JP3649652B2 - Lithium ion battery capacity estimation method, deterioration determination device, and lithium ion battery pack - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a capacity estimation method, a deterioration determination apparatus, and a lithium ion battery pack for a lithium ion battery.
[0002]
Here, the “battery pack” means a single battery (hereinafter referred to as a cell) or a plurality of cells connected in series, parallel connection, or a combination of both, a safety control circuit or a charge / discharge control circuit. It means what is integrated into a “secondary battery as a self-supporting power source”.
[0003]
[Prior art]
In recent years, the demand for batteries has increased due to the downsizing, high performance, and portability of various electronic devices. Accordingly, the improvement and development of batteries are becoming increasingly active. New application areas for batteries are also expanding.
[0004]
[Problems to be solved by the invention]
With the spread of batteries, there is an increasing demand for improving the reliability of these batteries. In particular, nickel-metal hydride batteries (hereinafter referred to as Ni / MH batteries) having a significantly higher energy density per volume or weight than conventional lead batteries and nickel cadmium batteries (hereinafter referred to as Ni / Cd batteries), Lithium-ion batteries (hereinafter referred to as Li-ion batteries) have a large amount of energy stored inside them, so the degree of damage caused by accidents that accompanies battery abnormalities can become more serious, ensuring reliability. It is an important issue.
[0005]
The above Li-ion battery is composed of a metal oxide that can insert and desorb lithium in the positive electrode active material, a carbon compound that can insert and desorb lithium in the negative electrode, and a non-aqueous organic compound that uses lithium salt as a solute in the electrolyte. The
[0006]
In addition, lead batteries, Ni / Cd batteries, and Ni / MH batteries have a reaction mechanism that absorbs gas generated by side reaction due to overcharging, whereas Li ion batteries absorb gas generated by overcharging. There are major restrictions in terms of maintaining safety, such as no response. Furthermore, when multiple Li-ion batteries are used in series, when battery deterioration progresses, the imbalance of individual battery characteristics leads to overcharge and overdischarge, which is a major factor in safety. sell.
[0007]
As one of means for ensuring reliability, grasping an accurate deterioration state of the on-board battery and timely battery replacement can be mentioned. For high energy density batteries such as Ni / MH batteries and Li-ion batteries, the smart battery system (SBS) advocated in 1994 has become popular as a battery management system including charge control and remaining capacity judgment. (See www.sbs-forum.org). These battery control / management uses only a method based on a huge amount of information data management that constantly monitors the current, voltage, temperature, etc. of the battery in addition to information on the manufacturer, battery type, etc. This method is extremely expensive, and the product price has been rising.
[0008]
In addition, regarding the monitoring of the deterioration state of the battery, which is important in terms of maintaining safety, it is important to secure and monitor the usage time because the model of the Li-ion battery mounted device is frequently changed. There is a tendency to be overlooked.
[0009]
In particular, SBS is a means to control and manage battery charge control, remaining capacity, etc., and does not have a function to grasp the deterioration state of the battery. Replacement of the battery or battery pack depends on the intuition of the user. It was the current situation.
[0010]
In addition to SBS, a method for controlling and managing a Li-ion battery mounted on a video camera has been proposed. In this method, battery deterioration is only judged from the display of the already measured capacity. It is not always possible to correctly determine whether or not the battery used after charging has deteriorated.
[0011]
The present invention has been made in view of the above points, and the problem is that a simple method for estimating the capacity of a Li-ion battery, a simple device for determining deterioration of the Li-ion battery, and the capacity of the battery are estimated. It is providing the Li ion battery pack provided with the function.
[0012]
[Means for Solving the Problems]
  In order to solve the above problems, in the present invention, as described in claim 1,
  Lithium ion battery capacity estimation methodRWhen the lithium ion battery is charged by the constant current constant voltage method, the nominal capacity of the lithium ion battery is expressed as C₀The charging current when C₀/ (20 hours) or less, a time t from when the charging voltage during constant current charging reaches the preset voltage Vs to the charging upper limit voltage Vc is obtained, and the estimated specific capacity C of the battery_e/ C₀(Here, C_eIs the estimated capacity of this battery)
  C_e/ C₀= At + B (1)
(Here, A and B are positive constants determined by the battery, voltage Vs, voltage Vc, and charging current during constant current charging).A method for estimating the capacity of a lithium ion battery, wherein the same type of lithium ion battery as the target of capacity estimation is used, and the total charge time for one time is 3 days or more and 30 days or less, and the lithium ion battery The nominal capacity of C ₀ The charging current is C ₀ / ( 20 hours) or less, the charging period by the constant current constant voltage method, and the discharge current is C ₀ / ( 5 hours) or more C ₀ / ( 0.5 hours) or less, and a charge / discharge cycle having a discharge period in which the discharge end voltage is Vd and a pause period provided between the charge period and the discharge period as necessary is repeated three or more times. In each cycle, the time t from when the charging voltage during constant current charging reaches the preset voltage Vs until the charging upper limit voltage Vc is reached _n (Where n is the number assigned to each cycle) and the discharge capacity C obtained by integrating the discharge current with respect to time for each cycle. _n And the recorded time t _n And the discharge capacity C _n From these, the values of A and B in the relational expression (1) are determined.The capacity | capacitance estimation method of the lithium ion battery characterized by the above is comprised.
[0014]
  In the present invention, the claims2As described in
  A lithium ion battery deterioration determination device,The capacity | capacitance estimation method of the lithium ion battery of Claim 1The estimated specific capacity C of the lithium ion battery_e/ C₀And an estimated specific capacity C_e/ C₀A determination calculation circuit for determining the deterioration state of the lithium ion battery based on the value of the battery, a means for displaying the determination result by the determination calculation circuit, or the deterioration of the lithium ion battery if necessary based on the determination result A deterioration determination device for a lithium ion battery, comprising: a means for generating a warning sound for warning.
[0015]
  In the present invention, the claims3As described in
  A lithium ion battery pack having a charge / discharge control means with a built-in IC, wherein the IC or an additional IC attached to the IC is a lithium ion battery in the lithium ion battery packGuessConstant capacity C_e/ C₀ When estimating the capacity of the lithium ion battery according to claim 1A memory for storing numerical values used in the case where the numerical values are stored in the memoryThe capacity estimation method for a lithium ion battery according to claim 1.Lithium ion batteryofEstimated specific capacity C_e/ C₀And an estimated specific capacity C calculated by the arithmetic circuit_e/ C₀And a means for outputting a calculation result.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
In the capacity estimation method of the Li ion battery according to the present invention,
When charging a lithium ion battery by a constant current constant voltage method, the nominal capacity of the lithium ion battery is expressed as C₀The charging current when C₀/ (20 hours) or less, a time t from when the charging voltage during constant current charging reaches the preset voltage Vs to the charging upper limit voltage Vc is obtained, and the estimated specific capacity C of the battery_e/ C₀(Here, C_eIs the estimated capacity of this battery)
C_e/ C₀= At + B (1)
(Here, A and B are positive constants determined by the battery, voltage Vs, voltage Vc, and charging current during constant current charging).
[0017]
The Li-ion battery capacity estimation method according to the present invention will be described in more detail with reference to the drawings.
[0018]
FIG. 1 is a diagram showing a change with time of a charging voltage (shown as battery voltage in the figure) and a charging current when a Li-ion battery is charged by a constant current constant voltage (CC-CV) method.
[0019]
In FIG. 1, a Li-ion battery or a Li-ion battery in a battery pack (hereinafter collectively referred to as a Li-ion battery) is first set in advance by a constant current (CC) mode at a predetermined constant current Ic. Charging to the upper limit voltage Vc (usually 4.1 V / cell or 4.2 V / cell), after the charging voltage reaches the upper limit voltage Vc, charging in the constant voltage (CV) mode is started, and the charging voltage The charging current decays with time while the voltage (indicated as battery voltage in FIG. 1) remains constant at Vc.
[0020]
In the method for estimating the capacity of a Li-ion battery according to the present invention, during charging in the CC-CV method, during the constant current (CC) mode charging, the voltage Vs set to be equal to or higher than the end-of-discharge voltage Vd and lower than the upper limit voltage Vc The elapsed time t from the time when the charging voltage reaches to the end of constant current mode charging (that is, the charging voltage reaches Vc) is monitored, and the estimated specific capacity of the Li-ion battery is measured using this time t. C_e/ C₀Is calculated by the above relational expression (1).
[0021]
In this case, in order to accurately estimate the capacity of the battery, the constant current Ic in charging by the CC-CV method is set to C₀/ (20 hours) or less. When charging is performed at a current exceeding this, an error in capacity estimation according to the relational expression (1) increases.
[0022]
Hereinafter, in general, the battery current is C₀In the case of / (T time), this current is expressed as (1 / T) CmA. For example, C₀/ (20 hours) is expressed as 0.05 CmA.
[0023]
Moreover, it is preferable that the Li ion battery to be subjected to capacity estimation in the present invention is used under use conditions such that the charging time per time is 30 days or less. A long charge time in which the charge time for one charge exceeds 30 days is not preferable because the degree of deterioration due to overcharge differs or the deterioration of the battery constituent material with time becomes significant, causing a large capacity estimation error.
[0024]
Furthermore, in carrying out the capacity estimation, it is preferable that the charging voltage Vs at the start of time measurement is a voltage equal to or higher than the discharge end voltage Vd and at least 0.2 V lower than the charging upper limit voltage Vc. When the time measurement start voltage Vs is within the voltage range of a difference of less than 0.2 V from the charge upper limit voltage Vc, the required time t to be measured becomes too short, which may cause a large estimation error.
[0025]
The application of the relational expression for capacity estimation in the present invention is nominally the discharge capacity C (which is obtained by integrating the discharge current with respect to time) when the battery deteriorates from the fully charged state to the discharge end voltage Vd. Capacity C₀It is limited to the case where it is in the range of 50% or more. Battery specific capacity C / C less than 50%₀Required time t and specific capacity C / C₀The linear relationship as shown in the above relational expression (1) (the left side of the expression is the specific capacity C / C₀This is not preferable because the error when the capacity is estimated using the relational expression becomes large.
[0026]
The above relational expression (1) is the constant current (CC) mode charging time t under the charging condition of the Li-ion battery mounted device or charger to which it is applied, and the specific capacity C / C under that condition.₀It is assumed that this is a relationship. If the charging current value in the CC mode when the relational expression (1) is created is different from the charging current value in the CC mode of the on-board device or the charger, the CC mode under each charging condition is separately provided in advance. The required charging time is obtained, and the ratio te / tm between the required time te in the condition at the time of creation of the relational expression (1) and the required time tm in the condition corresponding to the mounting device or the charger is expressed by the relational expression (1 ) To t.
[0027]
  This is because the charging rate in CC mode charging (the charging rate of CC mode charging during the entire charging period) increases as the current value decreases, that is, the charging achievement rate increases as the current value decreases. Further, since the ratio varies depending on the battery size, battery shape, manufacturer, battery constituent material, and the like, it is necessary to separately perform an actual test to grasp the influence of the current value.
  As aboveIn order to estimate the capacity of the Li-ion battery, the relational expression (1) must be created in advance. For this purpose, the values of the constants A and B in the relational expression (1) must be determined. In that case, it is most appropriate to determine the constants A and B by testing a battery or battery pack of the same type as the Li ion battery to be subjected to capacity estimation. This is because commercially available Li-ion batteries have a variety of types of positive electrode active contaminants, negative electrode carbons and electrolytes used, and not only changes in charging voltage behavior due to battery deterioration, but also initial battery charging behavior. Because they are different.
[0028]
Therefore, in the present invention,
Using the same type of lithium ion battery as the target of capacity estimation,
The total charge time for one time is 3 days or more and 10 days or less, and the nominal capacity of the lithium ion battery is C₀The charging current is C₀/ (20 hours) or less charge period by constant current constant voltage method, and discharge current is C₀/ (5 hours) or more C₀/(0.5 hours) or less, and a charge / discharge cycle having a discharge period in which the discharge end voltage is Vd and, if necessary, a pause period provided between the charge period and the discharge period is three or more times repeat,
In each cycle, the time t from when the charging voltage during constant current charging reaches the preset voltage Vs until the charging upper limit voltage Vc is reached._n(Where n is the number assigned to each cycle) and the discharge capacity C obtained by integrating the discharge current with respect to time for each cycle._nAnd the recorded time t_nAnd the discharge capacity C_nFrom these, the values of A and B in the relational expression (1) are determined.
[0029]
To explain the above operation in more detail,
In the present invention, a battery of the same type as the Li ion battery that is the target of capacity estimation is used, and 0.05 CmA or less (C₀/ (20 hours or less)) Charged to a maximum voltage Vc by constant current (CC) charging, and charged by constant voltage (CV) charging after the battery or battery pack voltage has reached the maximum voltage Vc. Is charged by the constant current constant voltage (CC-CV) method, and the charging time is set to 3 days or more and 30 days or less,
Discharge is 0.2 CmA or more and 2.0 CmA or less (C₀/ (5 hours) or more, C₀/(0.5 hours) or less) and a discharge end voltage Vd similar to the use condition of the battery, and if necessary, a certain pause time is provided between the charge and discharge. Perform three or more charge / discharge cycles,
Charging in constant current (CC) mode after the charging voltage reaches an arbitrary voltage Vs between Vd and (Vc−0.2V) between the charging upper limit voltage Vc and the discharge end voltage Vd in each charging / discharging cycle T required to complete (charging voltage reaches charging upper limit voltage Vc)_n(Where n is the number assigned to each cycle) and the discharge capacity C obtained by integrating the discharge current with respect to time for each cycle._nAnd the recorded time t_nAnd the discharge capacity C_nFrom these, the values of A and B in the relational expression (1) are determined. That is, the left side of the relational expression (1) is C_n/ C₀And t on the right side is t_nThe relational expression replaced with is C_n/ C₀And t_nThe values of A and B are determined so as to best represent the relationship between and.
[0030]
The charging time per cycle is 3 days or more and 30 days or less. By setting the charging time to 3 days or more and 10 days or less, the deterioration of the battery in each cycle proceeds moderately, and the data necessary for creating the accurate relational expression (1) can be efficiently acquired. When the charging time per cycle is longer than 30 days, the degree of deterioration due to overcharging becomes large, and the deterioration of the battery constituent material over time becomes significant, and the required time t_nAnd specific capacity C_n/ C₀Between the linear relationship represented by the above relational expression (1)_n/ C₀And t on the right side is t_nThe relational expression using the constants A and B determined from these data may cause a large error, which is not preferable.
[0031]
Further, if the charging time per cycle is set longer than 30 days, the elapsed time per cycle becomes long, and it takes time to acquire data, which is also not preferable.
[0032]
On the other hand, if the charging time per cycle is set to less than 3 days, the deterioration of the electrode due to the charge / discharge cycle becomes conspicuous, and conversely, the degree of deterioration due to overcharging becomes small, and the constants A and B determined in this case are applied. In the capacity estimation using the above relational expression (1), the capacity estimation error becomes large in an actual use in which the discharge and the charge are different each time except for a limited use method in which charging and discharging are frequently performed, which is not preferable. .
[0033]
The discharge current value in the charge / discharge cycle test is set to 0.2 CmA or more and 2.0 CmA or less. If it is set to 1.0 CmA or more and 2.0 CmA or less, more efficient data acquisition becomes possible. In the case of a low discharge current of less than 0.2 CmA, it takes time for complete discharge, which is not preferable. In addition, when the discharge current is larger than 2.0 CmA, the discharge time itself becomes too short, and when the measured value of the discharge capacity varies or deteriorates, the capacity rapidly decreases and the relational expression (1) with high accuracy. Since it becomes impossible to create, it is not preferable.
[0034]
In carrying out the charge / discharge cycle test, it is possible to set a pause for a certain time between charging and discharging, if necessary, due to device setting restrictions and the like.
[0035]
In the charge / discharge cycle test performed to create the relational expression (1), the discharge end voltage Vd in the constant current (CC) mode of charge is 0.2 V lower than the charge upper limit voltage Vc in each cycle (Vc). -0.2V) The time t from the arbitrary voltage Vs within the operating voltage range below to the end of the CC mode, and the charge specific capacity C of the subsequent discharge_n/ C₀Is measured for each charge / discharge cycle. Measured time t and specific capacity C_n/ C₀Are applied to relational expression (1) to determine constants A and B.
[0036]
The charge / discharge cycle test is performed with the capacity estimation result C_eIs required to achieve high accuracy so that is within ± 20% of the actual capacity C_nAnd specific capacity C_n/ C₀In order to satisfy the above data, charge / discharge is performed for 3 cycles or more.
[0037]
If the number of cycles is only two, only two points of data are obtained for the determination of the constants A and B in the relational expression (1), which makes it impossible to estimate the capacity with high accuracy.
[0038]
  The environmental temperature of the charge / discharge cycle test carried out to determine the constants A and B of the relational expression (1) is not particularly specified, but is within the temperature range recommended by the manufacturer as the operating temperature range of the Li ion battery. Therefore, it is preferable to carry out at a temperature similar to the environmental temperature actually used. If the environmental temperature at which the charge / discharge cycle test is carried out is significantly different from the actual environmental temperature at which the capacity is estimated, the constants A and B are determined by correcting the capacity from the temperature dependence data of the discharge capacity. To do.
(Embodiment2)
  In the Li ion battery deterioration determination device according to the present invention,
  Means for obtaining the time t when charging a lithium ion battery by a constant current constant voltage method, and using the time tCreated in the first embodimentThe estimated specific capacity C of the lithium ion battery according to the above relational expression (1)_e/ C₀And an estimated specific capacity C calculated by the arithmetic circuit_e/ C₀Means for displaying the value of or the estimated specific capacity C_e/ C₀Means for displaying a determination result of the deterioration state of the lithium ion battery based on the value of the battery, or a means for emitting a warning sound for warning the deterioration of the lithium ion battery based on the determination result, if necessary. It is characterized by.
[0039]
FIG. 2 shows an apparatus equipped with a Li-ion battery, a function of a method for estimating the capacity of a Li-ion battery according to the present invention, and a function of determining a deterioration state of the lithium-ion battery based on a result of the capacity estimation. 1 shows a configuration concept of an apparatus including
[0040]
In FIG. 2, reference numeral 1 denotes a power supply unit. The power supply unit 1 is equipped with Li ion batteries 2 a, 2 b, and 2 c, and these batteries 2 a, 2 b, and 2 c are charged and discharged by the battery control unit 3 in the power supply unit 1. Control regarding safety is performed. A charger 4 in the power supply unit 1 is charged by the battery control unit 3 to charge the batteries 2a, 2b, and 2c. Reference numeral 5 denotes a logic unit. The logic unit 5 includes an interface 6, a CPU 7, a memory 8, and a keyboard controller 9. The battery control unit 3 is connected to the CPU 7 through the interface 6 and relates to the mounted batteries 2 a, 2 b, and 2 c. In response to the information and the instruction to carry out the control, data relating to battery control is sent to the CPU 7. In the logic unit 5, the CPU 7 and the memory 8 perform control instruction, data calculation, accumulation of information related to battery control, data storage, and the like. The ID input of the batteries 2a, 2b, and 2c is performed via the keyboard controller 9. A wiring 10 for data transmission is connected to the keyboard controller 9.
[0041]
The relational expression (1) in the present invention is input in advance to an empty memory or the like of the CPU 7, or is input by adding a memory chip in addition to the CPU 7 if necessary. Further, the logic unit 5 includes an estimated specific capacity C of the lithium ion battery according to the relational expression (1)._e/ C₀And the estimated specific capacity C_e/ C₀A determination calculation circuit for determining the deterioration state of the lithium ion battery based on the value of the value is incorporated, and a determination result by the determination calculation circuit is formed in the logic unit 5. The CPU 7 instructs the battery control unit 3 to measure the time t from when the charging voltage in the constant current (CC) mode charging reaches the voltage Vs within the operating voltage range until the CC mode charging is switched to the CV mode charging. On the contrary, the data of the charging time t is received from the battery control unit 3. Further, the CPU 7 calculates the estimated specific capacity C by substituting the received time t into the relational expression (1)._e/ C₀And the estimated specific capacity C_e/ C₀The deterioration state of the lithium ion battery is determined based on the value of. That is, the logic unit 5 also includes a function for estimating the capacity of a Li-ion battery and determining a deterioration state according to the present invention. If necessary, this estimated specific capacity C_e/ C₀Is stored in the memory 8.
[0042]
The apparatus for determining deterioration of a Li-ion battery according to the present invention requires the apparatus shown in FIG. 2 based on means for displaying the determination result of the deterioration state of the lithium-ion battery via the wiring 10 or based on the determination result. Accordingly, it is configured by being connected to an apparatus provided with means for emitting a warning sound for warning the deterioration of the lithium ion battery. The device connected to the device shown in FIG. 2 via the wiring 10 is connected to the estimated specific capacity C calculated by the arithmetic circuit._e/ C₀It is advantageous to have a means for displaying the value of the value so that the deterioration of the lithium ion battery can be grasped quantitatively.
[0043]
  In this way, the deterioration determination device for a Li ion battery according to the present invention can be configured. However, the present invention is not limited to the above-described configuration as long as the Li-ion battery deterioration determination device according to the above concept can be configured.
(Embodiment3)
  The method for estimating the capacity of a Li ion battery according to the present invention can also be applied to a battery pack by providing a control microcomputer in the pack of Li ion batteries or, if necessary, a simple additional memory in the pack. Li-ion battery capacity estimation method in the present inventionThat is, the capacity estimation method of the Li ion battery described in the first embodimentFIG. 3 shows a specific configuration example of the Li-ion battery pack according to the present invention applied to the battery pack.
[0044]
FIG. 3 is a diagram showing a general circuit configuration of a Li-ion battery pack, and shows a case where three Li-ion batteries (12-1, 12-2, 12-3) are mounted in series.
[0045]
In FIG. 3, 11 is a battery pack body, and 12-1, 12-2, and 12-3 are Li ion batteries. Reference numeral 13 denotes a protection IC, which monitors voltage, current, temperature, etc. and performs software safety control. 14 -A, 14 -B, 14 -C, 14-1, 14-2, 14-3 are FETs for controlling the charging current in the pack body 11 and each battery, and 15 is a thermal fuse. The PTC element 16 is a current fuse, and plays the role of cutting off the current when the temperature rises and when the current is abnormally large. 17 is a plus terminal, 18 is a minus terminal, and 19 is a terminal for information output and control.
[0046]
In FIG. 3, a timer is mounted in the protection IC 13 of the safety mechanism, and the relational expression (1) is input in advance to an empty memory, and the estimated specific capacity C_e/ C₀An arithmetic circuit for calculating is formed in advance.
[0047]
When the present Li ion battery pack is mounted on a charging device and charging is performed by a constant current constant voltage (CC-CV) system, the Li ion batteries 12-1, 12-2, 12-3 in FIG. The protective IC 13 monitors the voltage, and the charging voltage in the constant current (CC) mode charging is set to an arbitrary starting voltage Vs set in advance so that the charging voltage is equal to or higher than the discharge end voltage Vd and lower than the charging upper limit voltage Vc. The elapsed time t from when reaching CC mode charging to switching to CV mode charging is counted, and the value of this measured time t is substituted and calculated in relational expression (1) to calculate the estimated specific capacity C_e/ C₀Is calculated. If necessary, an extension IC can be provided at an appropriate position in the pack separately from the protection IC 13.
[0048]
The calculation result is output to the main body of the charging device through the terminal 19 so as to be displayed on an appropriate display or to emit a warning sound.
[0049]
Thus, the Li ion battery pack according to the present invention can be configured with a minimum change of the existing Li ion battery pack. However, the present invention is not limited to the above configuration as long as the capacity estimation of the Li ion battery that is the above concept can be performed.
[0050]
As an application of the Li-ion battery capacity estimation method and the Li-ion battery pack provided with the capacity estimation function in the present invention, devices that require high reliability such as a backup power source can be considered. By grasping the state of deterioration of the battery and realizing timely battery replacement, troubles in the device are avoided. However, there is no problem in adopting the Li-ion battery pack having the capacity estimation method and the capacity estimation function as long as it is a device equipped with a Li-ion battery, and it is possible to realize battery replacement without waste. The advantage of using it is so great.
[0051]
【Example】
Although the capacity | capacitance estimation method of the Li ion battery which concerns on this invention, the deterioration determination apparatus, and a Li ion battery pack are demonstrated by a specific Example below, this invention is not limited to this at all.
Example 1
For a cylindrical Li-ion battery (18650 type, nominal capacity 1350 mAh), using a battery charge / discharge automatic test device having a data collection / storage function, the test temperature is set to 25 ° C., and the charge current value is 45 mA (0.033 CmA). Charging by the constant current constant voltage (CC-CV) system with a charging upper limit voltage of 4.1 V and a charging time of 30 days, discharging with a discharging current value of 1350 mAh (1.0 CmA), a discharge end voltage of 2.75 V, and charging and discharging 5 cycles of charge / discharge cycle test with 1 hour pause between and after the start of charging in each cycle until the completion of CC mode charging, and integration of discharge current with respect to time Discharge capacity C nominal capacity C₀Specific capacity for C / C₀Asked.
[0052]
The obtained data is shown in FIG. FIG. 4 shows the elapsed time t and the specific capacity C / C showing the result of the charge / discharge cycle test.₀The circles in the figure are the data obtained in the charge / discharge cycle test, and from these data, the estimated specific capacity C_e/ C₀The constants A and B in the above relational expression (1), which expresses as a function of time t, were obtained, and the following relational expression (2) was created.
[0053]
C_e/ C₀= 0.0263 x t + 0.207 (2)
Strictly speaking, t in the above formula (2) must be t / (1 hour), that is, t must be expressed as a dimensionless number in units of time. Represent. The same applies to the following equations.
[0054]
The relational expression (2) is shown by a straight line in FIG.
[0055]
Separately, a cylindrical Li ion battery of the same kind (nominal capacity 1350 mAh) is prepared, charging current 45 mA (0.033 CmA), charging upper limit voltage 4.1 V, constant current constant voltage (CC-CV) with a charging time of 30 days. ) Charging by the method, discharging current of 1350 mA (1.0 CmA), discharging end voltage 2.75 V, and charging / discharging cycle with a pause of 10 minutes between charging and discharging, CC mode charge time t (hr) and discharge capacity C nominal capacity C₀Specific capacity C / C for (1350 mAh)₀And the validity of the relational expression (2) shown above was examined.
[0056]
The results are indicated by black squares in FIG.
[0057]
As shown in FIG. 4, it can be seen that the data indicated by the black squares is very close to the value of the relational expression (2) indicated by the straight line and can show an excellent capacity estimation result.
[0058]
On the other hand, apart from the above examination, as a comparative example, when creating a relational expression, the same conditions were used except that a Li-ion battery of the same type as the above relational expression was used and the charging current value was set to 135 mA (0.1 CmA). An attempt was made to create a relational expression by testing. Acquired specific capacity C / C₀FIG. 5 shows the relationship between the time required to complete the CC mode charging and t.
[0059]
FIG. 5 shows, as a comparative example in the capacity estimation method of the present invention, the specific capacity C / C obtained by changing the charging current value to 0.1 CmA to create a relational expression.₀And the required time t until completion of charging in the CC mode. The mark ● in the figure indicates acquired data. As is apparent from FIG. 5, when the charging current value is larger than 0.05 CmA, the specific capacity C / C₀It can be seen that there is no linear relationship between the time t and the time t, and it is impossible to create a highly accurate relational expression.
(Example 2)
Using four square Li-ion batteries (nominal capacity 600 mAh), charging current value 20 mA (0.033 CmA), discharging current value 600 mA (1.0 CmA), charging time 2.5 days, 3 days, 30 days, Except for 35 days, a charge / discharge cycle test of up to 5 cycles was performed under the same conditions as in Example 1, and each relational expression was created during 153 days in the same procedure as shown in Example 1.
[0060]
As a result, the relational expression obtained from the batteries tested for charging time in 2.5 days is
C_e/ C₀= 0.00961 × t + 0.704 (3)
And the relational expression obtained from the battery tested with a charging time of 3 days is
C_e/ C₀= 0.0167 * t + 0.485 (4)
The relational expression obtained from the battery tested at the charging time of 30 days is
C_e/ C₀= 0.0180 × t + 0.447 (5)
Met. When the charging time is 35 days, the charge / discharge cycle was only 2 times, but a relational expression was created from the data of these 2 cycles.
C_e/ C₀= 0.00627 × t + 0.801 (6)
was gotten.
[0061]
In order to evaluate the estimation accuracy using the obtained relational expressions, the prismatic Li-ion battery (nominal capacity 600 mAh) mounted on the mobile phone is detached and connected to the positive terminal and the negative terminal to automatically charge and discharge the battery. Installed in the test equipment, charging current 20mA (0.033CmA), charging upper limit voltage 4.1V, total charging time 1 day, constant current constant voltage (CC-CV) system charging, after 1 hour rest, Discharge at a discharge current of 600 mA (1.0 CmA) and an end-of-discharge voltage of 2.75 V, the time t (hr) required for constant current (CC) charge and the specific capacity C / C of the discharge capacity C to the nominal capacity₀Asked. As a result, CC charging time t is 15.31 hours, specific capacity C / C₀Was 63.5%.
[0062]
The obtained CC charging time t, that is, t = 15.31 (hr) is substituted into each of the obtained relational expressions (3), (4), (5), and (6), and each estimated specific capacity C_e/ C₀And the estimation error Err = C / C₀-C_e/ C₀= 0.635-C_e/ C₀Asked.
[0063]
As a result, the relational expression (4) obtained in the test with a charging time of 3 days to 30 days and the charging time of 3 days, and the relational expression (5) obtained in the test with a charging time of 30 days Then, each estimated specific capacity C_e/ C₀74.1% and 72.3%, and the estimation error Err was -10.6% and -8.8%, and it was found that good estimation could be made within ± 20%.
[0064]
On the other hand, when the relational expression (3) obtained in the test with the charging time of 2.5 days is used, the estimated specific capacity is 85.1%, the estimated error is −21.6%, and the charging time is 35%. Using the relational expression (6) obtained in the day test, the specific capacity was 89.7% and the estimation error was 26.2%, and it was found that both errors were large and could not be used as the relational expression.
[0065]
For comparison, when the relational expression is created only from the initial two-cycle data obtained in the test when the charging time is 3 days among the tests for which the relational expression is obtained,
C_e/ C₀= 0.00579 × t + 0.819 (7)
In the same manner, t = 15.31 is substituted into the estimated specific capacity C_e/ C₀When the estimated error Err was calculated, the estimated specific capacity was 90.8% and the estimated error was −27.3%, and it was also clear that a good relational expression could not be provided with data of only two cycles in order to create the relational expression. Became.
(Example 3)
The same cylindrical Li ion battery (18650 type, nominal capacity 1350 mAh) as in Example 1 was used, and the discharge current values were 135 mA (0.1 CmA), 270 mA (0.2 CmA), 2700 mA (2.0 CmA), and A charge / discharge cycle test was performed using the same apparatus and test conditions as in Example 1 except that the flow rate was 3000 mA (2.2 CmA), and the relational expression was obtained in the same procedure as in Example 1.
[0066]
The results are shown in FIG. FIG. 6 is a diagram showing the results of a charge / discharge cycle test carried out in order to obtain the relational expression in this example, in which 6-1 is a relation obtained from a test with a charging current value of 0.1 CmA. formula
C_e/ C₀= 0.00918 x t + 0.727 (8)
6-2 is a relational expression obtained from a test with a charging current value of 0.2 CmA.
C_e/ C₀= 0.0242 x t + 0.255 (9)
6-3 is a relational expression obtained from a test with a charging current value of 2.0 CmA.
C_e/ C₀= 0.0205 × t + 0.372 (10)
6-4 is a relational expression obtained from a test with a charging current value of 2.2 CmA.
C_e/ C₀= 0.0521 * t-0.552 (11)
It is a straight line showing.
[0067]
Separately, the Li ion battery pack used in the laptop computer was disassembled, and one of the cylindrical Li ion batteries (18650 type, nominal capacity 1350 mAh) was taken out, and the positive electrode terminal and the battery side surface (negative electrode) ) Is soldered to a battery charging / discharging automatic testing device, the charging current value is 45 mA (0.033 CmA), the charging upper limit voltage is 4.1 V, and the constant charging voltage is constant for one day (CC) -CV) charging is performed, and after a pause of 1 hour, a discharge current value of 1350 mAh (1.0 CmA) and a discharge end voltage of 2.75 V are discharged, and a constant current (CC) mode charging time t (Hr) and the nominal capacity C of the discharge capacity C₀Specific capacity for C / C₀T = 19.34, C / C₀= 0.671 was obtained. By substituting the obtained value t = 19.34 into the relational expressions (8), (9), (10) and (11) shown above, the estimated specific capacity C_e/ C₀And the estimation error Err = C / C₀-C_e/ C₀= 0.671-C_e/ C₀The capacity estimation accuracy was evaluated.
[0068]
As a result, in the relational expression (9) obtained from the test in which the discharge current value was 0.2 CmA, the estimated specific capacity was 72.3%, the estimated error was -5.2%, and the discharge current value was 2.0 CmA. In the relational expression (10) obtained from the test, the estimated specific capacity is 76.8% and the estimation error is −9.7%, and the discharge current value of the test for obtaining the relational expression in the present invention is 0.2 CmA or more and 2.0 CmA. In these cases within the following range, good estimation results were obtained. On the other hand, in the relational expression (8) obtained in the test with the discharge current value of 0.1 CmA, the condition for obtaining the relational expression in the present invention deviates from the range of the discharge current value, the estimated specific capacity 90 In the relational expression (11) obtained in the test where the discharge current value deviating from the above range is 2.2 CmA, the estimated specific capacity is 45.6% and the estimated error is +21. It was found that it was difficult to estimate the capacity of the Li-ion battery with high accuracy.
Example 4
For charging a battery pack in series of three cylindrical Li-ion batteries (18650 type, nominal capacity 1350 mAh), a constant current with a charging upper limit voltage of 12.3 V, a charging current value of 45 mA (0.033 CmA), and a total charging time of 3 days A battery charger having a function of charging the battery pack by a constant voltage (CC-CV) method and determining deterioration of the battery pack during charging was manufactured.
[0069]
The configuration concept of the manufactured charger is shown in FIG. That is, FIG. 7 is a diagram showing the configuration of the charger manufactured in the present embodiment, in which 20 is the charger of the present invention manufactured in the present embodiment, and the charger 20 is connected to the commercial power source 21. 22 and 23 are connected. In addition, the Li-ion battery pack 24 is connected to and attached to the terminals 25 and 26 for charging with respect to the charger 20.
[0070]
The charger 20 converts electricity supplied from the commercial power source 20 into direct current by the AC / DC converter 27, monitors the charging current and the pack voltage, and monitors the temperature by the thermistor 28, while the power supply microcomputer 29 and the charging control. The microcomputer 30 charges the battery pack 24 by performing control for detecting and avoiding the above-described charging conditions and dangerous states such as overcharge, overdischarge, abnormally large current, and abnormal battery temperature rise. Charging is stopped by the switch 31 when charging is completed or when an abnormality is detected. The completion of charging, some abnormality is displayed on the display unit 32 from the control microcomputer 30.
[0071]
Degradation determination in this charger is performed by programming the charge control microcomputer 30 with the relational expression (2) created in the first embodiment and the flow procedure shown in FIG. 8 in advance and monitoring the battery voltage. The CC charging time t is measured by the built-in timer while being used, and applied to the above relational expression (2) to estimate the capacity of the Li-ion battery pack, determine the deterioration based on the result, and determine on the display unit 32 The result was displayed.
[0072]
The display unit 32 displays LEDs related to charging (red: being charged, green: fully charged), displays the deterioration determination result, and ED (red: changed battery, yellow: replaced battery soon, green: replaced battery) Unnecessary) and a numerical value display of the deterioration determination result, and an LCD for displaying an abnormality.
[0073]
In the charging-related LED, the green LED is lit only when charging is completed, the red LED is lit during charging, and both are not lit when other abnormalities are indicated.
[0074]
In the LED indicating the deterioration determination result, when the value of the estimated specific capacity, which is the capacity estimation result, is less than 60%, the red LED is turned on to indicate that it should be immediately replaced with a new battery pack. When the specific capacity is 60% or more and less than 70%, the yellow LED is turned on soon because the battery pack should be replaced within a few months, depending on use conditions. Further, when the specific capacity is 70% or more, the green LED is turned on because the battery pack is new or can be used for a considerably long time and does not need to be replaced.
[0075]
The LCD is installed for the purpose of displaying textual information. It indicates that it is difficult to perform normal charging, such as battery pack mounting failure, warning information related to safety, etc., and indicates a deterioration determination result by a numerical value. Further, in the case of a sudden stop of the commercial power source, only when the voltage of the attached battery pack is higher than 8.25 V, current is supplied from the attached battery pack to indicate power off.
[0076]
In the case of the charger of this embodiment, charging is not always performed after complete discharge. Therefore, data on the time change of the charging voltage is input in advance into the charging control microcomputer, and the battery at the start of charging is charged. The pack voltage is monitored, and the increment of 1.15 V is 8.25 V (2.75 V / cell) or more and 11.7 V (3.9 V / cell, 0.2 V / cell lower than the upper limit voltage 4.1 V / cell) or less. Voltage, ie
8.25V, 9.40V, 10.55V, 11.70V,
Among the four voltages shown in Fig. 4, the time measurement is started from a value that is higher than the charging start voltage and closest to the starting voltage, and reaches the charging upper limit voltage 12.3V until the CC mode charging is completed. Measurement was performed and comparison operation was performed with the input data, and the deterioration was determined by converting to a CC mode charge required time t from 8.25V to 12.3V.
[0077]
The deterioration determination procedure flow input to the charge control microcomputer 30 shown in FIG. 8 is as follows. That is,
Procedure A: Install the battery pack in the charger, start charging, monitor the pack voltage,
Pack voltage V is
V = 8.25, 9.40V, 10.55V, 11.70V
The voltage monitor monitors whether a value that satisfies the conditions has been reached
Procedure B: Time measurement starts when the pack voltage V reaches any of the above values,
Continue timer counter to charge upper limit voltage 12.3V
Procedure C: When the pack voltage V reaches the charge upper limit voltage 12.3V, the time measurement ends, and when the charge start voltage is the discharge end voltage 8.25V, the time t is deteriorated as it is.
Used for judgment
Procedure D: When the charging start voltage is higher than 8.25V, the measured time is compared with the built-in time change data of the charging voltage, and the CC mode from 8.25V to 12.3V is calculated. Converted to the required charging time, this value is used as t for deterioration determination. Substituting the obtained time t into the relational expression (2), the estimated specific capacity C_e/ C₀Calculate
Procedure E: The calculated result is displayed on the LCD and LED. Depending on the value of the estimated specific capacity, which is the estimation result, one of red, yellow, and green LEDs is turned on as described above, and at the same time, the numerical value of the estimated specific capacity is displayed on the LCD. LCD display for 30 seconds, LED
Lights up while the charger is connected to a commercial power source.
[0078]
Using the battery charger configured as described above, a used battery pack of the same type was mounted and charged. The deterioration determination result was displayed 15.7 hours after the start of charging, the (estimated) specific capacity 62.0% was displayed on the LCD, and the yellow LED was lit.
[0079]
The charged battery pack was installed in a battery charge / discharge automatic test device, and the discharge current value was set to 1350 mA (1.0 CmA) and the discharge end voltage was 8.25 V, and constant current discharge was performed to determine the discharge capacity. 860.0 mAh. This was 63.7% in terms of specific capacity, and the error in the estimated specific capacity was about 1.7%.
[0080]
As described above, it has been clarified that it is possible to perform highly accurate deterioration determination using the above-described Li-ion battery deterioration determination apparatus according to the present invention.
(Example 5)
It is mounted on a laptop computer having a function of performing constant current and constant voltage (CC-CV) mode charging under conditions of an upper limit voltage of charge 12.3 V, a charging current 45 mA (0.033 CmA), and a total charging time 3 days. A Li-ion battery pack having the structure shown in FIG. The battery pack is a 3-cell series pack of cylindrical cells (nominal capacity 1350 mAh) 12-1, 12-2, and 12-3, and the relational expression (2) and the example 4 are shown for the protection IC. As with, constant current (CC) from 8.25V to 12.3V even when charged with a pack voltage higher than the end-of-discharge voltage of 8.25V by inputting the basic data of the charging voltage over time. The mode charging time can be calculated.
[0081]
In addition, the memory of the protection IC 13 in the battery pack having the configuration shown in FIG. 3 monitors the voltage across each cell of the Li-ion batteries 12-1, 12-2, 12-3, and discharges in CC mode charging. Higher than Vs from an arbitrary preset start voltage Vs that is greater than or equal to end voltage Vd and less than or equal to charge upper limit voltage Vc
Charging voltage = 8.25V, 9.40V, 10.55V, 11.70V
The elapsed time t from the closest charging voltage that satisfies the condition until reaching the charging upper limit voltage 12.3V at which the CC mode charging is completed is counted, and the value of the measured time t is substituted into the relational expression (2) and calculated. Estimated specific capacity C_e/ C₀The program for calculating is input in advance.
[0082]
The calculated result is output through the terminal 19 to the apparatus main body for display on the liquid crystal display of the apparatus main body on which the battery pack is mounted.
[0083]
On the liquid crystal display, a numerical value as a calculation result is displayed as a percentage, and a ratio corresponding to a percentage value of the bar length is indicated by a solid color.
[0084]
The instruction for determining the deterioration is issued from the device body at the same time as the start of charging. The procedure flow for performing the deterioration determination is the same as that shown in FIG. 8 except that the result is sent to the main body in order to display the result on the display of the device main body in FIG.
[0085]
A battery pack having such a configuration is mounted on a device, used for 1 hour, then connected to a commercial power source to start charging, and when the display displayed after the start of charging is viewed, the specific capacity of the battery pack is estimated. The result was displayed as 73%. After confirming that the sign of the completion of charging appeared on the display, turn off the device, remove the battery pack, connect to the battery charge / discharge automatic test device using an appropriate connection cord, and discharge current 1350 mA. The battery was discharged at a discharge end voltage of 8.25 V (1.0 CmA), and the capacity was measured. As a result, the discharge capacity was 1093.5 mAh and the specific capacity was 81.0%.
[0086]
Therefore, it was revealed that the specific capacity estimation result by the specific capacity estimation function mounted on the battery pack according to the present invention shows an excellent estimation accuracy with an error of -8.0%.
[0087]
【The invention's effect】
As described above, by implementing the present invention, a simple method for estimating the capacity of a Li ion battery, a simple device for determining the deterioration of a Li ion battery, and a Li ion having a function for estimating the capacity of the battery A battery pack can be provided, which can make a very significant contribution to the management of Li-ion batteries.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram for explaining the concept of a temporal change in a charging voltage (battery voltage) and a charging current value in constant current constant voltage (CC-CV) charging, which is a general charging method for a Li-ion battery.
FIG. 2 is a diagram showing a configuration concept of the periphery of a general power supply unit of a Li ion battery mounting device to which the Li ion battery capacity estimation method according to the present invention is specifically applied.
FIG. 3 is a diagram showing a general circuit configuration example of a Li ion battery pack having a capacity estimation function in the present invention.
FIG. 4 is a graph showing the relationship between elapsed time t and specific capacity showing the results of a charge / discharge cycle test in Example 1 of the present invention.
FIG. 5 is a diagram showing a relationship between a required time t of CC mode charging and a specific capacity obtained by a charging / discharging cycle with a charging current value of 0.1 CmA as a comparative example in Example 1 of the present invention.
FIG. 6 is a diagram showing a relationship between a required time t of CC mode charging performed in Example 3 of the present invention and a specific capacity, and is a diagram showing an obtained relational expression.
FIG. 7 is a diagram showing a configuration of a charger manufactured in Example 4 of the present invention.
FIG. 8 is a flowchart showing a deterioration determination procedure performed in Example 4 of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Power supply part, 2a, 2b, 2c ... Li ion battery, 3 ... Battery control part, 4 ... Charger, 5 ... Logic part, 6 ... Interface, 7 ... CPU, 8 ... Memory, 9 ... Keyboard controller, 10 ... Wiring, 11 ... battery pack body, 12-1, 12-2, 12-3 ... Li-ion battery, 13 ... protection IC, 14-A, 14-B, 14-C, 14-1, 14-2, 14-3 ... FET, 15 ... PTC element, 16 ... current fuse, 17 ... plus terminal, 18 ... minus terminal, 19 ... terminal for information output and control, 20 ... charger, 21 ... commercial power supply, 22,23 Terminal for connecting commercial power source and charger, 24 Li-ion battery pack, 25, 26 Terminal for connecting charger and battery pack, 27 AC / DC converter, 28 Thermistor, 29 Microcomputer for power supply, 30 ... Charge control machine Icon, 31 ... switch, 32 ... display section.

Claims (3)

Ri capacity estimation method der of the lithium-ion battery,
When charging a lithium ion battery by the constant current constant voltage method, the charging current when the nominal capacity of the lithium ion battery is C ₀ is set to C ₀ / (20 hours) or less, and the charging voltage during constant current charging is A time t from reaching the preset voltage Vs to reaching the charging upper limit voltage Vc is obtained, and the estimated specific capacity C _e / C _{0 of the} battery (where C _e is the estimated capacity of the battery) is obtained. Relational expression,
C _e / C ₀ = At + B (1)
(Here, A and B are the battery, the voltage Vs, a positive value constants determined by the charging current of the voltage Vc and the constant current charging) a volume estimation method of a lithium ion battery you calculated by,
Using the same type of lithium ion battery as the target of capacity estimation,
Or less once total charge time of 3 days or more 30 days, charging by the constant current-constant voltage system the charging current is C _{0 /} (20 hours) or less when the nominal capacity of the lithium ion battery was C ₀ period and the discharge current of the C _{0 /} (5 hours) or C _{0 /} (0.5 hr) or less and the discharge period is a discharge end voltage Vd, optionally the charging period and the discharge period A charge / discharge cycle having a rest period provided in between is repeated three or more times,
In each cycle, a time t _n from when the charging voltage during constant current charging reaches a preset voltage Vs to the charging upper limit voltage Vc (where n is a number assigned to each cycle); the discharge capacity C _n obtained by integrating with respect to the discharge current time for each cycle was recorded, from the recorded said time t _n and the discharge capacity C _n, a and B in the above equation (1) A method for estimating the capacity of a lithium ion battery, characterized by determining a value . A lithium ion battery deterioration determination device,
An arithmetic circuit for calculating an estimated specific capacity C _e / C ₀ of the lithium-ion battery by the capacity estimation method of a lithium ion battery according to claim 1, wherein the lithium based on the value of the estimated specific capacity C _e / C ₀ Judgment arithmetic circuit for judging the deterioration state of the ion battery, means for displaying the judgment result by the judgment arithmetic circuit, or means for emitting a warning sound for warning the deterioration of the lithium ion battery based on the judgment result A deterioration determination device for a lithium ion battery, comprising: In the lithium-ion battery pack including the charge and discharge control means having a built-in IC, the IC or IC, which is added by attached to the IC is estimated stoichiometric capacity of the lithium ion battery in the lithium-ion battery pack C _e / a memory for storing a numerical value used in estimating the capacity estimation method of a lithium ion battery according to C ₀ to claim 1, when said numerical value is stored in the memory, a lithium ion battery according to claim 1 It has the arithmetic circuit for calculating an estimated specific capacity C _e / C ₀ of the lithium-ion battery by volume estimation method, and means for outputting the estimated specific capacity C _e / C ₀ calculated result the operational circuit is calculated A lithium ion battery pack characterized by having

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