JP2001289924A - Capacity estimating method of lithium ion battery, degradation judging method and degradation judging device for the lithium ion battery, and lithium ion battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple method for estimating capacity of a lithium ion battery, a simple method and a device for judging the degradation of the lithium ion battery, and a lithium ion battery pack having a means for warning the degradation of the battery when necessary by estimating the capacity of the battery. SOLUTION: The capacity estimating method of lithium ion battery is characterized by calculating estimative capacity of the lithium ion battery by using time t by determining the time t up to time when a charging current becomes αtimes (here, α is a positive value constant smaller than 1) of a charging current Ic at that time from when switching a charging condition to constant voltage CV from a constant current CC when charging the lithium ion battery by a constant current-constant voltage method, and the method and device for judging the degradation of lithium ion battery by the method and the lithium ion battery pack having a means for performing the capacity estimating method, are also provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

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.

[0003]

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 significantly 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.

Also, lead batteries, Ni / Cd batteries, and N
While the i / MH battery has a reaction mechanism for absorbing gas generated by a side reaction due to overcharging, the Li-ion battery does not have an absorption reaction for gas generated by overcharging. There are big restrictions. Further, a plurality of L
When i-ion batteries are arranged in series and used, as the battery deteriorates, the imbalance of the individual battery characteristics causes overcharging or overdischarging, which can be a major concern in terms of safety.

[0005] 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.

As for the monitoring of the state of deterioration of the battery, which is important in maintaining safety, the use of a Li-ion battery-equipped device is frequently changed, so that the usage time is secured and monitored. They tend to be neglected as much as possible.

[0007] In particular, 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.

[0008] 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 method and an apparatus for determining deterioration of a Li-ion battery, and a battery. It is an object of the present invention to provide a Li-ion battery pack provided with a means for estimating the capacity of a battery and warning the battery of deterioration as necessary.

[0010]

According to 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 voltage method,
From the time when the charging condition is switched from the constant current to the constant voltage, the charging current is α times the charging current Ic at that time (here,
a is a positive constant smaller than 1), and the estimated capacity of the lithium-ion battery is calculated using the time t. Configure the method.

In the present invention, as described in claim 2, in the method for estimating the capacity of a lithium ion battery according to claim 1, the value of α is set to 1/2 and the time t is determined. Using the time t, the estimated capacity C of the lithium ion battery is expressed by a relational expression, C / C ₀ = At + B (1) (where C ₀ is the nominal capacity of the lithium ion battery, and A and B are the lithium ion batteries. Battery and charging current Ic
And a positive value constant determined by the formula (1).

Further, in the present invention, as described in claim 3, a lithium ion battery whose capacity is to be estimated or a lithium ion battery of the same type as the lithium ion battery is used, and one full charging time is used. 3 hours or more and 10 days or less, and the charging current during constant current constant charging is C ₀ / (5 hours) or more and C ₀ /(0.5 hours) or less (where C ₀ is the nominal capacity of the lithium ion battery) A charge / discharge cycle having a constant current / constant voltage charging period, a discharging period, and a pause period provided between the charging period and the discharging period as necessary is repeated five times or more. In each cycle, from the time when the charging condition is switched from the constant current to the constant voltage, the charging current becomes one of the charging current Ic at the time.
The time t _n (where n is a number assigned to each cycle) up to the point of time when the time becomes / 2 times, and the discharge capacity C _n obtained by integrating the discharge current with respect to time for each cycle are recorded. From the recorded time t _n and the discharge capacity C _n ,
The capacity estimation method for a lithium ion battery according to claim 2, wherein the values of A and B in the relational expression (1) are determined.

According to a fourth aspect of the present invention, there is provided a method for judging deterioration of a lithium ion battery, wherein the estimated specific capacity C of the lithium ion battery is determined according to the first, second or third aspect. A lithium ion battery calculated by a method for estimating the capacity of a lithium ion battery, and determining that the lithium ion battery has deteriorated when the estimated capacity C is smaller than a preset limit capacity C _min. The method for judging the deterioration of is described.

According to the present invention, there is provided an apparatus for judging deterioration of a lithium ion battery according to claim 5, wherein the charging current when charging the lithium ion battery by a constant current and constant voltage method is equal to the charging current. Charge current Ic at time
(Where α is a positive constant less than 1)
Means for measuring the time t up to the point in time, and calculating the estimated capacity C of the lithium ion battery by the method for estimating the capacity of the lithium ion battery according to claim 1, 2 or 3, using the time t. And a means for outputting a signal indicating deterioration of the lithium ion battery when the estimated capacity C calculated by the arithmetic circuit becomes smaller than a preset limit capacity _Cmin . A deterioration determination device for a lithium ion battery is characterized in that:

According to the present invention, there is provided a lithium ion battery pack provided with a charge / discharge control means having a built-in IC.
C is a memory for storing a numerical value used for calculating the estimated capacity C of the lithium ion battery in the lithium ion battery pack, and an additional IC when the numerical value is stored in the memory. An arithmetic circuit for calculating the estimated capacity C by the method for estimating the capacity of a lithium ion battery according to claim 1, 2, or 3 from the time t and the numerical value when the ion battery is charged by the constant current and constant voltage method. A lithium ion battery pack characterized in that it has a lithium ion battery pack.

Further, in the present invention, the estimated capacity C of the lithium ion battery in the lithium ion battery pack calculated by the arithmetic circuit is set in advance in the lithium ion battery. 7. The lithium ion battery pack according to claim 6, further comprising means for outputting a warning indicating capacity deterioration when the capacity becomes smaller than the set limit capacity C _min .

In the present invention, the warning is a warning by an electric signal, a warning by displaying characters or images, a warning by a signal sound, or a warning by sound. A lithium ion battery pack according to claim 7 is constituted.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 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. In the following description, a "battery pack" refers to a unit cell or a plurality of unit cells connected in series, connected in parallel, or a combination of both, integrated with a safety control circuit or charge / discharge control circuit. It means what is referred to as a "secondary battery as an independent power source".

FIG. 1 is a diagram showing changes over time in battery voltage and current value during charging of a Li-ion battery. In FIG. 1, the battery or a Li-ion battery in the battery pack (hereinafter, these are collectively referred to as a Li-ion battery) is first set to a predetermined constant current I by a constant current (CC) mode.
c, a preset upper limit voltage Vc (normally 4.c).
1 V / cell, or 4.2 V / cell, where
After the charging voltage reaches the set voltage Vc, charging in the constant voltage (CV) mode is started, and the charging voltage (indicated as a battery voltage in FIG. 1). The charge current value attenuates with time while Vc remains constant at Vc.

In the method for estimating the capacity of a Li-ion battery according to the present invention, the charging current I is α times the charging current Ic at the time when the charging condition is switched from the constant current (CC) to the constant voltage (CV). (Where α is a positive constant smaller than 1) is monitored, and this time t is used for estimating the capacity of the Li-ion battery.

The reason why such estimation is possible will be described below.

In the charging process of the Li-ion battery, Li in the positive electrode becomes positive ions and moves in the electrolyte to enter the negative electrode. In the discharging process, on the contrary, Li in the negative electrode becomes positive ions. As it moves, it moves in the electrolyte and enters the positive electrode.

The repetition of charge / discharge, long-term rest, or overcharge causes Co, N
The i-compound is eluted into the electrolyte, Li and the electrolyte are chemically decomposed and decomposed on the negative electrode surface to form an inert film,
L no longer reacts with the Li reactant or electrode reaction in the electrode
i remains or the bonding of the particles of the electrode constituent material deteriorates, so that the movement of electrons and ions is not performed smoothly. As a result, the capacity of the battery decreases, and at the same time, the internal resistance of the battery increases, and the rate at which Li ions are separated from the positive electrode during charging and reach the negative electrode, and diffuse into the negative electrode, decreases. In such a state, the charging time in the constant current (CC) mode becomes shorter because the internal resistance of the battery is increased, and in the constant voltage (CV) mode charging, the diffusion of Li in the negative electrode becomes slower. In addition, the decrease in the charging current value is delayed.

The present inventors have found a remarkable correlation between the decrease in the capacity and the decrease in the charging current value during the constant voltage (CV) mode charging, and have reached the present invention. Was.

Hereinafter, embodiments of the present invention will be specifically described. (Embodiment 1) First, an embodiment of the invention according to claim 1 will be described. In the present embodiment, when charging the lithium-ion battery by the constant current / constant voltage method, the charging current is α times the charging current Ic at this time (here, the charging current is switched from the constant current to the constant voltage). Then, α is a positive value constant smaller than 1), and the estimated capacity of the lithium ion battery is calculated using the time t.

In order to make such estimation possible, it is necessary to previously obtain the correlation between the estimated capacity C and the time t. For example, the following method is used. There is. That is, a lithium ion battery having the same structure and the same specifications as the lithium ion battery whose capacity is to be estimated (hereinafter referred to as the same type) is prepared, and the charge / discharge cycle is repeated using the battery. and the time t _n in each cycle, the discharge current is obtained in advance the correlation between the discharge capacity C _n of the battery obtained by integrating with respect to time (here, n represents a number assigned to each cycle). In this case, since it is desirable that over the value a wide range of discharge capacity C _n, in which case the range is narrow, as for a plurality of lithium ion batteries with different capacities in the same type, to perform the above method It is hopeful.

The above correlation need not necessarily be represented by an analytical mathematical formula, but may be represented, for example, by a broken line connecting measurement points in a correlation diagram with a straight line.

As in the case of the second embodiment described below, when the correlation expressed by an analytic formula is adopted as the above-described correlation, the charging current Ic during the constant-current charging is used. There is a preferred range.

It should be noted that the value of the estimated capacity C of the battery calculated at the time of each charge is recorded, and a relationship between the estimated capacity C and the number of times of charging is obtained. The lifetime, that is, how many recharges / reuses are possible before deterioration can be predicted. If the lithium-ion battery is repeatedly used under the same or similar use conditions by repeated charge and discharge, the life expectancy becomes highly accurate. (Embodiment 2) Next, an embodiment of the invention according to claim 2 will be described. In the present embodiment, the value of the constant α in the first embodiment is set to を, the time t is determined, and the estimated capacity C of the lithium ion battery is calculated using the time t by the above-mentioned relational expression, that is, C / C ₀ = At + B (1) (where C ₀ is a nominal capacity of the lithium ion battery, and A and B are positive value constants determined by the lithium ion battery and the charging current Ic). I do. Except that the value of the constant α is set to ２, it is the same as the first embodiment. By setting the value of the constant α to ２, the above-mentioned relational expression (1) is approximately established, so that the estimated capacity C can be calculated using the above-mentioned time t using this relational expression.

For the above relational expression (1) to be effective in estimating the capacity of the battery, a preferable condition for the charging current Ic is that the nominal capacity of the lithium ion battery whose capacity is to be estimated is C
_{As 0} , it is expressed as C ₀ / (5 hours) ≦ Ic ≦ C ₀ /(0.5 hours). This condition is set to 0.
It is expressed as 2 CmA or more and 2.0 CmA or less.

When the charging current Ic does not satisfy the above condition, it is not preferable to calculate the estimated capacity C by the relational expression (1). That is, when the charging current Ic is smaller than the above-mentioned limit range, the charging is not performed sufficiently or the influence of the self-discharge cannot be ignored, and the capacity calculated by the relational expression (1) differs from the actual capacity. It is not preferable for deterioration judgment. 1.0 CmA
In the case of charging at a large electric power shallower than the above, the required charging time itself is short, a large error may occur in the measured value of the time t, and the change in the charging time due to deterioration may be different. Not preferred. Therefore, the charging current value applied to almost all the devices and chargers equipped with a Li-ion battery is in this range. Devices and chargers that use current values outside this range are used for very specific applications, such as those that require ultra-rapid charging for emergency use. An apparatus and a charger that hardly require the capacity estimation method of the present invention.

The above-mentioned relational expression (1) shows that Li
The required time t from the start of constant voltage (CV) mode charging to the halving of the current value under the charging conditions of the ion battery mounted device or the charger, and the estimated specific capacity C /
It is assumed that reflects the relationship between the C _0. If the initial charging current value when the relational expression (1) is created is different from the charging current value at the beginning of the constant voltage (CV) mode charging of the battery-equipped device or the charger, separate The required time from the start of the CV mode charging to the halving of the current value under each charging condition is determined in advance, and the required time te in the condition at the time of creating the relational expression (1) and the required time under the conditions corresponding to the mounted device or the charger The ratio te / tm with respect to tm is multiplied by the actually measured t and substituted into the relational expression (1).

This is because the charging rate in the constant current (CC) mode charging (the charging rate of the CC mode charging in the entire charging period) increases as the current value decreases. for that reason,
This is because the charging time in the CV mode changes depending on the charging rate in the CC mode, and the time required for halving the current value is also affected. In addition, since the influence differs 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.

In order to create the relational expression (1) used for estimating the capacity of the Li-ion battery, the values of the constants A and B in the relational expression (1) must be determined. In order to create the relational expression (1), it is most appropriate to determine the values of the constants A and B by testing a battery or a battery pack of the same type as the Li ion battery whose capacity is to be estimated. This is because commercially available Li-ion batteries use various types of positive electrode pollutants, negative electrode carbon, and electrolytes, and not only change in charging voltage behavior due to battery deterioration, but also initial charging behavior of batteries. Because it is.

The method for determining the values of the constants A and B will be described in detail in the following description of the third embodiment. (Embodiment 3) Next, an embodiment of the invention according to claim 3 will be described. In the present embodiment, using a lithium ion battery or a lithium ion battery of the same type as the lithium ion battery whose capacity is to be estimated,
A charging period based on a constant current / constant voltage method in which one full charging time is 3 hours or more and 10 days or less, a discharging period, and a pause period provided between the charging period and the discharging period as necessary. The charge / discharge cycle is repeated two or more times, and in each cycle, the charge current I is changed from the constant current to the constant voltage to the charge current I at the time.
The time t _n (where n is a number assigned to each cycle) until the time becomes α times c (where α is a positive constant smaller than 1), and the discharge capacity C _n obtained by the discharge current and integrating with respect to time is recorded, and a recorded said time t _n and the discharge capacity C _n, to confirm the value of a and B in the above equation (1) Using these values, the estimated capacity is calculated by the same method as in the first or second embodiment.

A more specific method for determining the values of A and B will be described below.

The same charge upper limit voltage V as that used for the lithium ion battery or battery pack whose capacity is to be estimated.
c, the charging current value Ic, and the discharge end voltage Vd are set, and the charging time is from 3 hours to 10 days, preferably the charging time is 3 days.
And set the discharge current value Id to 0.2C or less.
mA to 2.0 CmA or less, the number of charge / discharge cycles is preferably 5 or more, more preferably 6 or more, and the test temperature is 0 to 45 ° C, preferably 15 ° C.
A charge / discharge cycle test was performed with the temperature set to 30 ° C. or lower, and in the charge in each charge / discharge cycle, the charge current value was reduced to 1 / C after the constant voltage (CV) mode charge was started.
The required time t _n (where n is a number assigned to the cycle) required to decrease to 2 and the discharge capacity C _n obtained by integrating the discharge current with respect to time are recorded, and the relational expression (1)
Determine the values of the constants A and B so as to best represent the relationship between C _n / C ₀ and t.

The reason why the test is carried out at a temperature of 0 ° C. or more and 45 ° C. or less is that the temperature range is the normal operating temperature range of the Li-ion battery, and the time t and the time t reflecting the progress of the battery deterioration at this temperature. This is because grasping the relationship with the capacity C _n / C ₀ can realize more accurate capacity estimation. Further, when the test is carried out at a temperature of 15 ° C. or more and 30 ° C. or less, it is considered that the operating temperature condition in most cases is within this temperature range, and thus the time t and the specific capacity C reflecting the actual deterioration are considered. It will be able to understand the relationship between _n / C _0, and more preferable.

The charging time per cycle is 3
Set to more than 10 hours. With this setting, 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. In particular, when the charging time is set to 3 days or more and 10 days or less, a decrease in capacity due to a charge / discharge cycle is clearly recognized, and efficient data collection becomes possible to create the above relational expression (1). More preferred.

When the charging time is less than 3 hours, the progress of deterioration of the Li-ion battery is slow, and several hundred cycles are required to acquire data for creating the accurate relational expression (1), and a huge amount of time is wasted. In some cases, charging may be insufficient, and deterioration and poor charging may be mixed, making it impossible to accurately determine deterioration and characteristics, which are both undesirable.

The charging time per cycle is 10
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.

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 lower limit current is set to 1.0 CmA or more and 2.0 CmA or less, more efficient data acquisition becomes possible. 0.2Cm
In the case of a low discharge current of less than A, complete discharge takes a long time, 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 conducting the above-described charge / discharge cycle test, if necessary, a pause for a predetermined time is set between charging and discharging due to restrictions on the setting of the apparatus.

This is performed to create the above relational expression (1).
In the charge / discharge cycle test,
The charge constant current (CC) mode is set for each cycle.
Charge current value decreases after changing to voltage (CV) mode
T until the value reaches 1/2_nAnd continue
Discharge specific capacity C_n/ C₀Is measured. Measured time t _n
And specific capacity C_n/ C₀Is plotted, and the relation (1) is determined.
Determine the values of the numbers A and B.

In order to determine the values of the constants A and B in the relational expression (1), the time t _n after the fourth cycle and the specific capacity C _n /
The reason for adopting C ₀ is that the capacity change in the first third cycle from the start of the test is due to the decomposition reaction of impurities in the electrolyte of the Li-ion battery on the negative electrode carbon, etc.
This is because the change in capacity in subsequent cycles is often different, and using data up to the first three cycles may lead to a relational expression having a large determination error, which is not preferable.

The charge / discharge cycle test described above satisfies the data of the time t _n and the specific capacity C _n / C ₀ required to make the capacity estimation result highly accurate within ± 20% of the actual capacity.
Perform 5 or more cycles.

If data of only one cycle of the fourth cycle is used, the values of the constants A and B in the above-mentioned relational expression (1) cannot be determined, and the relational expression (1) cannot be created. Preferably, 6
By using data of more than one cycle, the relational expression (1) that enables more accurate capacity estimation can be created. (Embodiment 4) Next, an embodiment of the invention according to claim 4 will be described.

The estimated capacity C of the Li-ion battery is calculated by the method according to the first, second or third embodiment, and the estimated capacity C is replaced with a predetermined limit capacity C
_min , when C <C _min , the L
It is determined that the i-ion battery has deteriorated. However, this comparison is equivalent to the estimated specific capacity C / C ₀ (where C ₀
Is a nominal capacity) and the critical specific capacity C _min / C ₀ . For example, in Embodiments 2 and 3, C / C ₀ is directly calculated by the relational expression (1), so this comparison is more convenient.

As the limit capacity C _min , for example, a value of 60% of the nominal capacity C ₀ is used (in this case, C
_min / C ₀ = 0.6). (Embodiment 5) Next, an embodiment of the invention according to claim 5 will be described.

The entire apparatus capable of executing the deterioration judgment method in the fourth embodiment constitutes the present embodiment. For example, when charging a lithium ion battery by a constant current / constant voltage method, the charging current I is changed from a constant current to a constant voltage to a charging current I at the time.
4. A means for measuring a time t until a time becomes α times c (where α is a positive constant smaller than 1), and using the time t, the time t. An arithmetic circuit for calculating the estimated capacity C of the lithium ion battery by the method for estimating the capacity of the lithium ion battery according to the above, and the estimated capacity C calculated by the arithmetic circuit (or the estimated specific capacity C /
C ₀₎ is a means for outputting a signal indicating the deterioration of the lithium ion battery when it becomes smaller than the preset limit capacitance C _{mi n (or} limit specific capacity C _min / C ₀₎ The present embodiment is an apparatus having the above configuration.

FIG. 2 shows a more specific embodiment of the present invention.

FIG. 2 shows a general concept of the periphery of a power supply unit of a device in which a Li-ion battery is mounted. Reference numeral 1 denotes a power supply unit, and a power supply unit 1 includes a Li-ion battery 2a. , 2b, and 2c are mounted, and these batteries 2a, 2b, and 2c are mounted.
As for b and 2c, charging / discharging and safety control are performed by the battery control unit 3 in the power supply unit 1. Reference numeral 4 denotes a charger in the power supply unit 1, which is controlled by the control unit 3 and charges the batteries 2a, 2b, 2c. Reference numeral 5 denotes a logic unit, and the battery control unit 3 is connected to the logic unit 5 via an interface 6, and the on-board battery 2
a, 2b, and 2c, and receives an instruction to execute control, and transmits data related to control. In the logic unit 5, reference numeral 7 denotes a CPU, and reference numeral 8 denotes a memory, which accumulates information relating to battery control, instructs control, and calculates and stores data. The ID input of the batteries 2a, 2b, 2c and the like are performed via the keyboard controller 9. Wiring 10 for data transmission is connected to the keyboard controller 9.

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. The CPU 7 instructs the battery control unit 3 to measure the time t from when the charging mode is changed from the constant current (CC) mode to the constant voltage (CV) mode until the charging current value is reduced to half, or when the battery 7 is charged. The measurement result of the required time t is received from the control unit 3. Further, the CPU 7 calculates the estimated capacity (or estimated specific capacity) by substituting the received time t into the determination formula (1) and performing a calculation. If necessary, this result is stored in the memory 8. Estimated capacity (or estimated specific capacity)
Is input to the device main body via an appropriate wiring 10 such as a system management bus, and the device main body displays the deterioration determination result on the display unit of the device main body or makes the necessary judgment according to the input. In response, a warning by a signal sound or voice is issued. In this way, an apparatus having the function of determining deterioration of the Li-ion battery according to the present invention can be configured. However, the configuration is not limited to the above configuration as long as the deterioration determination of the Li ion battery according to the above concept can be performed. (Embodiment 6) Next, an embodiment of the invention according to claim 6, 7, or 8 will be described.

An example of the present embodiment will be described with reference to FIG. FIG. 3 is a diagram showing a general circuit configuration of a Li-ion battery pack, in which Li-ion batteries (12-1, 12-2,
12-3) shows a case where three cells are mounted in series.

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, a timer is mounted, and the above-described relational expression (1) is input in advance to the empty memory, and the voltage between both ends of the Li-ion batteries 12-1, 12-2, and 12-3 in FIG. The protection IC 13 monitors with Vcc and Vss, and measures the time t from when the charging mode is changed from the constant current (CC) mode to the constant voltage (CV) mode until the charging current value is reduced by half. The calculated value of the time t is substituted into the relational expression (1), and the calculated value is calculated. If necessary, an additional IC can be provided at an appropriate position in the pack separately from the protection IC 13. The calculated estimated capacity C (or estimated specific capacity C / C ₀ ) is set to a preset limit capacity C _min (or limit specific capacity C _min / C).
₀ ), a warning indicating the capacity degradation (in this case, a warning by an electric signal) is displayed on a suitable display or a warning sound through the terminal 19, and a pack is issued. Is output to the main unit equipped with.

In the case where the device main body on which the Li-ion battery pack is mounted is not provided with a means for warning of deterioration, the pack itself issues this warning, for example, by displaying characters or images, signal sounds or voices. It is convenient to have a means for outputting by means of the following. Such a Li-ion battery pack can be manufactured by using the present invention and the conventional technique together.

As described above, it is possible to provide a Li-ion battery pack provided with a means for executing the deterioration determination method according to the present invention by making a minimal change to an existing Li-ion battery pack. However, the configuration is not limited to the above configuration as long as the deterioration determination of the Li ion battery according to the concept can be performed.

As a method for determining the deterioration of a Li-ion battery according to the present invention and an object to which the Li-ion battery having the function of determining deterioration is applied, a device which particularly requires high reliability can be considered. By grasping the state of deterioration of the battery and realizing timely replacement of the battery, troubles in the device can be avoided. However, as long as the device is equipped with a Li-ion battery, there is no problem in adopting the above-described method of determining deterioration and adopting a Li-ion battery having a function of determining deterioration, and it is possible to realize battery replacement without waste. The advantage of using it is very large.

[0060]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for estimating the capacity of a Li-ion battery, a method for judging deterioration and a device for judging deterioration of a Li-ion battery according to the present invention will be described.
The i-ion battery pack will be described more specifically with reference to examples, but the present invention is not limited to these examples. (Example 1) Prismatic Li-ion battery (600 mA nominal capacity)
h) was placed in a constant temperature bath at 25 ° C., and the battery was connected to a battery charge / discharge automatic testing device having a data collection / storage function. The charge current value was 600 mA (1.0 CmA), and the charge upper limit voltage was 4.
Charging by constant current and constant voltage (CC-CV) method for 1 V and charging time of 7 days, and discharging current value of 600 mAh (1.0 Cm)
A). A charge-discharge cycle test in which a pause of one hour was interposed between a discharge at a discharge end voltage of 2.75 V and a charge and a discharge for 10 hours was performed.
The charge current value is １ of the initial value of the CV charge from the start of the constant voltage (CV) mode charge in each cycle.
The elapsed time t _n to reach the, the specific capacity C _n / C ₀ to the nominal capacity C ₀ of the discharge capacity C _n obtained discharge current by integrating with respect to time was measured (here, n represents each cycle Number.) The time t _n from the fourth cycle to the tenth cycle obtained by the test and the specific capacity C _n / C
_The following relational expression (2) was obtained from ₀ C.

C / C ₀ = 0.714t + 0.349 (2) Strictly speaking, t in the above equation (2) is t / (1 hour), that is, t is expressed by a dimensionless number in units of time. However, this is simply represented by t for convenience. The same applies to the following equations.

Separately, a prismatic Li-ion battery (nominal capacity 1300 mAh) was prepared, and the charging current was 1300 mA.
(1.0 CmA), charging by a constant current constant voltage (CC-CV) method with a charging upper limit voltage of 4.1 V and a charging time of 3 hours, a discharging current of 1300 mA (1.0 CmA), and a discharging end voltage of 2.
3 cycles of 75V discharge and 3 charge / discharge cycles with a 10 minute pause between charge and discharge are performed, and the current value is reduced by half after changing from CC mode charge to CV mode charge for each cycle. a required time t _n and a specific capacity C _n / C ₀ until were recorded and investigated the validity of above indicated equation (2).

FIG. 4 shows the results. Figure 4 is a diagram showing the relationship between the required time t _n and a specific capacity C _n / C ₀ until the current value half the CV mode charge start determined by said charging and discharging cycle, the data up to the third cycle It is plotted.
In FIG. 4, a straight line indicating the relational expression (2) is represented by 4-A.
The value 20% higher than the value of this judgment formula (that is, the error +20)
%) Is 4-B, and conversely, 20% from the value of the judgment formula.
The curve showing the low value (error -20%) is also shown at 4-C. As shown in FIG. 4, all data have an error of ± 2.
It falls within 0%, and the curve 4-A of the relational expression (2) is very close to the data point, and it can be seen that an excellent deterioration determination result can be shown. (Example 2) Prismatic Li-ion battery (nominal capacity 600 mA
h) Six batteries were placed in a 25 ° C. constant temperature bath, each battery was individually connected to a battery charge / discharge automatic test device having a data collection / storage function, and a charging current value of 600 mA (1.0 Cm)
A), charging by the constant current constant voltage (CC-CV) method by setting the charging upper limit voltage to 4.1 V and the charging time to 2 hours, 3 hours, 3 days, 7 days, 10 days, and 11 days. , A discharge current value of 600 mAh (1.0 CmA), a discharge end voltage of 2.75 V, and 10 charge / discharge cycle tests with a pause of 1 hour between charging and discharging, and a constant voltage in each cycle. (CV) mode charging current value from the beginning of charging was measured elapsed time and t _n, specific capacity C _n / C ₀ required for reaching 1/2 of the CV charge early.

From the fourth cycle obtained by the test, 10
The relational expression shown in Table 1 was obtained from the time t _n in the cycle and the specific capacity C _n / C ₀ .

[0065]

[Table 1]Separately, used prismatic Li-ion batteries (nominal capacity
1300 mAh) at room temperature and at a charging current of 1300 mAh).
mA (1.0 CmA), charge upper limit voltage 4.1 V, charge time
3 hours constant current constant voltage (CC-CV) charging
And discharge current 1300mA (1.0CmA), discharge end
10 minutes between discharge at a voltage of 2.75 V and charge and discharge
Three charge / discharge cycles with a pause
From the CC mode charge for each cycle to the CV mode charge.
Time required for the current value to be reduced by half after switching to electricity
t_nAnd discharge capacity to nominal capacity (1300 mAh)
Specific capacity C _n/ C₀And record the relational expression shown above
The validity of (2) was examined.

FIG. 5 shows the results. FIG. 5 is a diagram showing the relationship between the required time t from the start of CV mode charging to half the current value obtained in the above charge / discharge cycle and the specific capacity C _n / C ₀ . 2 shows the measurement data. Further, in FIG. 5, a relational expression created along with test data for creating each of the relational expressions shown in Table 1 is shown by a straight line, and 5-B is a judgment expression created from the data of the charging time of 2 hours. And 5-C is a relational expression created from test data for a charging time of 3 hours, 5-D is a relational expression created from test data for a charging time of 3 days, and 5-E is a test for a charging time of 7 days. 5-F is a relational expression created from test data for a charging time of 10 days, and 5-G is a relational expression created from test data for a charging time of 11 days.

The error between the specific capacity and the measured specific capacity calculated by substituting the required time t from the measured CC mode charging to the CV mode charging until the charging current value is reduced by half into each relational expression is calculated. Also shown in Table 1.

As shown in FIG. 5, the specific capacities calculated by the relational expressions obtained from the tests in which the charging time was set within the range of 3 hours to 10 days were all ± 20% error, and the results were excellent. showed that. In particular, as shown in Table 1, when the charging time is set to 3 days or more and 10 days or less, the judgment error is ±
Within 10%, it became clear that highly accurate judgment was possible.

On the other hand, according to the relational expression created from the test in which the charging time was set to 2 hours or 11 days, the judgment error exceeded ± 20%, indicating that it was difficult to judge the deterioration with high accuracy. . (Example 3) Prismatic Li-ion battery (600 mA nominal capacity)
h) The six batteries were placed in a 45 ° C. constant temperature bath, each battery was individually connected to a battery charge / discharge automatic test device having a data collection / storage function, and a charge current value of 600 mA (1.0 Cm)
A), charging by a constant current constant voltage (CC-CV) method with a charging upper limit voltage of 4.1 V and a charging time of 7 days, and a discharge current value of 600 mAh (1.0 CmA) and a discharge end voltage of 2.75 V 10 cycles of a charge / discharge cycle test in which a pause is interposed between discharge and charge / discharge for 1 hour are performed, and a charge current value in each cycle from the start of constant voltage (CV) mode charge is ２ of the initial value of CV charge. the elapsed time _{t n} to reach the measurement results of the specific volume _{C n} / _{C 0.}

From the data obtained by the test, from the time t _{n of} all the cycles and the specific capacity C _n / C ₀ , the time t _n of the fourth and fifth cycles and the specific capacity C _n / C ₀ , the fourth cycle From the time t _n of the sixth cycle and the specific capacity C _n / C ₀ , and the time t of the fourth to tenth cycles
_{From n} and specific capacity C _n / C ₀ , four relational expressions were obtained.

The four relational expressions are used for the used prismatic Li-ion battery (nominal capacity 1300) tested in Example 2.
Found an estimated specific capacity from the CC mode charge 3 cycles mAh) by applying the data of the required time t _n and a specific capacity C _n / C ₀ from when the change in the CV mode charge until the current value is reduced by half Was compared with the specific capacity.

FIG. 6 shows the results. Figure 6 is a time required until the current value half the CV mode charge start t _n and specific capacity C _n
FIG. 6C is a diagram showing the relationship with / C ₀ , 6-A is the data of the used prismatic battery measured in Example 2, and the straight line of 6-B is a relational expression created from the measurement data of all cycles. 6-
The straight line of C is a relational expression created from the data of the fourth and fifth cycles, 6-D is a relational expression created from the data of the fourth to sixth cycles, and the straight line of 6-E is four cycles. The relational expression created from the data from the first to the tenth cycle is shown.

As is clear from FIG. 6, according to the method of preparing the relational expression according to the present invention, it is possible to make a highly accurate determination, and the ratio calculated by the relational expression prepared from the data of the fourth and fifth cycles is obtained. The maximum error (absolute value) of the capacity value with respect to the actually measured value remains at 6.1%, and the value calculated by the relational formula created from the data from the fourth cycle to the sixth cycle is the largest error with respect to the actually measured value. (Absolute value) stayed at 2.7%, and the maximum error (absolute value) of the value calculated by the relational expression created from the data from the fourth cycle to the tenth cycle was 2.5% with respect to the actually measured value. Excellent judgment accuracy.

On the other hand, when calculation is performed using a relational expression created from all data up to the tenth cycle, the maximum error (absolute value) with respect to the actually measured value is 2 despite the large number of data.
0.4%, an error exceeding ± 20%, which was not preferable. (Example 4) Prismatic Li-ion battery (600 mA nominal capacity)
h) Five batteries were placed in a 5 ° C. constant temperature bath, each battery was individually connected to a battery charge / discharge automatic test device having a data collection / storage function, and the charging current value was 90 mA (0.1 mA).
5 mA), 120 mA (0.2 CmA), 600 mA
(1.0 CmA), 1200 mA (2.0 CmA), and 1500 mA (2.5 CmA), a charging upper limit voltage of 4.1 V, and a charging time of 7 days, and a constant current constant voltage (CC-CV) method. Charge and discharge current value 600m
Ah (1.0 CmA), a discharge at a discharge end voltage of 2.75 V, and a charge-discharge cycle test with a pause of 1 hour between charging and discharging, and 10 cycles of charge / discharge cycle tests were performed. Constant voltage (CV) mode charging in each cycle Charge current value is CV from the start
Elapsed and time _{t n} required for reaching 1/2 of the initial charging was determined specific capacity _{C n} / _{C 0.}

Of the data obtained by the test, five relational expressions were obtained from the time t _{n in the} fourth to tenth cycles and the specific capacity C _n / C _0, respectively.

These five relational expressions are used for the used prismatic Li-ion battery (nominal capacity 1300) tested in Example 2.
Found an estimated specific capacity from the CC mode charge 3 cycles mAh) by applying the data of the required time t _n and a specific capacity C _n / C ₀ from when the change in the CV mode charge until the current value is reduced by half Was compared with the specific capacity.

FIG. 7 shows the results. Figure 7 is a time required until the current value half the CV mode charge start t _n and specific capacity C _n
FIG. 7-A is a diagram showing the relationship with / C ₀ , 7-A is the data of the used prismatic battery measured in Example 2, and 7-B is a straight line created from the measurement data of the test with a charging current of 0.15 CmA. 7-C is a relational equation created from measurement data of a test at a charging current of 0.2 CmA, and 7-D is a relational equation created from measurement data of a test at a charging current of 1.0 CmA. The straight line -E indicates the relational expression created from the measurement data of the test at the charging current of 2.0 CmA, and the line 7-F indicates the relational expression created from the measurement data of the test at the charging current of 2.5 CmA.

As is apparent from FIG. 7, according to the method of preparing the relational expression according to the present invention, it is possible to make a highly accurate determination, and it is possible to perform the tests at charging current values of 0.2 CmA, 1.0 CmA, and 2.0 CmA. The value of the specific capacity calculated by the relational formula created from the measurement data of the above was excellent judgment with maximum errors (absolute values) of only 7.9%, 6.1%, and 5.1%, respectively, from the actually measured values. Accuracy.

On the other hand, charging current 0.15 CmA,
And the maximum error (absolute value) with respect to the actually measured value when calculated using the relational expression created from the measurement data of the 2.5 CmA test.
Were 20.6% and 27.4%, which was not preferable because the error exceeded ± 20%. (Example 5) Prismatic Li-ion battery (nominal capacity 600 mA
h) 6 pieces each were -5 ° C, 0 ° C, 15 ° C, 30 ° C,
Installed in each thermostat set at 45 ° C and 50 ° C,
Each battery is individually connected to an automatic battery charge / discharge test device having a data collection / storage function, and the charge current value is set to 600
mA (1.0 CmA), a charging upper limit voltage of 4.1 V, a charging time of 7 days, and charging by a constant current constant voltage (CC-CV) method, and a discharging current value of 600 mAh (110 Cm).
A). A charge-discharge cycle test in which a pause of one hour was interposed between a discharge at a discharge end voltage of 2.75 V and a charge and a discharge for 10 hours was performed.
The charge current value is １ of the initial value of the CV charge from the start of the constant voltage (CV) mode charge in each cycle.
The elapsed time t _n to reach the measurement results of the specific volume C _n / C ₀ to the nominal capacity.

Among the data obtained by the test, six relational expressions were obtained from the time t _{n in the} fourth to tenth cycles and the specific capacity C _n / C _0, respectively.

The six relations show that the used prismatic Li-ion battery (nominal capacity 1) tested at room temperature in Example 2 was used.
300mAh) from CC mode charge for 3 cycles to C
Required time t _n and the discharge capacity specific capacity measured and calculated specific capacity by applying data (specific capacity C _n / C ₀ to the nominal capacity _1300mAh) until the current value from a change in the V mode charging is halved Was compared.

FIG. 8 shows the results. Figure 8 is a time required until the current value half the CV mode charge start t _n and specific capacity C _n
FIG. 8 is a graph showing the relationship with / C ₀ , where 8-A is the data of the used prismatic battery measured in Example 2, and the straight line of 8-B was created from the measurement data of the test at −5 ° C. The relational expression
The 8-C line is a relational expression created from the measurement data of the test at 0 ° C., the 8-D is a relational expression created from the measurement data of the test at 15 ° C., and the 8-E line is a relational expression created at 30 ° C. The relational formula created from the measurement data of the test at 45.degree.
Indicates a relational expression created from measurement data of the test at 50 ° C.

As is clear from FIG. 8, according to the method of preparing the relational expression according to the present invention, it is possible to make a highly accurate determination, and the temperatures are set to 0 ° C., 15 ° C., 30 ° C., and 45 ° C., respectively.
The values of the specific capacities calculated by the relational expressions created from the measurement data of the test set at ℃ were 7.1%, 4.1%, and 6.4%, respectively, with respect to the actual measurement values. , And 6.8%, which was excellent determination accuracy. In particular, among them, it was found that in the tests set at 15 ° C. and 30 ° C., a relational expression showing more excellent judgment accuracy could be created.

On the other hand, the temperature was set to -5 ° C. and 50 ° C.
When calculated using a relational formula created from the measurement data of the test set to ° C, the maximum error (absolute value) with respect to the actually measured value was 58.
3% and 44.8%, which is an undesired error with an error exceeding ± 20%. (Example 6) Prismatic Li-ion battery (nominal capacity 600 mA)
h) For charging three battery packs in series, the charging upper limit voltage is 12.3 V (2.75 V / cell) and the charging current value is 600 mA.
(1.0 CmA), charging is performed by a constant current constant voltage (CC-CV) method in which a convergence current value which is a threshold value for terminating charging is 30 mA (0.05 CmA), and the battery pack deteriorates during charging. A charger having a function of making a determination was manufactured.

FIG. 9 shows the structural concept of the manufactured charger.
That is, FIG. 9 is a diagram showing the configuration of the charger manufactured in the present embodiment.
At terminals 22 and 23. Also, the charger 2
In contrast to Li, the Li-ion battery pack 24 is connected to the terminals 25 and 26 for charging and mounted.

The charger 20 converts the electric power supplied from the commercial power supply 21 into direct current by the AC / DC converter 27, monitors the charging current and the pack voltage, and monitors the temperature with the 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 abnormality are indicated by the control microcomputer 30 to the display unit 3.
2 is displayed.

The display section 32 is an LE for displaying charging-related information.
D (light emitting diode, red indicates charging, green indicates charging completed), and LED indicating deterioration determination result (red indicates battery replacement, yellow indicates battery replacement soon, green indicates battery replacement is unnecessary) and And an LCD (liquid crystal display) for displaying a numerical value of the deterioration determination result and displaying an abnormality.

In the charging-related LEDs, the green LED lights only when charging is completed, the red LED lights 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 C / C _{0 as} the deterioration judgment result is less than 60%, the red LED is turned on, and the battery should be immediately replaced with a new battery pack. Is shown. When the value of the estimated specific capacity C / C ₀ 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 the use conditions. Let it. Further, when the value of the estimated specific capacity C / C ₀ 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.

An LCD (Liquid Crystal Display) is provided for displaying information in characters. 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, a current is supplied from the attached battery pack and the power-off is displayed.

FIG. 10 shows a procedure for judging the deterioration of the battery charger manufactured in this embodiment.

The procedure of the deterioration judgment shown in FIG. 10 will be described.

Procedure A: The battery pack is mounted on the charger to start charging, and the pack voltage is monitored. When the pack voltage V reaches the charging upper limit value of 12.3 V (4.1 V / cell), time measurement for deterioration determination is started. At the same time, monitor the charging current value. Procedure B: When the current value reaches 300 mA (0.5 CmA), end the time measurement. The current value is 3 from the time when the charging upper limit voltage is reached.
Recording the time required t of 00mA until reaching, Step C: substituting required time t obtained in equation (2) to calculate the specific capacity C / _{C 0,} Step D: calculated results and LCD LED To be displayed.
According to the value of the specific capacity as the determination result, any one of the red, yellow, and green LEDs is turned on as described above, and
Display the numerical value on D. The LCD display lights for 30 seconds, and the LED turns on when the charger is connected to commercial power.

The deterioration determination according to the present invention is performed by the charge control microcomputer 30 by using the relational expression (2) created in the first embodiment.
And the flow procedure shown in FIG. 10 is programmed and input in advance, and the pack voltage is set to 1 by the built-in timer while monitoring the pack voltage and the charging current value.
The time t from when the charge reaches 2.3 V to change the charge mode from the CC mode charge to the CV mode charge until the charge current value reaches 300 mA of 1/2 is measured and applied to the above-mentioned relational expression (2). Deterioration determination of the Li-ion battery pack is performed, and the determination result is displayed on the display unit 32.

Note that the charger manufactured in this embodiment has a timer display on the LCD so that the charging time of the battery can be known.

Using the charger configured as described above,
A used battery pack of the same type was attached and charged.
This used battery pack has been changed from a constant current (CC) mode to a constant voltage (CV) mode after the charging mode has been changed.
The deterioration judgment result was displayed in 48 minutes, and charging was completed in 4 hours and 6 minutes. LCD shows 92% green LED
Lights up.

The charged battery pack was placed in an automatic battery charge / discharge test apparatus, and a discharge current value of 600 mA (1.0 C
mA), a constant current discharge was performed with the discharge end voltage set to 8.25 V, and the discharge capacity was determined to be 542 mAh. This was 90.3% in terms of specific capacity, and the estimation error was about 1.7%.

As described above, it has been clarified that the charger having the charging function according to the present invention can perform a highly accurate deterioration determination. (Example 7) Charge upper limit voltage 12.3 V, charge current 600
Li ion having a configuration shown in FIG. 3 which is mounted on a small portable information terminal device having a function of performing constant current constant voltage (CC-CV) mode charging under the condition of mA (1.0 CmA) and a convergence current value of 60 mA. A battery pack was manufactured. The battery pack is composed of square cells (nominal capacity 600 mAh) 12-1, 12-2,
And 12-3 three-cell series packs with protective I
The relational expression (2) has been input to C in advance.

The memory for protection 13 in the battery pack having the configuration shown in FIG.
2-2, 12-3 The voltage between both ends of each cell is connected to terminals Vcc and Vs.
s, and the charge upper limit voltage is 12.3 V (4.1 V
/ Cell) and the current value is monitored after the voltage is changed from CC mode charging to CV mode charging, and the current value is monitored.
Elapsed time t to reach 00 mA (0.5 CmA)
Is counted, and the value of the measured time t is substituted into the relational expression (2), and a program for calculating and calculating the specific capacity C / C ₀ is input in advance.

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

On the liquid crystal display, the numerical value as the determination 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.

An instruction for deterioration determination 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 FIG. 10 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 attaching the battery pack having such a configuration to the information terminal device and using it for one hour, it was connected to a commercial power supply and charging was started. When the display displayed after the charging was started, the battery pack determination result was obtained. Was displayed as 75%. After confirming that the sign of charge completion appears on the display, turn off this information terminal device, remove and attach the battery pack, connect to the battery charge / discharge automatic test device using an appropriate connection cord, and discharge. Current 600mA
(1.0 CmA), discharge end voltage 8.25 V (2.75 V
/ Cell) and the capacity was measured. As a result, the discharge capacity was 472 mAh, and the specific capacity was 78.7%.

Accordingly, it has been found that the judgment result by the deterioration judgment function mounted on the battery pack according to the present invention shows an excellent judgment accuracy with an error of -3.7%.

[0104]

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 Li-ion battery pack having a simple method and apparatus for determining the deterioration of an ion battery, and a Li-ion battery pack including means for estimating the capacity of the battery and warning the deterioration of the battery as necessary. It can make a huge contribution in the management of ion batteries.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the concept of changes in battery voltage and charging current value by a constant current constant voltage (CC-CV) method, which is a general charging method for 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 the method for determining deterioration of a lithium-ion battery according to the present invention is specifically applied.

FIG. 3 is a diagram illustrating a general circuit configuration example of a Li-ion battery pack having a deterioration determination function according to the present invention.

FIG. 4 is a diagram showing a relationship between a required time from the start of CV mode charging to half the current value and a specific capacity and a relationship according to a relational expression (2) in the first embodiment of the present invention.

FIG. 5 is a diagram showing the relationship between the required time from the start of charging in the CV mode to the halving of the current value and the specific capacity in the second embodiment of the present invention, and the relationship according to the respective relational expressions.

FIG. 6 is a diagram illustrating a relationship between a required time from the start of CV mode charging to a half of the current value and a specific capacity and a relationship based on respective relational expressions according to the third embodiment of the present invention.

FIG. 7 is a diagram showing the relationship between the required time from the start of charging in the CV mode to the halving of the current value and the specific capacity in Example 4 of the present invention, and the relationship according to the respective relational expressions.

FIG. 8 is a diagram showing the relationship between the required time from the start of charging in the CV mode to the halving of the current value and the specific capacity according to the fifth embodiment of the present invention, and the relationship according to the respective relational expressions.

FIG. 9 is a diagram showing a configuration of a charger manufactured in Embodiment 7 of the present invention.

FIG. 10

[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 CA00 CB13 CB31 CB32 CB33 CC04 CC06 CC27 CC28 CD06 CD09 CD14 CE02 CE31 5G003 AA01 BA01 CA03 CB06 EA05 EA08 GA01 GC05 5H030 AA03 AA04 AA06 AA08 AA10 AS11 BB02 DD03 DD03 DD03 FF52 FF68 5H040 AA06 AA36 AA40 AS11 AT02 AY08 JJ09 NN05

Claims (8)

[Claims] 1. A method for estimating the capacity of a lithium ion battery, the method comprising: when charging a lithium ion battery according to a constant current / constant voltage method, changing a charging condition from a constant current to a constant voltage; The time t until the charging current Ic becomes α times (here, α is a positive constant smaller than 1) is obtained, and the estimated capacity of the lithium ion battery is calculated using the time t. A capacity estimation method for a lithium ion battery. 2. The method for estimating the capacity of a lithium ion battery according to claim 1, wherein the value of α is １, the time t is obtained, and the estimated time C of the lithium ion battery is calculated using the time t. C / C ₀ = At + B (1) (where C ₀ is the nominal capacity of the lithium ion battery, A and B are the lithium ion battery and the charging current Ic, respectively)
A capacity constant of the lithium ion battery. 3. A lithium-ion battery whose capacity is to be estimated or a lithium-ion battery of the same type as the lithium-ion battery is used. charging current _{C 0} / (5 hours) or more _{C 0} / _(0.
5 hours) or less (where C ₀ is the nominal capacity of the lithium ion battery), the charging period by the constant current constant voltage method, the discharging period, and, if necessary, the charging period and the discharging period. A charge / discharge cycle having a rest period provided therebetween is repeated five times or more, and in each cycle, the charge current is changed to 1/2 of the charge current Ic at the time from the point in time when the charge condition is switched from the constant current to the constant voltage. The time t _n to the point of doubling (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
3. The method for estimating the capacity of a lithium ion battery according to claim 2, wherein the values of A and B in the relational expression (1) are determined from the following. 4. A method for judging deterioration of a lithium ion battery, wherein the estimated specific capacity C of the lithium ion battery is calculated by the method for estimating the capacity of a lithium ion battery according to claim 1, 2 or 3, and the estimated capacity is calculated. A method for determining deterioration of a lithium ion battery, comprising determining that the lithium ion battery has deteriorated when C becomes smaller than a predetermined limit capacity C _min . 5. A device for judging deterioration of a lithium ion battery, wherein a charging current when charging the lithium ion battery by a constant current / constant voltage method is a charging current Ic at the time.
(Where α is a positive constant less than 1)
Means for measuring the time t up to the point in time, and calculating the estimated capacity C of the lithium ion battery by the method for estimating the capacity of the lithium ion battery according to claim 1, 2 or 3 using the time t. And a means for outputting a signal indicating deterioration of the lithium ion battery when the estimated capacity C calculated by the arithmetic circuit becomes smaller than a preset limit capacity C _min . An apparatus for determining deterioration of a lithium ion battery. 6. A lithium ion battery pack provided with charge / discharge control means having a built-in IC.
C is a memory for storing a numerical value used for calculating the estimated capacity C of the lithium ion battery in the lithium ion battery pack, and an additional IC when the numerical value is stored in the memory. An arithmetic circuit for calculating the estimated capacity C by the method for estimating the capacity of a lithium ion battery according to claim 1, 2, or 3 from the time t and the numerical value when the ion battery is charged by the constant current and constant voltage method. A lithium-ion battery pack, comprising: 7. When the estimated capacity C of the lithium ion battery in the lithium ion battery pack calculated by the arithmetic circuit becomes smaller than a preset limit capacity C _{min of the} lithium ion battery. 7. The lithium ion battery pack according to claim 6, further comprising means for outputting a warning indicating capacity deterioration. 8. The lithium ion battery pack according to claim 7, wherein the warning is a warning by an electric signal, a warning by displaying characters or images, a warning by a signal sound, or a warning by voice.