JP2009097954A - Battery pack and residual capacity correction method of secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery pack and a residual capacity correction method of a secondary battery, capable of calculating a residual capacity correction voltage based on a smaller amount of data than hitherto, and correcting accurately the residual capacity of the secondary battery. <P>SOLUTION: This battery pack includes the secondary battery 7; a measuring part 12 for measuring a voltage, a current and an internal resistance when using the secondary battery 7; a residual capacity detection part for detecting the residual capacity of the secondary battery 7 based on a measurement result; and a residual capacity correction part for correcting the residual capacity detected by the residual capacity detection part, when the voltage of the secondary battery 7 becomes lower than the residual capacity correction voltage. The residual capacity correction part calculates the first open voltage when discharge from the secondary battery 7 is stopped by using the measured current and internal resistance, calculates the second open voltage when performing residual capacity correction of the secondary battery 7 from the first open voltage, and calculates a closed circuit voltage when performing residual capacity correction of the secondary battery 7 from the second open voltage and the measured current and internal resistance of the secondary battery 7, to thereby determine the residual capacity correction voltage. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a battery pack and a method for correcting a remaining capacity of a secondary battery, and more particularly, to a battery pack for calculating a remaining capacity correction voltage using an open voltage of a secondary battery and a method for correcting a remaining capacity of a secondary battery.

  Battery packs including secondary batteries are widely used as power sources for various electronic devices, and it is widely used to inform users of the remaining capacity of battery packs by flashing light emitting diodes, liquid crystal displays, alarms, etc. Yes.

  As a method of detecting the remaining capacity of the secondary battery, a detection method by a voltage method for detecting the remaining capacity of the secondary battery by measuring the battery voltage, and measuring and integrating the voltage and current, Examples include a detection method using an integration method for obtaining the remaining capacity of the battery.

  The remaining capacity detection by the voltage method is based on the correlation between the voltage of the secondary battery and the battery capacity (remaining capacity ratio) by measuring the terminal voltage (closed circuit voltage, CCV: Closed circuit voltage) when the battery cell is used. Calculate the remaining capacity. For example, in the case of a lithium ion battery, when the battery voltage is fully charged at 4.2 V / cell and becomes 2.4 V / cell, it can be determined that the battery is in an overdischarged state.

  In addition, the remaining capacity detection by the integration method measures the current, integrates the current accumulated every fixed time, measures the voltage and current, and multiplies them to calculate the power and calculates the power There is a power integration method that integrates. In either case, the amount of discharge current or the amount of discharge power can be determined, and the remaining capacity of the secondary battery can be determined from the ratio of the amount of current or power that the battery can use.

  However, in the remaining capacity detection by the voltage method, it is difficult to accurately detect the remaining capacity because the battery voltage varies depending on the flowing current and the change in internal resistance even if the remaining capacity is the same. Further, for example, in the case of a lithium ion battery, a voltage difference does not occur so much at the intermediate potential of the secondary battery, so that it is difficult to detect the remaining capacity by voltage.

  On the other hand, in the remaining capacity detection by the integration method, errors are accumulated together with the accumulated current or power due to voltage and current measurement errors and heat loss, so the accuracy of the remaining capacity detection deteriorates at the end of discharge. There is. In particular, it is difficult to detect the remaining capacity with high accuracy in a secondary battery whose performance has deteriorated.

  Depending on the electronic device using the secondary battery, it is required to accurately detect the remaining capacity. Therefore, the following Patent Document 1 discloses basic data on the relationship between the storage amount of the secondary battery that has not deteriorated, the open-circuit voltage, and the storage amount and the internal resistance, and the voltage of the secondary battery in use (closed voltage). And a method of calculating the remaining capacity according to the detected internal state by detecting the internal state of the battery by comparing the current value with the current value.

JP 2002-50410 A

  By the way, in a battery pack used for, for example, a notebook personal computer (PC), when the closed circuit voltage CCV per unit cell reaches a discharge stop voltage (for example, 3.0 V), the remaining capacity is 0%. Judgment is made and discharge is stopped. This is based on data in which the remaining voltage is 100% when the battery voltage is fully charged, the remaining capacity is decreased as the discharge current is integrated, and the remaining capacity is 0% at the discharge stop voltage of 3.0V. Such management is performed by a microcomputer (hereinafter referred to as a microcomputer) or a CPU (Central Processing Unit) incorporated in the battery pack. In this specification, the remaining capacity refers to a capacity ratio (RSOC: Relative State Of Charge) when the capacity from the discharge stop voltage to the full charge voltage of the secondary battery is 100%.

  However, if the internal resistance increases due to deterioration due to the use of the battery pack, a deviation occurs between the remaining capacity managed by the microcomputer or CPU and the remaining capacity actually detected by the integration method. The capacity cannot be displayed. As a result, the PC shuts down even though it is displayed that there is still remaining capacity, or the PC suddenly turns off without being able to perform hibernation.

  In order to avoid such a phenomenon, the remaining capacity is corrected by the closed circuit voltage at the end of discharge. With reference to FIG. 6, the remaining capacity correction by the closed circuit voltage will be described. In FIG. 6, the horizontal axis indicates the discharge time, and the vertical axis indicates the cell voltage (closed circuit voltage CCV) and the remaining capacity of the secondary battery. The remaining capacity of the secondary battery is calculated by current integration.

  For example, when the remaining capacity is corrected at a remaining capacity of 5% at the end of discharge, the remaining capacity correction voltage Va when the remaining capacity is 5% (remaining capacity correction point) is calculated, as shown by an arrow a in FIG. When the cell voltage reaches the remaining capacity correction voltage Va, the remaining capacity is corrected. The remaining capacity correction voltage Va is the closed circuit voltage CCV when the secondary battery in an undegraded state is discharged at each temperature and current, and the closed circuit voltage CCV and discharge current during actual discharge using the discharge capacity as basic data. , And a variable value calculated from the temperature. Here, when the cell voltage reaches the remaining capacity correction voltage Va, the remaining capacity detected by the integration method is corrected by reducing the remaining capacity to 5%.

  However, there is a problem that the data used for calculating the remaining capacity correction voltage Va becomes enormous and the calculation process becomes complicated. Also, it is difficult to accurately calculate the remaining capacity correction voltage Va that matches the actual remaining capacity due to deterioration of the secondary battery, temperature change, discharge current fluctuation, and the like. Therefore, as indicated by an arrow b in FIG. 6, the remaining capacity becomes 0% when the cell voltage is about 3170 mV, for example. That is, despite the remaining capacity correction, as shown by the arrow c, a deviation occurs between the corrected remaining capacity and the actual remaining capacity.

  The one described in Patent Document 1 described above has a problem that the detection process of the internal state of the battery pack is complicated and the data used for the remaining capacity calculation process becomes enormous. Further, Patent Document 1 does not correct an error of the detected remaining capacity.

  Accordingly, an object of the present invention is to provide a battery pack and a secondary battery remaining capacity correction method capable of accurately correcting the remaining capacity of a secondary battery based on less data than in the past.

In order to solve the above-described problem, the first invention includes a secondary battery,
A measuring unit for measuring voltage, current, and internal resistance when using a secondary battery;
Based on the result measured by the measurement unit, a remaining capacity detection unit that detects the remaining capacity of the secondary battery,
A remaining capacity correction unit that corrects the remaining capacity detected by the remaining capacity detection unit when the measured voltage of the secondary battery is equal to or lower than the remaining capacity correction voltage;
The remaining capacity correction unit
Using the measured current and internal resistance of the secondary battery, calculate the first open circuit voltage when the discharge of the secondary battery is stopped,
From the first open-circuit voltage, a second open-circuit voltage when correcting the remaining capacity of the secondary battery is calculated,
The remaining capacity correction voltage is obtained by calculating a closed circuit voltage when correcting the remaining capacity of the secondary battery from the second open circuit voltage, the measured current of the secondary battery, and the internal resistance. Battery pack.

2nd invention measures the voltage at the time of a secondary battery use, an electric current, and internal resistance,
Detecting the remaining capacity of the secondary battery based on the measured result;
Correcting the detected remaining capacity when the measured voltage of the secondary battery becomes equal to or less than the remaining capacity correction voltage, and
The remaining capacity correction voltage is
Using the measured current and internal resistance of the secondary battery, calculate the first open circuit voltage when the discharge of the secondary battery is stopped,
From the first open-circuit voltage, a second open-circuit voltage when correcting the remaining capacity of the secondary battery is calculated,
The secondary battery is obtained by calculating a closed circuit voltage when correcting the remaining capacity of the secondary battery from the second open circuit voltage, the measured current of the secondary battery, and the internal resistance. This is a remaining capacity correction method.

  In the first and second inventions, specifically, the second open circuit voltage is the first discharge depth corresponding to the first open circuit voltage based on the data on the open circuit voltage and the discharge depth of the secondary battery. From this, it is possible to obtain the second discharge depth by subtracting the remaining capacity when performing the remaining capacity correction, and obtain the open circuit voltage corresponding to the second discharge depth.

  In the first and second inventions, when the secondary battery discharge is stopped, the remaining capacity ratio of the secondary battery is 0%, and the voltage of the secondary battery reaches the remaining capacity correction voltage. In addition, the remaining capacity detected by the remaining capacity detecting unit can be corrected to the remaining capacity when performing the remaining capacity correction.

  In the first and second inventions, it is preferable that the remaining capacity correction voltage is calculated at regular intervals.

  In the first and second inventions, it is preferable to measure the temperature at the time of using the secondary battery and vary the remaining capacity correction voltage according to the measured temperature.

  In this invention, since the remaining capacity correction voltage is calculated using the open-circuit voltage of the secondary battery, the remaining capacity that matches the actual remaining capacity without being affected by an increase in internal resistance due to deterioration of the secondary battery. The correction voltage can be obtained.

  According to the present invention, the remaining capacity correction voltage is calculated using the open-circuit voltage of the secondary battery, so that the remaining capacity of the secondary battery can be accurately corrected regardless of the deterioration of the secondary battery or the usage situation of the user. It can be carried out. Further, the remaining capacity correction voltage can be calculated based on less data than in the past.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an example of the configuration of a battery pack according to an embodiment of the present invention. This battery pack mainly includes a secondary battery 7, an overvoltage detection unit 10, a measurement unit 12, a CPU 13, a clock terminal 3a, a communication terminal 3b, a temperature detection terminal 3c, and a charge / discharge control switch 4. The + terminal 1 of the battery pack is connected to the + terminal of the secondary battery 7 via the overvoltage protection fuse 11 and the charge / discharge control switch 4. On the other hand, the − terminal 2 is connected to the − terminal of the secondary battery 7 through the current detection resistor 9. The thermistor 14 is connected between the terminal 2 and the temperature detection terminal 3c.

  Note that the measurement unit, which is a component of the present invention, corresponds to the measurement unit 12, and the remaining capacity detection unit and the remaining capacity correction unit correspond to the CPU 13.

  In the battery pack, when an electronic device is used, the + terminal 1 and the −terminal 2 are connected to the + terminal and −terminal of the device, and discharging is performed. In addition, the battery pack is attached to the charger during charging, and the + terminal 1 and −terminal 2 are connected to the + terminal and −terminal of the charger, respectively, as in the case of using the electronic device, and charging is performed. The battery pack communicates with a connected charger or a load such as an electronic device via the communication terminal 3b so that information such as the remaining capacity of the secondary battery 7 can be notified. Yes. The device that receives this information displays the battery capacity, the remaining capacity rate, and the like on a display unit such as a liquid crystal display.

  The secondary battery 7 is a secondary battery such as a lithium ion battery, and has a configuration in which, for example, a cell block 7a, a cell block 7b, and a cell block 7c in which two battery cells are connected in parallel are connected in series. As the secondary battery 7, for example, a secondary battery having a full charge voltage per battery cell of 4.2V can be used.

  The measurement unit 12 measures the voltage and internal resistance of each of the cell block 7a, cell block 7b, and cell block 7c in the battery pack, and supplies the measured value to the CPU 13. Hereinafter, each voltage of the cell block 7a, the cell block 7b, and the cell block 7c including two single battery cells is referred to as a cell voltage.

  The measuring unit 12 measures the magnitude and direction of the current using the current detection resistor 9 and sends the measured value to the CPU 13. Furthermore, the measurement unit 12 also has a function as a regulator that stabilizes the voltage of the secondary battery 7 and generates a power supply voltage.

  When the cell voltage of any one of the cell block 7a, the cell block 7b, and the cell block 7c becomes an overcharge detection voltage, or when any of the cell voltages becomes less than the overdischarge detection voltage, the measurement unit 12 By sending a control signal to the charge / discharge control switch 4, overcharge and overdischarge are prevented. Here, in the case of a lithium ion battery, the overcharge detection voltage is determined to be 4.2 V ± 0.5 V, for example, and the overdischarge detection voltage is determined to be 2.4 V ± 0.1 V.

  The charge / discharge control switch 4 includes a charge control FET (Field Effect Transistor) 5 and a discharge control FET 6. Parasitic diodes 5 a and 6 a exist between the drain and source of the charge control FET 5 and the discharge control FET 6. Parasitic diode 5a has a reverse polarity with respect to a charging current flowing from + terminal 1 in the direction of secondary battery 7 and a forward polarity with respect to a discharging current flowing from −terminal 2 in the direction of secondary battery 7. The parasitic diode 6a has a polarity in the forward direction with respect to the charging current and in the reverse direction with respect to the discharging current.

  Control signals from the measurement unit 12 are supplied to the gates of the charge control FET 5 and the discharge control FET 6, respectively. In normal charging and discharging operations, the control signal is set to a low level, and the charge control FET 5 and the discharge control FET 6 are turned on. Since the charge control FET 5 and the discharge control FET 6 are P-channel type, they are turned on by a gate potential that is lower than the source potential by a predetermined value or more.

  When the battery voltage becomes the overcharge detection voltage, the charging control FET 5 is turned off and the charging current is controlled not to flow. Further, when the battery voltage becomes the overdischarge detection voltage, the discharge control FET 6 is turned off, and the discharge current is controlled not to flow.

  The overvoltage detection unit 10 is connected to the overvoltage protection fuse 11, and when each cell voltage of the secondary battery 7 exceeds a specified voltage, the + side connecting the + terminal of the secondary battery 7 and the + terminal 1 of the battery pack is connected. By cutting off the connection of the power line, the secondary battery 1, the device body, the circuit in the battery pack, and the like are protected.

  The CPU 13 measures the voltage value and integrates the current value using the voltage value and current value supplied from the measurement unit 12, and calculates the remaining capacity of the secondary battery 7. Further, the battery temperature measured by a temperature detecting element (for example, a thermistor) indicated by reference numeral 8 is taken in. These measured values and the like are stored in a nonvolatile memory EEPROM (Electrically Erasable and Programmable Read Only Memory) (not shown) built in the CPU 13.

Further, the CPU 13 calculates the open circuit voltage OCV of each cell block using the current value and the internal resistance supplied from the measurement unit 12. The following formula (1) is used for calculating the open circuit voltage OCV.
Open circuit voltage OCV = Circuit voltage CCV−Current × Internal resistance (1)

  Further, when the cell voltage reaches the discharge stop voltage (for example, 3 V), the CPU 13 determines that the remaining capacity of the secondary battery 7 has reached 0% and stops the discharge in the battery pack. At this time, if the internal resistance increases due to deterioration of the secondary battery 7 or the like, an error occurs between the remaining capacity calculated by current integration and the actual remaining capacity. Therefore, the CPU 13 calculates the closed-circuit voltage CCV at the remaining capacity correction point as the remaining capacity correction voltage at the end of discharging, and when the cell voltage of the secondary battery 7 becomes equal to or lower than the remaining capacity correction voltage, the remaining capacity of the secondary battery 7 is calculated. Make corrections.

  In one embodiment of the present invention, the remaining capacity correction voltage is calculated by using standard data of the open circuit voltage (OCV) and the depth of discharge of the secondary battery 7 as basic data. The depth of discharge is the ratio of the capacity taken out with respect to the capacity of the secondary battery 7.

  FIG. 2 shows an example of standard data of the open circuit voltage OCV and the discharge depth. As shown in FIG. 2, the standard data of the open circuit voltage OCV and the depth of discharge is that the open circuit voltage OCV at the time of full charge is 0% of the discharge depth, and the discharge depth is 100% when the open circuit voltage OCV is discharged to 3.0V. It is data indicating the proportion of the capacity that has been used. Since the standard data of the open circuit voltage OCV and the discharge depth is not affected by the internal resistance, the correspondence relationship does not change even if the secondary battery 7 is deteriorated or the discharge rate is changed. Such standard data of the open circuit voltage OCV and the depth of discharge is stored in a ROM (Read Only Memory) of the CPU 13.

  Hereinafter, the calculation of the remaining capacity correction voltage using the standard data of the open circuit voltage OCV and the discharge depth will be specifically described with reference to FIG. FIG. 3 is a graph showing standard data of the open circuit voltage OCV and the depth of discharge, and an example of the cell voltage when the secondary battery 7 is discharged. The horizontal axis indicates the depth of discharge (%), and the vertical axis indicates the voltage (mV). In addition, the voltage in the standard data of the open circuit voltage OCV and the depth of discharge indicates the value of the open circuit voltage OCV, and the voltage in the cell voltage of the secondary battery 7 indicates the value of the closed circuit voltage CCV.

  Here, this battery pack stops the discharge in the battery pack when the cell voltage in use reaches 3 V which is the discharge stop voltage. Therefore, first, the value of the open circuit voltage OCV1 when the cell voltage reaches the discharge stop voltage 3V is calculated with the current discharge current and internal resistance. Hereinafter, the open circuit voltage OCV1 when the cell voltage reaches the discharge stop voltage 3V is appropriately referred to as a first open circuit voltage OCV1.

The first open circuit voltage OCV1 is calculated using the above-described equation (1). To explain with a specific example, when the current discharge current is 2800 [mA], the internal resistance is 118 [mΩ], and the discharge stop voltage CCV is 3.0 V, the first open circuit voltage OCV1 is obtained by the following equation. It is done. In the following equation, since the current is a discharge current, it is a negative value.
First open circuit voltage OCV1 = 3000 [mV] − (− 2800 [mA]) × 118 [mΩ]
≒ 3331 [mV]

  From the obtained first open-circuit voltage OCV1, the discharge depth c corresponding to the first open-circuit voltage OCV1 is obtained by referring to the standard data of the open-circuit voltage OCV and the discharge depth shown in FIG. Hereinafter, the discharge depth c corresponding to the first open circuit voltage OCV1 is appropriately referred to as a first discharge depth c.

  For example, when the first open circuit voltage OCV1 is 3331 mV, the first discharge depth c is 97.5%. That is, the remaining capacity of the secondary battery is 0% at a discharge depth of 97.5%.

Subsequently, the discharge depth d at the remaining capacity correction point is obtained. Hereinafter, the discharge depth d at the remaining capacity correction point is appropriately referred to as a second discharge depth d. The second discharge depth d is obtained by the following equation (2).
Second discharge depth d = first discharge depth c-remaining capacity at remaining capacity correction point (2)

Therefore, for example, when performing remaining capacity correction with 5% remaining capacity,
Second discharge depth d = 97.5 [%]-5 [%]
= 92.5 [%]
It becomes.

  From the obtained second discharge depth d, the open voltage OCV2 at the remaining capacity correction point is obtained by referring to the standard data of the open circuit voltage OCV and the discharge depth shown in FIG. Hereinafter, the open circuit voltage OCV2 at the remaining capacity correction point is appropriately referred to as a second open circuit voltage OCV2. For example, when the second discharge depth d is 92.5%, the second open circuit voltage OCV2 is 3532 mV.

Subsequently, the closed circuit voltage CCV1 of the remaining capacity correction point is obtained based on the current discharge current and the value of the internal resistance. The closed circuit voltage CCV1 at the remaining capacity correction point is calculated using the following equation (3).
Closed circuit voltage CCV = open circuit voltage OCV + current × internal resistance (3)

Specifically, when the current discharge current is 2800 [mA], the internal resistance is 118 [mΩ], and the second open circuit voltage OCV2 at the remaining capacity correction point is 3532 mV, the closed circuit voltage CCV1 at the remaining capacity correction point. Is obtained by the following equation.
Closed circuit voltage CCV1 of remaining capacity correction point = 3532 [mV] + (− 2800 [mA]) × 118 [mΩ]
≒ 3202 [mV]

  Based on the closed circuit voltage CCV1 of the remaining capacity correction point obtained as described above, the remaining capacity is corrected when the cell voltage of the secondary battery 7 becomes equal to or lower than the closed circuit voltage CCV1 of the remaining capacity correction point.

  The closed-circuit voltage CCV1 at the remaining capacity correction point is recalculated when the closed-circuit voltage, temperature, and current of each battery cell are measured at a constant cycle, and the remaining capacity correction is performed in response to fluctuations in internal resistance and current. The closed circuit voltage CCV1 is constantly updated.

  Further, it is possible to vary the closed circuit voltage CCV1 at the time of remaining capacity correction according to the battery temperature measured by the temperature detecting element 8. For example, since the internal resistance value decreases as the temperature increases, the closed circuit voltage CCV1 at the time of remaining capacity correction is increased in accordance with the temperature increase. As a result, the remaining capacity correction voltage can be obtained more accurately.

  FIG. 4 shows an example of changes in the remaining capacity of the secondary battery 7 and the cell voltage when the remaining capacity is corrected with the closed circuit voltage CCV1 at the remaining capacity correction point. The horizontal axis shows the discharge time, and the vertical axis shows the cell voltage and the remaining capacity.

  As shown in FIG. 4, the remaining capacity calculated by integrating the current values is corrected when the cell voltage reaches the closed circuit voltage CCV1 at the remaining capacity correction point. That is, in the example shown in FIG. 4, since the closed circuit voltage CCV1 of the remaining capacity correction point when the remaining capacity is 5% is calculated, when the cell voltage reaches the closed circuit voltage CCV1 of the remaining capacity correction point, Correction is performed by reducing the remaining capacity to 5%.

  Thus, by correcting with the closed circuit voltage CCV1 of the remaining capacity correction point, the remaining capacity can be adjusted to 0% when the cell voltage is 3000 mV, as indicated by an arrow e in FIG. it can.

  FIG. 5 is a flowchart schematically showing a flow of processing for calculating the remaining capacity correction voltage based on the standard data of the open circuit voltage OCV and the discharge depth and performing the remaining capacity correction. Unless otherwise specified, the CPU 13 performs the following processing.

  First, in step S1, the measurement unit 12 measures each cell voltage, current, internal resistance, and temperature. The measured value is supplied to the CPU 13.

  Next, in step S2, the value of the first open circuit voltage OCV1 when the cell voltage reaches the discharge stop voltage (for example, 3 V) is calculated based on the supplied current discharge current and the value of the internal resistance. The Note that the above equation (1) is used to calculate the first open circuit voltage OCV1.

  Subsequently, in step S3, with reference to the standard data of the open circuit voltage OCV and the discharge depth, the first discharge depth when the discharge is stopped is determined from the first open circuit voltage OCV1 determined in step S2. .

  Next, in step S4, the second discharge depth d at the remaining capacity correction point (for example, the remaining capacity of the secondary battery 7 is 5%) is calculated. Note that the second discharge depth d is obtained using the above-described equation (2).

  Subsequently, in step S5, with reference to the standard data of the open circuit voltage OCV and the discharge depth, the second open circuit voltage OCV2 at the remaining capacity correction point is determined from the second discharge depth d determined in step S4. .

  Next, in step S6, the closed-circuit voltage CCV1 of the remaining capacity correction point is calculated based on the current discharge current and internal resistance values. Note that the above equation (3) is used to calculate the closed circuit voltage CCV1 of the remaining capacity correction point.

  Subsequently, in step S <b> 7, the closed circuit voltage CCV <b> 1 at the remaining capacity correction point is compared with the minimum cell voltage among the cell voltages of the secondary battery 7 measured by the measurement unit 12. When it is determined that the closed circuit voltage CCV1 at the remaining capacity correction point is larger than the minimum cell voltage of the secondary battery 7, the process proceeds to step S1.

  On the other hand, when it is determined in step S7 that the closed circuit voltage CCV1 at the remaining capacity correction point is equal to or lower than the minimum cell voltage of the secondary battery 7, the process proceeds to step S8. In step S8, the remaining capacity detected by integrating the current value is corrected. For example, when the remaining capacity correction point is set when the remaining capacity of the secondary battery becomes 5%, the remaining capacity detected by integration of the current value is corrected to 5%.

  As described above, in the embodiment of the present invention, the standard of the open circuit voltage OCV and the depth of discharge is not based on the data of the voltage and the discharge capacity when discharged at each temperature and each current as in the prior art. Based on the data, the closed-circuit voltage CCV1 of the remaining capacity correction point is calculated. Therefore, the closed circuit voltage CCV1 of the remaining capacity correction point can be easily calculated with less information than before.

  Further, since the closed-circuit voltage CCV1 of the remaining capacity correction point can be calculated without being affected by the deterioration of the secondary battery or the user's usage situation, the remaining capacity correction can be performed with high accuracy, and the cell voltage of the secondary battery 7 can be calculated. The error of the remaining capacity when the voltage reaches 3.0V can be reduced. Therefore, it is possible to solve the problem that the power is suddenly turned off or an alarm is generated even though the electronic device displays that there is still remaining capacity. Furthermore, when the remaining capacity is corrected, a so-called capacity jump in which the remaining capacity changes suddenly can be reduced.

  Although one embodiment of the present invention has been specifically described above, the present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible. is there.

  For example, the numerical values given in the above-described embodiment are merely examples, and different numerical values may be used as necessary. For example, in the above-described embodiment, the remaining capacity correction point is set when the remaining capacity of the secondary battery 7 becomes 5%. However, the remaining capacity correction point is not limited to when the remaining capacity becomes 5%, and is arbitrary. The remaining capacity can be corrected.

  In the above-described embodiment, the lithium ion battery is used as the secondary battery 7. However, the secondary battery 7 is not limited to this, and the open-circuit voltage OCV and the depth of discharge correspond one-to-one. Any battery having such characteristics may be used, and for example, it can be applied to various batteries such as a Ni-Cd (nickel) battery and a Ni-MH (nickel metal hydride) battery.

  In the above-described embodiment, the battery pack has two parallel secondary batteries provided in series in three blocks. However, the number and configuration of secondary batteries provided in the battery pack are particularly limited. is not.

  In the above-described embodiment, the remaining capacity of the secondary battery is detected by integrating the current value. However, the power amount is calculated from the measured current value and voltage value, and the power amount is integrated. It is good also as a structure which detects the remaining capacity of a secondary battery.

It is a basic diagram which shows an example of the structure of the battery pack by one embodiment of this invention. It is a graph which shows an example of the standard data of an open circuit voltage and the depth of discharge. It is a graph which shows an example of the standard data of an open circuit voltage and the depth of discharge, respectively, and the change of the cell voltage at the time of use. It is a graph which shows an example with the remaining capacity correction | amendment of a secondary battery and cell voltage by one Embodiment of this invention. It is a flowchart showing the flow of the process of calculation of the closed circuit voltage of a remaining capacity correction point, and remaining capacity correction. It is a graph which shows an example of the remaining capacity correction of a conventional secondary battery, and a cell voltage.

Explanation of symbols

1 ... + terminal 2 ...- terminal 4 ... charge / discharge control switch 5 ... charge control FET
6 ... Discharge control FET
DESCRIPTION OF SYMBOLS 7 ... Secondary battery 8 ... Temperature detection element 9 ... Current detection resistor 10 ... Overvoltage detection part 11 ... Overvoltage protection fuse 12 ... Measurement part 13 ... CPU
14 ... Thermistor

Claims (10)

A secondary battery,
A measurement unit for measuring voltage, current, and internal resistance when the secondary battery is used;
Based on the result measured by the measurement unit, a remaining capacity detection unit that detects the remaining capacity of the secondary battery;
A remaining capacity correction unit that corrects the remaining capacity detected by the remaining capacity detection unit when the measured voltage of the secondary battery is equal to or lower than a remaining capacity correction voltage;
The remaining capacity correction unit
Using the measured current and internal resistance of the secondary battery, calculate the first open circuit voltage when the discharge of the secondary battery is stopped,
From the first open-circuit voltage, a second open-circuit voltage when correcting the remaining capacity of the secondary battery is calculated,
Obtaining the remaining capacity correction voltage by calculating a closed circuit voltage when performing the remaining capacity correction of the secondary battery from the second open circuit voltage and the measured current and internal resistance of the secondary battery. A battery pack characterized by The second open circuit voltage is based on the data of the open circuit voltage and the discharge depth of the secondary battery, and the remaining capacity when performing the remaining capacity correction from the first discharge depth corresponding to the first open circuit voltage. The battery pack according to claim 1, wherein the battery pack is obtained by obtaining a second discharge depth by subtracting the capacity and obtaining an open circuit voltage corresponding to the second discharge depth. The remaining capacity rate of the secondary battery when the discharge of the secondary battery is stopped is 0%,
When the voltage of the secondary battery reaches the remaining capacity correction voltage, the remaining capacity detected by the remaining capacity detector is corrected to the remaining capacity when performing the remaining capacity correction. The battery pack according to claim 2. The battery pack according to claim 3, wherein the calculation of the remaining capacity correction voltage is performed at regular intervals. Measure the temperature when using the secondary battery,
The battery pack according to claim 4, wherein the remaining capacity correction voltage is varied in accordance with the measured temperature. Measuring voltage, current and internal resistance when using a secondary battery;
Detecting the remaining capacity of the secondary battery based on the measured result;
Correcting the detected remaining capacity when the measured voltage of the secondary battery is equal to or lower than a remaining capacity correction voltage, and
The remaining capacity correction voltage is
Using the measured current and internal resistance of the secondary battery, calculate the first open circuit voltage when the discharge of the secondary battery is stopped,
From the first open circuit voltage, a second open circuit voltage when correcting the remaining capacity of the secondary battery is calculated,
A secondary voltage obtained by calculating a closed circuit voltage when correcting the remaining capacity of the secondary battery from the second open-circuit voltage, the measured current of the secondary battery, and the internal resistance. Battery remaining capacity correction method. The second open circuit voltage is based on the data of open circuit voltage and discharge depth of the secondary battery, and the remaining capacity when performing the remaining capacity correction from the first discharge depth corresponding to the first open circuit voltage. The method for correcting a remaining capacity of a secondary battery according to claim 6, wherein the second battery depth is obtained by subtracting the capacity, and an open circuit voltage corresponding to the second depth of discharge is obtained. The remaining capacity rate of the secondary battery when the discharge of the secondary battery is stopped is 0%,
When the voltage of the secondary battery reaches the remaining capacity correction voltage, the remaining capacity detected by the remaining capacity detector is corrected to the remaining capacity when performing the remaining capacity correction. The method for correcting the remaining capacity of the secondary battery according to claim 7. The method for correcting the remaining capacity of the secondary battery according to claim 8, wherein the calculation of the remaining capacity correction voltage is performed at regular intervals. Measure the temperature when using the secondary battery,
The method for correcting the remaining capacity of the secondary battery according to claim 9, wherein the remaining capacity correction voltage is varied in accordance with the measured temperature.

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