JP2000195564A - Charge / discharge frequency detection device and battery pack using the same - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To realize a method of counting the number of times of charging and discharging with a simple configuration and accurately determining the degree of aging of a secondary battery. SOLUTION: A chargeable / dischargeable secondary battery is defined as one cycle of discharging until the battery has a predetermined discharge capacity or less and charging until reaching a fully charged state or a predetermined capacity. The number of times of charging / discharging is counted by adding the increase number of times multiplied by a coefficient set according to the change state of the battery temperature to the number of times of charging / discharging counted up to the previous cycle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention counts the number of charge / discharge repetitions on the basis of a discharge / charge capacity of a secondary battery and a change in current applied to a charge / discharge path to which the secondary battery is connected. For the detection of the number of times of charging and discharging, which applies this to the prediction of the period until the life of the secondary battery or the determination of whether or not the life has been reached. A charging / discharging number detecting device that is incorporated in a battery pack to be mounted and corrects the number of charging / discharging repetitions based on the temperature of the secondary battery, and a battery having the function of outputting the number of charging / discharging times to a device incorporating the detecting device About the pack.

[0002]

2. Description of the Related Art In recent years, a battery pack containing a chargeable / dischargeable secondary battery has been used as a power source for a vehicle equipped with a so-called power assist mechanism which uses power from a portable device such as a notebook personal computer or a camcorder or a motor as an auxiliary. Is used. The battery pack is provided with control means for controlling the charge / discharge state of the secondary battery and protecting the secondary battery in the event of an abnormality. In addition, in addition to these, the amount of charging electricity supplied to the battery pack and the amount of discharging electricity supplied to the device from the battery pack are measured, and the number of repetitions of charging and discharging is obtained from the measured value, and the life of the secondary battery is measured. There is also known a battery pack having a configuration provided with a function of detecting the number of times of charging and discharging applied to predicting a period until the battery life or determining whether or not the life has been reached.

[0003] The number of times of charge / discharge is counted as one cycle when the secondary battery in a fully charged state is discharged until it falls below a predetermined capacity value and then charged until it reaches a fully charged state. Assuming that the charge / discharge has been completed, one count is added to the count value from the start of use stored in the battery pack. FIG. 3 shows an example of a circuit of a device having such a counting function.

In FIG. 3, a battery pack 1 has a battery block 3 to which a plurality of secondary battery cells are connected, and a control unit 7 for measuring the number of times of charging and discharging. When the battery pack 1 is mounted on the main body device 2, the amount of charging electricity supplied to the secondary battery 3 and the amount of discharging electricity supplied from the battery block 3 to the main body device 2 are detected by the current detection resistor 6. . The control unit 7 calculates by converting a potential difference generated between both ends of the current detection resistor 6 due to charging and discharging currents applied to the charging and discharging paths to which the battery block 3 is connected. Further, by determining whether the potential difference is positive or negative, the charge / discharge detection circuit 9 detects whether the current applied to the battery block 3 is a charging current or a discharging current. For example, when the secondary battery 3 is in the discharging state, the discharge current is measured, and the discharge current value is calculated by integrating the discharge current value in the discharge current integration circuit 10. The obtained discharge electricity amount is compared with a discharge capacity value preset in the discharge capacity setting means 11 in a discharge capacity comparison 12. When the amount of discharged electricity exceeds the set discharge capacity and the secondary battery 3 is switched from the discharged state to the charged state, the count value stored in the charge / discharge repetition number counter 13 is increased by one, and The value of the amount of discharged electricity accumulated in the current accumulation circuit 10 is reset. After the charging state is continued and the secondary battery 3 is fully charged, discharging is started again. By repeating the above process, the number of times of charging and discharging is counted.

[0005]

In general, the life of a secondary battery is greatly affected by the temperature conditions of the environment in which it is used, in addition to the number of times of charging and discharging. For example, as shown in FIG.
40 ° C compared to a secondary battery used in a temperature environment of
The life of batteries used in high-temperature environments is shortened. Therefore, there is a problem that it is very difficult to predict and judge the life of the secondary battery from a value obtained by simply counting the number of times of charging and discharging.

In order to solve such a problem, a configuration is known in which the number of times of charging / discharging is predicted using data on the ambient temperature in addition to the discharge capacity of the secondary battery and the stored charge / discharge cycle deterioration coefficient data. (JP-A-9-318714).

However, according to this configuration, in order to predict the number of times of charging / discharging, arithmetic processing is performed using the measured values such as the discharge capacity and the temperature and the correction coefficients corresponding to the respective measurement items. It is necessary to use an element having an advanced arithmetic function in a device for estimating the number of times of charge and discharge, which not only complicates the device configuration but also increases the price of the device.

Further, the calculation of the number of times of charge / discharge refers to the discharge capacity of the secondary battery, and it is necessary to discharge the secondary battery every time the life of the secondary battery is determined. For this reason, prior to the life judgment, it takes time to perform the discharge, and in addition to being unable to judge the life instantly, it is necessary to recharge the discharged secondary battery again, which greatly impairs usability. I will.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has a simple configuration for counting the number of times of charging / discharging, thereby making it possible to accurately determine the degree of aging of a secondary battery. The purpose is to provide.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method of discharging a secondary battery capable of being charged and discharged, until the secondary battery has a predetermined discharge capacity or less, a fully charged state or a predetermined state. One cycle of charging until the capacity is reached,
A detection method for counting the number of times of charging / discharging by adding an increment value obtained by multiplying the coefficient set according to the change state of the battery temperature during one cycle to the number of times of charging / discharging repeated up to the previous cycle. It is an apparatus using the method, the amount of charge to the secondary battery, the amount of discharge from the secondary battery is measured, and the discharge capacity remaining in the secondary battery is detected, and the discharge capacity and the charge / discharge current of the secondary battery are measured. It comprises a control unit for detecting the number of times of charging and discharging from the change, and a temperature detecting means for detecting the temperature of the secondary battery.

According to the structure of the present invention, the count value of the number of times of charging and discharging is increased in accordance with the temperature around the battery, and the battery is used in an environment deviating from a normal temperature condition, that is, in a high or low temperature environment. Even if the secondary battery is used, the aging state of the battery expected from the number of times of charging and discharging counted by the detection device substantially matches the actual aging state of the battery. For this reason, even if the battery is placed in a temperature environment in which the period up to the battery life is greatly accelerated compared to the battery used in the normal temperature range, the life expectancy value with reference to the number of times of charge and discharge Can be greatly improved.

[0012]

Embodiments of the present invention will be described below.

According to the first aspect of the present invention, the charge / discharge state and the discharge capacity of the secondary battery are grasped by measuring the charge current to the chargeable / dischargeable secondary battery and the discharge current from the secondary battery. A detection device that counts the number of times of charging and discharging of the secondary battery, and measures the charging current and the discharging current, calculates the discharge capacity of the secondary battery from the measured values, and calculates the number of times of charging and discharging. And a temperature detecting means arranged in contact with or facing the surface of the battery in order to detect the temperature of the secondary battery, wherein the control unit has a discharge capacity of the secondary battery. After discharging until reaching a predetermined first capacity or less, when charged until reaching the second capacity, the number of times increase value corresponding to the temperature data output from the temperature detecting means, To the number of charge / discharge Calculated by, and to store as a new charge and discharge times.

The temperature detecting means detects the battery temperature and outputs information on the battery temperature to the control unit. The control unit selects a corresponding count increase value based on the received information, and adds the selected count increase value to the internally stored charge / discharge count value. At this time, the control unit determines the extent of the life acceleration from the change state of the battery temperature during one cycle. Therefore, the detected value of the number of times of charge / discharge will be different from the actual number of times of charge / discharge, but will indicate the number of times of charge / discharge in consideration of the accelerated deterioration due to temperature. Can be performed quantitatively. Further, it is possible to greatly improve the consistency between the actual life of the secondary battery and the predicted value.

The temperature data output from the temperature detecting means calculates the average value of the battery temperature during one cycle and compares the average value with the average temperature value under a normal temperature environment. It is possible to estimate the environmental temperature from the battery temperature by eliminating the accompanying effect.

In this embodiment, after the capacity of the secondary battery is reduced to a predetermined first capacity by discharging, charging is performed, and when the secondary battery is charged, the capacity is increased to a second capacity, and the discharging is performed. When implemented, the configuration is such that it is recognized that switching between charging and discharging has been performed. That is, after the discharge capacity of the battery reaches a predetermined capacity, from charging to discharging,
And when both the switch from discharge to charge is made,
This means that one cycle of charge / discharge has been performed. Here, the first capacity is set to a capacity that does not cause an overdischarge state, but is preferably about 20% of the nominal capacity in consideration of the influence on the battery. Similarly, the second capacity is set to be equal to or less than the capacity that does not cause an overcharge state, but is preferably about 80% of the nominal capacity.

Regarding the detection of the number of times of charge / discharge, when a battery in a fully charged state is discharged until it reaches a predetermined capacity or less, charging is performed, and when the battery is returned to a fully charged state again, Although the setting is made to increase the count value of the number of times of charge and discharge, it is also possible to set the count value to be increased when the battery in the discharged state is charged and the battery is discharged again by using the secondary battery. The count may be set to be performed in a specific state in a series of charge / discharge cycles.

Next, a second aspect of the present invention provides a chargeable / dischargeable secondary battery, a charge / discharge path extending from the secondary battery to an output terminal connected to a device, and a charge / discharge path applied to the charge / discharge path. A control unit that measures the charging current and the discharging current, calculates the discharging capacity of the secondary battery, and stores the number of charging and discharging of the secondary battery, and is arranged in a state of contacting or facing the surface of the secondary battery. A battery pack including a temperature detection unit for detecting a battery temperature, and an output unit for outputting the number of times of charge / discharge counted by the control unit to the device, wherein the control unit has a discharge capacity of the secondary battery of the first type. After the battery was discharged until it reached the capacity of less than or equal to the capacity, when the battery was charged until it reached the second capacity, the increase number of times corresponding to the temperature data output from the temperature detecting means was stored in the control unit. Add to the previous charge / discharge count and record as a new charge / discharge count. Characterized in that it.

According to this configuration, a conventional detection device configured to detect the number of times of charging and discharging from a change in the charging and discharging current has the following features:
Temperature control means for detecting changes in battery temperature is added, and the control unit uses a control method that combines temperature data and charge / discharge data to enable detection of the number of charge / discharge times in consideration of the effects of temperature. Pack can be provided. This battery pack does not require a significant modification to the circuit configuration, so that the device configuration does not become complicated or the price rises.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. The present embodiment shows an example of the configuration of the present invention, and does not limit the scope thereof. Components that perform the same functions as those of the conventional example are denoted by the same reference numerals, and detailed description is omitted.

FIG. 1 is a block diagram of an apparatus for detecting the number of times of charging and discharging according to an embodiment of the present invention. In FIG. 1, a battery pack 1 has a built-in battery block 3 in which a plurality of secondary battery cells are connected in series and a control unit 7, and is connected to a main device 2 having a load 5. The electrical connection between the battery pack 1 and the main unit is made from the terminals 41 to 46. Inside the battery pack 1, a current detection resistor 6 is interposed in a charging / discharging path connecting the battery block 3 with the terminals 42 and 43. The current detection resistor 6 measures a charging current supplied to the battery block 3 and a discharge current supplied from the battery block 3 to the load 5, and the value of each current is expressed as a potential difference between both ends of the detection resistor 6. The control unit 7 includes an AD conversion circuit 81 that converts the value measured by the current detection resistor 6 into a digital value, a charge / discharge detection circuit 9, a discharge current integration circuit 10, a discharge capacity setting circuit 11, a discharge capacity comparison circuit 12, a charge capacity A discharge counter 13 is provided.
The temperature of the battery block 3 is determined by a temperature sensor 14 disposed facing the battery block 3 and converted into a digital value by an AD conversion circuit 82. The temperature correction table circuit 15 selects a correction value corresponding to the battery temperature with reference to the measured battery temperature data. Based on the data output from the charge / discharge repetition counter 13 and the temperature correction table circuit, the numerical value correction circuit 16 corrects the detection value of the number of times of charge / discharge.

The charge / discharge count value detected by the control unit 7 is transmitted to the output unit 17. When the connection terminal 43 and the connection terminal 46 are connected, the battery pack 1 and the main body device 2
Communication is performed, and the number of times of charge / discharge is sent from the output unit 17 to the apparatus main body circuit 20. This makes it possible for the main unit 2 to determine the degree of battery aging based on the number of times of charging and discharging, and to inform the user of information such as the necessity of battery replacement through the main unit 2.

Next, the operation in which the control section 7 counts the number of times of charging and discharging and corrects the count value from the temperature information obtained from the temperature sensor will be described in detail below. In the present embodiment, the secondary battery in the discharged state is charged to give a fully charged state, then discharged to a predetermined discharge capacity, and reaches a stage where the discharge is terminated. Is one cycle.

The potential difference generated between both ends of the current detection resistor 6 interposed in the charge / discharge path is converted into digital data by the AD conversion circuit 81. Furthermore, if the potential difference generated at both ends is positive with respect to the installation potential, it is determined that the battery is charged,
If negative, discharge occurs. Accordingly, the charge / discharge detection circuit determines whether the current applied to the charge / discharge path is a discharge current or a charge current by determining whether the data output from the AD conversion circuit 81 is positive or negative. It is determined whether the battery block 3 is in a discharged state or a charged state. If the battery block 3 is in a discharged state, the discharge current integrating circuit 10 performs an integration operation of the discharge current supplied from the battery block 3 to the main unit 2. As the discharge proceeds, the discharge capacity of the battery block 3 gradually decreases.

The discharge capacity setting circuit 11 stores a preset discharge capacity value.
Is the set discharge capacity value and the discharge current integrating circuit 1
Compare with the capacity value integrated at 0. At this time, when the integrated capacity value exceeds the set capacity value, the discharge capacity comparison circuit 12 counts up the value of the number of times of charge / discharge counted by the charge / discharge repetition number counter 13. Further, when the discharge proceeds and the discharge capacity of the battery block 3 reaches a predetermined capacity, the battery block 3 stops supplying power to the main unit 2.

When the state is switched from the discharge state to the charge state, the direction of the current applied to the charge / discharge path is reversed,
The charge / discharge detection circuit 9 detects that the state has changed from the discharge state to the charge state. At the same time, the operation amount integrated in the discharge current integration circuit 10 is cleared to zero.

When one cycle of charging and discharging is completed,
The controller 7 grasps the temperature situation around the battery block 3 during the cycle and calculates a temperature correction coefficient. The temperature around the battery is detected by a temperature sensor arranged facing the battery. The temperature information output from the temperature sensor 14 is converted into a digital value by the AD conversion circuit 82 in the same manner as the charge / discharge current, and transmitted to the temperature correction table circuit 15. From the obtained temperature information, the temperature correction table circuit 15 averages the temperature information and selects a corresponding temperature correction coefficient.

The selected temperature correction coefficient is input to the numerical value correction circuit 16 together with the value output from the discharge capacity comparison circuit 12, and the number of times increase value is calculated. The selection of the temperature correction coefficient will be described in more detail with reference to FIG. 2 showing a detailed configuration of the temperature correction table circuit and the numerical value correction circuit.

The temperature correction table circuit 15 includes a temperature averaging circuit 15a for calculating an average temperature in one cycle from temperature information obtained from the temperature sensor, and a temperature multiplication coefficient conversion table in which a correction coefficient according to the temperature is set. And a temperature multiplication coefficient conversion circuit 15b. The temperature averaging circuit reads the temperature information measured by the temperature sensor 14 every predetermined period, and averages this value. When the end of one cycle is output from the charge / discharge detection circuit 9, the average value of the temperature information is output to the temperature multiplication coefficient conversion circuit 15b. At the same time, the temperature information of the cycle is reset to obtain the temperature information of the next cycle.

The temperature multiplication coefficient conversion circuit 15b stores a temperature multiplication coefficient conversion table and selects a correction coefficient according to the average value of the temperature information. (Table 1) shows an example of the temperature multiplication coefficient conversion table.

[0031]

[Table 1]

In Table 1, a temperature correction coefficient is determined by dividing the temperature into three temperature ranges, and a coefficient corresponding to the temperature range corresponding to the average value of the obtained temperature information is selected. For example, when the average value of the temperature information is 45 ° C., 2.0 is selected as the temperature correction coefficient. In this embodiment,
Although the correction coefficient is determined by dividing into three regions, the temperature range is subdivided, and the correction coefficient is set for each of them to obtain a correction coefficient in detail that reflects the influence on the battery life due to a change in the temperature environment. be able to.

The selected temperature correction coefficient is output to the numerical value correction circuit 16. The numerical value correction circuit 16 includes a multiplication circuit 16a and a correction value output circuit 16b. The multiplication circuit 16a multiplies a predetermined number of charge / discharge cycles by a temperature correction coefficient. In the present embodiment, the temperature correction coefficient is calculated for each cycle, and the value obtained by multiplying one cycle by the temperature correction coefficient is the increase number of times in the cycle. The calculated number increase value is output to the charge / discharge repetition number counter 13 via the correction value output circuit.

The charge / discharge repetition number counter 13 stores the number of charge / discharge times before the end of the previous cycle.
By adding the count increase value to this, the charge / discharge count up to the cycle is calculated. The calculated value is output to the output circuit 18 of the output unit 17 and transmitted to the device main circuit 20 in the main device 2 via the terminal 43 and the terminal 46 by the communication circuit 19. The main unit 2 is treated as information relating to battery information and determines the degree of deterioration of the battery.

[0035]

As described above, the present invention provides an actual battery by adding a method of correcting the number of times of charging and discharging according to the average value of the ambient temperature of the battery to the conventional method of detecting the number of times of charging and discharging. Correlation between the life characteristics of the battery and the calculated number of times of charge / discharge can be obtained, and the aging degree of the battery can be accurately grasped. For this reason, it is possible to easily determine when to replace the battery, and to realize excellent maintainability.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of a device for detecting the number of times of charging and discharging in this embodiment.

FIG. 2 is a block diagram showing a configuration of a temperature correction table circuit and a numerical value correction circuit according to the embodiment.

FIG. 3 is a block diagram showing a configuration of a conventional apparatus for detecting the number of times of charging and discharging.

FIG. 4 is a diagram showing a relationship between an environmental temperature and a cycle life of a battery.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Battery pack 2 ... Main body device 3 ... Battery block 5 ... Load 6 ... Current detection resistor 7 ... Control part

Claims (2)

[Claims] 1. A detecting device for measuring a charging current to a chargeable / dischargeable secondary battery and a discharging current from the secondary battery and counting the number of times of charging / discharging of the secondary battery, wherein the detecting device is A control unit that measures the charge current and the discharge current, calculates the discharge capacity of the secondary battery, and stores the number of times of charging and discharging, and is disposed in a state of contacting or facing the surface of the secondary battery, A temperature detecting means for detecting a temperature, the control unit is configured to discharge the secondary battery until the discharge capacity reaches the first capacity or less, and then perform charging when the secondary battery reaches the second capacity. Adding a count increase value corresponding to the temperature data output from the temperature detection means to the previous charge / discharge number stored in the control unit, and storing the result as a new charge / discharge number. Number detection device. 2. A chargeable / dischargeable secondary battery, a charge / discharge path from the secondary battery to an output terminal connected to a device,
A control unit that measures the charging current and the discharging current applied to the charging / discharging path, calculates the discharging capacity of the secondary battery, and stores the number of charging / discharging of the secondary battery. A battery pack provided with a temperature detecting means for detecting a battery temperature, and an output unit for outputting the number of times of charging / discharging counted by the control unit to a device, wherein the control unit includes: After being discharged until the discharge capacity of the secondary battery reaches the first capacity or less, when the battery is charged until the secondary battery reaches the second capacity, the secondary battery corresponds to the temperature data output from the temperature detection means. A battery pack provided with a charging / discharging frequency detecting device, wherein a frequency increment value is added to a previous charging / discharging frequency stored in the control unit and stored as a new charging / discharging frequency.