JP2010127773A - Method for calculating remaining capacity of battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To calculate a remaining capacity of a battery obtained by the first charge after a reset operation, while compensating it to a correct value. <P>SOLUTION: A method for calculating the remaining capacity of the battery is provided, which includes: a step of calculating a real capacity (Ah) of the battery by adding an integrated value (Ah) of charge current and by subtracting a product of an integrated value (Ah) of discharge current and a discharge coefficient; and a step of calculating the remaining capacity (%) of the battery from a ratio of the calculated real capacity (Ah) to a full charge capacity (Ahf) of the battery, by using an arithmetic circuit. Furthermore, the method for calculating the remaining capacity includes: a step of specifying the discharge coefficient of the battery to be charged after the arithmetic circuit is reset due to a voltage drop of the battery, by using the following equation: discharge coefficient=full charge capacity (Ahf)/[full charge capacity (Ahf)+corrected value]; and a step of calculating the remaining capacity by using an integrated value of the discharge coefficient and the charge current. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for detecting a remaining capacity of a battery, and more particularly, to a method for more accurately detecting a remaining capacity immediately after a battery voltage is lowered and a circuit for calculating the remaining capacity is reset.

  The battery can calculate a substantial capacity (Ah) that can be substantially discharged by adding the integrated value of charging current and subtracting the integrated value of discharging current. When the real capacity (Ah) is detected, the remaining capacity (%) can be calculated by calculating the ratio to the full charge capacity (Ahf). The remaining capacity (%) calculated from the integrated value of the charging current and discharging current can be detected more accurately by correcting with the battery voltage. This method sets the remaining capacity of a fully charged battery to 100% and the remaining capacity of a fully discharged battery to 0%. Battery full charge and complete discharge can also be detected by the battery voltage. For example, a lithium-ion battery is determined to be fully charged when the discharged battery voltage drops to the lowest voltage of 3V, the remaining capacity is 0%, and the charged battery voltage rises to the highest voltage of 4.2V. The remaining capacity is set to 100%. Furthermore, in the constant voltage charging, it can be determined that the battery is fully charged when the charging current becomes a predetermined value or less.

  FIG. 1 is a graph showing a characteristic in which a voltage is lowered by discharging a battery with a constant current. This figure shows the discharge capacity (Ah) of the discharged battery on the horizontal axis and the voltage of the battery on the vertical axis. Curve A shows the characteristic of discharging at the rated current, and curve B shows the characteristic of discharging at a larger current than the rated current. As shown by curve B in this figure, when the discharge current is increased, the capacity (Ah) that can be discharged before the battery is reduced to the minimum voltage is reduced. In addition, although not shown, the capacity (Ah) of the battery that can be discharged before the battery voltage is lowered to the minimum voltage is reduced even in a low temperature state. For example, in a battery discharged with a large discharge current or a low temperature, the total discharge capacity (Ahf) that can be discharged before the voltage drops to the lowest voltage may be reduced to about 50%. A battery in which the total discharge capacity (Ahf) discharged until the voltage drops to the lowest voltage is halved is fully charged with half the charge capacity.

  A battery in which the total discharge capacity (Ahf) that can be discharged before the voltage drops to the minimum voltage is halved cannot accurately calculate the actual capacity (Ah) by subtracting the integrated value of the discharge current. The battery discharged on the curve B has a remaining capacity reduced to 0% at half the total discharge capacity (Ahf) compared to the battery discharged on the curve A. In order to reduce the remaining capacity to 0% with half the total discharge capacity (Ahf), the remaining capacity can be accurately detected by subtracting twice the discharge capacity. In order to realize this calculation method, a method for detecting the discharge capacity in consideration of the discharge coefficient has been developed (see Patent Document 1). In the method described in Patent Document 1, the remaining capacity is accurately calculated by subtracting the product of the integrated value of the discharge current and the discharge coefficient. Since curve B has half the discharge capacity compared to curve A and the remaining capacity is 0%, the discharge capacity is substantially twice the capacity to be discharged. It can be detected.

From the above, the remaining capacity can be accurately calculated by detecting the discharge coefficient by the following equation and subtracting the product of the discharge coefficient and the integrated value of the discharge current.
Discharge coefficient = full charge capacity (Ahf) / total discharge capacity (Ahf)
The total discharge capacity (Ahf) is a capacity (Ah) until the fully charged battery is completely discharged, that is, a capacity for discharging the remaining capacity from 100% to 0%.
For example, as shown in curve B of FIG. 1, a battery having a full charge capacity (Ahf) of 1000 mAh is discharged until it is fully charged and completely discharged, and the total discharge capacity (Ahf) that can be substantially discharged is 500 mAh. If so, the discharge coefficient is 2 at 1000 mAh / 500 mAh. That is, the battery discharged along the curve B can accurately detect the remaining capacity with a discharge coefficient of 2. Therefore, the circuit for calculating the remaining capacity detects the total discharge capacity (Ahf) from the past history, calculates the discharge coefficient from the total discharge capacity (Ahf), and accurately calculates the remaining capacity using the calculated discharge coefficient. It has been calculated.
JP-A-10-274670

  2 and 3 show the discharge capacities of a battery discharged with a discharge coefficient of 1 (FIG. 2) and a battery discharged with a discharge coefficient of 2 (FIG. 3). A battery discharged with a discharge coefficient of 1 discharges a capacity corresponding to the full charge capacity (Ahf) of the battery, and the remaining capacity becomes 0%. On the other hand, a battery discharged with a discharge coefficient of 2 discharges half the full charge capacity (Ahf) to a remaining capacity of 0%. Therefore, the battery of FIG. 2 is fully charged by charging the full charge capacity (Ahf), but the battery of FIG. 3 is fully charged by charging half of the full charge capacity (Ahf). Therefore, as shown in FIG. 3, a battery discharged with a discharge coefficient of 2 needs to calculate the charge capacity (Ah) by multiplying the integrated value of the charge current in a state of being charged. This is because the battery is fully charged with half the charge capacity (Ah). For this reason, in order to accurately calculate the remaining capacity (%) of the battery, it is necessary to calculate in consideration of the discharge coefficient with which the battery is discharged.

  By the way, an arithmetic circuit for detecting the remaining capacity of a battery may be reset if the battery voltage is lowered to the minimum voltage and then left without being further charged. Furthermore, before the battery is discharged at a high rate and the discharge is stopped, the battery voltage may drop to a voltage at which the microcomputer is reset, or the arithmetic circuit may be reset due to noise or the like. Since the reset arithmetic circuit loses the total discharge capacity (Ahf), the discharge coefficient cannot be specified in the state of being charged thereafter, and the remaining capacity is calculated with the discharge coefficient being 1. However, with this method, the remaining capacity that gradually increases cannot be accurately calculated in the state of being charged for the first time after resetting. For example, if a discharged battery is reset with a discharge coefficient of 2 and the remaining capacity is calculated with the discharge coefficient set to 1, the calculated remaining capacity becomes smaller than the actual remaining capacity of the battery. Immediately after increasing to 50%, a harmful effect of changing to 100% occurs. This is because a battery discharged with a discharge coefficient of 2 is fully charged with half the charge capacity (Ah) of a battery discharged with a discharge coefficient of 1, and the remaining capacity becomes 100%.

  After a battery discharged with a discharge coefficient of 2 is reset and the remaining capacity is calculated and displayed with a discharge coefficient of 1, the battery continuously increases up to 50% as shown by curve A in FIG. From 100% to 100%, it changes instantaneously, and a “flying” occurs in the display of the remaining capacity of the battery so that it cannot be displayed accurately. The substantial remaining capacity of this battery increases continuously as shown by the chain line of curve B. Furthermore, after the discharged battery with a discharge coefficient of 1 is reset, if the battery is left to stand for a considerable period of time and becomes self-discharged, when it is reset and charged for the first time, as shown by curve C, ”Occurs and the calculated remaining capacity becomes 100%, the actual remaining capacity of the battery does not become 100%.

  The present invention has been developed for the purpose of solving such drawbacks. An important object of the present invention is to provide a method for calculating a remaining battery capacity that can be calculated by correcting the remaining capacity of a battery that is initially charged after being reset to an accurate value.

Means for Solving the Problems and Effects of the Invention

The battery remaining capacity calculation method according to the present invention calculates the actual battery capacity (Ah) by adding the integrated value (Ah) of the charging current and subtracting the product of the integrated value (Ah) of the discharging current and the discharge coefficient. Then, the remaining capacity (%) of the battery is calculated by an arithmetic circuit from the ratio between the calculated actual capacity (Ah) and the full charge capacity (Ahf) of the battery. Further, the remaining capacity is calculated by specifying the discharge coefficient of the battery to be charged by the following formula after the arithmetic circuit is reset due to the voltage drop of the battery, and using the integrated value of the discharge coefficient and the charging current. Is calculated.
Discharge coefficient = full charge capacity (Ahf) / [full charge capacity (Ahf) + correction value]

  The above calculation method can be performed by correcting the remaining capacity of the battery that is charged first to an accurate value after the battery voltage is lowered and reset. In the state where the remaining capacity is calculated after the total discharge capacity (Ahf) disappears after being reset, the full charge capacity (Ahf) discharged before the reset is corrected to specify the total discharge capacity (Ahf). This is because the discharge coefficient is calculated from the corrected total discharge capacity (Ahf), and the first remaining capacity after the reset is calculated using the calculated discharge coefficient. For example, in a battery having a timer that counts a period from reset to charge, the self-discharge capacity (Ah) from reset to charge of the battery is estimated and this self-discharge is estimated. By subtracting the capacity from the full charge capacity (Ahf), the total discharge capacity (Ahf) is specified, and the remaining capacity that is initially charged can be accurately calculated with the discharge coefficient calculated from the total discharge capacity (Ahf). . In addition, in a battery that does not have a timer, the correction value is set to a negative value so that the total discharge capacity (Ahf) is estimated by subtracting the correction value from the full charge capacity (Ahf). ) To correct the discharge coefficient to a value larger than 1, the remaining capacity of the battery discharged with a discharge coefficient larger than 1 can be calculated more accurately. Further, when a discharged battery is reset with a discharge coefficient of 1 and then charged for the first time, the discharge coefficient is set to 1 with the total discharge capacity (Ahf) obtained by subtracting the correction value from the full charge capacity (Ahf). If the remaining capacity is calculated using the discharge coefficient, the calculated remaining capacity becomes larger than the actual remaining capacity. When the remaining capacity calculated in this state is displayed, the “jump” shown by the curve A in FIG. 4 does not occur, and the remaining capacity continuously increases as shown by the chain line in the curve D. It does not give a natural display image.

  In the battery remaining capacity calculation method according to the present invention, the discharge coefficient can be calculated by setting the correction value to 0.1 to 0.5 times the full charge capacity (Ahf). In the battery capacity calculation method of the present invention, the discharge coefficient can be calculated by setting the correction value to -0.1 to -0.5 times the full charge capacity (Ahf).

  The battery remaining capacity calculation method of the present invention can use a battery as a power source for a laptop microcomputer.

  The battery remaining capacity calculation method of the present invention counts the time from reset to restart, specifies the correction value by the counted time, and increases the correction as the counted time becomes longer The value can be increased.

  The battery remaining capacity calculation method of the present invention can set the correction value to a specific negative value in the restarted state without counting the time from the reset to the restart.

  Embodiments of the present invention will be described below with reference to the drawings. However, the examples shown below exemplify a method for calculating the remaining capacity of the battery for embodying the technical idea of the present invention, and the present invention uses the following method for calculating the remaining capacity of the battery. Not specified.

  Hereinafter, the Example which uses a battery as a lithium ion battery or a lithium polymer battery is explained in full detail. However, the remaining capacity calculation method of the present invention can be any rechargeable battery such as a nickel metal hydride battery or a nickel cadmium battery, instead of a lithium ion battery or a lithium polymer battery.

  Here, an example of a battery pack in which the remaining battery capacity is calculated by the calculation method of the present invention is shown in FIG. The battery pack shown in this figure is a battery 1 that can be charged, a current detector 2 that detects the charge / discharge current of the battery 1, a voltage detector 3 that detects the voltage of the battery 1, and a temperature of the battery 1. A temperature detection unit 4, a current detection unit 2, a voltage detection unit 3, and a calculation circuit 5 that calculates the remaining capacity of the battery 1 from the detection values of the temperature detection unit 4 and monitors and controls charging / discharging of the battery 1 are provided. . Outputs from the current detection unit 2, the voltage detection unit 3, and the temperature detection unit 4 are digitally converted by the A / D converter 6 and input to the arithmetic circuit 5. The battery pack also includes a communication unit 8 that transmits various battery information such as battery voltage, remaining capacity, charge / discharge current value, battery temperature, and various command information to the main device. Further, the arithmetic circuit 5 includes a memory 9 for storing various data.

  The arithmetic circuit 5 performs calculations, comparisons, determinations, and the like based on data input from the A / D converter 6. That is, the arithmetic circuit 5 calculates the remaining capacity by integrating the charging / discharging current of the battery 1, detects the full charge of the battery 1 from the charging current and the battery voltage, and detects abnormal current, abnormal temperature, abnormal voltage, etc. Is detected to control charging / discharging. The arithmetic circuit 5 controls the charging / discharging of the battery 1 by controlling the charging / discharging switch 7 on and off. The charge / discharge switch 7 is a switching element made of, for example, an FET, and is turned on / off by the arithmetic circuit 5 and is turned off when an abnormal current, abnormal temperature, or abnormal voltage is detected to cut off the current. Further, the arithmetic circuit 5 calculates the remaining capacity (%) of the battery 1 from the data digitally converted by the A / D converter 6. In the present embodiment, the arithmetic circuit 5 performs the following processing to calculate the remaining capacity.

  The arithmetic circuit 5 calculates the remaining capacity with the integrated value (Ah) of the current that charges and discharges the battery 1. In this method, the integrated value of the charging current is added, the integrated value of the discharging current is subtracted to calculate the actual capacity (Ah) of the battery 1, and the calculated actual capacity (Ah) with respect to the full charge capacity (Ahf). Calculate remaining capacity (%) as a percentage. The remaining capacity of a fully charged battery is 100%, and the remaining capacity of a fully discharged battery is 0%. Further, the arithmetic circuit 5 also determines the remaining capacity (%) of the battery 1 based on the voltage of the battery 1. The remaining capacity (%) due to voltage can be accurately discriminated between a fully charged state of 100% and a completely discharged remaining capacity of 0%. Therefore, when the voltage of the battery 1 increases to the maximum voltage, the remaining capacity is determined to be 100%, and when the voltage decreases to the minimum voltage, it is determined to be 0%, and the remaining capacity (%) calculated by integrating the charge / discharge current can be corrected.

  For example, when the battery having a full charge capacity (Ahf) of 1000 mAh is fully charged to 100% and then discharged until the integrated value of the discharge current reaches 400 mAh, the arithmetic circuit 5 has a substantial capacity (Ah) of 1000 mAh. -400 mAh and 600 mAh. Since the real capacity (Ah) is 60% with respect to the full charge capacity (Ahf) of 1000 mAh, the remaining capacity is determined to be 60%. The actual capacity (Ah) of the battery 1 is calculated by subtracting the integrated value (Ah) of the discharge current and adding the integrated value (Ah) of the charging current. When the real capacity (Ah) is calculated, the remaining capacity (%) can be calculated by calculating the ratio to the full charge capacity (Ahf).

  However, when calculating the remaining capacity (%) by the above method, the remaining capacity (%) may not be accurately calculated depending on the discharge current and temperature of the battery. FIG. 6 shows the characteristics of fully discharging a battery that is fully charged and has a remaining capacity of 100%. In this figure, curve A shows a state in which the remaining capacity (%) of the battery discharged at the rated current decreases. The total discharge capacity (Ahf) for discharging the battery from 100% to 0% is the full charge capacity (Ahf) of the battery. In the battery discharged in this state, the accumulated value of the charging current is added, and the accumulated value of the discharging current is subtracted to calculate the real capacity (Ah). From the real capacity (Ah) and the full charge capacity (Ahf) The remaining capacity (%) can be calculated accurately.

  However, when the discharge current is increased or the battery is discharged at a low temperature, the cell voltage reaches 3 V with a small discharge capacity, so the remaining capacity becomes 0 and the remaining capacity with respect to the discharge capacity (Ah). The capacity (%) rapidly decreases (see curve B in FIG. 6). Therefore, the total discharge capacity (Ahf) for discharging the battery from 100% to 0% is smaller than the full charge capacity (Ahf) of the battery. Therefore, a battery discharged in this state can be accurately calculated by calculating the remaining capacity (%) from the actual capacity (Ah) calculated by subtracting the integrated value (Ah) of the discharge current. become unable. The battery discharged by curve B in FIG. 6 can accurately calculate the remaining capacity (%) by subtracting the product of the integrated value of the discharge current and the discharge coefficient represented by one or more coefficients. A battery discharged in a state where the total discharge capacity (Ahf) is smaller than the full charge capacity (Ahf) is the integrated value of the discharge coefficient specified by the full charge capacity (Ahf) / total discharge capacity (Ahf) and the discharge current. The real capacity (Ah) is calculated by subtracting the product with (Ah), and the ratio of the calculated real capacity (Ah) to the full charge capacity (Ahf) is calculated to accurately calculate the remaining capacity (%). . For example, a battery that is discharged in a state where the total discharge capacity (Ahf) is half of the full charge capacity (Ahf) is calculated by subtracting a value obtained by doubling the integrated value (Ah) of the discharge current with a discharge coefficient of 2. The real capacity (Ah) is calculated, the remaining capacity (%) is calculated from the real capacity (Ah), and the remaining capacity (%) can be accurately detected. That is, a battery whose total discharge capacity (Ahf) is half of the full charge capacity (Ahf) can be accurately detected by calculating that the battery is discharged at twice the current.

  As described above, the battery discharged by the curve B in FIG. 6 can accurately detect the remaining capacity (%) by correcting and subtracting the discharge capacity (Ahf) with the discharge coefficient. That is, in order to accurately calculate the remaining capacity (%) of the battery to be charged, the discharge coefficient of the discharged battery is required. The arithmetic circuit can detect the total discharge capacity (Ahf) of the battery from the integrated value of the discharge current that discharges the battery from 100% to 0%. Therefore, the discharge coefficient is calculated from the total discharge capacity (Ahf) and the full charge capacity (Ahf), and the remaining capacity (%) of the battery to be charged can be accurately calculated using the calculated discharge coefficient.

  Further, since the battery discharged by curve B in FIG. 6 has a total discharge capacity (Ahf) that is half of the full charge capacity (Ahf), the battery discharges from 100% to 0%. It is half of the charge capacity (Ahf). Therefore, as shown in FIG. 3, the battery discharged to 0% on the curve B is charged with the charge capacity (Ah) corresponding to the total discharge capacity (Ahf), that is, half the full charge capacity (Ahf). The charging capacity (Ah) is charged and fully charged. Therefore, when charging a battery discharged to 0% on the curve B, the integrated value (Ah) of the charging capacity is added to calculate the real capacity (Ah), and the remaining capacity (%) is calculated from the real capacity (Ah). Is increased as shown by the chain line of the curve C in FIG. 6, and the remaining capacity (%) cannot be calculated accurately. For this reason, the battery discharged by the curve B needs to calculate the remaining capacity (%) by correcting the integrated value (Ah) of the discharge capacity with the discharge coefficient. As shown by curve B in FIG. 6, a battery discharged from 100% to 0% with a discharge coefficient (full charge capacity (Ahf) ÷ total discharge capacity (Ahf)) of 2 is an integrated value of charge current. The remaining capacity (%) can be accurately calculated by adding the product of the discharge coefficient 2 and the discharge coefficient 2. That is, a battery charged from 0% to 100% can accurately calculate the remaining capacity (%) by correcting the integrated value of the charging current with the discharge coefficient specified by the discharge condition. For example, when a discharged battery is charged in a state where the discharge coefficient is 2, the real capacity (Ah) and the full charge capacity (Ahf) calculated by adding the capacity obtained by doubling the accumulated value of the charging current The remaining capacity (%) can be calculated from the ratio and accurately detected.

  The battery may be further deeply discharged from the state where the remaining capacity becomes 0%, and the battery voltage may be abnormally reduced. When discharged to this state, the arithmetic circuit 5 including the microcomputer is shut down due to a decrease in battery voltage as a power source, and then activated and reset when power is supplied and the battery is charged. In this state, since the discharge history is reset and the total discharge capacity (Ahf) disappears, the discharge coefficient cannot be detected with the total discharge capacity (Ahf). Since the discharge coefficient cannot be calculated from the total discharge capacity (Ahf), assuming that the total discharge capacity (Ahf) is the full charge capacity (Ahf), that is, assuming the discharge coefficient as 1, the subsequent remaining capacity (%) is calculated. For this reason, when the battery is reset, it can be determined that the voltage has dropped and the remaining capacity has reached 0%. However, whether the battery has been discharged in the state indicated by curve A or in the state indicated by curve B. Cannot be determined. When the reset battery is charged for the first time, the actual capacity (Ah) is calculated by adding the integrated value (Ah) of the charging current, and the remaining capacity is calculated from the ratio of the actual capacity (Ah) to the full charge capacity (Ahf). Although the capacity (%) is calculated, since the discharge coefficient cannot be accurately specified, the accurate remaining capacity (%) cannot always be calculated.

  For example, when the battery discharged in the state shown by the curve B in FIG. 6 is further deeply discharged and the voltage drops abnormally and the arithmetic circuit 5 is reset, this battery is charged with the integrated value (Ah) of charging current. The remaining capacity (%) calculated by adding and detecting the real capacity (Ah) increases in a state indicated by a curve C in FIG. That is, in a state where the capacity corresponding to the total discharge capacity (Ahf) is charged, the remaining capacity calculated from the integrated value of the charging current is 50%. However, when the battery is charged with a capacity (Ah) corresponding to the total discharge capacity (Ahf), the battery is fully charged (the battery voltage is detected to rise to the maximum voltage, or the current falls below a predetermined value. The remaining capacity (%) detected is 100%. Therefore, after increasing linearly to 50%, a “jump” that suddenly changes from 50% to 100% occurs.

  On the other hand, when the battery discharged to 0% in the curve A of FIG. 6 is deeply discharged by the discharge current of the system that cannot be detected by the microcomputer and the arithmetic circuit is reset, the battery is fully charged (Ahf). ) And self-discharge (Ah). This battery is in a state of being discharged to a capacity larger than the full charge capacity (Ahf). When the battery is charged after being reset, and the remaining capacity (%) is calculated by adding the integrated value of the charging current from 0%, the battery is charged to the full charge capacity (Ahf). The battery is not fully charged. This is because the discharged capacity is larger than the full charge capacity. Therefore, the battery is charged from the reset, and the real capacity (Ah) is calculated by adding the integrated value of the charge capacity, and the remaining capacity (%) is compared with the full capacity (Ahf). 4 is displayed, as indicated by curve C in FIG. 4, it is displayed that the battery is fully charged in a state where it is not fully charged, and is further charged in a state where the calculated remaining capacity (%) indicates 100%. The Therefore, the remaining battery capacity (%) is displayed in a “hold” state in which the state of displaying 100% is continued.

The arithmetic circuit 5 calculates the discharge coefficient used to calculate the remaining capacity (%) of the battery to be charged after being reset in order to avoid “jump” or “hold” indicating the remaining capacity (%). The calculation is performed using the following formula.
Discharge coefficient = full charge capacity (Ahf) / [full charge capacity (Ahf) + correction value]
That is, by correcting the full charge capacity (Ahf) and calculating the discharge coefficient, “jump” and “hold” in the remaining capacity display are reduced. The correction value is set in a range of 0.1 to 0.5 times, or −0.1 to −0.5 times the full charge capacity (Ahf).

  In a battery having a timer that counts after being reset, the correction value is specified by the count value of the timer. This is because the battery discharged to 0% is further discharged and the total discharge capacity (Ahf) increases as time elapses after resetting. The method of estimating the total discharge capacity (Ahf) by correcting the full charge capacity (Ahf) with the count value of the timer is a positive value (0.1 to 0.5 times the full charge capacity (Ahf)). ). In this method, for example, the time from reset to restart is counted, the correction value is specified by the counted time, and the positive correction value is increased as the counted time becomes longer. .

  An arithmetic circuit not equipped with a timer stores a correction value of − (−0.1 to −0.5 times the full charge capacity (Ahf)). This is because a battery that is discharged after resetting has a total discharge capacity (Ahf) that is smaller than a full charge capacity (Ahf) due to a large current or low-temperature discharge if it does not depend on self-discharge. Therefore, the reset battery can correct the total discharge capacity (Ahf) to be smaller than the full charge capacity (Ahf), thereby reducing the “jump” and calculating the remaining capacity (%) more accurately. The battery pack for calculating the remaining capacity (%) by this method includes a non-volatile memory 9 for storing a correction value in the arithmetic circuit 5. When the arithmetic circuit 5 is reset and the battery 1 is charged for the first time, the discharge coefficient is specified by using the correction value stored in the memory 9, and the accumulated value of the charge current is corrected by the discharge coefficient to remain. Calculate capacity (%). In the case of a battery pack that is used for discharging at a high current or low temperature, a correction value optimum for the application is stored in the memory 9.

  The present invention accurately detects a remaining capacity calculation in a state where the battery is charged first after the arithmetic circuit in which the battery is deeply discharged is reset, thereby displaying “jump” or “hold” for displaying the remaining capacity. Can be used conveniently with less.

It is a graph which shows the characteristic which discharges a battery with a fixed electric current and a voltage falls. It is a conceptual diagram which shows the state of the battery discharged in the state which sets a discharge coefficient to 1. It is a conceptual diagram which shows the state of the battery discharged in the state which makes a discharge coefficient 2. It is a figure which shows the difference of the remaining capacity calculated with the actual remaining capacity of a battery. It is a block circuit diagram which shows an example of the battery pack in which the remaining capacity of a battery is calculated with the calculation method concerning one Example of this invention. It is a figure which shows the characteristic which discharges the fully charged battery completely.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Battery 2 ... Current detection part 3 ... Voltage detection part 4 ... Temperature detection part 5 ... Arithmetic circuit 6 ... A / D converter 7 ... Charge / discharge switch 8 ... Communication part 9 ... Memory

Claims (6)

The accumulated value (Ah) of the charging current is added, the product of the accumulated value (Ah) of the discharge current and the discharge coefficient is subtracted to calculate the actual capacity (Ah) of the battery, and the calculated actual capacity (Ah) and the battery The remaining capacity (%) of the battery is calculated by a calculation circuit from the ratio to the full charge capacity (Ahf) of the battery,
A battery characterized in that after the arithmetic circuit is reset due to a battery voltage drop, a discharge coefficient of the battery to be charged is specified by the following formula, and a remaining capacity is calculated by an integrated value of the discharge coefficient and the charging current. To calculate the remaining capacity of the.
Discharge coefficient = full charge capacity (Ahf) / [full charge capacity (Ahf) + correction value]   The battery remaining capacity calculation method according to claim 1, wherein the discharge coefficient is calculated by setting the correction value as 0.1 to 0.5 times the full charge capacity (Ahf).   The battery remaining capacity calculation method according to claim 1, wherein the discharge coefficient is calculated by setting the correction value as -0.1 to -0.5 times the full charge capacity (Ahf).   2. The battery remaining capacity calculation method according to claim 1, wherein the battery is a power source of a laptop microcomputer.   The time from a reset to restart is counted, the correction value is specified by the counted time, and the positive correction value is increased as the counted time becomes longer. To calculate the remaining battery capacity.   The battery remaining capacity calculation method according to claim 1, wherein the correction value is set to a specific negative value in the restarted state without counting the time from the reset to restarting.

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