JP2001332310A - Capacity estimating method and deterioration judging apparatus for lithium ion cell and lithium ion cell pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a convenience method to estimate capacity of a Li ion cell, a convenient apparatus to judge deterioration of an Li ion cell and an Li ion cell pack equipped with a function of estimating the capacity of the cell. SOLUTION: The method of estimating the capacity of the Li ion cell sets a charging current at Co/(20 hr) or lower when the nominal capacity of the cell is regarded as Co upon charging the cell by a constant-current constant- voltage system, finds time t required until the charging voltage during the constant current charging reaches an upper limit charging voltage Vc from the predetermined voltage Vs, and calculates an estimated specific capacity Ce/Co in accordance with the relational expression: Ce/Co=At+B, (wherein, A and B are positive constants). The apparatus for judging the deterioration of the Li ion cell utilizes this method, and the Li ion cell pack is equipped with a means for practicing the method of estimating the capacity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for estimating the capacity of a lithium ion battery, a device for determining deterioration, and a lithium ion battery pack.

[0002] Here, a "battery pack" refers to a unit cell (hereinafter, referred to as a cell) or a plurality of cells connected in series, in parallel, or in a combination of both.
It means that it is integrated with a safety control circuit or a charge / discharge control circuit to form "a secondary battery as an independent power supply".

[0003]

2. Description of the Related Art In recent years, demands for batteries have been increasing due to miniaturization, high performance, and portableness of various electronic devices. In response, battery improvements and developments are becoming more active. Also, new application areas of batteries are expanding.

[0004]

With the spread of batteries,
There is a growing demand for improved reliability of these mounted batteries. In particular, nickel-metal hydride batteries (hereinafter, referred to as Ni / MH batteries) having a much higher energy density per volume or weight than conventional lead batteries and nickel cadmium batteries (hereinafter, referred to as Ni / Cd batteries) and Lithium-ion batteries (hereinafter referred to as Li-ion batteries) have a large amount of energy stored inside, and the degree of damage caused by accidents caused by battery abnormalities can be even more severe, ensuring reliability. It is an important issue.

The above-mentioned Li-ion battery uses a metal oxide capable of inserting and releasing lithium in the positive electrode active material, a carbon compound capable of inserting and releasing lithium in the negative electrode, and a non-aqueous organic compound using a lithium salt as a solute as an electrolyte. It is composed.

Also, lead batteries, Ni / Cd batteries, and N
While the i / MH battery has a reaction mechanism that absorbs the gas generated by the side reaction due to overcharge, the Li-ion battery does not have an absorption reaction of the gas generated by overcharge. There is a big restriction. Furthermore, when a plurality of Li-ion batteries are used in series, as the battery deteriorates, the imbalance of individual battery characteristics causes overcharging and overdischarging, which is a major concern in terms of safety. sell.

As one of the reliability securing means, there is a method of accurately grasping the state of deterioration of the mounted battery and replacing the battery in a timely manner. Regarding high energy density batteries such as Ni / MH batteries and Li-ion batteries, the smart battery system (SBS) proposed in 1994 has become popular as a battery management system including charge control and remaining capacity determination, with improvements. (Www.sbs-fo
rum.org). These battery controls / managements include information such as the manufacturer and battery type, as well as the battery current, voltage,
Only a method based on enormous information data management for monitoring temperature and the like is employed, and such a method is an extremely expensive method and has resulted in a rise in product prices.

[0008] As for the monitoring of the state of deterioration of the battery, which is important for maintaining safety, the model equipped with the Li-ion battery is frequently changed. They tend to be neglected as much as possible.

In particular, the SBS is a means for controlling and managing the charge and remaining capacity of the battery, and has no function of grasping the state of deterioration of the battery. It was the present situation that relied on intuition.

[0010] Apart from SBS, a control / management method of a Li-ion battery mounted on a video camera has been proposed. In this method, the deterioration of the battery is determined from the display of the measured capacity. That is, it is not always possible to correctly determine whether or not a battery used after charging has deteriorated.

The present invention has been made in view of the above points, and has as its object a simple method for estimating the capacity of a Li-ion battery, a simple device for determining deterioration of the Li-ion battery,
Another object of the present invention is to provide a Li-ion battery pack having a function of estimating the capacity of a battery.

[0012]

According to a first aspect of the present invention, there is provided a method for estimating the capacity of a lithium ion battery, comprising the steps of: When charging by the 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 the constant current charging reaches the preset voltage Vs. seek time t to reach the charging upper limit voltage Vc from the estimated ratio of the battery capacity C _e / C _{0 (here,} C _e is the estimated volume of the battery) relational expression, C _e / C ₀ = At + B (1) (where A and B are positive value constants determined by the battery, the voltage Vs, the voltage Vc, and the charging current during the constant current charging). capacity Configure the estimation method.

According to the present invention, there is provided a method for estimating the capacity of a lithium ion battery according to claim 1, wherein the lithium ion battery is of the same type as the lithium ion battery whose capacity is to be estimated. Using a lithium ion battery, the total charging time is 3 days or more and 10 days or less, and the charging current is C when the nominal capacity of the lithium ion battery is C _{0.
0 /} and the charge period by the constant current and constant voltage system lying in (20 hours) or less, the discharge current C _{0 /} (5 hours) or C ₀ /(0.5 hours) or less and the discharge end voltage is Vd discharge Duration and
If necessary, a charge / discharge cycle having a pause period provided between the charge period and the discharge period is repeated three times or more, and in each cycle, a charge voltage during constant current charge is set to a predetermined voltage Vs and _(here, n represents an is number assigned to each cycle) time t _n to reach the charging upper limit voltage Vc from reaching the discharge capacity C _n obtained by integrating with respect to the discharge current time for each cycle Wherein the values of A and B in the above relational expression (1) are determined from the recorded time t _n and the discharge capacity C _n. I do.

According to the present invention, there is provided a lithium ion battery deterioration judging device according to claim 3, wherein the time t for charging the lithium ion battery by the constant current and constant voltage method is obtained. And an arithmetic circuit for calculating the estimated specific capacity C _e / C ₀ of the lithium ion battery by the relational expression (1) using the time t, and the lithium based on the value of the estimated specific capacity C _e / C _0. A judgment operation circuit for judging the deterioration state of the ion battery, and means for displaying the judgment result by the judgment operation circuit or based on the judgment result,
A means for issuing a warning sound to warn the deterioration of the lithium ion battery, if necessary.

Further, according to the present invention, in a lithium ion battery pack provided with charge / discharge control means having a built-in IC, the IC or the I-type battery pack may be provided.
The additional IC attached to C is the estimated specific capacity C _e / of the lithium ion battery in the lithium ion battery pack.
A memory for storing a numerical value used for calculating C ₀ , and the relational expression based on the time t and the numerical value when the lithium ion battery is charged by the constant current and constant voltage method when the numerical value is stored in the memory. According to (1), the estimated specific capacity C _e /
An arithmetic circuit for calculating the C _0, constituting a lithium ion battery pack, characterized in that it has a means for outputting the estimated specific capacity C _e / C ₀ calculated result the operational circuit is calculated.

[0016]

(Embodiment 1) L according to the present invention
In the capacity estimation method of i-ion battery, a lithium-ion battery when charged by the constant current and constant voltage mode, the charging current when the nominal capacity the lithium ion battery was C ₀ C _{0 /} (20 hours) or less The time t from when the charging voltage during constant current charging reaches the preset voltage Vs to when the charging voltage reaches the charging upper limit voltage Vc is determined, and the estimated specific capacity C _e / C ₀ (here, C _e determined in relation to the estimated capacity is) of the battery, to _{C e / C 0 = at +} B (1) ( wherein, a and B are the battery, voltage Vs, the charging current of the voltage Vc and the constant current charging (A positive value constant).

The method for estimating the capacity of a Li-ion battery according to the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a diagram showing a change over time of a charging voltage (indicated as a battery voltage in the figure) and a charging current when a Li-ion battery is charged by a constant current and constant voltage (CC-CV) method. .

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 charged in a constant current (CC) mode at a predetermined constant current Ic. The battery is charged to the set upper limit voltage Vc (normally, 4.1 V / cell or 4.2 V / cell), and after the charging voltage reaches the upper limit voltage Vc, charging in the constant voltage (CV) mode is started. The charging current attenuates with time while the charging voltage (shown as battery voltage in FIG. 1) remains constant at Vc.

Method of estimating capacity of Li-ion battery according to the present invention
In the law, the charge smell by the CC-CV method
And the discharge end voltage Vd during charging in the constant current (CC) mode.
As described above, the voltage Vs set to be equal to or lower than the upper limit voltage Vc is charged.
After the voltage reaches, the constant current mode charging ends
Elapsed time until charging voltage reaches Vc
t, and using this time t, the Li-ion battery
Above estimated specific capacity C_e/ C ₀Is given by the above relational expression (1).
Is calculated.

In this case, the constant current Ic in charging by the CC-CV method is set to C ₀ / (20 hours) or less so that the capacity of the battery can be accurately estimated.
When charging is performed with a current exceeding this, the error in estimating the capacity according to the above relational expression (1) increases.

Hereinafter, generally, when the battery current is C ₀ / (T time)
Where, this current is expressed as (1 / T) CmA. For example, C ₀ / (20 hours) is represented as 0.05 CmA.

Further, the Li-ion battery for which the capacity estimation in the present invention is performed has a charging time of 30 times.
Preferably, it is used under usage conditions that are not more than days. A long charging time in which a single charging time exceeds 30 days is not preferable because the degree of deterioration due to overcharging is different or deterioration of battery constituent materials with time becomes remarkable, which may cause a large capacity estimation error.

Further, in carrying out the capacity estimation, it is preferable that the charging voltage Vs at the start of the time measurement be equal to or higher than the discharge end voltage Vd and at least 0.2 V lower than the upper charging voltage Vc. Time measurement start voltage Vs is charging upper limit voltage V
When the difference is within a voltage range of less than 0.2 V from c, the required time t to be measured becomes too short and a large estimation error may occur, which is not preferable.

The application of the relational expression for estimating the capacity in the present invention is based on the assumption that the deterioration of the battery causes
Discharge capacity when discharged to C (which is obtained by integrating with respect to the discharge current time) is limited to the case in more than 50% range of the nominal capacity C _0. When the battery is significantly deteriorated such that the specific capacity C / C ₀ is reduced to less than 50%, a linear relationship as shown by the above relational expression (1) between the required time t and the specific capacity C / C ₀ is obtained. (The left side of the equation is the specific capacity C
/ C ₀ ) is not satisfied, and an error in estimating the capacity using the relational expression increases, which is not preferable.

The above relational expression (1) indicates that the Li
It is assumed that there is a relationship between the charging time t in the constant current (CC) mode under the charging condition of the ion battery mounted device or the charger and the specific capacity C / C ₀ under the condition. If the CC when the above relational expression (1) is created
Mode charging current value and CC of onboard equipment or charger
If the charging current values of the modes are different, the required charging time of the CC mode under the respective charging conditions is separately obtained in advance, and the required time te and the mounting device or the charger at the time of creating the relational expression (1) are obtained. The ratio te / tm to the required time tm under conditions corresponding to
Needs to be multiplied by t.

This is because the charging rate in the CC mode charging (the charging rate of the 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. In addition, 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. (Embodiment 2) In Embodiment 1, in order to estimate the capacity of a Li-ion battery, the above relational expression (1) must be created in advance. For that purpose, the values of the constants A and B in the relational expression (1) must be determined. In that case, Li which is the target of capacity estimation
It is most reasonable to determine the above constants A and B by testing a battery or battery pack of the same type as the ion battery.
This is because commercially available Li-ion batteries use various types of positive electrode active pollutants, negative electrode carbon and electrolyte, and not only change in charging voltage behavior due to battery deterioration,
This is because the initial battery charging behavior is also different.

Therefore, in the present invention, a lithium ion battery of the same type as the lithium ion battery whose capacity is to be estimated is used, and the total charging time for one time is 3 days or more and 10 days or less. The charging period by the constant current constant voltage method in which the charging current when the nominal capacity is C ₀ is C ₀ / (20 hours) or less, and the discharging current is C ₀ / (5 hours).
Is not more than C ₀ /(0.5 hours) and the discharge end voltage is Vd
And a charge / discharge cycle having a pause period provided between the charge period and the discharge period as required is repeated three times or more, and in each cycle, the charge voltage during the constant current charge is reduced. A time t _n (where n is a number assigned to each cycle) from when the voltage reaches a preset voltage Vs to when the charge upper limit voltage Vc is reached, and a discharge current is integrated with respect to time for each cycle. the resulting discharge capacity C a _n records, from the recorded said time t _n and the discharge capacity C _n, a and B in the above equation (1)
Determine the value of.

The above-mentioned operation will be described in more detail. A battery of the same type as the Li-ion battery for which the capacity estimation is to be performed in the present invention is used. C ₀ / (20 hours or less)
The upper limit voltage V by constant current (CC) charging of the charging current value of
c, and after the voltage of the battery or the battery pack reaches the upper limit voltage Vc, charging is performed by a constant current constant voltage (CC-CV) method in which charging is continued by constant voltage (CV) charging. Set to 3 days or more and 30 days or less, discharge is 0.2 CmA or more and 2.0 CmA or less (C ₀ / (5 hours)
As described above, a current value of C ₀ /(0.5 hours or less) and a discharge end voltage Vd similar to the use condition of the battery are set, and a fixed pause time is provided between these charge and discharge if necessary. Such a charge / discharge cycle is performed three times or more, and the charge upper limit voltage Vc and the discharge end voltage Vc in each charge / discharge cycle.
During the period d, the charging in the constant current (CC) mode is completed after the charging voltage reaches an arbitrary voltage Vs not lower than Vd and not higher than (Vc-0.2 V) (the charging voltage reaches the charging upper limit voltage Vc). ) time t _{n (here} the required until, n represents the a is) number assigned to each cycle, and records the discharge capacity C _n obtained by integrating with respect to the discharge current time for each cycle, it is recorded and a said time t _n and the discharge capacity C _n was to determine the values of a and B in the above equation (1). That is, the left side of the relational expression (1) is replaced with C _n / C ₀ ,
The relational expression in which t on the right side is replaced by t _n is C _n / C
Best represents like the relationship between the ₀ and t _n, to determine the values of A and B.

The charging time per cycle is 3 days or more and 3
0 days or less. Set the charging time between 3 days and 10 days
The battery deterioration in each cycle
The data necessary to create the accurate relational expression (1).
Data can be obtained efficiently. When charging per cycle
If the time is longer than 30 days, it will deteriorate due to overcharging.
And the deterioration of battery components over time
Become an author and take time t _nAnd specific capacity C_n/ C₀During the above
The linear relationship represented by the relational expression (1) (the left side of the expression is the specific capacity C
_n/ C₀And replace t on the right side with t_nReplace with
Is not satisfied, these data
In the relational expression using the constants A and B determined from the data,
A large error may occur, which is not preferable.

The charging time per cycle is 30
If the time is set longer than the day, the elapsed time per cycle becomes longer, and it takes time to acquire data, which is not preferable.

On the other hand, when the charging time per cycle is set to less than 3 days, the electrode deterioration due to the charge / discharge cycle becomes remarkable, and conversely, the degree of deterioration due to overcharge becomes small. In the capacity estimation using the above-described relational expression (1) to which B is applied, the capacity estimation error increases in actual use in which discharge and charge are different each time, except for a limited use method in which charge and discharge are frequently performed. Is not preferred.

The discharge current value in the above charge / discharge cycle test is set at 0.2 CmA or more and 2.0 CmA or less.
If the value 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 a long time for complete discharge, which is not preferable. Further, when the discharge current is greater than 2.0 CmA, the discharge time itself becomes too short, and when the measured value of the discharge capacity varies or the deterioration progresses, the capacity sharply decreases and the relational expression (1) with high accuracy is obtained. It is not preferable because it becomes impossible to create

In carrying out the above-described charge / discharge cycle test, if necessary, a pause for a fixed time can be set between charging and discharging due to restrictions on the setting of the apparatus.

In the charge / discharge cycle test performed to create the above relational expression (1),
Discharge end voltage Vd in constant current (CC) mode of charging
As described above, the charge upper limit voltage Vc is lower by 0.2 V (Vc−0.2
And time t from any voltage Vs in the voltage range of V) below to CC mode ends, measuring the charging specific capacity C _n / C ₀ of the subsequent discharge per KakuTakashi discharge cycle. The measured time t and the specific capacity C _n / C ₀ are plotted and applied to the relational expression (1) to determine the constants A and B.

[0036] The charging and discharging cycle test, the capacity estimation result C _e is the time t _n and a specific capacity C _n / C ₀ necessary for the high precision to be in the range of within ± 20% of the real capacity C In order to satisfy the data, charge and discharge are performed for 3 cycles or more.

If the number of cycles is only two, the determination of the constants A and B in the relational expression (1) requires only two cycles.
This becomes point data, making it impossible to estimate the capacity with high accuracy, which is not preferable.

Note that the constants A and B in the above relational expression (1)
The environmental temperature of the charge / discharge cycle test to be performed to determine the temperature is not particularly specified, but within the temperature range recommended by the manufacturer as the operating temperature range of the Li-ion battery, preferably the same as the environmental temperature actually used. It is preferably carried out at a temperature. If the environmental temperature at which the charge / discharge cycle test is performed is significantly different from the actual environmental temperature at which the capacity is to be estimated, the capacities are corrected from the temperature dependence data of the discharge capacity to determine the constants A and B. I do. (Embodiment 3) In the apparatus for judging deterioration of a Li-ion battery according to the present invention, means for calculating the time t when the lithium-ion battery is charged by a constant current and constant voltage method;
An operation circuit above relationship with between t said time by (1) calculating the estimated specific capacity C _e / C ₀ of the lithium ion battery, the estimated ratio calculated by the arithmetic circuit capacitance C _e /
Means for displaying the value of C ₀ or the estimated specific capacity C _e / C
Means for displaying a judgment result of the deterioration state of the lithium ion battery based on the value of ₀ , or means for emitting a warning sound for warning the deterioration of the lithium ion battery as necessary based on the judgment result. It is characterized by the following.

FIG. 2 shows an apparatus equipped with a Li-ion battery. The function of the method for estimating the capacity of a Li-ion battery according to the present invention and the deterioration state of the lithium-ion battery are determined based on the result of the capacity estimation. 1 shows a configuration concept of an apparatus having a function of performing the following.

In FIG. 2, reference numeral 1 denotes a power supply unit. The power supply unit 1 has Li-ion batteries 2a, 2b, and 2c mounted thereon.
These batteries 2a, 2b, and 2c are controlled by a battery control unit 3 in the power supply unit 1 for charge / discharge and safety. Reference numeral 4 denotes a charger in the power supply unit 1, which charges the batteries 2a, 2b, 2c under the control of the battery control unit 3. Reference numeral 5 denotes a logic unit. The logic unit 5 includes an interface 6, a CPU 7, and a memory 8.
And a keyboard controller 9. The battery control unit 3 is connected to the CPU 7 via the interface 6, receives information on the mounted batteries 2 a, 2 b, and 2 c and an instruction to perform control, and conversely, sends data related to battery control to the CPU 7. Send out. In the logic unit 5, the CPU 7 and the memory 8
It instructs control, calculates data, accumulates information related to battery control, and stores data. Battery 2a, 2b, 2c
Is input via the keyboard controller 9. Wiring 10 for data transmission is connected to the keyboard controller 9.

In the present invention, the above-mentioned relational expression (1) is
7 is input in advance into an empty memory or the like, or is input by adding a memory chip in addition to the CPU 7 if necessary. Further, in the logic unit 5, an arithmetic circuit for calculating the estimated specific capacity C _e / C ₀ of the lithium ion battery by the relational expression (1) and the lithium based on the value of the estimated specific capacity C _e / C ₀ are provided. A judgment operation circuit for judging the deterioration state of the ion battery is incorporated, and a judgment result by the judgment operation circuit is formed in the logic unit 5. CPU7
Gives an instruction to 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 working voltage range to when the CC mode charging is switched to the CV mode charging. On the contrary, data of the charging time t is received from the battery control unit 3. Further, the CPU 7
Calculates the value of the estimated specific capacity C _e / C ₀ by substituting the received time t into the relational expression (1), and further calculates the value of the estimated specific capacity C _e / C ₀ based on the value of the estimated specific capacity C _e / C _0. The deterioration state of the lithium ion battery is determined. That is, the logic unit 5
It also has a function of estimating the capacity of the Li-ion battery and determining the deterioration state of the battery according to the present invention. If necessary, the value of the estimated specific capacity C _e / C ₀ is stored in the memory 8.

The apparatus for judging the deterioration of a Li-ion battery according to the present invention uses the apparatus shown in FIG. And, if necessary, by connecting to a device provided with a means for issuing a warning sound for warning of the deterioration of the lithium ion battery. Wiring 10
Is connected to the apparatus shown in FIG. 2 through the estimated specific capacity C _e / calculated by the arithmetic circuit.
If also includes means for displaying the values of C ₀ it is advantageous to be able to quantitatively grasp the deterioration of the lithium ion battery.

Thus, the apparatus for determining deterioration of a Li-ion battery according to the present invention can be constructed. However,
The present invention is not limited to the above-described configuration at all if the device for determining deterioration of a Li-ion battery according to the above concept can be configured. (Embodiment 4) The method for estimating the capacity of a Li-ion battery according to the present invention is also applied to a battery pack by providing a control microcomputer in the pack of the Li-ion battery or a simple additional memory if necessary in the pack. can do. FIG. 3 shows a specific configuration example of a Li-ion battery pack according to the present invention, in which the method for estimating the capacity of a Li-ion battery according to the present invention is applied to a battery pack.

FIG. 3 is a diagram showing a general circuit configuration of a Li-ion battery pack.
12-2, 12-3) are mounted in series with three cells.

In FIG. 3, reference numeral 11 denotes a battery pack body, and reference numerals 12-1, 12-2, and 12-3 denote Li-ion batteries. A protection IC 13 monitors voltage, current, temperature, and the like, and performs software-based safety control. 14-A, 14-
B, 14-C, 14-1, 14-2, and 14-3 are FEs for the purpose of controlling the charging current of the inside of the pack body 11 and each battery.
T is a PTC element which is a thermal fuse;
Is a current fuse, which has a role of interrupting the current at the time of temperature rise and abnormally large current, respectively. 17 is a plus terminal,
Reference numeral 18 denotes a negative terminal, and 19 denotes a terminal for information output and control.

In FIG. 3, a protection IC for the above-mentioned safety mechanism is shown.
13 is provided with a timer, the above-mentioned relational expression (1) is previously input to a free memory, and an arithmetic circuit for calculating the estimated specific capacity C _e / C ₀ is formed.

When the present Li-ion battery pack is mounted on a charger and charged by a constant current / constant voltage (CC-CV) method, the Li-ion battery 12-1 shown in FIG.
The protection IC 13 monitors the voltage between both ends of 12-2 and 12-3 so that the charging voltage in the constant current (CC) mode charging of the charging is equal to or higher than the discharge end voltage Vd and lower than the charging upper limit voltage Vc. Any starting voltage V set in advance
s, the elapsed time t from when the CC mode charging is switched to the CV mode charging is counted, and the value of the measured time t is substituted into the relational expression (1), and the estimated specific capacity C _e / is calculated. to calculate the C _0. If necessary, protection IC1
Apart from the above, an additional IC may be provided at an appropriate position in the pack.

The calculation result is output to the main body of the charging device through a terminal 19 to be displayed on an appropriate display or to emit a warning sound or the like.

As described above, 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 at all if the capacity estimation of the Li-ion battery according to the above concept can be performed.

As a method for estimating the capacity of the Li-ion battery and the application of the Li-ion battery pack having the capacity estimation function according to the present invention, equipment requiring high reliability such as a backup power supply can be considered. By grasping the state of deterioration of the battery accurately and realizing the replacement of the battery in a timely manner, the trouble of the device is avoided.
However, there is no problem in adopting a method for estimating the capacity and adopting a Li-ion battery pack having a capacity estimating function as long as the apparatus is equipped with a Li-ion battery, and realizing battery replacement without waste. The advantage of using it is very great.

[0051]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for estimating the capacity of a Li-ion battery, a deterioration judging device, and a Li-ion battery pack according to the present invention will be described with reference to specific examples, but the present invention is not limited thereto. . (Example 1) For a cylindrical Li-ion battery (18650 type, nominal capacity 1350 mAh), the test temperature was set to 25 ° C using a battery charge / discharge automatic test apparatus having a data collection / storage function, and the charge current value was 45 mA. (0.033C
mA), a charging upper limit voltage of 4.1 V, charging by a constant current constant voltage (CC-CV) method for a charging time of 30 days, a discharging current value of 1350 mAh (1.0 CmA), and a discharging end voltage.
Five cycles of a charge / discharge cycle test in which a pause between charge and discharge and discharge between 75 V were performed for 1 hour were performed, and an elapsed time t (hr) from the start of charging to completion of charging in the CC mode in each cycle, and a discharge specific capacity for the nominal capacity C ₀ of the discharge capacity C obtained by integrating with respect to the current time C / C ₀
I asked.

FIG. 4 shows the obtained data. FIG. 4 is a diagram showing the relationship between the elapsed time t and the specific capacity C / C ₀ showing the results of the charge / discharge cycle test, and the circles in the figure represent data obtained in the charge / discharge cycle test. From these data, the constants A and B in the above-mentioned relational expression (1) representing the estimated specific capacity C _e / C ₀ as a function of time t were obtained, and the following relational expression (2) was created.

C _e / C ₀ = 0.0263 × t + 0.207 (2) t in the above equation (2) is strictly t / (1 hour), that is, t is dimensionless in units of time. It must be represented by a number, which is simply represented by t for convenience. The same applies to the following equations.

The above relational expression (2) is shown by a straight line in FIG.

Separately, a cylindrical Li-ion battery of the same type (nominal capacity of 1350 mAh) was prepared, and the charging current was set to 45 mA.
mA (0.033 CmA), charge upper limit voltage 4.1 V, charge by a constant current constant voltage (CC-CV) method for a charge time of 30 days, and discharge at a discharge current of 1350 mA (1.0 CmA) and a discharge end voltage of 2.75 V And between charging and discharging
A charge / discharge cycle with a pause of one minute is performed, and the required time t (hr) of CC mode charging and the specific capacity C / C _{0 of the} discharge capacity C with respect to the nominal capacity C ₀ (1350 mAh) are recorded for each cycle. Then, the validity of the relational expression (2) shown above was examined.

The results are shown by black squares in FIG.

As shown in FIG. 4, the data shown by the black squares are very close to the values of the relational expression (2) shown by the straight lines, and it can be seen that the data can show excellent capacity estimation results.

On the other hand, apart from the above examination, as a comparative example,
When creating the relational expression, the same type of Li ion
The charging current value was 135 mA (0.1 Cm
The relational formula was created by the test under the same conditions except for A).
Tried. Acquired specific capacity C / C ₀And CC mode charging completed
FIG. 5 shows the relationship with the required time t.

FIG. 5 shows, as a comparative example in the capacity estimation method of the present invention, a charging current value of 0.1 Cm
FIG. 9 is a diagram showing the relationship between the specific capacity C / C ₀ obtained by changing to A and the required time t until the completion of the charging in the CC mode, and the black circles in the figure show the obtained data. As is clear from FIG. 5, when the charging current value is larger than 0.05 CmA, a linear relationship does not hold between the specific capacity C / C ₀ and the time t, and it is impossible to create a highly accurate relational expression. It can be seen that it is. (Example 2) Prismatic Li-ion battery (nominal capacity 600 mA
h) Charge current value of 20 mA (0.033 C
mA), a discharge current value of 600 mA (1.0 CmA), and a charge / discharge cycle test up to a maximum of 5 cycles under the same conditions as in Example 1 except that the charging time was 2.5 days, 3 days, 30 days, and 35 days. Is performed, and 1 is performed in the same procedure as described in the first embodiment.
Each relational expression was made during 53 days.

[0060] As a result, the relational expression obtained from the battery of testing the charge time by two. 5th is _{C e / C 0 = 0.00961 ×} t + 0.704 (3), batteries tested in charging time 3 days was determined from the equation is _{C e / C 0 = 0.0167 ×} t + 0.485 (4), the relational expression obtained from the battery tested at charging time 30 days _{C e / C 0 = 0.0180 ×} t + 0 0.447 (5). If the 35 days charging time, the charge-discharge cycles but was only twice, was to create a relational expression from the data of the two-cycle _{C e / C 0 = 0.00627 ×} t + 0.801 (6) is Obtained.

In order to evaluate the estimation accuracy using the obtained relational expression, a rectangular Li-ion battery (nominal capacity: 600 mAh) mounted on a mobile phone was detached and connected to a positive electrode terminal and a negative electrode terminal. Installed in a charge / discharge automatic test apparatus, charge current 20 mA (0.033 CmA), charge upper limit voltage 4.1 V, total charge time 1 day, constant current constant voltage (CC
-CV) charge, and after a pause of 1 hour, a discharge current of 600 mA (1.0 CmA) and a discharge end voltage of 2.75 V
And the time required for constant current (CC) charge t (hr)
And the specific capacity C / C ₀ of the discharge capacity C with respect to the nominal capacity. As a result, the CC charging time t was 15.31 hours, and the specific capacity C / C ₀ was 63.5%.

The calculated CC charging time t, that is, t = 1
5.31 (hr) is calculated by using the obtained relational expressions (3),
Substituting in (4), (5) and (6), the respective estimated specific capacities C _e / C ₀ and the estimation errors Err = C / C ₀ −C _e
/ Was determined the _{C 0 = 0.635-C e /} C 0.

As a result, the relational expression (4) obtained by the test in which the charging time was 3 days and the charging time was 3 days or less and 30 days or less, and the relational expression obtained by the test in which the charging time was 30 days. In (5), the estimated specific capacity C _e / C ₀ is 74.1% and 72.3%, respectively, and the estimation error Err is −1.
It was found that good estimation can be performed within ± 20% for both 0.6% and -8.8%.

On the other hand, using the relational expression (3) obtained in the test in which the charging time was 2.5 days, the estimated specific capacity 8
5.1%, estimation error -21.6%, and using the relational expression (6) obtained in a test in which the charging time was 35 days, the specific capacity was 89.7%, and the estimation error was 26.2%. However, it was found that each of them had a large error and was not used as a relational expression.

[0065] For comparison, among the studies seeking the relational expression, creating a relational expression only early two cycles of data obtained in tests in the case of the 3 days charging time C _e / C ₀ = 0.00579 × t + 0.819 (7) was obtained. In the same manner, the estimated specific capacity C _e / C ₀ and the estimated error Err were calculated by substituting t = 15.31 in the same manner. 8% and an estimation error of -27.3%. It was also clarified that data for only two cycles could not provide a good relational expression in order to create a relational expression. (Example 3) Four cylindrical Li-ion batteries (18650 type, nominal capacity 1350 mAh) similar to those in Example 1 were used, and the discharge current value was 135 mA (0.1 CmA), 270
mA (0.2 CmA), 2700 mA (2.0 Cm
A) and a charge / discharge cycle test were performed under the same apparatus and test conditions as in Example 1 except that the current was changed to 3000 mA (2.2 CmA), and a relational expression was obtained in the same procedure as in Example 1.

FIG. 6 shows the results. FIG. 6 is a diagram illustrating the results of a charge / discharge cycle test performed to determine the relational expression in the present example. In the figure, 6-1 indicates a relationship determined from a test in which the charge current value was set to 0.1 CmA. a straight line indicating the formula _{C e / C 0 = 0.00918 ×} t + 0.727 (8), 6-2 is, 0.2 cm the charging current value
A straight line indicating the relational expression C _e / C ₀ = 0.0242 × t + 0.255 (9) obtained from the test set to A, and 6-3 indicates a charging current value of 2.0 CmA.
2.2CmA and a straight line showing the relation _{C e / C 0 = 0.0205 ×} t + 0.372 (10) obtained from the test, 6-4 charging current value
Is a straight line showing the relation _{C e / C 0 = 0.0521 ×} t-0.552 (11) obtained from the the test.

Separately, the Li-ion battery pack used for the laptop computer was disassembled, and one cylindrical Li-ion battery (18650 type, nominal capacity of 1350 mAh) was taken out therefrom. A lead wire was soldered to the side surface (negative electrode), and this was installed in a battery charge / discharge automatic test apparatus, and a charge current value of 45 mA (0.033
CmA), a charging upper limit voltage of 4.1 V, and charging by a constant current constant voltage (CC-CV) method for a total charging time of one day.
After a pause of time, the discharge current value is 1350 mAh
(1.0 CmA), discharge at a discharge end voltage of 2.75 V, and obtain a required time t (hr) of constant current (CC) mode charging and a specific capacity C / C ₀ of the discharge capacity C with respect to a nominal capacity C ₀ , t = 19.34, to obtain a _C / C 0 = 0.671. The obtained value t = 19.34 is calculated by the relational expression (8) shown above,
The estimated specific capacity C _e / C ₀ is calculated by substituting into (9), (10) and (11), and the estimation error Err = C / C ₀ −C _e /
C ₀ = 0.671−C _e / C ₀ was obtained to evaluate the capacity estimation accuracy.

As a result, in the relational expression (9) obtained from the test in which the discharge current value was set to 0.2 CmA, the estimated specific capacity 72.
3%, an estimation error of -5.2%, and a discharge current value of 2.0
In the relational expression (10) obtained from the test using CmA, the estimated specific capacity was 76.8% and the estimation error was -9.7%. The discharge current value of the test for obtaining the relational expression in the present invention was 0.2%.
In these cases within the range of CmA to 2.0 CmA, good estimation results were obtained in all cases. On the other hand, the condition for obtaining the relational expression in the present invention is such that the discharge current value is out of the above-described range of the discharge current value and the discharge current value is 0.1%.
In the relational expression (8) obtained in the CmA test, the estimated specific capacity 9
In the relational expression (11) obtained in a test in which the discharge current value deviated from the above range was 2.2 CmA, the estimated specific capacity was 45.6%, the estimated error was −23.4%. + 21.5%, all of which have large estimation errors, and it is clear that it is difficult to accurately estimate the capacity of the Li-ion battery. (Example 4) In order to charge a battery pack in series of three cylindrical Li-ion batteries (18650 type, nominal capacity 1350 mAh), a charging upper limit voltage of 12.3 V and a charging current value of 45 mA.
(0.033 CmA), and a charger having a function of determining deterioration of the battery pack at the time of charging by charging using a constant current / constant voltage (CC-CV) method with a total charging time of 3 days was produced.

FIG. 7 shows the structural concept of the manufactured charger.
That is, FIG. 7 is a diagram showing the configuration of the charger manufactured in the present embodiment. In the drawing, reference numeral 20 denotes a charger of the present invention manufactured in the present embodiment, and the charger 20 is a commercial power supply 2
1 at terminals 22 and 23. Further, the Li-ion battery pack 24 is connected to the terminals 25 and 26 for charging and attached to the charger 20.

The charger 20 converts the electric power supplied from the commercial power supply 20 into a direct current by an AC / DC converter 27, monitors a charging current and a pack voltage, and monitors a temperature with a thermistor 28,
9. The charge condition described above is calculated by the charge control microcomputer 30;
The battery pack 24 is charged by performing control for detecting and avoiding a dangerous state such as overcharge, overdischarge, abnormal large current, abnormal battery temperature rise, and the like. The charging is stopped by the switch 31 when the charging is completed or when an abnormality is detected. Completion of charging and any abnormalities are displayed on the display unit 32 from the control microcomputer 30.

The determination of deterioration in the present charger is performed by inputting the relational expression (2) created in the first embodiment and the flow procedure shown in FIG. The charging time t is measured by the built-in timer using the monitoring of the above, the capacity of the Li-ion battery pack is estimated by applying to the above relational expression (2), and the deterioration is determined based on the result. The judgment result is displayed at 32.

The display unit 32 is an LE for displaying charging-related information.
D (red: charging, green: charging completed) and the deterioration determination result are displayed. ED (red: battery replacement, yellow: battery replacement soon, green: battery need not be replaced) and deterioration determination result numerical display, And an LCD for displaying an abnormality.

As for the charging-related LEDs, the green LED is turned on only when charging is completed, the red LED is turned on during charging,
If any other abnormality is indicated, neither is lit.

In the LED indicating the deterioration judgment result, when the value of the estimated specific capacity as the capacity estimation result is less than 60%, the red L
The ED lights up, indicating that a new battery pack should be replaced immediately. In addition, when the specific capacity is 60% or more and less than 70%, shortly, that is, depending on use conditions,
Yellow L should be replaced within a few months
Turn on the ED. 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 long time and does not need to be replaced.

The LCD is provided for displaying character information. It indicates that it is difficult to perform normal charging, such as warning information relating to safety, such as improper installation of a battery pack, and indicates a deterioration determination result by a numerical value. In addition, in the case of a sudden stop of the commercial power supply, only when the voltage of the attached battery pack is higher than 8.25 V, the current is supplied from the attached battery pack to display the power-off.

In the case of the charger of this embodiment, since charging is not always performed after complete discharging, data on the time change of the charging voltage is input in advance to the charging control microcomputer, and charging is started. The battery pack voltage at the time is monitored, and 8.25V (2.75V / cell) or more and 11.7V
(3.9V / cell, 0.2V from the upper limit voltage 4.1V / cell)
(/ Cell low value) The following voltage of 1.15V: 8.25V, 9.40V, 10.55V, 11.70
V, higher than the charging start voltage among the four voltages indicated by
7. Start time measurement from the value closest to this start voltage, measure the time t "from when the charge upper limit voltage reaches 12.3 V to when the CC mode charging is completed, and compare the input data with the input data to perform a calculation. Deterioration determination is made by converting the required charging time t in the CC mode from 25 V to 12.3 V.

The procedure of the deterioration judgment procedure input to the charge control microcomputer 30 shown in FIG. 8 is as follows. That is, Procedure A: Attach the battery pack to the charger and start charging,
The pack voltage is monitored, and the pack voltage V becomes V = 8.25, 9.40V, 10.55V, 11.70
Step B: When the pack voltage V reaches any of the above values, time measurement is started and the timer counter is set to the charging upper limit voltage 1
Procedure C: When the pack voltage V reaches the charging upper limit voltage 12.3 V, the time measurement ends, and when the charging start voltage is the discharge end voltage 8.25 V, this time t is used for deterioration determination as it is. Procedure D: When charging start voltage is higher than 8.25V,
The measured time is compared with data of the time change of the charging voltage stored in advance, and is calculated and calculated from 8.25 V to 1
It is converted to the required CC mode charging time up to 2.3 V, and this value is used as t for deterioration determination. Substituting the determined time t into the relational expression (2) to calculate the estimated specific capacity C _e / C ₀ Procedure E: Display the calculated result on the LCD and the LED.
According to the value of the estimated specific capacity as the estimation result, any one of the red, yellow, and green LEDs is turned on as described above,
The numerical value of the estimated specific capacity is displayed on the CD. LCD display is 30
For a second, the LED lights up while the charger is connected to commercial power.

Using the thus configured charger,
A used battery pack of the same type was attached and charged.
At 15.7 hours after the start of charging, the deterioration judgment result is displayed.
The CD indicated (estimated) specific capacity of 62.0% and the yellow LED was lit.

The charged battery pack was set in a battery charge / discharge automatic test apparatus, and the discharge current value was 1350 mA (1.0 mA).
CmA), a constant current discharge was performed at a discharge end voltage of 8.25 V, and the discharge capacity was determined to be 860.0 mA.
h. This was 63.7% in terms of specific capacity, and the error in the estimated specific capacity was about 1.7%.

As described above, it has been clarified that highly accurate deterioration judgment can be performed by using the above-described deterioration judgment apparatus for a Li-ion battery according to the present invention. (Example 5) Charge upper limit voltage 12.3 V, charge current 45 m
A (0.033 CmA), a Li-ion battery pack having a configuration shown in FIG. 3 and mounted on a laptop computer having a function of performing constant current constant voltage (CC-CV) mode charging under a condition of a total charging time of 3 days. Produced. The battery pack is a cylindrical cell (1350 mAh nominal capacity) 12-1, 1
2-2 and 12-3 are a 3-cell series pack,
In the same manner as shown in the relational expression (2) and the fourth embodiment, the basic data of the change of the charging voltage with time was previously input to the protection IC, and the protection IC was charged from the pack voltage higher than the discharge end voltage 8.25V. Even in this case, the constant current (CC) mode charging time from 8.25 V to 12.3 V can be calculated.

The memory of the protection IC 13 in the battery pack having the structure shown in FIG.
1, 12-2, 12-3 The voltage at both ends of each cell is monitored, and a charge higher than Vs from a preset arbitrary start voltage Vs not lower than the discharge end voltage Vd and not higher than the charge upper limit voltage Vc in CC mode charging. Voltage = 8.25V, 9.40V, 10.55V, 1
Elapsed time t from the closest charging voltage that satisfies 1.70 V to the charging upper limit voltage 12.3 V at which CC mode charging is completed.
Is counted, and the value of the measured time t is substituted into the above-mentioned relational expression (2), and a program for calculating and calculating the estimated specific capacity C _e / C ₀ is input in advance.

The calculation result is output to the main body of the apparatus through the terminal 19 for display on the liquid crystal display of the main body of the apparatus on which the battery pack is mounted.

On the liquid crystal display, the numerical value as the calculation result is displayed in percentage, and the ratio corresponding to the percentage numerical value of the length of the bar is indicated by solid color.

The deterioration determination instruction is issued from the device main body at the same time as the start of charging. The procedure flow for performing the deterioration determination is the same as FIG. 8 except that the result is displayed on the display of the device main body and the result is sent to the main body in FIG.

After the battery pack having such a configuration was mounted on the device and used for one hour, charging was started by connecting to a commercial power supply, and the display displayed after the charging was started. The specific capacity estimation result was displayed as 73%. After confirming that the sign of charge completion appears on the display, turn off the device, remove and attach the battery pack, connect to the battery charge / discharge automatic tester using an appropriate connection cord, and discharge 1350 mA of discharge current. (1.0 Cm
A), discharge was performed at a discharge end voltage of 8.25 V, and the capacity was measured. As a result, the discharge capacity was 1093.5 mAh, and the specific capacity was 81.0%.

Therefore, the specific capacity estimation result obtained by the specific capacity estimation function mounted on the battery pack according to the present invention has an error of -8.0.
% And excellent estimation accuracy.

[0087]

As described above, by implementing the present invention, a simple method for estimating the capacity of a Li-ion battery, Li
It is possible to provide a simple device for determining the deterioration of an ion battery and a Li-ion battery pack having a function of estimating the capacity of the battery, and can make an extremely large contribution in the management of the Li-ion battery. .

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the concept of a change over time of a charging voltage (battery voltage) and a charging current value in a constant current constant voltage (CC-CV) method charging, which is a general charging method of a Li-ion battery.

FIG. 2 is a diagram showing one configuration concept around a general power supply unit of a Li-ion battery mounted device to which a method for estimating the capacity of a Li-ion battery 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 according to the present invention.

FIG. 4 is a diagram showing a relationship between an elapsed time t and a specific capacity showing a result of a charge / discharge cycle test in Example 1 of the present invention.

FIG. 5 is a comparative example in Example 1 of the present invention, in which a charging current value was set to 0.1 CmA and CC obtained in a charging / discharging cycle.
FIG. 4 is a diagram showing a relationship between a required time t for mode charging and a specific capacity.

FIG. 6 is a diagram showing a relationship between a required time t of CC mode charging and a specific capacity performed in Embodiment 3 of the present invention;
FIG. 9 is a diagram showing a relational expression obtained.

FIG. 7 is a diagram showing a configuration of a charger manufactured in Embodiment 4 of the present invention.

FIG. 8 is a flowchart showing a deterioration determination procedure performed in Embodiment 4 of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Power supply part, 2a, 2b, 2c ... Li ion battery, 3 ...
Battery control unit, 4 charger, 5 logic unit, 6 interface, 7 CPU, 8 memory, 9 keyboard controller, 10 wiring, 11 battery main unit, 12-
1, 12-2, 12-3: Li-ion battery, 13: IC for protection, 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, 1
9: terminal for information output and control, 20: charger, 21: commercial power supply, 22, 23 ... terminal for connecting the commercial power supply and the charger, 24: Li-ion battery pack, 25,
26 ... A terminal for connecting the charger and the battery pack, 27 ... A
C / DC converter, 28 ... Thermistor, 29 ... Power supply microcomputer, 30 ... Charge control microcomputer, 31 ... Switch,
32 ... Display unit.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G016 CB31 CB32 CC01 CC04 CC07 CC10 CC16 CC23 CC25 CC27 CC28 CE05 CE07 CE31 5G003 AA01 BA01 CA03 CC02 EA05 EA09 GA01 GC05 5H030 AS11 FF41 FF52 FF61

Claims (4)

[Claims] 1. A capacity estimation method of a lithium ion battery, a lithium-ion battery when charged by the constant current and constant voltage method, C ₀ charging current when the nominal capacity of the lithium ion battery was C ₀ / (20 hours) or less, and the time t from when the charging voltage during constant current charging reaches the preset voltage Vs to when the charging voltage reaches the charging upper limit voltage Vc is obtained.
Estimated specific capacity _{C e} / _{C 0} of the battery (here, _{C e} is the estimated volume of the battery) relational expression, the _{C e / C 0 = At +} B (1) ( wherein, A and B are the battery , Which is a positive constant determined by the voltage Vs, the voltage Vc, and the charging current during the constant current charging). 2. The method for estimating the capacity of a lithium ion battery according to claim 1, wherein a lithium ion battery of the same type as the lithium ion battery whose capacity is to be estimated is used, and one full charge time is three days. more than 10 days at most, and the charge period by the constant current and constant voltage mode charging current when the nominal capacity of the lithium ion battery was C ₀ is a C _{0 /} (20 hr) or less, the discharge current C ₀ / (5 hours) or more C ₀ / (0.
5 hours) or less, and repeating a charge / discharge cycle having a discharge end voltage of Vd and a pause period provided between the charge period and the discharge period if necessary three or more times. In the cycle, after the charging voltage during constant current charging reaches the voltage Vs set in advance, the charging upper limit voltage Vc
To time t _{n (here,} n represents an is number assigned to each cycle) of reach and to record the discharge capacity C _n obtained by integrating with respect to the discharge current times for each cycle were recorded A method for estimating the capacity of a lithium ion battery, wherein the values of A and B in the relational expression (1) are determined from the time t _n and the discharge capacity C _n . 3. An apparatus for determining deterioration of a lithium ion battery, comprising: means for determining the time t when the lithium ion battery is charged by a constant current / constant voltage method; An arithmetic circuit for calculating an estimated specific capacity C _e / C ₀ of the lithium ion battery _;
A judgment operation circuit for judging the deterioration state of the lithium ion battery based on the value of C ₀ , and a means for displaying the judgment result by the judgment operation circuit or, if necessary, the lithium ion battery Means for emitting a warning sound for warning of deterioration. 4. A lithium ion battery pack provided with charge / discharge control means having a built-in IC.
The additional IC attached to C is the estimated specific capacity C _e / of the lithium ion battery in the lithium ion battery pack.
A memory for storing a numerical value used for calculating C ₀ , and the relational expression based on the time t and the numerical value when the lithium ion battery is charged by the constant current and constant voltage method when the numerical value is stored in the memory. According to (1), the estimated specific capacity C _e /
Arithmetic circuit and a lithium-ion battery pack, characterized in that it has a means for outputting the estimated specific capacity C _e / C ₀ calculated result the operational circuit is calculated to calculate the C _0.