JP2005315730A - Method of calculating remaining capacity rate of secondary battery and battery pack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of calculating the remaining capacity rate of a battery capable of detecting the remaining capacity or the remaining capacity rate with a high precision, and to provide a battery pack. <P>SOLUTION: At the beginning of discharge, the remaining capacity rate by an integration method is used, then gradually transferred to the remaining capacity rate by a voltage method, at the vicinity of the end of discharge the remaining capacity is detected by the voltage method and at the end of the discharge the detection method is completely replaced by the voltage method. At the switching between the voltage method and integration method (current integration or voltage integration), the remaining capacity rate is calculated by the weighted addition of the remaining capacity rate by voltage method and the remaining capacity rate by integration method using a parameter of reliability of voltage method provided previously. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for calculating a remaining capacity ratio of a secondary battery and a battery pack.

  In recent years, the number of electric and electronic devices used using rechargeable batteries has increased, and the frequency of use has also increased. In these devices, the battery capacity is expressed using a lamp, liquid crystal, or the like, so that the user can know the approximate usable time.

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

  The remaining capacity detection by the voltage method measures the terminal voltage of the battery cell and calculates the remaining capacity based on the correlation between the voltage of the secondary battery and the battery capacity (remaining capacity ratio). 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, and measurement can be facilitated.

  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 amount of power, and then powers every fixed time. There is a power integration method that integrates quantities. In either case, the amount of discharge current or the amount of discharge power can be obtained, and the remaining capacity of the secondary battery can be obtained from the ratio of the battery's usable current amount or amount of power, so that it is not affected by voltage fluctuations. Stable remaining capacity detection becomes possible.

  However, at the time of discharging, there is a problem that the accuracy of detection of the remaining capacity becomes very poor at the intermediate potential of the secondary battery when the voltage method is used. This is because, for example, in the case of a lithium ion battery, the voltage at the intermediate potential is almost constant as shown in FIG.

  In addition, when the integration method is used, there is a problem that accuracy is deteriorated at the end of discharge. This is because errors are accumulated together with the accumulated current or power due to voltage and current measurement errors and heat loss, and a large error occurs at the end of discharge, which leads to deterioration of accuracy.

  Therefore, a method of detecting the battery capacity using both the integration method and the voltage method is used. In the voltage method, when the current of the secondary battery is small, the capacity calculation accuracy is high, and when the current is large, an accurate open-circuit voltage cannot be obtained due to the battery internal Imp (impedance) or the DC Imp variation due to the environmental temperature. The battery capacity cannot be calculated. In addition, in the integration method, the capacity calculation accuracy is high when the current of the secondary battery is large, and when the current is small, the integration error increases and the capacity calculation accuracy deteriorates.

Patent Document 1 below describes a method for detecting battery capacity by using a current integration method and a voltage method in combination. The invention of Patent Document 1 uses a voltage method when it is smaller than a preset current value, and uses a current integration method when it is larger. By measuring the battery capacity by switching each method, it is possible to improve the calculation accuracy of the battery capacity.
International Publication No. 98/056059 Pamphlet

  However, in the method described above, when switching between the integration method and the voltage method, the battery capacity measured by the integration method and the battery capacity measured by the voltage method do not necessarily match, and there may be a sense of incongruity in switching between measured values. It was.

  When the remaining capacity detection accuracy at the time of discharging is low, there is a problem that the remaining usable time and battery capacity displayed on the device are drastically reduced and the battery cannot be used until the scheduled time. In particular, in business equipment using battery packs, if there is an error in the measurement of the remaining capacity or the remaining capacity rate, it may be possible to hinder the work, and it is necessary to detect the remaining capacity with very high accuracy. It is done.

  Therefore, an object of the present invention is to provide a method for calculating a remaining capacity ratio of a secondary battery and a battery pack that can detect the remaining capacity or the remaining capacity ratio with higher accuracy.

  In order to solve the above-mentioned problem, according to a first aspect of the present invention, in a method for detecting a remaining capacity ratio of a secondary battery, the battery capacity is calculated by integrating the current value or power value of the secondary battery at regular intervals. Detecting the remaining capacity ratio of the secondary battery using the integrating method, measuring the voltage value of the secondary battery, and using the voltage method to calculate the remaining capacity ratio based on the correlation between the voltage value and the remaining capacity ratio The remaining capacity ratio of the secondary battery is detected, and the remaining capacity ratio detected by the integration method and the remaining capacity ratio detected by the voltage method are weighted and added according to the remaining capacity ratio of the secondary battery to obtain the final remaining capacity. This is a method for detecting the remaining capacity rate of a secondary battery, characterized by performing rate detection.

  According to a second aspect of the present invention, in the battery pack of the secondary battery, the battery pack includes a measurement unit that measures the voltage, current, and temperature of the secondary battery, and a battery capacity calculation unit. A detecting means for detecting a remaining capacity rate of the secondary battery using an integration method for calculating the battery capacity by integrating the current value or power value of the secondary battery at regular intervals; Detecting means for detecting the remaining capacity ratio of the secondary battery using a voltage method for measuring the voltage value and calculating the remaining capacity ratio based on the correlation between the voltage value and the remaining capacity ratio; A battery pack comprising means for performing weighted addition of the remaining capacity rate detected by the integration method and the remaining capacity rate detected by the voltage method according to the capacity rate, and performing final remaining capacity rate detection .

  As described above, according to the present invention, even if an error occurs in the remaining battery capacity obtained by the power integration method (or current integration method), the correction by the voltage method is performed as it approaches the end of discharge. The remaining capacity can be detected with high accuracy.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 2 schematically shows an example of the configuration of a battery pack to which the present invention can be applied.

  In the battery pack, when an electric 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 a charger during charging, and the + terminal 1 and the −terminal 2 are connected to the + terminal and −terminal of the charger, respectively, as in the case of using an electric device, and charging is performed.

  The battery pack mainly includes a battery cell 7, a microcomputer 10, a measurement circuit 11, a protection circuit 12, a switch circuit 4, and communication terminals 3a and 3b.

  The battery cell 7 is a secondary battery such as a lithium ion battery, in which four secondary batteries are connected in series.

  The microcomputer 10 uses the voltage value and current value input from the measurement circuit 11 to measure the voltage value and integrate the current value. Further, the battery temperature measured by a temperature detection element (for example, a thermistor) indicated by reference numeral 8 is taken in. Further, the measured values and the like are stored in a nonvolatile memory EEPROM (Electrically Erasable and Programmable Read Only Memory) indicated by reference numeral 13. Further, the microcomputer 10 also performs voltage method reliability detection as needed.

  The measurement circuit 11 measures the voltage of each cell of the battery cell 7 in the battery pack and supplies the measured value to the microcomputer 10. Further, the current detection resistor 9 is used to measure the magnitude and direction of the current, and the measured value is sent to the microcomputer 10. Furthermore, the measurement circuit 11 also has a function as a regulator that stabilizes the voltage of the battery cell 7 and generates a power supply voltage.

  The protection circuit 12 sends a control signal to the switch circuit 4 when the voltage of any of the battery cells 7 becomes an overcharge detection voltage or when the voltage of the battery cell 7 becomes equal to or lower than the overdischarge detection voltage. This prevents overcharge and overdischarge. 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 switch circuit 4 includes a charge control FET (Field Effect Transistor) indicated by reference numeral 5 and a discharge control FET indicated by reference numeral 6. 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. Note that after the charge control FET 5 is turned off, only discharge is possible through a parasitic diode indicated by reference numeral 5a.

  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. Note that after the discharge control FET 6 is turned off, only charging is possible through a parasitic diode indicated by reference numeral 6a.

  The communication terminals 3a and 3b are used for transmitting information on the remaining battery capacity to an apparatus when the terminal is attached to an electric apparatus such as a camcorder (camcorder: camera and recorder). Upon receiving this information, the device side displays the battery capacity, the remaining capacity rate, the remaining usable time, etc. on a display unit such as a liquid crystal display.

  In this invention, the remaining capacity rate (battery capacity) is detected by using the integration method (current integration or voltage integration) and the voltage method in combination, but instead of completely switching between the integration method and the voltage method at a certain threshold, The remaining capacity rate is measured by both the integration method and the voltage method. In addition, the voltage method reliability that defines how reliable the remaining capacity rate obtained by the voltage method is calculated from the value of the remaining capacity rate, and the remaining capacity rate obtained by the voltage method is integrated according to the value. The final remaining capacity ratio is obtained by weighting and adding the remaining capacity ratio obtained by the method. By such weighted addition using the voltage method remaining capacity rate, the integration method gradually shifts to the voltage method.

  In addition, when calculating the remaining capacity ratio using the integration method, if division processing is added, the value after the decimal point in the data is rounded off by truncation, etc., and the value (power value or current value) that has been lost is added up. The error is accumulated in the integration result. As a result, the accuracy of the integrated value deteriorates, and the accuracy of detection of the remaining capacity rate also deteriorates.

  In order to prevent the accumulation of errors, the method for dealing with errors caused by dropping digits by increasing the number of effective digits, conversely, increases the memory usage of the microcomputer and puts pressure on the processing. In addition, when the memory of the microcomputer is insufficient, the number of effective digits cannot be increased, and the data with the digits dropped is accumulated, leading to deterioration in accuracy.

  Therefore, in order to reduce the influence of the digit loss as much as possible, the following integration method is used in one embodiment.

  As shown in FIG. 3, an amplifier 23 having a gain of 24 and an amplifier 24 having a gain of 125 are connected via an input terminal 21 and a switch 22 when measuring a current value, and the output voltage of each amplifier is connected to a microcomputer. 10 A / D converters 25 for conversion to digital data. Each amplifier is selectively used according to the current value. When the current is larger than 2A, a 24 × amplifier is used. When the current is 2A or less, a 125 × amplifier is used. With this configuration, it is possible to reduce the difference in the effective digits between when the current value is small and when the current value is large.

  However, the measured value passing through the 24 × amplifier 23 and the measured value passing through the 125 × amplifier 24 have different digit weights, and cannot be simply added together. Therefore, the following method is used to reduce the influence of digit loss.

For example, the hardware conditions for current measurement are as follows.
A / D reference voltage (AVREF): 3000 mV
A / D resolution: 1024 (10 bits)
Current detection resistor (resistor 9 in FIG. 2): 5 mΩ

At this time, the voltage value input to the A / D converter 25 per 1 A of current flowing through the battery cell 7 is
In the case of the 24 × amplifier 23: 5 mΩ × 1 A × 24 = 120 (mV / A) (1)
In the case of 125 times amplifier 24: 5mΩ × 1A × 125 = 625 (mV / A) (2)

  Further, the voltage sensitivity per resolution of the A / D converter 25 is 3000 mV / 1024 = 2.930 (mV). When this is converted into current sensitivity when using the 24 × amplifier 23, it becomes 2.930 (mV) / 120 (mV / A) × 1000≈24.41 (mA).

  Based on the above-described values, the flow of integration processing will be described with reference to the flowchart of FIG.

  First, when integration processing is started in step S1, the current value input to the A / D converter is measured by the current detection resistor 9 in FIG. 2, and the measured current value is input to the microcomputer 10 as the A / D input value. (Step S2). Next, in step S3, it is determined which of the 24 × amplifier 23 and the 125 × amplifier 24 is used to measure the input value calculated in step S2. When the current value at the current detection resistor 9 is larger than 2A, the 24 × amplifier 23 is used. When the current value is 2A or less, the 125 × amplifier 24 is used.

When the 24-times amplifier 23 is used, the A / D input voltage is calculated from the above equation (1). For example, when the discharge current is 2.5 A,
A / D input voltage is 120 (mV / A) × 2.5A = 300 (mV)
It becomes. When the A / D input voltage is converted into digital data,
The input value (integrated value) after A / D conversion is 300 (mV) /2.930 (mV) ≈102.
It becomes. When the 24-times amplifier 23 is used, the obtained integrated value is added to the integration area as it is.

When the 125 × amplifier 24 is used, the A / D input voltage is calculated from the above equation (2). For example, when the discharge current is 0.8A,
A / D input voltage is 625 (mV / A) × 0.8 A = 500 (mV)
It becomes. Also,
The input value (BATT_CURRENT_BIT) after A / D conversion is 300 (mV) /2.930 (mV) ≈170.
It becomes.

  When the 125-times amplifier 24 is used, the integration is performed after converting the weights of the digits so as to be the same as when the 24-times amplifier 23 is used in step S5 (the first accumulation is the previous remainder 0). When the input value 170 after A / D conversion is converted when the 24-times amplifier 23 is used, 170 / 5.208 = 32 is obtained as the remainder 3.344. By rounding off the remainder after the decimal point in step S6, the integrated value 32 and the remainder 3 are obtained, and 32 is added to the integration area.

  Here, the case where the discharge current is accumulated 10 times with 0.8 A will be described. When the remainder is ignored and the remainder addition is not performed, the integrated value is 32 × 10 (times) = 320. However, theoretically, when the calculation is performed using the input value 170 before conversion, {170 × 10 (times)} /5.208≈326, resulting in a deviation of 6 in the integrated value.

  Therefore, the remainder obtained by the previous division is added during the next calculation to perform the integration process. That is, the second integrated value is determined by adding the first remainder 3 to the input value 170 before conversion obtained the second time and converting the total value. From the third time on, the whole is converted after adding the previous remainder to the input value before conversion as in the second time.

  The status of the integration process up to the tenth time is shown in FIG. As a result of the integration process performed by adding the remainder, in this example, the value of the integration area is 326, and no error occurs. Therefore, by adding the remainder at the time of the previous calculation to the A / D input value and then dividing, it is possible to minimize the influence of the digit loss.

  Further, since it is not necessary to increase the number of significant digits, the memory used in the microcomputer 10 can be minimized.

  In the present invention, the remaining capacity rate by the integration method is used at the start of discharge, and gradually changed to the remaining capacity rate by the voltage method. In addition, the remaining capacity is detected by the voltage method near the end of the discharge, and the voltage method is completely switched to ensure that the cutoff voltage and the remaining capacity ratio 0% coincide with each other at the end of the discharge.

  To switch between the voltage method and the integration method (current integration or voltage integration) when detecting the remaining capacity ratio, a parameter called voltage method reliability is provided, and the remaining capacity ratio obtained by the voltage method according to the voltage method reliability The final remaining capacity ratio is obtained by weighting and adding the remaining capacity ratio obtained by the integration method. By such weighted addition using the voltage method remaining capacity ratio, stable detection is performed without the remaining capacity ratio changing rapidly.

  The voltage method reliability is a parameter for determining at what ratio the measurement value obtained by the voltage method is to be trusted and used for detection according to environmental conditions and load conditions. Here, the reliability of the integration method is {100 (%) − voltage method reliability (%)}. For the voltage method reliability, a reliability coefficient based on the discharge voltage, a reliability coefficient based on the voltage method remaining capacity ratio, and a reliability coefficient based on temperature are calculated, and the final reliability is calculated by combining these three coefficients.

  Hereinafter, a method for obtaining each coefficient of the reliability coefficient based on the discharge voltage, the reliability coefficient based on the voltage method remaining capacity ratio, and the reliability coefficient based on the temperature, and a method for calculating the voltage method reliability will be described.

  As shown in FIG. 6, the reliability coefficient due to the discharge voltage is such that the reliability coefficient increases as the voltage decreases, and can be calculated by the following equation. Here, when the reliability coefficient obtained by the following equation is less than 1, the reliability coefficient is 1.

  Reliability coefficient by discharge voltage = −0.002 × discharge voltage (mV) +33

  For example, when the discharge voltage value is 12800 mV, the reliability coefficient by the discharge voltage = −0.002 × 12800 + 33 = 7.

  As shown in FIG. 7, the reliability coefficient due to the voltage method remaining capacity ratio increases rapidly as the voltage method remaining capacity ratio decreases, and can be calculated by the following equation. Here, when the reliability coefficient obtained by the following equation is less than 1, the reliability coefficient is 1. For example, when the voltage method remaining capacity ratio is 20%, a value 2000 obtained by multiplying 20% by 100 is substituted for the voltage method remaining capacity ratio in the following equation.

Reliability factor by voltage method remaining capacity ratio = (10000−voltage method remaining capacity ratio (% × 100))
/ (Voltage method remaining capacity ratio (% × 100) × 1.2) +0.1

  For example, when the voltage method remaining capacity rate is 20%, the reliability coefficient by the voltage method remaining capacity rate = (10000−2000) / (2000 × 1.2) + 0.1 = 3.43.

  In addition, since the internal resistance of the secondary battery increases as the temperature decreases, it is necessary to take into account changes due to temperature. For example, it is fully conceivable that the environmental temperature at which an electric device equipped with a secondary battery is used varies from 30 ° C. to below freezing. In this case, the internal resistance becomes several times or more, and this difference deteriorates the remaining capacity ratio measurement accuracy.

  As shown in FIG. 8, the reliability coefficient due to temperature increases linearly with increasing temperature, and can be calculated by the following equation.

  Reliability coefficient according to temperature = 0.16 × temperature (° C.) − 5.6

  For example, when the temperature is 15 ° C., the reliability coefficient according to temperature = 016 × 15−5.6 = −3.2.

  By using each of the above three reliability coefficients and substituting each coefficient into the following equation, the voltage method reliability defining how reliable the value obtained in the above is calculated.

Voltage method reliability (%) = (Reliability coefficient by discharge voltage + Reliability coefficient by temperature)
× Reliability coefficient by voltage method residual capacity ratio

  For example, when the reliability coefficient by the discharge voltage is 7, the reliability coefficient by the voltage method remaining capacity rate temperature is 3.43, and the reliability coefficient by temperature is -3.2, the voltage method reliability (%) is (7− 3.2) × 3.43 = 13.03 (%). Here, when (reliability coefficient by discharge voltage + reliability coefficient by temperature) is 1 or less, this value is set to 1.

  FIG. 9 shows the relationship between the voltage method remaining capacity ratio (%) and the voltage method reliability (%) obtained by the above method. Each graph in FIG. 9 is displayed for each temperature. The formula for calculating the reliability of the voltage method has two characteristics: the accuracy of the remaining capacity at the intermediate potential is poor when the voltage method is used, and the measurement accuracy at the end of discharge is poor when the power integration method is used. In consideration of the above, the characteristics of the voltage method reliability are as follows. The voltage method reliability is calculated in the range of 0 to 100%, and the higher the reliability, the higher the remaining capacity ratio of the voltage method is used.

1. 1. The remaining capacity rate detection result in the power integration method is used up to the remaining capacity rate of 100 to 30%. 2. In the vicinity of the remaining capacity ratio of 30 to 5%, a value obtained by adding the remaining capacity by the power integration method and the remaining capacity ratio by the voltage method according to the ratio based on the voltage method reliability is used. When the remaining capacity rate is 5% or less, the remaining capacity rate detection result by the voltage method is used.

  In the present invention, as shown in FIG. 10, the integration method is used at the start of discharge, the voltage method is used at the end of discharge, and the residual voltage method is used in the intermediate potential section according to the voltage method reliability obtained from the above formula. The final remaining capacity ratio (%) is calculated by weighting and adding the capacity ratio and the integration method remaining capacity ratio. By such weighted addition using the voltage method remaining capacity rate, the integration method gradually shifts to the voltage method.

  Hereinafter, a method for detecting the remaining capacity of the battery pack using the voltage method reliability as described above will be described with reference to the flowchart of FIG.

  When the remaining capacity calculation process is started, the battery cell 7 in FIG. 2 measures the discharge voltage, the current measurement resistor 9 measures the discharge current, the thermistor 8 measures the battery temperature, and supplies each measured value to the microcomputer 10 ( Step S11).

  In the microcomputer 10, the remaining capacity is detected by the voltage method based on the supplied voltage value (step S12). Characteristic curve data showing the relationship between the voltage and the remaining capacity ratio of the secondary battery by calculating the no-load measurement voltage by adding the drop voltage calculated by (current x impedance) to the supplied measurement voltage To determine the remaining capacity of the secondary battery. The data representing the relationship between the voltage and the remaining capacity ratio of the secondary battery is derived in advance from the test data, a data table corresponding to the voltage and the capacity is prepared, and the corresponding capacity is calculated from the voltage.

  Next, in the microcomputer 10, the discharge power is calculated from the measured current and voltage (power = current × voltage). The calculated discharge power is integrated every fixed time, and the integrated power amount from the start of discharge is obtained (step S13). In step S14, the remaining capacity ratio is calculated from the integrated power amount obtained in step S13 and the ratio to the dischargeable power of the secondary battery obtained from the test data in advance. Specifically, the remaining capacity rate is obtained from the following equation.

  Remaining capacity ratio (%) = integrated power / dischargeable power × 100

  Next, the voltage method reliability for determining which of the remaining capacity rate calculated by the voltage method and the remaining capacity rate calculated by the power integration method is used preferentially is calculated (step S15). The voltage method reliability is calculated using a reliability coefficient based on a discharge voltage, a reliability coefficient based on a voltage method remaining capacity ratio, and a reliability coefficient based on temperature.

  When the voltage method reliability is calculated in step S15, (1-voltage method reliability (%)) is calculated using the voltage method reliability (%) to obtain the integration method reliability (%). Furthermore, the final remaining capacity ratio is obtained by adding the value obtained by multiplying the voltage method remaining capacity ratio (%) by the voltage method reliability and the value obtained by multiplying the accumulation method remaining capacity ratio (%) by the accumulation method reliability. Is calculated by weighted addition using the voltage method reliability (step S16).

  For example, when the voltage method remaining capacity ratio is 30%, the power integration method remaining capacity ratio is 40%, and the voltage method reliability is 20%, the final remaining capacity ratio is 30 × 0.20 + 40 × (1-0 20), 38%.

  The remaining capacity rate is measured by such a method, and the discharge is terminated when the remaining capacity rate becomes 0%.

  By using this method, the voltage method is used near the end of discharge, so that the remaining capacity ratio can be detected with high accuracy. For example, when a lithium ion battery is used, the accuracy is poor in the voltage method near the intermediate potential. Since the remaining capacity can be detected by the power integration method (or the current integration method), it is possible to always detect the remaining capacity rate with high accuracy from the start of discharge to the end of discharge.

  The embodiment of the present invention has been specifically described above, but 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.

  For example, the numerical values given in the above-described embodiment are merely examples, and different numerical values may be used as necessary.

  The present invention can be applied to various batteries such as a Ni-Cd (nickel) battery and a Ni-MH (nickel metal hydride) battery in addition to a lithium ion battery.

  Further, the microcomputer constituting the battery pack may have a function of a protection circuit.

  In addition, when performing the integration process, not only power integration but also current integration may be performed, and the remaining capacity ratio may be obtained from the ratio with the total current amount obtained in advance.

It is a graph which shows the voltage at the time of discharging a secondary battery, and a remaining capacity rate. It is a basic diagram which shows an example of the structure of the battery pack which can apply this invention. It is a basic diagram of the structure used in order to perform current integration or electric power integration more precisely. It is a flowchart showing the flow of processing for performing current integration or power integration more precisely. It is a figure which shows an example of the data integration at the time of using the integration method which performs remainder addition. It is a graph which shows the relationship between the discharge voltage of a secondary battery, and the reliability coefficient by discharge voltage. It is a graph which shows the relationship between the voltage method remaining capacity rate of a secondary battery, and the reliability coefficient by a voltage method remaining capacity rate. It is a graph which shows the relationship between the temperature of a secondary battery, and the reliability coefficient by temperature. It is the graph which showed the relationship between the voltage method remaining capacity ratio of a secondary battery, and voltage method reliability according to temperature. It is a figure which shows the detection method of the voltage method reliability and residual capacity which are calculated | required by applying the voltage of the secondary battery during discharge, a remaining capacity rate, and applying this invention. It is a flowchart which shows the method of calculating remaining capacity using a voltage method reliability.

Explanation of symbols

4 ... Switch circuit 5 ... Charge control FET
6 ... Discharge control FET
5a, 6a ... Parasitic diode 7 ... Battery cell 8 ... Temperature detection element 9 ... Current detection resistor 21 ... Input terminal 22 ... Switch

Claims (6)

In the secondary battery remaining capacity rate detection method,
Detection of the remaining capacity rate of the secondary battery using an integration method of calculating the battery capacity by integrating the current value or power value of the secondary battery at regular intervals;
Measuring the voltage value of the secondary battery, and performing the remaining capacity rate detection of the secondary battery using a voltage method for calculating the remaining capacity rate based on the correlation between the voltage value and the remaining capacity rate,
In accordance with the remaining capacity ratio of the secondary battery, the remaining capacity ratio detected by the integration method and the remaining capacity ratio detected by the voltage method are weighted and added to perform final remaining capacity ratio detection. A method for detecting the remaining capacity of the secondary battery. In the secondary battery remaining capacity rate detection method according to claim 1,
When the remaining capacity ratio of the secondary battery is high, the remaining capacity ratio is detected by an integration method. When the remaining capacity ratio of the secondary battery is low, the weight is determined according to the remaining capacity ratio. A remaining capacity ratio is detected by weighted addition of the remaining capacity ratio and the remaining capacity ratio by the voltage method, and the remaining capacity ratio is detected by the voltage method at the end of discharge of the secondary battery. Remaining capacity rate detection method. In the secondary battery remaining capacity rate detection method according to claim 1,
The weights used for the weighted addition are the reliability coefficient based on the discharge voltage obtained from the discharge voltage of the secondary battery, the reliability coefficient based on the voltage method remaining capacity ratio obtained from the voltage method, and the battery of the secondary battery. A method for detecting a remaining capacity ratio of a secondary battery, which is obtained from a voltage method reliability combining a reliability coefficient according to a temperature obtained from a temperature. In secondary battery packs,
The battery pack includes a measurement unit that measures the voltage, current, and temperature of the secondary battery, and a battery capacity calculation unit.
The battery capacity calculator is
Detecting means for detecting the remaining capacity rate of the secondary battery using an integration method for calculating the battery capacity by integrating the current value or power value of the secondary battery at regular intervals;
Detecting means for measuring the voltage value of the secondary battery and detecting the remaining capacity rate of the secondary battery using a voltage method for calculating the remaining capacity rate based on the correlation between the voltage value and the remaining capacity rate; ,
According to the voltage method remaining capacity rate of the secondary battery, there is a means for performing weighted addition of the remaining capacity rate detected by the integration method and the remaining capacity rate detected by the voltage method, and performing a final remaining capacity rate detection. A battery pack characterized by that. The battery pack according to claim 4,
The battery capacity calculation unit performs a remaining capacity rate detection by an integration method when the remaining capacity rate of the secondary battery is high, and according to the remaining capacity rate when the remaining capacity rate of the secondary battery is low. The remaining capacity rate is detected by weighting and adding the remaining capacity rate by the integration method and the remaining capacity rate by the voltage method using weights, and the remaining capacity rate is detected by the voltage method at the end of discharge of the secondary battery. Battery pack featuring. The battery pack according to claim 4,
The battery capacity calculation unit includes a reliability coefficient based on a discharge voltage obtained from the discharge voltage of the secondary battery, and a reliability coefficient based on a voltage method remaining capacity ratio obtained from the voltage method. A battery pack obtained from voltage method reliability obtained by combining reliability coefficients according to temperatures obtained from the battery temperature of the secondary battery.

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