JP2012200113A - Battery pack and charging system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery pack conforming to an upper limit charging voltage regulation specified in a verification test for overcharge protection of an assembled battery, and in which a cell can be charged to a state closer to full charge.SOLUTION: A battery pack including: a chargeable/dischargeable cell; a switching element disposed in a charge path including the cell, for controlling charging of the cell; a protection circuit for turning off the switching element when a voltage of the cell reaches a predetermined overcharge voltage; a temperature detection circuit for detecting ambient temperature of the cell; and a temperature detection terminal for outputting a value detected by the temperature detection circuit to the outside, comprises: a charge detection circuit for detecting a voltage of the cell to compare the voltage of the cell with a charge control voltage set to a voltage lower than an overcharge voltage; and short-circuiting means controlled by the charge detection circuit, for short-circuiting the temperature detection circuit. When a charge voltage of the cell reaches the charge control voltage, the charge detection circuit turns on the short-circuiting means and outputs from the temperature detection terminal a result that the temperature of the cell is out of a chargeable temperature range, to perform charge control.

Description

  The present invention relates to a battery pack using a lithium secondary battery and the like, and a charging system including a battery pack and a charging device for charging the battery pack.

  A battery pack using a lithium secondary battery is suitable for portable electronic devices that consume a large amount of power, such as notebook PCs and mobile phones. However, in these devices, a further increase in battery capacity is desired with the spread of devices with large power consumption and the rapid market expansion of highly functional devices represented by smartphones. There is also a high demand for shortening the charging time, and the charging current is also increasing.

  On the other hand, an increase in battery capacity greatly affects its safety. In Japan, in order to improve the safety of lithium secondary batteries for portable electronic devices, lithium secondary batteries were added to the conventional Electrical Appliance and Material Safety Law in 2007, and the Electrical Appliance and Material Safety Law was enforced in 2008. A ministerial ordinance has been promulgated that establishes regulations and technical standards for electrical appliances. Furthermore, the Ministerial Ordinance quotes JIS standards JIS C 8712 “Safety of sealed small secondary batteries” and JIS C 8714 “Safety tests of single-cell batteries and assembled batteries for portable electronic devices” as technical standards. Yes. These standards mainly target cells that are single cells of lithium secondary batteries and assembled batteries that combine these cells, and stipulate requirements for ensuring safety in design standards, normal use, and foreseeable misuse. .

  Furthermore, the ministerial ordinance has tightened the test conditions since 2011, and the unit cell is set at 45 ° C. and 10 ° C. as the upper and lower test temperatures, and the evaluation in the state of charging is added to the requirements. Moreover, in the assembled battery, the overcharge protection function and the safety of the assembled battery when the device is dropped are added to the requirements.

  The requirements for the overcharge protection function are stipulated in the confirmation test for overcharge protection of an assembled battery in JIS C 8714 (hereinafter referred to as “technical standard”). It is required not to exceed.

  In order to respond to this requirement, in a battery pack in which a plurality of cells are connected in series, the voltage for each cell is detected, and control is performed so that all of these voltage values are below a certain value, or in the battery pack It is necessary to adopt measures such as a configuration in which the charging device combined with the pack controls the charging voltage so that each cell does not exceed a predetermined voltage (for example, described in Patent Document 1), and adapt to the technical standards. is there.

  A battery pack using a lithium secondary battery has a protection function against overcharging of a cell. Furthermore, a battery pack in which a plurality of cells are connected in series employs a configuration in which a voltage value for each cell is detected and overcharge protection is performed on the voltage value. FIG. 3 shows a circuit configuration of a conventional battery pack in which two cells are connected in series, and the operation will be described.

  The battery pack 10 includes a cell 1, a cell 2, a protection circuit 3 for controlling the charge / discharge state of these cells, and a thermistor element 7 for detecting the ambient temperature of the cell. The protection circuit 3 determines the voltage of each cell. It is configured to be individually measurable. In addition, the cells 1 and 2 connected in series are connected to the positive and negative terminals of the battery pack 10, and the overcharge FET 4 and the over discharge FET 5 are connected to the charge / discharge path from the positive terminal to the negative terminal through each cell. Has been placed. The protection circuit 3 detects the voltage of each cell, and determines that the cell is overcharged or overcharged when the voltage of at least one cell exceeds a threshold value for overcharging or overdischarging. The corresponding FET is turned off. For example, when the voltage of the cell 1 increases until it exceeds a threshold value (for example, 4.3 V) that is regarded as overcharge, the protection circuit 3 operates the overcharge FET 4, and the charging device 20 switches to the cells 1 and 2. Overcharging is prevented by stopping the current supply. The thermistor terminal 6 is disposed in the vicinity of the cell 1 and the cell 2 and is connected to a thermistor element 7 that detects the ambient temperature of the cell. The thermistor element 7 detects that the ambient temperature of the cell exceeds the predetermined temperature range where charging can be performed from the change in the resistance value, and transmits it to the charging device 20 via the thermistor terminal 6. The charging device 20 is configured to limit or stop the charging current.

  Charging of the battery pack 10 having such a configuration is started when the charging device 20 detects the mounting of the battery pack 10 from the connection state of the thermistor terminal 6. In the charging control of the charging device 20, the charging voltage of the battery pack 10 is detected by the internal charging control circuit 21, and the charging current is detected by the detection resistor arranged in the charging path, so that the battery pack 10 is fully charged. Similarly, the charge control circuit 21 controls the constant voltage / constant current. For example, in the case of this conventional example in which two cells are connected in series, the charging device 20 charges the battery pack 10 at a constant voltage and a constant current of 8.4 V · 1 A.

JP 2010-259128 A

  Regarding the overcharge protection requirement in the technical standards, in order to satisfy the requirement in the battery pack alone, each cell in the battery pack is limited to the upper limit charging voltage (4.25V, in this specification, the upper limit charging voltage The overcharge protection function, which is completed only by the battery pack, is required so as not to exceed 4.25V defined by the standard. Therefore, as a measure corresponding to the technical standards, there is a control method that stops the charging when the cell voltage reaches the upper limit charging voltage by utilizing the function of detecting the voltage for each cell by the overcharge and overdischarge protection circuit. is assumed.

  For example, in the conventional example of FIG. 3, the threshold value (hereinafter referred to as overcharge detection voltage) that the protection circuit 3 in the battery pack 10 considers as overcharge is set to a value equal to or less than the upper limit charge voltage, and the cell 1, The protection circuit 3 for detecting the voltage of the cell 2 turns off the charge FET 4 before at least one of the cells reaches the upper limit charging voltage, and controls the function of the protection circuit 3 so as not to exceed the upper limit charging voltage. The conditions required by technical standards can be satisfied.

  However, in the above control, the overcharge protection functions in a state where the charging voltage of either the cell 1 or the cell 2 is equal to or lower than the upper limit charging voltage, and the charging from the charging device 20 is continued. The battery pack 10 forcibly stops charging. In this case, the charging device 20 determines to stop under a condition different from the normal end condition, that is, an abnormal stop.

  Therefore, in addition to the above control, charging is performed in a region where the charging device 20 is below the upper limit charging voltage, so that the charging device 20 can normally finish charging. At this time, the charging voltage of the charging device 20 is set with reference to a value lower than a value obtained by multiplying the overcharge detection voltage and the number of cells connected in series, and taking into account errors in control and detection. Since the charging voltage based on this setting is lower than the conventional charging voltage, the charging capacity of the cell is reduced and the driving time of the device using the battery pack 10 is shortened compared to the conventional example. Arise.

  Furthermore, in the battery pack employing the above-described configuration, when voltage variation occurs between the cells during charging, the charging ends when the highest voltage cell reaches the upper limit charging voltage. At this time, the other cells have not reached the upper limit charging voltage, and the charging is terminated at an early stage, which promotes a shortage of charging capacity.

  Therefore, in order to achieve both the avoidance of the above-described problems and the correspondence to the technical standards, the charging device of Patent Document 1 measures the voltage for each cell, and is predetermined as the highest voltage among the measured values. A configuration is proposed in which a constant voltage control voltage of a charging device is set so as not to exceed the voltage value, and constant voltage charging is performed.

  However, in this proposal, the battery pack is provided with a configuration in which the cell voltage is individually measured and the measured value is transmitted to the charging device, and a voltage for performing constant voltage control is set in the charging device from the cell voltage value. It is necessary to add a configuration for carrying out constant voltage control at As a result, it is necessary to introduce a new configuration for both the battery pack and the charging device, leading to an increase in development man-hours and an increase in component costs due to the addition of new components. In particular, in a configuration in which the battery pack and the device are integrated, and the device charges the battery pack, it becomes necessary to reconstruct the entire device configuration in order to comply with the technical standard, and the technical standard becomes stricter. Will have a wide range of effects. In addition, existing charging devices sold before the introduction of technical standards are not compatible with battery packs that employ the above configuration, and charging is performed when the battery pack is purchased as an alternative. It is assumed that it will fall into an impossible state, and it will be necessary to purchase both a battery pack and a charging device newly.

  The present invention solves the above-mentioned problems caused by the response to technical standards, and supports the overcharge protection function required by the technical standards by controlling the battery pack, and the cell is more fully charged. A battery pack that can be charged to a state and a charging system that includes a charging device for charging the battery pack.

  The battery pack according to the present invention includes a chargeable / dischargeable cell, a switch element that is arranged in a charging path including the cell, and controls the charging of the cell, and the cell voltage reaches a preset overcharge voltage. A battery pack comprising a protection circuit that turns off the switch element, a temperature detection circuit that detects the ambient temperature of the cell, and a temperature detection terminal that outputs the value of the temperature detection circuit externally, and detects the voltage of the cell A charge detection circuit that compares the charge control voltage set to a voltage lower than the overcharge voltage, and a short-circuit means that is controlled by the charge detection circuit and that short-circuits the temperature detection circuit. When the voltage is reached, the charge detection circuit turns on the short-circuit means.

  The charging system according to the present invention is a charging system including a battery pack and a charging device for charging the battery pack. The battery pack is arranged in a chargeable / dischargeable cell, a charging path including the cell, and the battery. Switch element for controlling charging of the pack, protection circuit for performing overcharge protection by turning off the switch element when the cell voltage reaches a preset overcharge detection voltage, and temperature detection circuit for detecting the temperature of the cell A charge detection circuit comprising a temperature detection terminal for outputting the value of the temperature detection circuit to the charging device, further detecting the cell voltage and comparing it with a charge control voltage set to a voltage lower than the overcharge voltage; The charging device is controlled by a detection circuit and includes a short-circuit means connected in parallel to the temperature detection circuit. The charging device controls a charging current and a charging voltage supplied to the battery pack and a temperature detection terminal. Based on the temperature detection of the input cell, charging is performed when the temperature is within a predetermined range, and when the charging voltage of the cell reaches the charging control voltage, the charging detection circuit turns on the short-circuit means. The temperature detection terminal outputs that the temperature of the cell is outside the chargeable temperature range, and the charging device receives the output from the temperature detection terminal and stops supplying the charging current to the battery pack. And

  The battery pack of the present invention makes the charging device recognize that the temperature of the cell exceeds a predetermined range by setting the thermistor terminal in a short-circuited state when the voltage of the cell reaches a predetermined upper limit charging voltage, The supply of the charging current is stopped, and the configuration corresponding to the control of the upper limit charging voltage required by the technical standard with the battery pack alone is realized.

  This configuration makes cell voltage detection and charge control related to the upper limit charge voltage independent of cell voltage detection and overcharge protection related to overcharge protection, and the threshold of the voltage related to overcharge protection is used to control the upper limit charge voltage. By setting the voltage higher than the threshold value, the battery cell can be charged until it reaches the upper limit charging voltage, and even a battery pack that introduces control related to the upper limit charging voltage in accordance with the technical standard is charged. There is an effect that the capacity can be secured.

  Further, the charging system according to the present invention stops the current supply from the charging device by short-circuiting the thermistor terminal when the voltage of the cell reaches a predetermined upper limit charging voltage, and the upper limit charging voltage is reduced. When it falls below, the short-circuit state is canceled to perform control for starting or resuming charging, and the charging device performs control of the charging state so as not to exceed the charging upper limit voltage. It becomes possible to complete the charging procedure based on current and constant voltage.

  In addition, even if the upper limit charging voltage is exceeded, the battery pack or charger will not forcibly stop charging, so it is possible to avoid interruption of charging unintended by the user of the battery pack and the charging device. It has the effect of improving the convenience of the user.

The figure which shows the circuit structure of the battery pack which concerns on this embodiment. The flowchart which shows the charge procedure in the battery pack which concerns on this embodiment, and the charging device combined with this The figure which shows the circuit structure of the conventional battery pack The flowchart which shows the charge procedure in the conventional battery pack

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In addition, embodiment shown below demonstrates this invention concretely, Comprising: The battery pack which concerns on this invention is not limited to the following structures. Moreover, although this embodiment is set as the structure which connected two cells in series, it is not limited to this structure, When three or more cells are connected in series, the block which connected the several cell in parallel is connected in series. Even in the connected configuration or a combination thereof, the same effect can be obtained by the configuration in which the voltage for each cell or block is individually detected. In the case of a single cell, it can be applied by simplifying the configuration for measuring the voltage individually.

  FIG. 1 is a diagram showing a circuit configuration of a battery pack according to the present invention. In FIG. 1, parts having the same configurations as those in FIG. 3 showing the conventional circuit configuration are given the same numbers, and detailed descriptions thereof are omitted.

  The battery pack 10 is connected to the charging device 20 together with the cell 1, the cell 2, the protection circuit 3 that protects these cells from overcharge and overdischarge, the thermistor element 7 that detects the ambient temperature of the cell, and the positive and negative terminals. A thermistor terminal 6 that is electrically connected, a charge detection circuit 8 that detects the charge states of the cells 1 and 2, and a short-circuit means that is controlled by the charge detection circuit 8 to short-circuit the thermistor element 7. Some switch means 9 is added.

  The thermistor element 7 is arranged in the vicinity of the cell as in the conventional case, detects the temperature of the cell 1 and cell 2, and the resistance value changes depending on the ambient temperature of these cells. The charging control circuit 21 estimates the ambient temperature of the cell from the resistance value of the thermistor element 7. The charging control circuit 21 performs charging only when the ambient temperature of the cell is within a predetermined range, and the charging current supplied to the battery pack 10 is Take control.

  In the present invention, the thermistor element 7 detects the ambient temperature of the cell, but the thermistor element 7 is used as a kind of temperature detection circuit. Therefore, another temperature detection circuit may be used instead of the thermistor element 7.

  In the present invention, the thermistor element 7 is short-circuited by the switch means 9, but a short circuit in which the switch means 9 and a resistor having a smaller resistance value than the thermistor element 7 are connected in series may be used. By forming a short circuit with a resistance value of 0 from the thermistor element 7, the device-side charge control circuit 21 that receives the output from the thermistor terminal 6 may malfunction due to a sudden change in data. The switch circuit 9 and a short circuit of a resistor having a small resistance value can alleviate a sudden change in data.

  In this embodiment, it is set as the structure which detects the ambient temperature of the cell matched with the test conditions which a technical standard defines. On the other hand, JIS C 8714 including technical standards requires that a standard temperature range is set as a temperature condition for charging the cell and the assembled battery, and the surface temperature of the cell is detected. Therefore, it is preferable to select the ambient temperature of the cell and the surface temperature of the cell as the temperature of the cell detected by the thermistor element according to the temperature detection method required by the technical standards. In order to detect the surface temperature of the cell, a thermistor element is arranged in the vicinity of the cell as in this embodiment, and in addition to the configuration for estimating the surface temperature of the cell, the thermistor is used to increase the detection accuracy of the surface temperature. A configuration in which the element 7 is brought into contact with the surface of the cell and the temperature of the cell surface is directly detected may be used.

  The charge detection circuit 8 is configured to be able to individually measure the voltage of each cell, like the protection circuit 3. Further, the charging state is determined from the measured voltage value of the cell, and on / off control of the switch means 9 is performed in order to indirectly control the charging current from the charging device 20. The charge detection circuit 8 sets the upper limit charging voltage defined by the technical standards as a threshold value, and when the voltage of at least one of the cells is 4.25 V or more, the switch means 9 is turned on. The thermistor element 7 is brought into a short circuit state. Further, when both the voltages of the cell 1 and the cell 2 are lower than 4.25V, the thermistor element 7 is returned from the short-circuited state by turning off the switch means 9.

  As a result, the state of charge of the cells varies during the charging period, and when the voltage of either cell 1 or cell 2 reaches 4.25 V, the switch means 9 is turned on so that both cells 4. When the voltage drops below 25 V, the switch means 9 is turned off. That is, the charge detection circuit 8 detects each cell voltage during the charging period, and compares the voltage with the upper limit charging voltage required by the technical standard, so that the voltage of each cell becomes the upper limit charging voltage of the charging voltage. It is to be controlled so as not to exceed.

  When the ambient temperature of the cell 1 and the cell 2 exceeds the chargeable temperature range, the thermistor element 7 has a resistance value for stopping the current supply from the charging device 20 regardless of the detection state from the charge detection circuit 8. Will be shown.

  As for the charge detection circuit 8, it is preferable to take into consideration that a detection error occurs in the cell voltage detection. At this time, the detection error is assumed to be about ± 0.03 V, and the charge detection circuit 8 is set to operate at a voltage of 4.25 V or more even with the maximum value of this error.

  On the other hand, the charging control circuit 21 of the charging device 20 is connected to the thermistor element 7 via the thermistor terminal 6 and detects that the thermistor element 7 of the battery pack is short-circuited. At this time, the charging control circuit 21 determines that the temperature of at least one of the cell 1 and the cell 2 exceeds the chargeable temperature range, and performs control so as to stop the charging current supplied to the battery pack. Do.

  When the charging current from the charging device 20 is stopped, the cells 1 and 2 of the battery pack 10 are in a state indicating the open circuit voltage of each cell, and the charge detection circuit 8 is in a state of detecting the open circuit voltage for each cell. At this time, if both of the open circuit voltage values are lower than the upper limit charging voltage, the charging detection circuit 8 turns off the switch means 9 so that both the temperatures of the cells 1 and 2 are charged in the charging device 20. Indicates that the product has recovered within the possible temperature range. As a result, the charging device 20 resumes the supply of the charging current to the battery pack 10, and the charging of the cell 1 and the cell 2 is continued as long as all other conditions for continuing the charging are satisfied. Become.

  As is clear from the above, the battery pack 10 according to the present embodiment shorts the short circuit to the charging device 20 by short-circuiting the thermistor element 7 when the voltage of at least one of the cells reaches the upper limit charging voltage. It is configured to detect and indirectly stop the charging current. With this configuration, the charging current can be controlled so that the upper limit charging voltage is not exceeded by the control of the battery pack alone.

  In addition to the above configuration, the battery pack 10 includes a protection circuit 3 that measures the voltage of each cell individually and prevents overcharge / overdischarge, as in the conventional configuration. The protection circuit 3 controls the overcharge FET 4 and the overdischarge FET 5 arranged in the charge / discharge path. When the cell voltage exceeds the voltage value for overcharge and overdischarge protection, the cell is overcharged. It is determined that the battery is charged or overcharged, and the corresponding FET is turned off.

  In the battery pack according to the present invention, the overcharge protection voltage needs to be set to a value exceeding the upper limit charging voltage, for example, about 4.35V. If the overcharge protection voltage is set to a value lower than the upper limit charge voltage, the overcharge protection by the protection circuit 3 is activated prior to the charge control by the charge detection circuit 8, and it is assumed that charging is insufficient due to this. Is done.

  In the present invention, the overcharge FET 4 and the overdischarge FET 5 set the cell overcharge or overcharge state to the OFF state, but an FET is used as a kind of switch element. Therefore, a switch element may be used instead of the FET.

  In the charging device 20, the charging control circuit 21 controls charging. The charge control circuit 21 does not individually detect the voltages of the cell 1 and the cell 2, but performs control based on the output voltage of the battery pack 10, that is, the total value of the voltages of the cell 1 and the cell 2.

  Normally, charging of a lithium ion battery uses constant current / constant voltage control. The charging control circuit 21 performs charging with a constant current until a predetermined voltage is reached. In this embodiment, cell 1 and cell 2 are connected in series, and constant current charging is performed until 8.4 V is reached. Then, after reaching a predetermined voltage value, the voltage is maintained at a constant voltage, and charging is continued while gradually decreasing the charging current until full charge is reached. At this time, the charging control circuit 21 detects and controls the current by a charging current detection resistor arranged in the charging path in the charging device 20. In the present embodiment, if the voltages of the cells 1 and 2 do not vary, the predetermined voltage value is reached without reaching the upper limit charging voltage.

  In the present embodiment, the charge detection circuit 8 and the protection circuit 3 are configured as separate circuits. Both of these circuits are identical in the configuration in which the voltage for each cell is individually detected, and a means for detecting the voltage for each cell block connected individually or in parallel with the cells accommodated in the battery pack is provided. The voltage value is input to the charge detection circuit 8 and the protection circuit 3 from the means, or the charge detection circuit and the protection circuit are configured by a single microcomputer, and the microcomputer controls the switching means and the overcharge / overdischarge FETs. You may employ | adopt the structure to do. In these structures, since the site | part which detects the voltage of a cell is integrated, the reduction effect of the number of parts of a battery pack is acquired.

  In the present embodiment, the charging device 20 and the battery pack 10 are independent components, and the charging system is configured to perform charging in a state in which these are combined. However, the present invention is not limited to the present embodiment, and the function of the charging device 20 is assigned to a device that uses the battery pack 10 and further combined with the device and the battery pack, or the battery pack 10 is used as the device. The present invention can also be applied to a housing and the like.

  Next, the charging procedure in the present embodiment will be described according to the flowchart shown in FIG. In this flowchart, a charging procedure in a state where the battery pack 10 and the charging device 20 are combined is shown, and each step is given a number such as S01.

  The charging device 20 detects that the battery pack 10 is mounted by connecting the thermistor terminal 6 provided in the battery pack 10 to the charging device 20. Upon receiving this detection, the charging device 20 and the battery pack 10 start a charging process including the steps shown in FIG.

  Prior to the start of charging, in step S01, in the battery pack 10, the charge detection circuit 8 detects the voltages of the cell 1 and the cell 2. At this time, no charging current is supplied to the cell, and each of the above voltages indicates the open circuit voltage of the cell. If both the voltages of the cells are lower than the upper limit charging voltage, the charging detection circuit 8 maintains the switch means 9 in the OFF state in step S02, and the value of the thermistor element 7 is supplied to the charging device 20 via the thermistor terminal 6. Is input.

  In step S01, if the value exceeds the upper limit charging voltage, in step S11, the charge detection circuit 8 turns on the switch means 9 and puts the thermistor element 7 into a short circuit state. Thereby, the value of a short circuit state is input into the charging device 20 through the thermistor terminal 6 as step S12.

  Next, the charging device 20 determines whether or not charging can be started. In step S03, the charging control circuit 21 estimates the ambient temperature of the cells 1 and 2 from the value input from the thermistor terminal 6, and this temperature is within a predetermined range (from 10 ° C. in a battery pack using a lithium ion battery). If it is determined that the temperature is within the range of 45 ° C., the charging control circuit 21 starts charging (step S04).

  In step S03, when the short-circuited value of the thermistor element 7 is input to the charge control circuit 21, the charge control circuit 21 determines that the cell temperature is outside the chargeable range, as in step S31. Refrain from starting charging. For this reason, charging is not started and the standby state is maintained. When the charge control circuit 21 determines that charging is not started (standby state), the battery pack 10 returns to step S01 for detecting each voltage of the cell again. Therefore, as is apparent from the above steps, the charging device 20 remains in the standby state until each voltage of the cell falls below 4.25 V and the charging control circuit 21 determines that the temperature is within the chargeable temperature range. The charging of the battery pack 10 is not started.

  When charging from the charging device 20 is started in step S04, the charging control circuit 21 detects the charging current from the total voltage of the cells 1 and 2 and the detection resistor provided in the charging path, and is supplied to the battery pack 10. The battery is charged by controlling the voltage and current.

  Next, as shown in step S05, the battery pack 10 compares the voltages of the cells 1 and 2 with the overcharge protection voltage in the protection circuit 3. When the charging current is supplied, that is, during the charging, when the voltage value detected in one of the cells reaches the overvoltage protection value (4.3 V) set in advance in the battery pack 10 In accordance with step S51, the protection circuit 3 operates the overcharge FET 4, interrupts the charge / discharge path in the battery pack 10, and stops supplying the charging current to each cell. At this time, as shown in step S <b> 52, the voltage of the battery pack 10, that is, the pack voltage between the positive and negative terminals, indicates the voltage applied from the charging device 20.

  On the other hand, in step S05, if the voltage of each cell does not reach the overcharge protection voltage in the protection circuit 3 during the charging, the overcharge FET 4 maintains the normal state and charges the battery pack 10. Supply of current continues. At this time, as shown in step S06, the voltage of the battery pack 10, that is, the voltage between the positive and negative terminals is the sum of the voltages of the cells 1 and 2, that is, the sum of the closed circuit voltage values of each cell.

  Next, the charging device 20 confirms the voltage of the battery pack 10 in step S07 and determines the state of charge of the battery pack. As described above, when the overcharge voltage is equal to or higher in step S05, in the state where the overcharge FET 4 is activated in step S51, the output voltage of the battery pack 10 is the same as the output voltage from the charging device 20, and The charging current that is interrupted by the charge / discharge circuit is not supplied. The charging device 20 is in a state where the overcharge FET 4 is operated in the battery pack 10 based on the output voltage and the charging current of the battery pack 10, and at least one of the cell 1 and the cell 2 is in an overcharged state. Judge.

  In this case, in order to notify the charging device 20 and the user of the battery pack 10 that charging has stopped due to an abnormality, the charging device 20 operates a means for indicating charging abnormality in step 71 and the charging control circuit 21 is abnormal. Maintain a stop by condition. In addition, as means for indicating the charging abnormality, blinking by an LED or the like can be used. Further, when the user tries to charge again, this flowchart can be implemented from the beginning by resetting the charging control circuit 21.

  On the other hand, if the overcharge voltage is not reached in step S05, that is, if the overcharge FET 4 is not operating, the output voltage of the battery pack 10 in step S07 is the voltage output in step S06, that is, cell 1, cell 2, and the supply of the charging current to the battery pack 10 is continued. The charging device 20 determines that charging of the battery pack 10 is proceeding normally from the status of the output voltage and charging current of the battery pack 10 as described above.

  Subsequently, the charging device 20 determines the state of charge of the battery pack 10 from the output voltage and the charging current of the battery pack 10 in step S08. As described above, the charging device 20 charges the battery pack 10 with constant current / constant voltage control. The output voltage of the battery pack 10 increases with the progress of charging, and after reaching a predetermined voltage value for shifting to constant voltage charging, the voltage value is gradually maintained, the charging current is lowered, and the charging current is charged. It is determined that the cells in the battery pack are in a fully charged state at a stage where the current value is reduced to a predetermined current value, which is the end condition of the above.

  As described above, the charging device 20 determines the charging termination condition from the charging voltage and the charging current in step S08, and determines that the charging is normally completed in a state where the charging current is reduced to the predetermined value. Furthermore, based on this determination, the user can be notified of the completion of charging by notifying the normal end of charging by means of a display means or the like.

  On the other hand, if the charging termination condition is not satisfied, charging device 20 determines to continue charging in step S08, and returns to the step after the start of charging. Thereby, in step S01 in which the charge detection circuit 8 in the battery pack 10 measures the charging voltage of each cell, this flowchart is executed again and the charging is continued. In this case, since charging is continued, each voltage of the cell 1 and the cell 2 indicates the value of the closed circuit voltage.

  Furthermore, charging is continued by repeating the above-described operation, and the output voltage of the battery pack 10 rises to a predetermined voltage value. In this embodiment, the output voltage of the battery pack is set to a predetermined value (4.2 V per cell). In this embodiment, after rising to 8.4 V), the predetermined voltage value (8.4 V) is maintained, and charging is performed by gradually reducing the charging current. The charging termination condition is normally set to a state in which the charging current has decreased to a predetermined current value or a state in which the charged capacity has reached a predetermined capacity value, and charging is continued until these states are reached. The As described above, the battery pack of this embodiment is controlled so that the voltage of each cell does not exceed the upper limit charging voltage, and by sufficiently increasing the capacity of the battery, a sufficient charging capacity of the battery pack 10 can be ensured. Is possible.

  In the present embodiment, when the charging detection circuit 8 of the battery pack 10 reaches the upper limit charging voltage in a state where charging is continued, charging is set in a standby state and supply of charging current from the charging device 20 is stopped. The method to do was adopted. At this time, each voltage of the cell 1 and the cell 2 of the battery pack 10 indicates the value of the open circuit voltage, and the voltage drop due to the internal resistance during charging is excluded from the voltage during the charging period, that is, the closed circuit voltage. Value. For this reason, the standby for charging is maintained for a long time, which may increase the charging time. For this reason, when charging is continued, it is possible to reduce the charging current, lower the voltage value of each cell, and adopt a configuration that continues charging, so it is possible to avoid prolonged charging time It is.

  In addition, when employ | adopting the said structure, in order to control the charging current of the charging device 20 from the battery pack 10, it is necessary to make the charging device 20 recognize that the ambient temperature of a cell rises and the restriction | limiting of a charging current is required. There is. Therefore, the charging detection circuit 8 switches the switch means 9 to bring the resistance value of the thermistor element 7 into a reduced state, thereby causing the charging device 20 to recognize that the ambient temperature of the cell has increased, and to charge the charging current. It can be reduced.

  As described above, in the battery pack according to the present embodiment, the charge detection circuit 8 detects the charging voltage of the cell, and when the charging upper limit voltage is reached, the thermistor terminal 6 is short-circuited, and the charging current from the charging device 20 is It has the feature in the point which restrict | limits. In order to clarify this feature, the charging procedure in the battery pack having the conventional configuration shown in FIG. 3 will be described with reference to FIG. 4 and compared with the procedure according to the present embodiment. In FIG. 4, steps that are the same as in the present embodiment are denoted by the same reference numerals (steps).

  In the procedure shown in FIG. 4, prior to the start of charging, the charging device 20 estimates the ambient temperature of the cells 1 and 2 from the value input from the thermistor terminal 6 of the battery pack 10 in step S02, and each cell in step S03. When the ambient temperature is within a predetermined range, charging is started. At this time, the voltage of each cell by the charge detection circuit 8 is not measured, and the start of charging is determined only by the ambient temperature of the cell.

  The subsequent procedure is the same as the procedure according to the present embodiment shown in FIG. When the charging device 20 determines to continue charging, the charging device 20 does not include the charge detection circuit 8, does not perform determination based on the charging voltage of each cell, and detects the ambient temperature of the cell detected by the thermistor element 7. Whether or not to continue the charging is determined with reference to the output voltage and the charging current of the battery pack detected by its own charge control circuit 21. Therefore, in the battery pack that adopts the configuration shown in FIG. 3 and performs charging according to the procedure shown in FIG. 4, the control based on the upper limit charging voltage required by the technical standard is not performed, and the technical standard is satisfied. The situation is impossible.

  Therefore, similarly to the configuration described in the section of the problem to be solved by the invention of the present application, a configuration in which the upper limit charging voltage is set to the value of the voltage for performing overcharge protection, and the protection circuit 3 controls the charging voltage. To consider.

  In FIG. 4, when the charging device 20 starts charging, the voltage of each cell rises. Charging is continued in step S04, and in step S05, the charge voltage of at least one of cell 1 and cell 2 is compared with the overcharge voltage set in the protection circuit 3. At this time, when the overcharge voltage, that is, 4.25 V is reached, the protection circuit 3 turns off the overcharge FET 4 according to step S51. Thereby, supply of the charging current from the charging device 20 to the battery pack 10 is stopped, and the output voltage of the battery pack 10 becomes the charging voltage of the charging device 20 as shown in step S52. If the overcharge voltage has not been reached in step S05, charging is continued, and the pack voltage in step S06 is the sum of the voltages of cell 1 and cell 2.

  In the next step S07, the charging device 20 determines the voltage of the battery pack 10 from the status of the output voltage and the charging current. If the voltage of the battery pack 10 is the charging voltage in step S07, the overcharge FET 4 operates, and it is determined in step S71 that at least one cell is in the overcharged state. By this determination, charging stops due to an abnormality, charging is interrupted, and a state of insufficient charging is caused. Further, in the configuration provided with means for indicating charging abnormality of the charging device 20, since the means operates, there is a possibility that the user may recognize that charging is stopped due to abnormality of the battery pack 10.

  Furthermore, as a means for avoiding the interruption of charging as described above, a configuration in which the charging device 20 sets the charging voltage to a voltage lower than the upper limit charging voltage is also assumed. In this case, as described above, it is avoided that the overcharge FET 4 operates and the charging is terminated in the interrupted state. However, when the charging voltage is set to be low, the charging device 20 has a small constant current charging region, and in this state, the charging device 20 shifts to a constant voltage charging control region. For this reason, not only the charging time is increased, but the final charging capacity value has a low charging voltage, so that a sufficient charging capacity cannot be ensured.

  The battery pack of the present invention inputs the apparent abnormal value to the charging device 20 by short-circuiting the thermistor element 7 only when the charging upper limit voltage detected by the charging detection circuit 8 is reached. It is in a charging standby state, and charging is not interrupted in the middle. Further, since the battery pack 10 is charged up to a predetermined voltage value without exceeding the upper limit charging voltage, it is possible to sufficiently ensure the electric capacity.

  The battery pack according to the present invention is premised on a combination with a charging device that performs charging control based on temperature information and output voltage from the battery pack, and individually measures the charging voltage of the accommodated cell, When the battery reaches the specified upper limit charging voltage, the charging current supplied to the battery pack is stopped or the current value is controlled to achieve a configuration that allows cells to continue charging without exceeding the upper limit charging voltage. To do. Furthermore, by continuing the control during the charging period, the battery capacity is gradually increased, and the charged cell can be charged to a state close to full charge, so that the charging capacity of the cell is sufficiently secured. Is possible.

1, 2 cell 3 protection circuit 4 overcharge FET
5 Overdischarge FET
6 Thermistor terminal 7 Thermistor element 8 Charge detection circuit 9 Switch means 10 Battery pack 20 Charging device 21 Charge control circuit

Claims (3)

A chargeable / dischargeable cell;
A switching element disposed in a charging path including the cell and controlling charging of the cell;
A protection circuit that turns off the switch element when the voltage of the cell reaches a preset overcharge voltage;
A temperature detection circuit for detecting the ambient temperature of the cell;
A battery pack provided with a temperature detection terminal for externally outputting the value of the temperature detection circuit,
A charge detection circuit that detects the voltage of the cell and compares it with a charge control voltage set to a voltage lower than the overcharge voltage;
Controlled by the charge detection circuit, comprising short-circuit means for short-circuiting the temperature detection circuit,
The battery pack, wherein when the charge voltage of the cell reaches the charge control voltage, the charge detection circuit turns on the short-circuit means.   2. The battery pack according to claim 1, wherein the value of the charging control voltage is set to 4.25 V, which is an upper limit charging voltage defined in a confirmation test for overcharge protection of a JIS C 4714 battery pack. A charging system comprising a battery pack and a charging device for charging the battery pack;
The battery pack is a chargeable / dischargeable cell, a switching element that is arranged in a charging path including the cell, and controls the charging of the battery pack, and the switching element when the voltage of the cell reaches a preset overcharge detection voltage A protection circuit that performs overcharge protection in an off state, a temperature detection circuit that detects a temperature of the cell, a temperature detection terminal that outputs a value of the temperature detection circuit to a charging device, and further detects a voltage of the cell, A charge detection circuit for comparing with a charge control voltage set to a voltage lower than the overcharge voltage, comprising a short-circuit means controlled by the charge detection circuit and connected in parallel to the temperature detection circuit;
The charging device controls the charging current supplied to the battery pack, the charging voltage, and based on the temperature detection of the cell input from the temperature detection terminal, performs charging when the temperature is in a predetermined range,
When the charge voltage of the cell reaches a charge control voltage, the charge detection circuit turns on the short-circuit means, and outputs that the temperature of the cell is out of the temperature range that can be charged from the temperature detection terminal,
The charging device receives the output from the temperature detection terminal and stops supplying a charging current to the battery pack.