JP2009043554A - Battery pack, charging device, and charging system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery pack, a charging device and a charging system, capable of reducing a possibility of deterioration when a secondary battery is charged at a temperature unsuitable for charging regardless of if the temperature of the secondary battery is a low temperature or a high one. <P>SOLUTION: This is equipped with the charging device 3 to output a charging current in order to charge a battery pack 14 including the secondary batteries 141, 142, 143, a temperature sensor 17 to detect the temperature of the battery pack 14, and a charging voltage control part 212 in which in the case the temperature of the secondary battery detected by the temperature sensor 17 is outside a range of 10°C to 45°C previously set as the temperature suitable for charging of the secondary battery, the charging voltage of the secondary batteries 141, 142, 143 based on an output current of the charging device 3 is reduced lower than a first voltage previously set as the voltage at every cell for the purpose of constant voltage charging. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a battery pack provided with a secondary battery, a charging device for charging the secondary battery, and a charging system using the secondary battery.

  Conventionally, as a charging method for charging a secondary battery such as a lithium ion secondary battery or a nickel hydride secondary battery, a constant current (CC) is charged by supplying a constant current to the secondary battery at the initial stage of charging. When charging is performed and the terminal voltage of the secondary battery reaches a predetermined end voltage, a constant voltage (CV) for charging the secondary battery by applying a constant charging voltage equal to the terminal voltage when the secondary battery is fully charged. ) Constant current constant voltage (CCCV) charging is known.

  In CCCV charging, constant current (CC) charging is performed at the beginning of charging when the output voltage of the secondary battery is low, thereby preventing an excessive charging current from flowing into the secondary battery and degrading the secondary battery. . And after charging progresses and the output voltage of the secondary battery rises to some extent, by performing constant voltage (CV) charging, the charging current gradually decreases as the output voltage increases with the charging of the secondary battery. It is easy to avoid overcharging. In such CCCV charging, when the charging current decreases below a predetermined charging end current value, it is determined that the secondary battery is fully charged and charging is terminated.

  By the way, it is known that the degree of deterioration of the secondary battery varies depending on the temperature at the time of charging. For example, in the case of a lithium ion secondary battery, the charge acceptability of the lithium ion of the negative electrode is lowered in a low temperature environment. That is, in a lithium ion secondary battery, in a low temperature environment, metallic lithium is deposited on the surface of the negative electrode, and the deposited metallic lithium reacts with an electrolytic solution or the like to form an insulator. If it does so, there exists a property that the internal resistance of a lithium ion secondary battery will increase by the insulator formed in this way, and charge acceptance property will fall. And if a lithium ion secondary battery is charged in the state in which such charge acceptability fell, deterioration of a lithium ion secondary battery will be accelerated.

  On the other hand, when a lithium ion secondary battery is charged at a high temperature, the dissolution reaction of the positive electrode active material inside the battery and the decomposition reaction of the electrolyte solution are accelerated, and therefore, the battery tends to deteriorate as the battery temperature rises. There is.

Therefore, a technique for reducing deterioration of a secondary battery by overheating the secondary battery using a heater at a low temperature and charging the secondary battery by raising the temperature of the secondary battery is known (see, for example, Patent Document 1). .) In addition, before performing constant current charging in CCCV charging, the charging current value is lowered at low temperatures, and the charging current value for the battery is gradually increased as the battery temperature rises due to self-heating of the battery by energizing the battery. A technique for reducing deterioration of a secondary battery by increasing the number is known (for example, see Patent Document 2).
Japanese Patent Laid-Open No. 10-284133 JP-A-11-341698

  However, the technique described in Patent Document 1 has a disadvantage in that a heater for heating the secondary battery is required, resulting in an increase in cost and deterioration of the secondary battery at a high temperature. Further, in the technique described in Patent Document 2, although a heater is not required, the temperature of the secondary battery is increased by the self-heating of the secondary battery, and the charging current value is increased as the temperature increases. When the battery is at a high temperature, the charging current is increased to accelerate the deterioration of the secondary battery.

  The present invention has been made in view of such circumstances, and the secondary battery is charged at a temperature not suitable for charging regardless of whether the temperature of the secondary battery is low or high. An object of the present invention is to provide a battery pack, a charging device, and a charging system that can reduce the risk of deterioration due to the above.

  The battery pack according to the present invention includes a secondary battery, a connection terminal for receiving the output charging current from a charging unit that outputs a charging current for charging the secondary battery, and the secondary battery. A temperature detection unit that detects the temperature of the secondary battery, and a temperature of the secondary battery detected by the temperature detection unit is a second temperature different from a first temperature preset as a temperature suitable for charging the secondary battery. In some cases, a charging voltage controller that lowers the charging voltage of the secondary battery based on the current received by the connection terminal from a first voltage preset as a voltage for charging the secondary battery at a constant voltage; Is provided.

  According to this configuration, when the temperature of the secondary battery is a second temperature different from the first temperature set in advance as a temperature suitable for charging the secondary battery, the charging voltage controller controls the secondary battery. The charging voltage is lowered from a first voltage set in advance as a voltage for charging the secondary battery at a constant voltage. Therefore, at a temperature that is not suitable for charging, deterioration of the secondary battery is reduced by lowering the charging voltage. Therefore, regardless of whether the temperature of the secondary battery is low or high, The possibility of deterioration due to charging can be reduced.

  The switching device further includes a switching element that turns on and off a charging current flowing from the connection terminal to the secondary battery, and a voltage detection unit that detects a terminal voltage of the secondary battery, and the charging voltage control unit includes the temperature When the temperature of the secondary battery detected by the detection unit is the first temperature, the switching element is turned on, and the temperature of the secondary battery detected by the temperature detection unit is the second temperature The switching element is turned off when the terminal voltage of the secondary battery detected by the voltage detector exceeds a second voltage lower than the first voltage, and the detected terminal voltage of the secondary battery is the first voltage. It is preferable to turn on the switching element when the voltage is lower than two voltages.

  According to this configuration, when the temperature of the secondary battery detected by the temperature detection unit is the first temperature suitable for charging the secondary battery, the switching element is turned on by the charging voltage control unit, and the connection terminal The secondary battery is charged with the received voltage. In addition, when the temperature of the secondary battery is a second temperature different from the first temperature, the switching voltage is controlled by the charging voltage control unit when the terminal voltage of the secondary battery exceeds the second voltage lower than the first voltage. Is turned off to decrease the terminal voltage, and when the terminal voltage of the secondary battery is lower than the second voltage, the switching element is turned on by the charging voltage control unit to increase the terminal voltage. Therefore, when the temperature of the secondary battery is the second temperature, the charging voltage of the secondary battery can be lowered to a second voltage that is approximately lower than the first voltage while increasing or decreasing.

  The charging voltage control unit may detect the secondary voltage detected by the voltage detection unit even when the switching element is turned off when the temperature of the secondary battery detected by the temperature detection unit is the second temperature. When the terminal voltage of the battery becomes equal to or higher than the second voltage, it is preferable to end the charging of the secondary battery.

  According to this configuration, when the temperature of the secondary battery detected by the temperature detection unit is the second temperature, the terminal voltage of the secondary battery when the switching element is turned off and the charging current becomes zero, that is, When the open circuit voltage (OCV) becomes equal to or higher than the second voltage, the charging voltage control unit ends the charging of the secondary battery. According to this, when the temperature of the secondary battery is the second temperature, when the open circuit voltage (OCV) of the secondary battery becomes a second voltage lower than the first voltage which is a charging voltage in constant voltage charging. Since charging can be terminated, deterioration of the secondary battery can be reduced.

  The charging voltage control unit may be configured such that when the temperature of the secondary battery detected by the temperature detection unit is the first temperature, the terminal voltage of the secondary battery detected by the voltage detection unit is the first voltage. Preferably, the switching element is turned off when a third voltage higher than the voltage is exceeded, and the switching element is turned on when the detected terminal voltage of the secondary battery is equal to or lower than the first voltage.

  According to this configuration, when the temperature of the secondary battery detected by the temperature detection unit is the first temperature, when the terminal voltage of the secondary battery exceeds the third voltage higher than the first voltage, the charging voltage When the switching unit is turned off by the control unit and the terminal voltage decreases, and when the terminal voltage of the secondary battery is equal to or lower than the first voltage, the switching element is turned on by the charging voltage control unit and the terminal voltage increases. In this case, since the charging voltage of the secondary battery can be suppressed so as not to exceed the third voltage on the battery pack side regardless of the output voltage of the charging unit, the deterioration of the secondary battery can be reduced. .

  The charging voltage control unit may detect the secondary voltage detected by the voltage detection unit even when the switching element is turned off when the temperature of the secondary battery detected by the temperature detection unit is the first temperature. When the terminal voltage of the battery exceeds the first voltage, it is preferable to end the charging of the secondary battery.

  According to this configuration, when the temperature of the secondary battery is the first temperature, the terminal voltage of the secondary battery when the switching element is turned off and the charging current becomes zero, that is, the open circuit voltage (OCV) is the first. When the voltage exceeds 1, the charging voltage control unit ends the charging of the secondary battery. If the open circuit voltage (OCV) of the secondary battery exceeds the first voltage, it is considered that the secondary battery is fully charged, so that the charging of the secondary battery is terminated by the charging voltage control unit. This reduces the risk that the secondary battery will be overcharged.

  In addition, the battery pack further includes a voltage detection unit that detects a terminal voltage of the secondary battery, and the charging unit adjusts a supply current to the secondary battery according to an instruction from the charging voltage control unit, When the temperature of the secondary battery detected by the temperature detection unit is the second temperature, the charging voltage control unit is configured such that the terminal voltage of the secondary battery detected by the voltage detection unit is the first voltage. When the lower second voltage is exceeded, an instruction to reduce the supply current by the charging unit may be performed so that the detected terminal voltage of the secondary battery is equal to or lower than the second voltage.

  According to this configuration, when the temperature of the secondary battery detected by the temperature detection unit is the second temperature, charging is performed when the terminal voltage of the secondary battery exceeds the second voltage lower than the first voltage. The voltage control unit gives an instruction to reduce the supply current by the charging unit so that the terminal voltage of the secondary battery becomes equal to or lower than the second voltage. As a result, when the temperature of the secondary battery is the second temperature, the charging voltage of the secondary battery can be lowered to the second voltage lower than the first voltage by the charging unit.

  The charging voltage control unit further includes a current detection unit configured to detect a charging current of the secondary battery, and the charging current detected by the current detection unit is set in advance as a current value at which the constant voltage charging is to be terminated. When the charging end current value is less than or equal to the set charging end current value, it is preferable to terminate the charging of the secondary battery by giving an instruction to stop the current supply by the charging unit.

  According to this configuration, when the charging current of the secondary battery becomes equal to or lower than the charging end current value set in advance as the current value at which constant voltage charging should be terminated, the charging voltage control unit supplies current by the charging unit. As a result of the instruction to stop, the charging of the secondary battery by the charging unit can be terminated.

  Further, the charging unit adjusts an output voltage according to an instruction from the charging voltage control unit, and the charging voltage control unit is configured such that the temperature of the secondary battery detected by the temperature detection unit is When the temperature is the first temperature, the charging unit supplies the first voltage to the secondary battery to perform constant voltage charging, and the temperature of the secondary battery detected by the temperature detection unit is the second temperature. In some cases, constant voltage charging may be performed by causing the charging unit to supply a second voltage lower than the first voltage to the secondary battery.

  According to this configuration, when the temperature of the secondary battery is the first temperature suitable for charging, the supply voltage to the secondary battery by the charging unit is set to the first voltage by the charging voltage control unit. Further, when the temperature of the secondary battery is a second temperature different from the first temperature, the supply voltage to the secondary battery by the charging unit is set to a second voltage lower than the first voltage by the charging voltage control unit. Thereby, when the temperature of a secondary battery is 2nd temperature, the charging voltage of a secondary battery can be reduced to 2nd voltage lower than 1st voltage.

  Further, the secondary battery is an assembled battery in which a plurality of secondary batteries are connected in series, and the first voltage is set as a charging voltage per secondary battery in the constant voltage charging, The voltage detection unit detects terminal voltages of the plurality of secondary batteries, and the charging voltage control unit calculates a maximum voltage among the terminal voltages of the plurality of secondary batteries detected by the voltage detection unit. The terminal voltage of the secondary battery detected by the voltage detector is preferably used.

  According to this configuration, the terminal voltage of the plurality of secondary batteries connected in series is detected by the voltage detector. The charging voltage control unit uses the maximum voltage among the terminal voltages of the plurality of secondary batteries as the terminal voltage of the secondary battery detected by the voltage detection unit, so that the temperature of the secondary battery is the second voltage. In the case of temperature, the maximum voltage among the charging voltages in the plurality of secondary batteries can be reduced to a second voltage that is lower than the first voltage. Therefore, even if there is a difference in the terminal voltage of each secondary battery, it is possible to reduce the deterioration of all the secondary batteries.

  The charging device according to the present invention includes a connection terminal for connecting a secondary battery, a charging unit that outputs a charging current for charging the secondary battery, and a temperature for detecting the temperature of the secondary battery. When the temperature of the secondary battery detected by the detection unit and the temperature detection unit is a second temperature different from the first temperature preset as a temperature suitable for charging the secondary battery, the charging unit A charging voltage control unit that lowers the charging voltage of the secondary battery based on the charging current output from the first voltage preset as a voltage for charging the secondary battery at a constant voltage.

  The charging system according to the present invention includes a secondary battery, a charging unit that outputs a charging current for charging the secondary battery, a temperature detection unit that detects a temperature of the secondary battery, and the temperature detection. When the temperature of the secondary battery detected by the charging unit is a second temperature different from the first temperature preset as a temperature suitable for charging the secondary battery, the charging current output by the charging unit is A charging voltage control unit configured to lower a charging voltage of the secondary battery based on a first voltage preset as a voltage for charging the secondary battery at a constant voltage.

  According to this configuration, since the deterioration of the secondary battery is reduced by lowering the charging voltage at a temperature not suitable for charging, regardless of whether the temperature of the secondary battery is low or high, The possibility that the secondary battery is deteriorated by being charged can be reduced.

  In the battery pack, the charging device, and the charging system having such a configuration, since the deterioration of the secondary battery is reduced by reducing the charging voltage at a temperature that is not suitable for charging, the temperature of the secondary battery is low. Regardless of whether there is a high temperature or not, it is possible to reduce the possibility that the secondary battery is deteriorated by being charged.

  Embodiments according to the present invention will be described below with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted.

(First embodiment)
FIG. 1 is a block diagram illustrating an example of a configuration of a charging system including a battery pack according to the first embodiment of the present invention. The charging system 1 shown in FIG. 1 is configured by connecting a battery pack 2 and a charging device 3 (charging unit). The charging system 1 may be configured as an electronic device system that further includes a load device (not shown) that receives power from the battery pack 2. In that case, although the battery pack 2 is charged from the charging device 3 in FIG. 1, the battery pack 2 may be attached to the load device and charged through the load device.

  The battery pack 2 includes connection terminals 11 and 12, an assembled battery 14, a voltage detection circuit 15 (voltage detection unit), a current detection resistor 16 (current detection unit), a temperature sensor 17 (temperature detection unit), a control IC 18, and a switching element. Q1 and Q2 are provided. The control IC 18 includes an analog / digital (A / D) converter 201 and a control unit 202.

  The connection terminal 11 is connected to the positive electrode of the battery pack 14 via a switching element Q1 for charging and a switching element Q2 for discharging. As the switching elements Q1 and Q2, for example, FET (Field Effect Transistor) is used. The switching element Q1 has a parasitic diode cathode in the direction of the connection terminal 11, and the switching element Q2 has a parasitic diode cathode in the direction of the assembled battery 14.

  The connection terminal 12 is connected to the negative electrode of the assembled battery 14 via the current detection resistor 16, and the connection terminal 12 is connected from the connection terminal 11 via the switching elements Q 1 and Q 2, the assembled battery 14, and the current detection resistor 16. The charge / discharge path leading to is configured. The negative electrode of the assembled battery 14 is a circuit ground.

  The current detection resistor 16 converts the charging current and discharging current of the assembled battery 14 into voltage values. The assembled battery 14 is an assembled battery in which a plurality of, for example, three secondary batteries 141, 142, and 143 are connected in series. The secondary batteries 141, 142, and 143 are secondary batteries such as a lithium ion secondary battery and a nickel hydride secondary battery.

  The assembled battery 14 is not limited to a plurality of secondary batteries connected in series. For example, a plurality of secondary batteries may be connected in parallel, or a combination of series and parallel may be connected. Good. A single secondary battery may be used instead of the assembled battery 14.

  The temperature sensor 17 is a temperature sensor that detects the temperature of the assembled battery 14. Then, the temperature of the assembled battery 14 detected by the temperature sensor 17 is input to the analog / digital converter 201. The terminal voltage Vt of the assembled battery 14 and the terminal voltages V1, V2, and V3 of the secondary batteries 141, 142, and 143 are detected by the voltage detection circuit 15 and input to the analog-digital converter 201. Furthermore, the current value of the charge / discharge current Ic detected by the current detection resistor 16 is also input to the analog-digital converter 201. The analog-digital converter 201 converts each input value into a digital value and outputs the digital value to the control unit 202.

  The control unit 202 includes, for example, a CPU (Central Processing Unit) that executes predetermined arithmetic processing, a ROM (Read Only Memory) that stores a predetermined control program, and a RAM (Random Access Memory) that temporarily stores data. And these peripheral circuits and the like. The control unit 202 functions as a charge / discharge control unit 211 and a charge voltage control unit 212 by executing a control program stored in the ROM.

  The charge / discharge control unit 211 is configured such that, from each input value from the analog-digital converter 201, a short circuit between the connection terminals 11 and 12, an abnormal current from an unillustrated load device body connected to the connection terminals 11 and 12, etc. Abnormalities such as an abnormality outside the battery pack 2, an abnormal temperature rise of the assembled battery 14, and overcharging of the assembled battery 14 are detected. Specifically, for example, when the current value detected by the current detection resistor 16 exceeds a preset abnormal current determination threshold value, the charge / discharge control unit 211 short-circuits between the connection terminals 11 and 12 or an unillustrated load. It is determined that an abnormality based on the abnormal current from the device body has occurred.

  Further, for example, when the temperature of the assembled battery 14 detected by the temperature sensor 17 exceeds a preset abnormal temperature determination threshold, the charge / discharge control unit 211 determines that an abnormality has occurred in the assembled battery 14. When such an abnormality is detected, the charge / discharge control unit 211 turns off the switching elements Q1 and Q2, and performs a protective operation for protecting the assembled battery 14 from abnormalities such as overcurrent and overheating.

  Further, when the terminal voltages V1, V2, V3 detected by the voltage detection circuit 15 exceed a preset overcharge detection voltage, the charge / discharge control unit 211 determines that overcharge has occurred, and switches the switching element Q1. The protection operation which protects the assembled battery 14 from an overcharge by turning off is performed.

  In addition, the charge / discharge control unit 211 prevents any of the terminal voltages V1, V2, and V3 of the secondary batteries 141, 142, and 143 detected by the voltage detection circuit 15, for example, from preventing overdischarge of the secondary battery. When the voltage is lower than the preset discharge inhibition voltage, the switching element Q2 is turned off to prevent the secondary batteries 141, 142, 143 from being deteriorated due to overdischarge.

  The charging voltage control unit 212 is configured such that the temperature of the assembled battery 14 detected by the temperature sensor 17 is a first temperature set in advance as a temperature suitable for charging the secondary batteries 141, 142, 143, for example, 10 ° C. or higher, 45 When it is in the temperature range of 10 ° C. or lower (10 ° C. to 45 ° C.), the switching elements Q1 and Q2 are turned on. Further, the charging voltage control unit 212 is configured such that the temperature of the assembled battery 14 detected by the temperature sensor 17 is a second temperature different from the first temperature, for example, less than 10 ° C. or exceeds 45 ° C. When the maximum voltage among the terminal voltages V1, V2, and V3 detected by the voltage detection circuit 15 exceeds the voltage Vc2 (second voltage) lower than the preset voltage Vc1 (first voltage), the switching element Q1 is turned off, and the switching element Q1 is turned on when the maximum voltage among the terminal voltages V1, V2, and V3 is lower than the voltage Vc2.

  The voltage Vc1 is the upper limit value of the charging voltage per cell in the secondary batteries 141, 142, 143, and is, for example, the charging end voltage per cell at which the charging device 3 ends constant current charging and starts constant voltage charging. In addition, the charging voltage per cell for constant voltage charging in the charging device 3. In the case of a lithium ion secondary battery, the voltage Vc1 (first voltage) is, for example, a potential difference between the positive electrode potential and the negative electrode potential (for example, positive electrode potential) when the negative electrode potential of the lithium ion secondary battery is substantially 0V. When lithium cobaltate is used as the active material, about 4.2 V is set, and when lithium manganate is used as the positive electrode active material, about 4.3 V) is set.

  Note that “the negative electrode potential is substantially 0 V” means that 0 V includes a range of environmental conditions such as the temperature of the secondary batteries 141, 142, and 143, variations in manufacturing characteristics, measurement errors, and the like. For example, it is assumed that the negative electrode potential is in the range of 0V ± 0.1V.

  Further, when the temperature of the assembled battery 14 detected by the temperature sensor 17 is the second temperature, for example, when the temperature of the assembled battery 14 is less than 10 ° C. or exceeds 45 ° C., the charging voltage control unit 212 switches the switching element Q1. When the maximum voltage among the terminal voltages V1, V2, and V3 detected by the voltage detection circuit 15 does not fall below the voltage Vc2 even when the voltage detection circuit 15 is turned off, the switching element Q1 is turned off and the charging of the assembled battery 14 is terminated.

  Further, the charging voltage control unit 212 is a terminal detected by the voltage detection circuit 15 when the temperature of the assembled battery 14 detected by the temperature sensor 17 is the first temperature (for example, a temperature range of 10 ° C. to 45 ° C.). When the maximum value among the voltages V1, V2, and V3 exceeds the voltage Vc3 (for example, 4.22V) which is the third voltage higher than the voltage Vc1 (for example, 4.2V), the switching element Q1 is turned off and the detection is performed. The switching element Q1 is turned on when the maximum value of the terminal voltages V1, V2, and V3 to be applied is equal to or lower than the voltage Vc1 (for example, 4.2 V).

  The charging voltage control unit 212 is configured such that the temperature of the assembled battery 14 detected by the temperature sensor 17 is the first temperature (for example, a temperature range of 10 ° C. to 45 ° C.). In some cases, when the maximum value of the terminal voltages V1, V2, and V3 detected by the voltage detection circuit 15 does not become equal to or lower than the voltage Vc1 (for example, 4.2 V) even when the switching element Q1 is turned off, the switching element Q1 is turned on. It turns off and the charge of the assembled battery 14 is complete | finished.

  The charging device 3 includes connection terminals 31 and 32. Further, when the battery pack 2 is attached to the charging device 3, the connection terminals 31 and 32 and the connection terminals 11 and 12 are connected. The charging device 3 supplies a charging current and a charging voltage for charging the assembled battery 14 to the battery pack 2 via the connection terminals 31 and 32 and the connection terminals 11 and 12, so-called constant current constant. Voltage (CCCV) charging is performed.

  Specifically, the charging device 3 performs constant current charging by supplying a charging current Ic having a current value Icc from the connection terminals 31 and 32 to the battery pack 2, and the voltage Vout between the connection terminals 31 and 32 is When the reference voltage Ve1 set in advance is reached, the reference voltage Ve1 is applied as a charging voltage between the connection terminals 31 and 32 to switch to constant voltage charging for charging the assembled battery 14. Furthermore, when the charging current Ic flowing through the assembled battery 14 becomes equal to or less than the charging end current value Ia, the charging device 3 determines that the assembled battery 14 is fully charged and ends the charging.

  FIG. 2 is a block diagram showing an example of the configuration of the charging device 3 shown in FIG. The charging device 3 shown in FIG. 2 includes connection terminals 31 and 32, a DC power supply circuit 35, a DC-DC converter 36, a charge control unit 37, error amplifiers 38, 39, and 40, reference voltage sources 41, 42, and 43, and a current. A detection resistor RS is provided. The reference voltage sources 41, 42, and 43 are constant voltage circuits that output preset reference voltages Ve1, Ve2, and Ve3.

  The DC power supply circuit 35 converts, for example, a commercial AC power supply voltage into a DC voltage and outputs it. The high-potential side output terminal of the DC power supply circuit 35 is connected to the connection terminal 31 via the switching element Q4 and the coil L1, the low-potential side output terminal is connected to the ground, and via the current detection resistor RS. It is connected to the connection terminal 32.

  The DC-DC converter 36 includes, for example, an FET switching element Q4, a coil L1, a diode D1, a capacitor C1, and a PWM (Pulse Width Modulation) signal generation circuit 361. The connection point between the switching element Q4 and the coil L1 is connected to the cathode of the diode D1, and the anode of the diode D1 is connected to the ground. A capacitor C1 is connected in parallel with the series circuit of the diode D1 and the coil L1. The PWM signal generation circuit 361 outputs a PWM control signal whose pulse width is changed according to the control signal from the charge control unit 37 to the gate of the switching element Q4 to turn on and off the switching element Q4. A direct current and a direct voltage corresponding to a control signal from the charge control unit 37 are generated and supplied to the battery pack 2 via the connection terminals 31 and 32.

  The charge control unit 37 is configured using, for example, a sequential circuit, a logic circuit, an oscillation circuit, or the like. Then, as will be described later, the charging control unit 37 outputs the control signal to the PWM signal generation circuit 361 according to the output signals of the error amplifiers 39 and 40, thereby connecting the connection terminals 31 and 32 from the DC-DC converter 36. For example, CCCV (constant current constant voltage) charging is performed by controlling a charging voltage and a charging current output to the battery pack 2 via the charging voltage.

  The error amplifier 40 compares the voltage across the current detection resistor RS with the reference voltage Ve2 output from the reference voltage source 42. If the voltage across the current detection resistor RS is equal to or lower than the reference voltage Ve2, the error amplifier 40 detects a low level current detection. If the voltage across the resistor RS exceeds the reference voltage Ve2, a high level signal is output to the charge control unit 37.

  The reference voltage Ve2 is set to a voltage generated at both ends of the current detection resistor RS when a current having a current value Icc (set current) set as a charging current Ic for constant current charging flows through the current detection resistor RS. .

  Then, if the output voltage of the error amplifier 39 is at a low level, the charge control unit 37 outputs a control signal to the PWM signal generation circuit 361 to increase the output current of the DC-DC converter 36, while the error amplifier 39 If the output voltage is at a high level, a control signal is output to the PWM signal generation circuit 361 to reduce the output current of the DC-DC converter 36, thereby making the charging current Ic supplied to the battery pack 2 constant at the current value Icc. To perform constant current charging.

  The current value Icc is, for example, a level at which the nominal capacity value NC per cell of the secondary batteries 141, 142, 143 is discharged at a constant current and can be discharged in one hour is 1 It (= 1C = battery capacity (Ah) / 1 ( h)), the current value obtained by multiplying 70% by the number of parallel cells PN (for example, NC = 2000 mAh, and when two are in parallel, 70% is set to 2800 mA).

  The error amplifier 39 compares the voltage Vout between the connection terminals 31 and 32 supplied to the battery pack 2 with the reference voltage Ve1 output from the reference voltage source 41. If the voltage Vout is equal to or lower than the reference voltage Ve1, the error amplifier 39 is low. When the level and voltage Vout exceed the reference voltage Ve1, a high level signal is output to the charge control unit 37. The reference voltage Ve1 is set in advance as, for example, a charging end voltage (charging voltage for constant voltage charging) that ends constant current charging, and is an upper limit value of the charging voltage. As the reference voltage Ve1, a voltage (for example, 12.6 V) obtained by multiplying the voltage Vc1 (for example, 4.2 V) by the number of series cells 3 is set in advance.

  Then, when the output voltage of the error amplifier 39 becomes high level during constant current charging, the charging control unit 37 shifts to constant voltage charging. When the charging control unit 37 shifts to constant voltage charging, if the output voltage of the error amplifier 39 is low level, the charging control unit 37 outputs a control signal to the PWM signal generation circuit 361 to increase the output current of the DC-DC converter 36. On the other hand, if the output voltage of the error amplifier 39 is at a high level, the charge control unit 37 outputs a control signal to the PWM signal generation circuit 361 to reduce the output current of the DC-DC converter 36, thereby outputting the output voltage Vout. Is controlled to be constant at the reference voltage Ve1, and constant voltage charging is executed.

  The error amplifier 38 compares the voltage across the current detection resistor RS with the reference voltage Ve3 output from the reference voltage source 43. If the voltage across the current detection resistor RS is equal to or lower than the reference voltage Ve3, the error amplifier 38 detects the low level. If the voltage across the resistor RS exceeds the reference voltage Ve3, a high level signal is output to the charge control unit 37.

  The reference voltage Ve3 is set to a voltage generated at both ends of the current detection resistor RS when a current having a charge end current value Ia set in advance as a current value at which the charging of the battery pack 2 should be terminated flows through the current detection resistor RS. ing. Then, when the output voltage of the error amplifier 39 is maintained at a low level for a preset monitoring time tw, the charging control unit 37 determines that the assembled battery 14 is fully charged, and the PWM signal generation circuit 361. To output the control signal to turn off the switching element Q4, thereby terminating the charging of the battery pack 2. The charge termination current value Ia is set to 0.05 It, for example.

  Note that the charging system 1 is not necessarily limited to one configured to be separable into the battery pack 2 and the charging device 3, and the charging system 1 as a whole may be configured as one circuit. Further, the charging device 3 may be configured by including components other than the assembled battery 14 in the battery pack 2 in the charging device 3, and the components other than the assembled battery 14 in the battery pack 2 are shared by the battery pack and the charging device. It may be configured to be provided. Further, the battery pack 14 may be charged while supplying a load current to a load circuit (not shown).

  Next, the operation of the charging system 1 configured as described above will be described. 3 and 4 are flowcharts showing an example of the operation of the battery pack 2 shown in FIG. In the following flowchart, the same operation is given the same step number, and the description thereof is omitted. 5-8 is explanatory drawing for demonstrating operation | movement of the charging system 1 shown in FIG. Hereinafter, the first temperature is in the range of 10 ° C. to 45 ° C., the second temperature is in the range of less than 10 ° C., and the range is over 45 ° C., the voltage Vc1 (first voltage) is 4.2V, and the voltage Vc2 (second voltage) is The case of 4.15V will be described as an example.

  First, the charging device 3 starts constant current charging and outputs a charging current Ic having a current value Icc (timing T1). Moreover, the switching elements Q1 and Q2 are turned on by the charge / discharge control unit 211 (step S1).

  Then, the assembled battery 14 is charged, and the terminal voltages V1, V2, and V3 of the secondary batteries 141, 142, and 143 gradually increase. At this time, if the secondary batteries 141, 142, 143 have characteristic variations due to, for example, different degrees of deterioration of the secondary batteries 141, 142, 143, there is a difference between the terminal voltages V1, V2, V3. Arise. 5, 6, and 7 show examples in which the voltages are higher in the order of terminal voltages V3, V2, and V1.

  Next, whether or not the temperature t of the assembled battery 14 detected by the voltage detection circuit 15 by the charging voltage control unit 212 is within the range of 10 ° C. to 45 ° C., that is, the temperature at which the assembled battery 14 is suitable for charging. Is confirmed (step S2). If the temperature t is in the range of 10 ° C. to 45 ° C. (YES in step S2), the process proceeds to step S3 to charge the assembled battery 14 with a standard charging voltage (eg, 4.20 V per cell). .

  FIG. 5 is an explanatory diagram showing an example of the operation of the charging system 1 when charging is performed at a standard charging voltage after step S3. In step S3, the charging voltage control unit 212 compares the voltage Vmax, which is the maximum voltage value among the terminal voltages V1, V2, and V3 detected by the voltage detection circuit 15, with 4.22 V (step S3). Here, the comparison voltage is, for example, a voltage obtained by adding 0.02 V to 4.20 V, and a hysteresis voltage of 0.02 V is provided between the voltage at which the switching element Q1 is turned on and the voltage at which it is turned off. Yes. Although it is not always necessary to provide the hysteresis voltage, the operation can be stabilized by providing the hysteresis.

  Hereinafter, the maximum value among the terminal voltages V1, V2, and V3 detected by the voltage detection circuit 15 is referred to as a voltage Vmax.

  If voltage Vmax is 4.22 V or less (NO in step S3), the process proceeds to step S2 again. On the other hand, if voltage Vmax exceeds 4.22 V (YES in step S3), switching element Q1 is turned off by charging voltage control unit 212 (step S4, timing T2).

  Then, the charging current Ic becomes zero, and the terminal voltages V1, V2, and V3 become the open circuit voltage (OCV). As a result of the elimination of the voltage drop caused by the charging current Ic flowing through the internal resistances of the secondary batteries 141, 142, 143, the terminal voltages V1, V2, V3 are lowered.

  Next, the charging voltage control unit 212 compares the voltage Vmax with 4.20 V (step S5). If voltage Vmax is 4.20 V or less (YES in step S5), the process proceeds to step S1 again to turn on switching element Q1 (step S1, timing T3). When the switching element Q1 is turned on, the secondary batteries 141, 142, and 143 are charged, and the total voltage of the terminal voltages V1, V2, and V3, that is, the terminal voltage Vt of the assembled battery 14 is 12.6V (= 4.20V). If exceeding (3) (timing T4), the charging device 3 shifts from constant current charging to constant voltage charging, and the charging current Ic gradually decreases.

  Thereafter, steps S1 to S5 are repeatedly executed until timing T5. Then, during the period from timing T2 to T5, the charging current Ic is turned on and off in a pulsed manner, and the assembled battery 14 is pulse-charged. This suppresses the voltage Vmax (terminal voltage V3 in the example of FIG. 5) from exceeding 4.22 V, thereby reducing the possibility of accelerating the deterioration of the secondary battery having the highest terminal voltage.

  When such pulse charging is performed, the open circuit voltage (OCV) of the secondary batteries 141, 142, and 143 gradually increases, and a preset monitoring time tw elapses after the switching element Q1 is turned off. However, the voltage Vmax does not drop below 4.20 V (NO in step S5, YES in step S6, timing T6). Then, the charging voltage control unit 212 determines that at least the secondary battery having the maximum terminal voltage (secondary battery 143 in the example of FIG. 5) is fully charged, and ends the charging.

  Although not shown in FIG. 3, a step similar to step S2 is provided in the loop of steps S5 and S6 (NO in step S6) and is detected by the voltage detection circuit 15. When the temperature t of the assembled battery 14 falls outside the range of 10 ° C. to 45 ° C., the process proceeds to step S9 to charge the assembled battery 14 with a low voltage (eg, 4.15 V per cell).

  In this case, when the switching element Q1 is turned off, the current Ic is zero and is less than the charge end current value Ia, so that the output signal level of the error amplifier 40 becomes a low level for the monitoring time tw. 37, the output current of the DC-DC converter 36 is made zero, and the charging device 3 stops charging.

  Next, the operation of the charging system 1 when the assembled battery 14 is not at a temperature suitable for charging will be described. FIG. 6 is an explanatory diagram for explaining the operation of the charging system 1 when the assembled battery 14 is not at a temperature suitable for charging.

  In step S2, when the temperature t of the assembled battery 14 detected by the voltage detection circuit 15 is not within the range of 10 ° C to 45 ° C, the temperature t of the assembled battery 14 is lower than 10 ° C or higher than 45 ° C. If the battery pack 14 is not at a temperature suitable for charging regardless of whether the battery pack 14 is at a low temperature or a high temperature, the battery pack 14 is at a low voltage (eg, 4.15 V per cell). To step S7 in order to charge the battery.

  In step S7, the charging voltage control unit 212 compares the voltage Vmax with 4.15V lower than 4.20V (step S7). When voltage Vmax exceeds 4.15 V (YES in step S7), switching element Q1 is turned off by charging voltage control unit 212 (step S8, timing T11).

  Although not shown in FIG. 3, when the voltage Vmax is 4.15 V or less (NO in step S7) in step S7, a step similar to step S11 described later is provided. When the temperature t of the assembled battery 14 detected by the voltage detection circuit 15 falls within the range of 15 ° C. to 40 ° C., the process proceeds to step S3 to charge the assembled battery 14 with a standard voltage (eg, 4.20 V per cell). To do.

  Then, the charging current Ic becomes zero, and the terminal voltages V1, V2, and V3 become the open circuit voltage (OCV). As a result of the elimination of the voltage drop caused by the charging current Ic flowing through the internal resistances of the secondary batteries 141, 142, 143, the terminal voltages V1, V2, V3 are lowered.

  Next, the charge voltage control unit 212 compares the voltage Vmax with 4.13 V (step S9). Here, the comparison voltage is, for example, a voltage obtained by subtracting 0.02V from 4.15V, and a hysteresis voltage of 0.02V is provided between the voltage at which the switching element Q1 is turned on and the voltage at which it is turned off. ing. Although it is not always necessary to provide the hysteresis voltage, the operation can be stabilized by providing the hysteresis.

  If voltage Vmax is 4.15 V or less (YES in step S9), the process proceeds to step S11. In step S11, the charging voltage control unit 212 turns on the switching element Q1 (step S11, timing T12). When the switching element Q1 is turned on, the secondary batteries 141, 142, and 143 are charged, and the total voltage of the terminal voltages V1, V2, and V3, that is, the terminal voltage Vt of the assembled battery 14 is 12.6V (= 4.20V). When exceeding (× 3) (timing T13), the charging device 3 shifts from constant current charging to constant voltage charging, and the charging current Ic gradually decreases.

  Next, whether or not the temperature t of the assembled battery 14 detected by the voltage detection circuit 15 by the charging voltage control unit 212 is within a range of 15 ° C. to 40 ° C., that is, the assembled battery 14 is at a temperature suitable for charging. It is confirmed whether or not there is (step S12). If the temperature t is within the range of 15 ° C. to 40 ° C. (YES in step S12), the process returns to step S3 again, and thereafter, steps S3 to S6 are executed as described above.

  In this case, for example, the temperature range to be compared is set such that the lower limit temperature is 5 ° C. higher than the first temperature and the upper limit temperature is 5 ° C. lower. This provides a 5 ° C hysteresis for temperature conditions when transitioning from a charging mode at a low voltage (eg 4.15 V per cell) to a charging mode at a standard voltage (eg 4.20 V per cell). ing. Although it is not always necessary to provide hysteresis in the temperature condition, the operation can be stabilized by providing hysteresis.

  If the temperature t is not within the range of 10 ° C. to 45 ° C. (NO in step S12), the process returns to step S7 again, and thereafter, steps S7 to S12 are repeatedly executed until timing T14. Then, during the period from timing T11 to T14, the charging current Ic is turned on and off in a pulsed manner, and the assembled battery 14 is pulse charged. As a result, the voltage Vmax (terminal voltage V3 in the example of FIG. 6) is suppressed from exceeding 4.15 V. Therefore, when the temperature t of the assembled battery 14 is lower than 10 ° C. or higher than 45 ° C. In other words, when the assembled battery 14 is not at a temperature suitable for charging, the charging voltage is lower than a standard charging voltage (for example, 4.20 V) at a temperature suitable for charging the assembled battery 14 (for example, 4.20 V). 4.15V), regardless of whether the assembled battery 14 is at a low temperature or a high temperature, the possibility that the assembled battery 14 is deteriorated by being charged at a temperature not suitable for charging is reduced.

  When such pulse charging is performed, the open circuit voltage (OCV) of the secondary batteries 141, 142, and 143 gradually increases, and a preset monitoring time tw elapses after the switching element Q1 is turned off. However, the voltage Vmax does not drop below 4.13 V (NO in step S9, YES in step S13, timing T15). Then, the charging voltage control unit 212 determines that at least the secondary battery having the maximum terminal voltage (the secondary battery 143 in the example of FIG. 6) is fully charged, and ends the charging.

  In this case, when the switching element Q1 is turned off, the current Ic is zero and is less than the charge end current value Ia, so that the output signal level of the error amplifier 40 becomes a low level for the monitoring time tw. 37, the output current of the DC-DC converter 36 is made zero, and the charging device 3 stops charging.

  FIG. 7 shows terminal voltages V1, V2, and V3 when the temperature t of the assembled battery 14 changes from the first temperature suitable for charging to the second temperature unsuitable for charging during charging of the assembled battery 14 by constant current charging. And an example of a change in the charging current Ic. In the example shown in FIG. 7, the case where the temperature t of the assembled battery 14 falls below, for example, 10 ° C. or exceeds 45 ° C. after the voltage Vmax (terminal voltage V3) exceeds 4.15 V at the timing T21. Show.

  In this case, at timing T21, it is detected in step S2 that the temperature t is outside the range of 10 ° C. to 45 ° C. (NO in step S2), and the process proceeds to step S7. Even if the temperature t of the assembled battery 14 changes after the voltage exceeds 4.15 V, the charging voltage can be changed according to the change in the temperature t.

  FIG. 8 shows the voltage Vmax and the charging current Ic when the temperature t of the assembled battery 14 changes from the first temperature suitable for charging to the second temperature unsuitable for charging during charging of the assembled battery 14 by constant voltage charging. An example of the change is shown. In the example shown in FIG. 8, at the timing T22, the charging device 3 switches from constant current charging to constant voltage charging, and the temperature t of the assembled battery 14 is, for example, 10 ° C. in the process of gradually decreasing the charging current Ic. It shows a case where the temperature falls below or exceeds 45 ° C.

  In this case, at timing T23, it is detected in step S2 that the temperature t is outside the range of 10 ° C. to 45 ° C. (NO in step S2), and the process proceeds to step S7. Even when the temperature t of 14 changes, the charging voltage can be changed according to the change of the temperature t. Note that the temperature range used for determining the temperature t of the assembled battery 14 may be provided in multiple stages, and the upper limit value of the charging voltage may be set in multiple stages according to the stage of each temperature range.

  According to the battery pack 2 shown in FIG. 1, the charging voltage applied to the assembled battery 14 is set according to the temperature of the assembled battery 14 using the charging device 3 in which the charging voltage is set regardless of the temperature of the assembled battery 14. Can be changed.

  In addition, if the charging device 3 attempts to reduce the charging voltage in constant voltage charging, a reference voltage source corresponding to a low voltage serving as a determination criterion for shifting from constant current charging to constant voltage charging is set as a reference. Since it is necessary to provide in addition to the voltage source 41, to provide a reference voltage source switching circuit, and to add a control circuit for lowering the charging voltage in constant voltage charging to the charging control unit 37, the cost is reduced. To rise. On the other hand, some battery packs are conventionally provided with a control unit 202 (charge / discharge control unit 211) to perform overcharge and overdischarge protection, and in order to make this a battery pack 2, a charge voltage control unit is provided. It is only necessary to store the control program 212 in the ROM, and it is easy to reduce the increase in cost.

  Further, in an inexpensive charging apparatus that does not have a communication function with the battery pack 2 such as the charging apparatus 3, the charging current and the charging voltage are controlled by the terminal voltage Vt (terminal voltages V1, V2) of the assembled battery 14. , V3). Therefore, as described above, when a difference occurs between the terminal voltages V1, V2, and V3, an overvoltage may be applied to the secondary battery having a high terminal voltage to cause deterioration. On the other hand, in the battery pack 2 shown in FIG. 2, the charging voltage is controlled so that the voltage Vmax does not exceed the specified voltage (for example, 4.22 V or less) on the battery pack 2 side. Even if there is a difference between V2 and V3, it is possible to reduce the possibility that an overvoltage is applied to the secondary battery having a high terminal voltage and deteriorated.

(Second Embodiment)
Next, a charging system including the battery pack according to the second embodiment of the present invention will be described. FIG. 9 is a block diagram showing an example of the configuration of the charging system 1a according to the second embodiment of the present invention. The charging system 1a shown in FIG. 9 is different from the charging system 1 shown in FIG. 1 in the following points. That is, in the charging system 1 a shown in FIG. 9, the battery pack 2 a further includes a connection terminal 13 for communication and a communication unit 203. The charging device 3a includes a connection terminal 33. When the battery pack 2a is attached to the charging device 3a, the connection terminal 13 and the connection terminal 33 are connected to communicate between the charging device 3a and the battery pack 2a. It has been made possible.

  The charging voltage control unit 212a is configured such that the temperature t of the assembled battery 14 detected by the temperature sensor 17 is set in advance as a temperature suitable for charging the assembled battery 14 (for example, a temperature in the range of 10 ° C. to 45 ° C.). In the case, the communication unit 203 transmits an instruction signal to the battery pack 2a to set a voltage obtained by multiplying the voltage Vc1 (for example, 4.20V) by 3 of the number of series cells as the end voltage Vf. Further, the charging voltage control unit 212a terminates when the temperature t of the assembled battery 14 detected by the temperature sensor 17 is the second temperature different from the first temperature (for example, when the temperature t is out of the range of 10 ° C to 45 ° C). As the voltage Vf, an instruction signal for setting a voltage obtained by multiplying the voltage Vc2 (for example, 4.15V) by 3 of the number of series cells is transmitted to the battery pack 2a by the communication unit 203.

  The charging device 3 a includes connection terminals 31, 32, 33, a control IC 50, and a charging current supply unit 356. The control IC 50 includes a control unit 51 and a communication unit 52. The communication units 203 and 52 are, for example, SMBus (System Management Bus) (registered trademark) or other communication interface circuits. The charging current supply unit 356 is a power supply circuit that supplies a current corresponding to a control signal from the control unit 51 to the battery pack 2a via the connection terminals 31 and 32. For example, the DC power supply circuit 35 and the DC-DC converter 36 are provided. It consists of and. The control unit 51 is a control circuit configured using, for example, a microcomputer.

  The control unit 51 performs constant current charging by supplying a charging current Ic having a current value Icc from the charging current supply unit 356 via the connection terminals 31 and 32 to the battery pack 2, and the voltage between the connection terminals 31 and 32. When Vout reaches the end voltage Vf set by the instruction signal from the charge voltage control unit 212a, the end voltage Vf is applied as a charge voltage between the connection terminals 31 and 32 for constant voltage charging to charge the assembled battery 14. Switch. Furthermore, when the charging current Ic flowing through the assembled battery 14 becomes equal to or less than the charging end current value Ia, the charging device 3 determines that the assembled battery 14 is fully charged and ends the charging.

  The charging device 3a is not limited to the one that charges the battery pack 2a, but includes the control unit 202a, the voltage detection circuit 15, the current detection resistor 16, and the like, and charges the assembled battery 14 directly connected to the connection terminals 31 and 33. You may do.

  Since the other configuration is the same as that of the charging system 1 shown in FIG. The operation of this embodiment will be described below. FIG. 10 is a flowchart showing an example of the operation of the battery pack 2a shown in FIG. Moreover, FIG. 11 is explanatory drawing for demonstrating an example of operation | movement of the charging system 1a shown in FIG.

  First, the charging device 3a starts constant current charging and outputs a charging current Ic having a current value Icc (timing T31). Moreover, the switching elements Q1 and Q2 are turned on by the charge / discharge control unit 211 (step S21). If it does so, the assembled battery 14 will be charged and the terminal voltage Vt of the assembled battery 14 will rise gradually.

  Next, whether or not the temperature t of the assembled battery 14 detected by the voltage detection circuit 15 by the charging voltage control unit 212a is within the range of 10 ° C. to 45 ° C., that is, the assembled battery 14 is at a temperature suitable for charging. It is confirmed whether or not there is (step S22). And if temperature t is in the range of 10 degreeC-45 degreeC (it is YES at step S22), in order to charge the assembled battery 14 with a standard charging voltage (for example, 4.20V per cell), as final voltage Vf, An instruction signal for setting a voltage obtained by multiplying the voltage Vc1 (for example, 4.20V) by the number 3 of the series cells is transmitted to the battery pack 2a by the communication unit 203. In the control unit 51, the end voltage Vf is 12.6V. (= 4.20 × 3) is set (step S23).

  When the terminal voltage Vt indicated by the solid line in FIG. 11 reaches 12.6V, the output of the charging current supply unit 356 is controlled by the control unit 51 so that the voltage Vout between the connection terminals 31 and 32 is constant at 12.6V. The current Ic is adjusted, and constant voltage charging with a charging voltage of 4.20 V per cell is executed (timing T32).

  Furthermore, when the charging current Ic indicated by the solid line in FIG. 11 becomes equal to or less than the charge termination current value Ia, the control unit 51 determines that the assembled battery 14 is fully charged, and the current output from the charging current supply unit 356 is It is set to zero and charging is finished (timing T33).

  On the other hand, in step S22, the temperature t of the assembled battery 14 detected by the voltage detection circuit 15 is not within the range of 10 ° C to 45 ° C, and the temperature t of the assembled battery 14 is lower than 10 ° C or 45 ° C. When the temperature is higher, that is, whether the assembled battery 14 is not at a temperature suitable for charging regardless of whether the assembled battery 14 is at a low temperature or a high temperature, the battery is assembled at a low voltage (eg, 4.15 V per cell). The process proceeds to step S24 to charge the battery 14.

  In step S24, an instruction signal for setting a voltage obtained by multiplying the voltage Vc2 (for example, 4.15V) by 3 of the number of series cells as the end voltage Vf is transmitted to the battery pack 2a by the communication unit 203, and the control unit 51 , The end voltage Vf is set to 12.45V (= 4.15V × 3) (step S24).

  When the terminal voltage Vt reaches 12.45 V, the control unit 51 adjusts the output current Ic of the charging current supply unit 356 so that the voltage Vout between the connection terminals 31 and 32 is constant at 12.45 V. Then, constant voltage charging is performed with a charging voltage of 4.15 V per cell (voltage Vt indicated by a broken line) (timing T34).

  Furthermore, when the charging current Ic indicated by the broken line in FIG. 11 becomes equal to or less than the charge termination current value Ia, the control unit 51 determines that the assembled battery 14 is fully charged, and the current output from the charging current supply unit 356 is It is set to zero and charging is finished (timing T35).

  In step S24, after the end voltage Vf is set to 12.45V (= 4.15V × 3), the temperature t of the assembled battery 14 detected by the voltage detection circuit 15 by the charge voltage control unit 212a is 15%. It is confirmed whether or not the temperature is in the range of 40 ° C. to 40 ° C., that is, whether or not the assembled battery 14 is at a temperature suitable for charging (step S25). If the temperature t is in the range of 15 ° C. to 40 ° C. (YES in step S25), the process proceeds to step S23, and the end voltage Vf is set to 12.45V (= 4.15V × 3). .

  In this case, the temperature range compared in step S25 is set such that the lower limit temperature is 5 ° C. higher than the first temperature and the upper limit temperature is 5 ° C. lower, for example. This provides a 5 ° C hysteresis for temperature conditions when transitioning from a charging mode at a low voltage (eg 4.15 V per cell) to a charging mode at a standard voltage (eg 4.20 V per cell). ing. Although it is not always necessary to provide hysteresis in the temperature condition, the operation can be stabilized by providing hysteresis.

  Note that the temperature range used for determining the temperature t of the assembled battery 14 may be provided in multiple stages, and the upper limit value of the charging voltage may be set in multiple stages according to the stage of each temperature range.

(Third embodiment)
Next, a charging system including the battery pack according to the third embodiment of the present invention will be described. The charging system 1b provided with the battery pack 2b according to the third embodiment is shown in FIG. 9 like the charging system 1a according to the second embodiment. In the charging system 1b and the charging system 1a shown in FIG. 9, the operations of the charging voltage control unit 212b and the control unit 51b are different.

  In response to each input value from the analog-to-digital converter 201, the charging voltage control unit 212b calculates the voltage value and current value of the charging current that requires output from the charging device 3b, and connects from the communication unit 203. By transmitting to the charging device 3 via the terminals 13 and 33, so-called CCCV (constant current constant voltage) charging is executed.

  In the charging device 3b, the request from the charging voltage control unit 212b is received by the communication unit 52, the control unit 51b controls the charging current supply unit 356, and the voltage value according to the request from the charging voltage control unit 212b, and The charging current is supplied at the current value.

  Specifically, the charging voltage control unit 212a is configured such that the temperature t of the assembled battery 14 detected by the temperature sensor 17 is a first temperature set in advance as a temperature suitable for charging the assembled battery 14 (for example, 10 ° C. to 45 ° C. When the voltage Vmax reaches the voltage Vc1 (first voltage), the charging device 3b supplies the charging current Ic having the current value Icc, and the voltage Vmax reaches the voltage Vc1 (first voltage). It switches to the constant voltage charge which charges and the assembled battery 14 is applied. Then, when the charging current Ic flowing through the assembled battery 14 becomes equal to or less than the charging end current value Ia, the charging voltage control unit 212b determines that the assembled battery 14 is fully charged and ends the charging.

  Further, the charging voltage control unit 212a is configured such that the temperature t of the assembled battery 14 detected by the voltage detection circuit 15 is not within the range of 10 ° C. to 45 ° C., and the temperature t of the assembled battery 14 is lower than 10 ° C. If the battery pack 14 is not at a temperature suitable for charging regardless of whether the battery pack 14 is at a low temperature or a high temperature, the current value Icc is The constant current charging is executed by supplying the charging current Ic, and when the voltage Vmax reaches the voltage Vc2 (second voltage), the voltage Vc2 is applied to switch to the constant voltage charging for charging the assembled battery 14. Then, when the charging current Ic flowing through the assembled battery 14 becomes equal to or less than the charging end current value Ia, the charging voltage control unit 212b determines that the assembled battery 14 is fully charged and ends the charging.

  Since other configurations are the same as those of the charging system 1a shown in FIG. 9, the description thereof will be omitted, and the characteristic points of the present embodiment will be described below. FIG. 12 is a flowchart illustrating an example of the operation of the charging system 1b according to the third embodiment.

  First, the switching elements Q1, Q2 are turned on by the charge / discharge control unit 211 (step S31). Then, the charging voltage control unit 212b transmits an instruction signal indicating that the charging current Ic should be set to the current value Icc from the communication unit 203 to the charging device 3b (step S32). Then, charging current Ic having current value Icc is output from charging device 3b, and constant current charging is started.

  Next, whether or not the temperature t of the assembled battery 14 detected by the voltage detection circuit 15 by the charging voltage control unit 212b is within a range of 10 ° C. to 45 ° C., that is, the assembled battery 14 is at a temperature suitable for charging. It is confirmed whether or not there is (step S33). And if temperature t is in the range of 10 degreeC-45 degreeC (it is YES at step S33), it will transfer to step S34.

  In step S34, constant current charging is performed with the charging current Ic having the current value Icc, the assembled battery 14 is charged, and the terminal voltages V1, V2, V3 of the secondary batteries 141, 142, 143 gradually increase. Next, the voltage Vmax is compared with 4.20 V by the charging voltage control unit 212b (step S35). If voltage Vmax does not reach 4.20 V (NO in step S35), the process proceeds to step S33 again. On the other hand, if the voltage Vmax is 4.20 V or more (YES in step S35), the temperature t of the assembled battery 14 detected by the voltage detection circuit 15 by the charging voltage control unit 212b is within the range of 10 ° C to 45 ° C. It is confirmed whether or not there is (step S36). If the temperature t is within the range of 10 ° C to 45 ° C (YES in step S36), the process proceeds to step S37. If the temperature t is out of the range of 10 ° C to 45 ° C (NO in step S36), the process proceeds to step S40. To do.

  In step S <b> 37, an instruction signal for instructing the output voltage of the charging device 3 b is sent via the communication unit 203 so that the charging voltage control unit 212 b has a standard charging voltage (for example, 4.20 V per cell). To 3b. Then, for example, the assembled battery 14 is charged at a constant voltage of 4.20 V per cell (step S37).

  When the charging current Ic detected by the current detection resistor 16 becomes equal to or lower than the charging end current value Ia, the charging voltage control unit 212b transmits an instruction signal indicating that the charging current Ic should be zero to the charging device 3b. The control unit 51b sets the charging current Ic to zero and terminates normal CCCV charging.

  Next, the operation of the charging system 1b when the assembled battery 14 is not at a temperature suitable for charging will be described. FIG. 13 is an explanatory diagram for explaining the operation of the charging system 1b when the assembled battery 14 is not at a temperature suitable for charging.

  After the constant current charging is started in step S32 (timing T41), the temperature t of the assembled battery 14 detected by the voltage detection circuit 15 is not in the range of 10 ° C. to 45 ° C. in step S33. When the temperature t is lower than 10 ° C. or higher than 45 ° C. (NO in step S33), that is, regardless of whether the assembled battery 14 is at a low temperature or a high temperature, the assembled battery 14 is charged. If the temperature is not suitable, the process proceeds to step S39 to charge the battery pack 14 at a low voltage (eg, 4.15 V per cell).

  In step S39, the charge voltage control unit 212b compares the voltage Vmax with 4.15V lower than 4.20V (step S39). When the voltage Vmax is 4.15V or less (NO in step S39), the process proceeds to step S41. To do. If the charging current Ic detected by the current detection resistor 16 exceeds the charging end current value Ia (NO in step S41), the charging current Ic is maintained as it is and constant current charging is continued (step S42). .

  Next, in step S43, whether or not the temperature t of the assembled battery 14 detected by the voltage detection circuit 15 is within a range of 15 ° C. to 40 ° C., that is, the assembled battery 14 is charged. It is confirmed whether or not the temperature is appropriate (step S43). If the temperature t is within the range of 15 ° C. to 40 ° C. (YES in step S43), the process returns to step S34 again, and thereafter, steps S34 to S38 are executed as described above.

  In this case, for example, the temperature range to be compared is set such that the lower limit temperature is 5 ° C. higher than the first temperature and the upper limit temperature is 5 ° C. This provides a 5 ° C hysteresis for temperature conditions when transitioning from a charging mode at a low voltage (eg 4.15 V per cell) to a charging mode at a standard voltage (eg 4.20 V per cell). ing. Although it is not always necessary to provide hysteresis in the temperature condition, the operation can be stabilized by providing hysteresis.

  If the temperature t is not within the range of 10 ° C. to 45 ° C. (NO in step S43), the process returns to step S39, and the charging voltage control unit 212b sets the voltage Vmax to 4.15V lower than 4.20V. Comparison is made (step S39). When voltage Vmax exceeds 4.15 V (YES in step S39), the charging voltage controller 212b reduces the charging current from communication unit 203 to charging device 3b by a preset current value Id. An instruction signal indicating that the current value of Ic should be set as a new charging current Ic is transmitted (step S40). As a result, the charging current Ic from the charging device 3b is reduced by the current value Id, and the voltage drop caused by the charging current Ic flowing through the internal resistances of the secondary batteries 141, 142, 143 is reduced. As a result, the terminal voltage V1 , V2 and V3 are decreased, and the voltage Vmax is decreased to 4.15 V or less (timing T42).

  The current Id is set to a current value such that a voltage drop caused by the internal resistances of the secondary batteries 141, 142, and 143 can reduce the voltage Vmax to 4.15V or less.

  Thereafter, steps S41 to S40 are repeatedly executed until timing T43. Then, during the period from timing T42 to T43, the charging current Ic is decreased step by step by the current value Id, so that the voltage Vmax is suppressed from exceeding 4.15V, so the temperature t of the assembled battery 14 is 10 ° C. When the temperature is lower or higher than 45 ° C., that is, when the assembled battery 14 is not at a temperature suitable for charging, the charging voltage is a standard value at a temperature at which the assembled battery 14 is suitable for charging. As a result of being held at a voltage (for example, 4.15 V) lower than the charging voltage (for example, 4.20 V), the assembled battery 14 is charged at a temperature that is not suitable for charging regardless of whether the assembled battery 14 is at a low temperature or a high temperature. This reduces the possibility of deterioration.

  When the charging current Ic detected by the current detection resistor 16 becomes equal to or lower than the charging termination current value Ia (YES in step S41), the charging voltage control unit 212b generates an instruction signal indicating that the charging current Ic should be zero. Transmitted to the device 3b, the charging current Ic is made zero by the control unit 51b, and normal CCCV charging is terminated (timing T44).

  FIG. 14 shows terminal voltages V1, V2, and V3 when the temperature t of the assembled battery 14 changes from the first temperature suitable for charging to the second temperature unsuitable for charging during charging of the assembled battery 14 by constant current charging. And an example of a change in the charging current Ic. In the example shown in FIG. 14, the case where the temperature t of the assembled battery 14 falls below, for example, 10 ° C. or exceeds 45 ° C. after the voltage Vmax (terminal voltage V 3) exceeds 4.15 V at the timing T45. Show.

  In this case, at timing T45, it is detected in step S33 that the temperature t is outside the range of 10 ° C. to 45 ° C. (NO in step S33), and the process proceeds to step S39. Even if the temperature t of the assembled battery 14 changes after the voltage exceeds 4.15 V, the charging voltage can be changed according to the change in the temperature t.

  FIG. 15 shows the voltage Vmax and the charging current Ic when the temperature t of the assembled battery 14 changes from the first temperature suitable for charging to the second temperature unsuitable for charging during charging of the assembled battery 14 by constant voltage charging. An example of the change is shown. In the example shown in FIG. 15, at the timing T46, the charging device 3b switches from constant current charging to constant voltage charging, and at the timing T47 in the process in which the charging current Ic gradually decreases, the temperature t of the assembled battery 14 is, for example, A case where the temperature falls below 10 ° C or exceeds 45 ° C is shown.

  In this case, at timing T47, it is detected in step S33 that the temperature t is out of the range of 10 ° C. to 45 ° C. (NO in step S33), and the process proceeds to step S39. Even when the temperature t of 14 changes, the charging voltage can be changed according to the change of the temperature t. Note that the temperature range used for determining the temperature t of the assembled battery 14 may be provided in multiple stages, and the upper limit value of the charging voltage may be set in multiple stages according to the stage of each temperature range.

  The present invention relates to a battery pack used as a power source for a battery-mounted device such as a portable personal computer, a digital camera, an electronic device such as a mobile phone, a vehicle such as an electric car or a hybrid car, a charging circuit for charging a secondary battery, and It can be suitably used as a charging system.

It is a block diagram which shows an example of a structure of the charging system provided with the battery pack which concerns on the 1st Embodiment of this invention. It is a block diagram which shows an example of a structure of the charging device shown in FIG. 3 is a flowchart showing an example of the operation of the battery pack shown in FIG. 3 is a flowchart showing an example of the operation of the battery pack shown in FIG. It is explanatory drawing for demonstrating operation | movement of the charging system shown in FIG. It is explanatory drawing for demonstrating operation | movement of the charging system shown in FIG. It is explanatory drawing for demonstrating operation | movement of the charging system shown in FIG. It is explanatory drawing for demonstrating operation | movement of the charging system shown in FIG. It is a block diagram which shows an example of a structure of the charging system which concerns on the 2nd, 3rd embodiment of this invention. It is a flowchart which shows an example of operation | movement of the battery pack which concerns on 2nd Embodiment. It is explanatory drawing for demonstrating an example of operation | movement of the charging system which concerns on 2nd Embodiment. 6 is a flowchart illustrating an example of an operation of a battery pack according to a third embodiment. It is explanatory drawing for demonstrating an example of operation | movement of the charging system which concerns on 3rd Embodiment. It is explanatory drawing for demonstrating an example of operation | movement of the charging system which concerns on 3rd Embodiment. It is explanatory drawing for demonstrating an example of operation | movement of the charging system which concerns on 3rd Embodiment.

Explanation of symbols

1, 1a, 1b Charging system 2, 2a, 2b Battery pack 3, 3a, 3b Charging device 11, 12, 13, 31, 32, 33 Connection terminal 14 Battery assembly 15 Voltage detection circuit 16 Current detection resistor 17 Temperature sensor 51, 51b control unit 52, 203 communication unit 141, 142, 143 secondary battery 202, 202a, 202b control unit 211 charge / discharge control unit 212, 212a, 212b charge voltage control unit 356 charge current supply unit 361 PWM signal generation circuit Ia charge termination Current value Ic Charging current Icc Current value Id Current value Q1, Q2 Switching element V1, V2, V3 Terminal voltage

Claims (11)

A secondary battery,
From a charging unit that outputs a charging current for charging the secondary battery, a connection terminal for receiving the output charging current,
A temperature detector for detecting the temperature of the secondary battery;
When the temperature of the secondary battery detected by the temperature detection unit is a second temperature different from the first temperature preset as a temperature suitable for charging the secondary battery, power is received by the connection terminal. A battery pack comprising: a charging voltage controller configured to lower a charging voltage of the secondary battery based on a current from a first voltage preset as a voltage for charging the secondary battery at a constant voltage. A switching element for turning on and off a charging current flowing from the connection terminal to the secondary battery;
A voltage detection unit for detecting a terminal voltage of the secondary battery,
The charging voltage controller is
When the temperature of the secondary battery detected by the temperature detection unit is the first temperature, the switching element is turned on,
When the temperature of the secondary battery detected by the temperature detection unit is the second temperature, the terminal voltage of the secondary battery detected by the voltage detection unit exceeds a second voltage lower than the first voltage. 2. The battery pack according to claim 1, wherein the switching element is turned off when the switch is turned on, and the switching element is turned on when a terminal voltage of the detected secondary battery is lower than the second voltage. The charging voltage controller is
When the temperature of the secondary battery detected by the temperature detection unit is the second temperature, the terminal voltage of the secondary battery detected by the voltage detection unit even when the switching element is turned off is the second voltage. The battery pack according to claim 2, wherein the charging of the secondary battery is terminated when the above is reached. The charging voltage controller is
When the temperature of the secondary battery detected by the temperature detector is the first temperature, the terminal voltage of the secondary battery detected by the voltage detector exceeds a third voltage higher than the first voltage. 4. The battery pack according to claim 2, wherein the switching element is turned off when the switch is turned on, and the switching element is turned on when a terminal voltage of the detected secondary battery is equal to or lower than the first voltage. The charging voltage controller is
When the temperature of the secondary battery detected by the temperature detection unit is the first temperature, the terminal voltage of the secondary battery detected by the voltage detection unit even when the switching element is turned off is the first voltage. The battery pack according to claim 4, wherein charging of the secondary battery is terminated when the value exceeds. A voltage detection unit for detecting a terminal voltage of the secondary battery;
The charging unit is
Adjusting the supply current to the secondary battery according to the instruction from the charging voltage control unit,
The charging voltage controller is
When the temperature of the secondary battery detected by the temperature detection unit is the second temperature, the terminal voltage of the secondary battery detected by the voltage detection unit exceeds a second voltage lower than the first voltage. 2. The battery pack according to claim 1, wherein an instruction to reduce a supply current by the charging unit is performed so that a terminal voltage of the detected secondary battery becomes equal to or lower than the second voltage. A current detection unit for detecting a charging current of the secondary battery;
The charging voltage controller is
When the charging current detected by the current detection unit is equal to or lower than a charge termination current value set in advance as a current value to end the constant voltage charging, an instruction to stop the current supply by the charging unit is performed. The battery pack according to claim 6, wherein charging of the secondary battery is terminated. The charging unit is
The output voltage is adjusted according to the instruction from the charging voltage control unit,
The charging voltage controller is
When the temperature of the secondary battery detected by the temperature detection unit is the first temperature, constant voltage charging is performed by supplying the first voltage to the secondary battery by the charging unit,
When the temperature of the secondary battery detected by the temperature detection unit is the second temperature, the charging unit performs constant voltage charging by supplying a second voltage lower than the first voltage to the secondary battery. The battery pack according to claim 1. The secondary battery is an assembled battery in which a plurality of secondary batteries are connected in series,
The first voltage is set as a charging voltage per secondary battery in the constant voltage charging,
The voltage detection unit detects terminal voltages of the plurality of secondary batteries,
The charging voltage control unit uses a maximum voltage among terminal voltages of the plurality of secondary batteries detected by the voltage detection unit as a terminal voltage of the secondary battery detected by the voltage detection unit. The battery pack according to any one of claims 2 to 7. A connection terminal for connecting a secondary battery;
A charging unit that outputs a charging current for charging the secondary battery;
A temperature detector for detecting the temperature of the secondary battery;
When the temperature of the secondary battery detected by the temperature detection unit is a second temperature different from the first temperature preset as a temperature suitable for charging the secondary battery, the temperature is output by the charging unit A charging voltage controller configured to lower a charging voltage of the secondary battery based on a charging current from a first voltage preset as a voltage for charging the secondary battery at a constant voltage; . A secondary battery,
A charging unit that outputs a charging current for charging the secondary battery;
A temperature detector for detecting the temperature of the secondary battery;
When the temperature of the secondary battery detected by the temperature detection unit is a second temperature different from the first temperature preset as a temperature suitable for charging the secondary battery, the temperature is output by the charging unit A charging voltage control unit configured to lower a charging voltage of the secondary battery based on a charging current from a first voltage preset as a voltage for charging the secondary battery at a constant voltage. .

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