponding to the specified type of the battery pack 2, and serially connects the battery cell charging voltage. The battery pack charging voltage is calculated by multiplying the number of battery cells 2a connected to the battery pack, and the charging voltage of the charging voltage control circuit 100 is set to the calculated battery pack charging voltage. As described above, the battery pack charging voltage is set by switching the FETs 122, 124, 109, 113, 117 on and off. That is, in step 214, the microcomputer 50 changes the charging voltage applied to the battery cell 2a from V1 to V2. Thereafter, in step 216, the microcomputer 50 waits until full charge is detected. Specifically, after the voltage of the battery cell 2a reaches the charging voltage V2, it is determined that the battery is fully charged when the charging current drops to a predetermined value.

  If an affirmative determination is made in step 213 (step 213: YES), in step 215, the microcomputer 50 selects the battery cell charging voltage V3 corresponding to the specified type of the battery pack 2, and serially connects the battery cell charging voltage. The battery pack charging voltage is calculated by multiplying the number of battery cells 2a connected to the battery pack, and the charging voltage of the charging voltage control circuit 100 is set to the calculated battery pack charging voltage. As described above, the battery pack charging voltage is set by switching the FETs 122, 124, 109, 113, 117 on and off. That is, in step 215, the microcomputer 50 changes the charging voltage applied to the battery cell 2a from V1 to V3. Thereafter, in step 216, the microcomputer 50 waits until full charge is detected. Specifically, after the voltage of the battery cell 2a reaches the charging voltage V3, it is determined that the battery is fully charged when the charging current drops to a predetermined value.

  When full charge is detected in step 216 (step 216: YES), in step 217, the microcomputer 50 controls the PWM control IC 23 via the photocoupler of the charge control signal transmission unit 4 to supply power to the battery pack 2. Charging is terminated by shutting off the supply.

  In step 218, the microcomputer 50 turns on the LED 131 in green and notifies that the charging is finished. In step 219, the microcomputer 50 determines whether or not the battery pack 2 has been removed from the charging device 1. When the battery pack 2 is removed from the charging device 1 (step 219: YES), the process returns to step 201. When the battery pack is not removed from the charging device (step 219: NO), step 220 is performed. Repeat to enter standby mode.

  As described above, according to the charging process according to the present embodiment, by detecting the temperature gradient of the battery cell 2a during charging, it is determined whether or not the battery cell 2a has deteriorated, and the temperature gradient, that is, the deterioration of the battery cell 2a. The charging voltage is changed according to the progress. That is, as the deterioration of the battery cell 2a progresses, the battery cell 2a can be charged with no burden by setting the charging voltage lower. Thus, if it charges by setting a charging voltage low, it can avoid that the battery cell 2a reaches an overcharge state, and can further avoid deterioration of the battery cell 2a.

  In addition, when charging and discharging are repeated, the degree of deterioration varies among the plurality of battery cells 2a. In the present embodiment, charging can be stopped by overcharging in order to avoid overcharging of the battery cell 2a that has deteriorated by reducing the charging voltage. Therefore, it is possible to sufficiently charge the battery cell 2a that has not deteriorated so much, and as a result, it is possible to maintain a large discharge capacity of the battery pack 2 for a long period of time.

  For example, the temperature of the battery pack 2 increases immediately after discharging, whereas the temperature of the battery pack 2 decreases when left in a cold environment for a long time. For this reason, the initial temperature is significantly different between when charging is started immediately after discharging and when charging is started after being left in a cold environment for a long time. If the initial temperature differs greatly, the temperature change during charging also changes. In the present embodiment, the predetermined values b and c in steps 212 and 213 are set so as to change according to the initial temperature. For this reason, it is possible to appropriately determine the deterioration degree of the battery cell 2a regardless of the initial temperature.

  The charging device according to the present invention is not limited to the above-described embodiment, and various modifications and improvements can be made within the scope described in the claims.

  In the above embodiment, the battery cell charging voltage is set from three types (V1, V2, V3) for the same type of battery cell 2a. As long as it is set.

  The charging current is also set from three types (I1, I2, and I3) with respect to the type of the battery cell 2a. However, the charging current is not limited to three types and may be set from a plurality of types.

  Further, the temperature gradient is calculated based on the initial temperature and the temperature of the battery cell 2a after a predetermined time has elapsed, but the timing for acquiring the temperature when calculating the temperature gradient is not limited to the above. For example, the temperature gradient is obtained by dividing the difference between the initial temperature and the temperature of the battery cell 2a at the timing when the battery voltage reaches a predetermined value by the time interval from the start of charging to the timing when the battery voltage reaches the predetermined value. You may ask for. If the time interval for measuring the temperature is always constant, the difference between the two temperatures may be used as the temperature gradient (without dividing the difference between the two temperatures by the time interval).

  In the above embodiment, the battery voltage is set by determining the deterioration degree of the battery based on the temperature gradient. However, for example, the rate of voltage increase with respect to time (hereinafter referred to as voltage gradient) is used instead of the temperature gradient. The battery voltage may be set by judging the deterioration of the battery. As shown in FIGS. 2 (d), 2 (e), and 2 (f), as the battery cell 2a deteriorates, the battery voltage rises faster. For example, the voltage gradient from the start of charging to after the elapse of a predetermined period increases in the order of FIGS. 2 (d), 2 (e), and 2 (f). Accordingly, the battery cell voltage is set to V1 when the voltage gradient is less than the first value, and the battery cell voltage is set to V2 when the voltage gradient is greater than or equal to the first value and less than the second value greater than the first value. The battery cell voltage V3 may be set when the voltage gradient is equal to or greater than the second value. That is, the initial voltage value is detected in step 207, the voltage gradient is compared with a predetermined value in steps 212 and 213, and the charging voltage is set in accordance with the result in steps 214 and 215. Further, the threshold value of the voltage gradient may be changed according to the initial voltage value.

  In steps 214 and 215, the charging voltage is changed from V1 to V2 and V3, respectively, but the charging current may be changed from I1 to a value lower than I1. In this case, it is preferable that the current value set in step 214 is larger than the current value set in step 215. Alternatively, in steps 214 and 215, only the charging current may be changed without changing the charging voltage. In any case, it is possible to prevent the battery cell 2a having deteriorated from being charged as rapidly as possible, so that it is possible to avoid overcharging the battery cell 2a.

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

Claims (8)

Obtaining means for obtaining state information indicating a state of the secondary battery;
Setting means for setting a charging condition in accordance with a time change of the state information;
Charging control means for charging the secondary battery under the charging conditions,
The state information includes information on the temperature of the secondary battery,
The charging condition is a charging voltage of the secondary battery,
The setting means sets the charging voltage to a first voltage if the rate of increase of the temperature of the secondary battery with respect to time is less than a threshold, and the rate of increase of the temperature of the secondary battery with respect to time is a threshold. If so, the charging voltage is set to a second voltage lower than the first voltage,
The charging device is characterized in that charging is performed such that a voltage value of the secondary battery becomes the charging voltage. The charging condition is a charging current of the secondary battery,
The setting means sets the charging current to a first current value when the rate of increase of the temperature of the secondary battery with respect to time is less than a threshold, and the rate of increase of the temperature of the secondary battery with respect to time is If it is greater than or equal to the threshold, the charging current is set to a second current value lower than the first current value,
The charging device according to claim 1, wherein the charging control unit charges the secondary battery with the charging current.   The charging device according to claim 1, wherein the setting unit changes the threshold according to an initial temperature of the secondary battery. Obtaining means for obtaining state information indicating a state of the secondary battery;
Setting means for setting a charging condition in accordance with a time change of the state information;
Charging control means for charging the secondary battery under the charging conditions,
The state information includes information on the voltage of the secondary battery,
The charging condition is a charging voltage of the secondary battery,
The setting means sets the charging voltage to a first voltage if the rate of increase of the voltage of the secondary battery with respect to time is less than a threshold, and the rate of increase of the voltage of the secondary battery with respect to time is a threshold. If so, the charging voltage is set to a second voltage lower than the first voltage,
The charging device is characterized in that charging is performed such that a voltage value of the secondary battery becomes the charging voltage. The charging condition is a charging current of the secondary battery,
The setting means sets the charging current to a first current value if an increase rate of the voltage of the secondary battery with respect to time is less than a threshold, and an increase rate of the voltage of the secondary battery with respect to time is If it is greater than or equal to the threshold, the charging current is set to a second current value lower than the first current value,
The charging device according to claim 4, wherein the charging control unit charges the secondary battery with the charging current.   The charging device according to claim 4, wherein the setting unit changes the threshold according to an initial voltage of the secondary battery. Obtaining means for obtaining state information indicating a state of the secondary battery;
Setting means for setting charging conditions according to the state information;
Charging control means for charging the secondary battery under the charging conditions,
The state information includes information on the temperature of the secondary battery before starting charging,
The charging condition is a charging voltage of the secondary battery,
The said setting means sets the threshold value for changing the said charging voltage larger when the said temperature before charge start is low than when the said temperature is high, The charging device characterized by the above-mentioned. Obtaining means for obtaining state information indicating a state of the secondary battery;
Setting means for setting charging conditions according to the state information;
Charging control means for charging the secondary battery under the charging conditions,
The state information includes information on the voltage of the secondary battery before the start of charging,
The charging condition is a charging voltage of the secondary battery,
The said setting means sets the threshold value for changing the said charging voltage larger when the said voltage before the charge start is low than when the said voltage is high, The charging device characterized by the above-mentioned.

Images