JPH11271408A - Method for detecting degradation of secondary battery and charger equipped with degradation detecting function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect with precision degree of ordinary battery's degradation caused by battery's degradation mode, or by high-temperature storage and charging discharging cycle. SOLUTION: Related to a secondary battery wherein charging is performed with a constant current and a constant voltage, a charged capacity at constant current is obtained and based on relationship between the charged capacity and a buttery capacity, degradation degree of a secondary battery is assumed. In addition, after charging is started, a current drop amount directly after charging is switched to a constant voltage mode is measured, and based on the relationship between the current drop and the buttery capacity, degradation degree of the secondary battery is assumed. Further, after charging is started, degradation degree of the secondary battery is assumed based on current-change ratio or a current value after switching from the constant current charging mode to the constant voltage mode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting the degree of deterioration of a secondary battery such as a lithium ion secondary battery, and a charger having such a function of detecting deterioration.

[0002]

2. Description of the Related Art At present, high-capacity secondary batteries are rapidly spreading as power supplies for electronic devices such as notebook personal computers and video cameras. However, when these secondary batteries are stored in an extremely high-temperature environment or repeated charge / discharge cycles, battery characteristics may be deteriorated. In many cases, such a deteriorated battery does not recover to the initial battery capacity even if it is charged by a predetermined method.

[0003] Such deterioration of battery characteristics greatly depends on the storage time and the number of charge / discharge cycles in a high-temperature environment, and the degree of deterioration of the battery gradually increases as the storage time and the number of charge / discharge cycles increase. Will increase. For this reason, it is practically indispensable to accurately measure the degree of deterioration of the battery and correct the battery capacity when fully charged.

[0004] However, at present, there is no example in which the degree of deterioration is sufficiently detected, and in many cases, only deterioration of battery characteristics is roughly detected and estimated. The secondary battery deterioration detection methods proposed so far can be broadly classified into the following methods. (1) Methods for measuring the internal impedance of a battery: JP-A-53-42327, JP-A-61-170678, JP-A-1-253175, JP-A-4-141966, JP-A-8-254573, and JP-A-8-273705. (2) A method of measuring the internal impedance of a battery with signals having different frequencies and processing the value according to an arithmetic expression: JP-A-8-43506, JP-A-8-250159. (3) A method for measuring the electric resistance of an active material which is a component of a battery: JP-A-56-103875. (4) A method of measuring a voltage when a predetermined current is applied and comparing the voltage with a predetermined reference value:
661, JP-A-3-95872, JP-A-8-25457
3, JP-A-8-55642 and JP-A-9-33620. (5) Method for counting the number of charge / discharge cycles: JP-A-5-74501 and JP-A-6-20724.

[0005]

In the deterioration detection methods described in (1) to (4) above, the deterioration of the battery characteristics naturally depends greatly on the use method, use environment, and the like. Is difficult to grasp universally. In addition, when the above deterioration detection method is used, it is difficult to perform measurement during use of the device or during charging work, and it is necessary to temporarily stop charging and discharging of the battery and perform a specific operation separately to detect the degree of deterioration. is there.

Further, in the detection method described in (5) above, even if the number of charge / discharge cycles is simply counted, the same charge / discharge cycle is repeated when the charge / discharge cycle is shallow and when the charge / discharge cycle is close to complete discharge. Even a battery that has undergone a discharge cycle has a different performance, and it is naturally difficult to accurately estimate the degree of deterioration.

[0007]

In view of the problem to be solved, in the method for detecting deterioration of a secondary battery according to the present invention, a test secondary battery is charged at a constant current with a specified current value, and the secondary battery is closed by the charging. After the voltage reaches the specified value, in a constant current constant voltage charging step of continuously maintaining the closed circuit voltage of the battery at the specified voltage value, the charging capacity during the constant current charging is measured, and the charging capacity and the charging capacity are measured. The degree of deterioration of the battery is estimated from the correlation between the rated capacities of the batteries.

Further, the test secondary battery is discharged at a constant current at a specified current value, and after the closed circuit voltage of the secondary battery reaches a specified voltage value by the constant current discharge, the secondary battery is discharged at a specified current value. When the charging operation is performed, the charging capacity from the start of the constant current charging to the closing voltage of the secondary battery reaching a specified voltage value is measured, and the correlation between the charging capacity and the rated capacity of the battery is measured. From the above, the degree of deterioration of the battery is estimated.

Further, the test secondary battery is charged at a constant current with a specified current value, and after the closed circuit voltage of the secondary battery reaches a specified value, the closed circuit voltage of the battery is continuously maintained at the specified value. In the constant voltage charging, the closed circuit voltage of the secondary battery reaches the specified value by the constant current charging, and the amount of current drop flowing through the battery after the charging method is switched to the constant voltage charging is measured. The degree of deterioration of the secondary battery is estimated from the correlation between the amount and the rated capacity of the battery.

In addition, the test secondary battery is charged at a constant current at a specified current value, and after the closed circuit voltage of the secondary battery reaches a specified value, the closed circuit voltage of the battery is continuously maintained at the specified value. In the constant-voltage charging, the closed-circuit voltage of the secondary battery reaches a specified value by the constant-current charging, and the degree of deterioration of the battery is determined from the rate of change in current flowing through the battery after the charging method is switched to the constant-voltage charging. presume.

[0011] In addition, after the voltage of the secondary battery reaches a predetermined value, the voltage of the battery is continuously maintained at the predetermined voltage value. In the constant current constant voltage charging to perform, after the start of charging, measure the current value flowing to the battery after switching from the constant current charging to the constant voltage charging, from the correlation between the current value and the battery capacity of the secondary battery Estimate the degree of deterioration of the secondary battery.

Further, by providing the above-described deterioration detecting function in the charger, charging can be performed effectively.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As electronic devices have become higher in performance and smaller in size, small and high-capacity lithium ion secondary batteries have been used as power supplies for these power devices. However, current lithium-ion secondary batteries are stored under extremely high-temperature environments, or when repeated charge / discharge cycles are repeated, cause deterioration of battery characteristics, and then, for example, if a predetermined charge is performed. However, a phenomenon occurs in which the battery capacity does not recover to the initial battery capacity.

The cause of such deterioration is considered to be the deterioration of the active material in the battery or the decomposition of the electrolyte solution. Since the degradation phenomenon is closely entangled with the electrode reaction in the battery,
When the deterioration occurs, the charge / discharge behavior of the secondary battery is greatly affected.

[0015] The method of charging a lithium secondary battery currently on the market is to charge the battery with a constant current until the battery voltage reaches a set value, and then maintain the battery voltage at this set voltage for a predetermined time or when the charging current is reduced to a predetermined value. A so-called constant current / constant voltage charging method is adopted in which the charging is completed when the charging is reduced to the following. In the above charging method, the set voltage at the time of normal constant voltage is
4.1V to 4.2V is adopted.

If the lithium ion battery is left in an extremely high temperature environment or if an excessive charge / discharge cycle is repeated, capacity deterioration occurs. At this time, when charging is performed by the above-described charging method, the voltage at the time of constant current charging has a larger rate of increase in voltage than that before the capacity deterioration occurs, and reaches the predetermined voltage more quickly. This corresponds to the increase in the electrochemical polarization voltage in the battery due to the deterioration of the active material in the battery and the decomposition of the electrolytic solution, as described above. The degree of deterioration of the battery can be estimated from the charging capacity during current charging.

Normally, when a constant current / constant voltage charging method is adopted, charging is performed, and after switching from constant current charging to constant voltage charging, the current actually flowing gradually decreases to a predetermined current value. At that time, the charging process is completed. The current behavior during constant voltage charging, particularly the current change rate, corresponds to the degree of battery deterioration as described above. Therefore, if the degree of deterioration increases, the current change rate changes greatly.
The degree of battery deterioration can be estimated from the current change rate during constant voltage charging.

Further, when the degree of deterioration further increases, when charging is started, the voltage reaches the set upper limit voltage in a very short time, and is switched to constant voltage charging. At this time, the flowing current value corresponds to the degree of deterioration, and when switching from constant current charging to constant voltage charging, a so-called current value drop (current drop) corresponding to the polarization voltage of the battery appears. This phenomenon is caused by the deterioration of the battery, for example, due to a decrease in the amount of active material, diffusion of lithium ions in the battery is not performed quickly, and the drop of this current value also depends on the degree of deterioration. Change. Therefore, even when the charging capacity at the time of constant current charging is not obtained, the degree of deterioration of the battery can be estimated from the drop at the time of constant voltage charging or the current value after the drop.

As described above, in any case, since the measurement can be performed during charging, measurement conditions are unified, and comparison of measured values becomes easy.

The following embodiments will specifically describe the deterioration detection method of the present invention. (Example 1) In order to accelerate the deterioration of the test battery, 85 ° C
, A total of four types of high-temperature storage were performed for 0 hour, 1 week, 2 weeks, and 3 weeks. For these batteries, the deterioration detection measurement of the secondary battery according to the present invention was performed, and the effectiveness of the detection method of the present invention was verified. The evaluation method is described below.

The test battery has a nominal discharge capacity of 720 mAh,
A lithium ion battery having a nominal voltage of 3.6 V was used. The charging conditions are as follows: a constant current-constant voltage charging method, which is a recommended charging method for the present battery, and a constant current of 500 mA and a constant voltage of 4.1 V
Was reached, charging was completed in a total of 2 hours by a method of maintaining a constant voltage of 4.1 V, and this state was defined as a battery remaining capacity of 100%.

The high-temperature storage was performed at 85 ° C. with 100% of the remaining battery capacity, and the storage time was 0 hours, 1 week, 2 weeks, and 3 weeks, for a total of four times.

Next, after the above-mentioned storage was completed, a discharge test was performed on each battery. The test method was as follows: each battery that had undergone the above storage was discharged at a constant current of 144 mA,
The capacity up to the discharge stop voltage of V was measured. The discharge test described above was performed in a thermostat at 20 ° C.

FIG. 1 shows the results of the discharge test. FIG.
, The vertical axis represents voltage, and the horizontal axis represents 720 mAh.
The discharge capacity was shown as 00%. FIG. 1 shows that as the storage time at 85 ° C. increases to one week, two weeks, and three weeks, the battery capacity gradually decreases and deterioration progresses.

Next, these batteries were charged. As described above, according to the constant current-constant voltage charging method, a constant current of 500 mA is applied, and when the constant voltage reaches 4.1 V, the voltage is maintained at 4.1 V. did. The result is shown in FIG. FIG. 2 shows a change in the battery voltage during the constant current charging in the charging process. In FIG. 2, the vertical axis represents the voltage, and the horizontal axis represents the charging capacity with 720 mAh as 100%.

FIG. 2 shows that the storage time was one week, two weeks,
It was found that as the number of weeks increased, the voltage rise during constant current charging increased. With this result,
It has been found that when a battery that has undergone the above-described high-temperature storage is charged, the time required for switching from constant-current charging to constant-voltage charging is shortened, and the charging capacity during constant-current charging is gradually reduced.

When this result and the result shown in FIG. 1 are considered together, the discharge capacity of the battery deteriorates due to high-temperature storage.
In this case, when the suspended battery is charged with a constant current, the rate of increase of the battery voltage with respect to the charging time can be detected in reverse.

Next, in the above-mentioned charging, the charging capacity at the time of low-voltage charging after the constant current charging step was measured, and is shown in Table 1. Table 1 also shows the high-temperature storage time, discharge capacity, charge capacity at constant current charge, charge capacity at constant voltage charge, and the degree of deterioration. The degree of deterioration used here is
720 mAh as 100% discharge capacity. Deterioration degree (%) = 100−discharge capacity after storage.

[0029]

[Table 1]

It can be seen from Table 1 that the discharge capacity of the battery and the charge capacity during constant current charging decrease linearly with an increase in the high-temperature storage time. From this, it has been found that the degree of deterioration of the secondary battery can be estimated from the charging capacity during constant current charging.

In this embodiment, the degree of deterioration of the secondary battery is estimated from the correspondence table between the battery capacity and the charging capacity at the time of constant current charging. A relational expression may be obtained, and the degree of deterioration may be estimated from the relational expression.

Further, it goes without saying that the degree of deterioration of the secondary battery can be estimated from the charging time required to reach a predetermined voltage at the time of constant current, in addition to the charge capacity at the time of constant current charging.

(Embodiment 2) In Embodiment 1 described above, the temperature was 85 ° C.
In this example, a storage test was performed for up to three weeks. In this example, a storage test was performed for up to two months, and the detection method of the present invention was evaluated.

The test battery used in this example was of the same type as that used in Example 1, and the test method was the same as in Example 1 except that the storage time at 85 ° C. was set. Identical.

FIG. 3 shows the results of a discharge test of the test battery that had been stored at 85 ° C. In FIG. 3, the vertical axis is voltage,
The horizontal axis is the discharge capacity. According to FIG. 3, the storage time is one month,
It was confirmed that the battery deteriorated extremely in two months, and the battery capacity was nearly half of the nominal battery capacity.

FIG. 4 shows the relationship between the current and the charging time during the constant voltage charging in the constant current constant voltage charging, as in the evaluation in the first embodiment. Charge mode is 500m first
The battery was charged with the constant current of A and switched to the constant voltage mode when the battery voltage reached 4.1 V. The time when this switching was performed was set to time 0, and the current flowing through the battery during application of a voltage of 4.1 V was measured. In FIG. 4, this current value is shown on the vertical axis, and the time is shown on the horizontal axis.

In FIG. 4, immediately after switching from the constant-current charging to the constant-voltage charging mode in the charging process, a sharp drop in the current appears, which corresponds to the high-temperature storage time of the test battery.

Table 2 shows the relationship between the degree of deterioration of the secondary battery, the battery capacity, and the amount of voltage drop. The degree of deterioration used here is calculated as follows: degree of deterioration (%) = 100−battery capacity.

[0039]

[Table 2]

According to Table 2, the discharge capacity of the battery decreases as the storage time increases. At this time, as described above, the amount of current drop immediately after switching from constant current during charging to constant voltage charging increases. I found that. Using this phenomenon, the degree of deterioration of the secondary battery can be estimated from the amount of current drop during constant voltage charging.

In this embodiment, the degree of deterioration of the secondary battery is estimated from the correspondence table between the battery capacity and the current drop amount at the time of constant voltage charging. It is also possible to obtain a relational expression with respect to and estimate the degree of deterioration of the secondary battery from this relational expression.

Example 3 In order to accelerate the deterioration of the test battery, the test was conducted at 85 ° C. for 0 hour, 1 week, 2 weeks,
A total of four types of high-temperature storage were performed for three weeks. For these batteries, the deterioration detection measurement of the secondary battery according to the present invention is performed,
The effectiveness of the detection method of the present invention was verified. The evaluation method is described below.

The test battery used was the same as that used in Examples 1 and 2. The charging condition is a constant current-constant voltage charging method, which is a recommended charging method of the present battery, and a constant current of 500 mA is applied. When the constant voltage reaches 4.1 V, the constant voltage is maintained at 4.1 V for a total of 2 hours. At the end of charging, and this state was defined as a battery remaining capacity of 100%. High temperature storage is 85 ° C with 100% remaining battery capacity
And the storage time was 0 hours, 1 week, 2 weeks, and 3 weeks, for a total of four times.

Next, after the above-mentioned storage was completed, each battery was discharged. The battery was discharged at a constant current of 144 mA for each of the batteries that had undergone the above-mentioned storage, and the capacity up to a discharge stop voltage of 3.0 V was measured. The discharge test described above was performed in a thermostat at 20 ° C.

The test battery having undergone the above steps was charged at a constant current and a constant voltage. FIG. 5 shows the current change during constant voltage charging in this charging process. The horizontal axis of FIG. 5 shows the charging time, and the vertical axis shows the current.

As shown in FIG. 5, the current value during constant voltage charging decreases with the constant voltage charging time, but the current behavior corresponds to the high temperature storage time of the battery, that is, the degree of deterioration. I understand. The time change rate of the current flowing through the test battery during constant voltage charging is defined as ΔI, and the relationship between this and the degree of deterioration is shown in Table 3.
It was shown to. The ΔI is ΔI = (I ₁ −I ₂ ) / (t ₁ −
t ₂ ). Here, I ₁ and I ₂ are current values after the constant voltage charging times t ₁ and t ₂ , respectively.

[0047]

[Table 3]

In Table 3, as the storage period increases, the current change rate ΔI decreases, and the degree of deterioration is determined by the current change rate Δ
It was found to increase in proportion to I. As a result, in the constant current / constant voltage charging process, the degree of deterioration of the secondary battery can be detected from the time change rate ΔI of the current during constant voltage charging after constant current charging.

In this embodiment, the degree of deterioration of the secondary battery is estimated from the relational expression between the battery capacity and the current change rate during constant voltage charging. However, the battery capacity and the current change rate during constant voltage charging are estimated. And a degree of deterioration of the secondary battery can be estimated from this relational expression.

(Embodiment 4) The above embodiment shows that the battery is accelerated by putting the test battery in a high-temperature atmosphere for a long time, and that the detection method of the present invention is effective for this. Was.

Next, this embodiment shows the usefulness of the detection method of the present invention with respect to battery deterioration due to charge / discharge cycles.

A charge / discharge cycle test was performed by the following method to promote deterioration, and one cycle, 200 cycles,
For the test battery after a total of three kinds of charge / discharge cycles of 1200 cycles, the deterioration detection measurement of the secondary battery according to the present application was performed, and its validity was verified. The measuring method is described below.

The test batteries used were the same as those used in Examples 1 and 2. The charging condition is a constant current-constant voltage charging method, which is a recommended charging method of the present battery, and a constant current of 500 mA is applied. When the constant voltage reaches 4.1 V, the constant voltage is maintained at 4.1 V for a total of 2 hours. At the end of charging, and this state was defined as a battery remaining capacity of 100%. All the battery tests in this example were performed in a thermostat at 20 ° C.

FIG. 6 shows the results of the discharge test at the first cycle, the 200th cycle, and the 1200th cycle in the above charge / discharge cycle. In FIG. 6, the vertical axis is voltage,
The horizontal axis is the discharge capacity. FIG. 6 shows that as the charge / discharge cycle progresses, the discharge capacity of the battery gradually decreases.

Next, the first cycle, the 200th cycle,
FIG. 7 shows the results of the charge test at the 1200th cycle.
In FIG. 7, the vertical axis represents the voltage, and the horizontal axis represents the charging capacity at the time of constant current charging as 720% with 720 mAh as 100%. FIG.
Thus, it was found that as the number of cycles increases, the rise of the voltage at the time of constant current charging increases, and the constant current charging switches to constant voltage charging earlier. From this result, it was confirmed that when the above-described constant current and constant voltage charging was performed on a battery that had undergone a charge / discharge cycle, the charging time during constant current charging, that is, the charging capacity gradually decreased.

Table 4 shows the number of charge / discharge cycles, the discharge capacity and the degree of deterioration, and the charge capacity at constant current charge and the charge capacity at constant voltage charge in constant current constant voltage charge.
The degree of deterioration used here is the degree of deterioration (%) = 100
-Battery capacity.

[0057]

[Table 4]

Table 4 shows that the discharge capacity and the charge capacity at the time of constant current charging decrease as the number of charge / discharge cycles increases. From these results, it was possible to show the validity of detecting the degree of deterioration of the secondary battery from the charging capacity during constant current charging, which is the detection method of the present invention.

(Embodiment 5) In this embodiment, the validity of the detection method according to claim 5 was verified. As a test battery, a lithium ion battery (upper limit voltage: 4.1 V, lower limit voltage: 3.0 V, battery capacity: 720 mAh) was used and stored in an atmosphere at 85 ° C. in order to accelerate deterioration of the test battery. Battery storage is
It was left for 1 month and 2 months at an environmental temperature of 85 ° C. with 100% of the remaining capacity.

After the above storage was completed, a charge / discharge test of the battery was performed to confirm the degree of capacity deterioration. The charging conditions were in accordance with the constant current and constant voltage charging method for charging the battery. The constant voltage charging after the constant current charging is performed by setting the closed circuit voltage of the battery to 4.1 V.
, And the charging was completed after charging for a total of 2 hours in combination with constant current and constant voltage charging. The discharge was performed in a constant current mode of 144 mA, and the discharge stop voltage was 3.0 V, which is a common value.
And The above charge / discharge test was performed in a thermostat at 20 ° C.

FIG. 3 shows the results of the discharge test. In FIG. 3, the vertical axis represents voltage, and the horizontal axis represents discharge capacity. From FIG. 3, it was confirmed that the deterioration progressed as the storage time became longer.

Using the battery stored at the high temperature described above,
According to the following process, the method for detecting the degree of deterioration of the battery according to claim 5 was evaluated. First, a test battery that had been stored at a high temperature for one month and two months by the above-described method was used for 500 hours.
The battery is charged at a constant current of mA and the closed circuit voltage of the test battery is 4.1 V
Then, the mode was switched to the 4.1 V constant voltage charging mode. 100 seconds after the start of the constant voltage charging, the current value Iv (100 seconds) flowing in the test battery was measured, and the value is shown in Table 5. Table 5 also shows the storage period of the test battery, the battery capacity after storage, and the degree of deterioration.
The degree of deterioration used here is the degree of deterioration (%) = 100
-Calculated as battery capacity (%).

[0063]

[Table 5]

From Table 5, it was found that the test battery deteriorated with the high-temperature storage period, and at the same time, the Iv (100 seconds) decreased. That is, it has been found that the degree of deterioration of the test battery can be detected by measuring the Iv (100 seconds). In order to quantify the degree of deterioration, for example, it is possible to actually measure Iv and compare it with a predetermined Iv-deterioration degree correspondence table.

In the above process, the constant current mode at the time of constant current and constant voltage charging was performed at 500 mA. However, the same process was performed at 1500 mA, and the current value flowing through the test battery after switching to the constant voltage charging mode was performed. Was measured. The results are shown in FIG. The test battery used in this measurement was
The above-mentioned high-temperature storage was performed for two months. In FIG. 8, after switching from constant-current charging to constant-voltage charging, a current drop appears, but the current value after that showed a constant value irrespective of the difference in the current value of the constant-current charging. With this result,
It was confirmed that the value of the degree of deterioration obtained in this measurement was not affected by the value of the current supplied during constant-current charging.

Further, in this embodiment, the degree of deterioration of the secondary battery is estimated from the correspondence table between the battery capacity and the current value during constant voltage charging, but the relationship between the battery capacity and the current value during constant voltage charging is estimated. An expression is obtained, and the degree of deterioration of the secondary battery can be estimated from this relational expression.

In this embodiment, the deterioration due to high-temperature storage has been described, but the same can be said for the deterioration due to charge / discharge cycles.

In the above embodiments, the detection method of the present invention has been described. However, by incorporating this detection means in the charger of the secondary battery, it is possible to perform optimal control of the charging method according to the state of each battery. I can do it.

[0069]

As is apparent from the above embodiments, according to the present invention, the degradation mode of a battery which is normally assumed, that is, the degree of degradation of a battery which has been degraded by high-temperature storage and charge / discharge cycles can be accurately determined. Can be detected.

[Brief description of the drawings]

FIG. 1 is a diagram showing discharge curves of batteries having different storage times used for evaluation of a first embodiment of the detection method of the present invention.

FIG. 2 is a diagram showing charging curves of batteries having different storage times used for evaluating the first embodiment of the detection method of the present invention.

FIG. 3 is a diagram showing discharge curves of batteries having different storage times and used for evaluation of a second embodiment relating to the detection method of the present invention.

FIG. 4 is a diagram showing the relationship between the current and the charging time during constant voltage charging of batteries having different storage times and used in the evaluation of the second embodiment relating to the detection method of the present invention.

FIG. 5 is a diagram showing the relationship between the current and the charging time during constant voltage charging of batteries having different storage times and used for evaluation of the third embodiment of the detection method of the present invention.

FIG. 6 is a diagram showing the relationship between the voltage and the discharge time at the time of constant current discharge of batteries having different numbers of charge / discharge cycles used in the evaluation of the fourth embodiment relating to the detection method of the present invention.

FIG. 7 is a diagram showing the relationship between the voltage and the charging time at the time of constant current charging of batteries having different numbers of charge / discharge cycles used for evaluation of the fourth embodiment relating to the detection method of the present invention.

FIG. 8 is a diagram showing a relationship between a current at the time of constant voltage charging and a charging time, which was used for evaluation of a fifth embodiment relating to the detection method of the present invention.

Continued on the front page (72) Inventor Yoshinori Yamada 1006 Kadoma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. (72) Inventor Kenichi Takeyama 1006 Odakadoma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd.

Claims (6)

[Claims] 1. A test secondary battery is charged at a constant current with a specified current value, and after the closed voltage of the secondary battery reaches a specified value by the charging, the closed circuit voltage of the battery is continuously reduced to the specified voltage. In the constant current / constant voltage charging step of maintaining the value, the charging capacity during the constant current charging is measured, and the degree of deterioration of the battery is estimated from the correlation between the charging capacity and the rated capacity of the battery. To detect the deterioration of the secondary battery. 2. The test secondary battery is discharged at a constant current at a specified current value, and after the closed circuit voltage of the secondary battery reaches a specified voltage value by the constant current discharge, the secondary battery is discharged at a specified current value. When the charging operation is performed, the charging capacity from the start of the constant current charging to the closing voltage of the secondary battery reaching a specified voltage value is measured, and the correlation between the charging capacity and the rated capacity of the battery is measured. A method for detecting deterioration of a secondary battery, comprising estimating a degree of deterioration of the battery from the following. 3. The test secondary battery is charged at a constant current with a specified current value, and after the closed circuit voltage of the secondary battery reaches a specified value, the closed circuit voltage of the battery is continuously maintained at the specified value. In the constant voltage charging, the closed circuit voltage of the secondary battery reaches the specified value by the constant current charging, and the amount of current drop flowing through the battery after the charging method is switched to the constant voltage charging is measured. A method for detecting deterioration of a secondary battery, comprising estimating a degree of deterioration of the secondary battery from a correlation between an amount and a rated capacity of the battery. 4. The test secondary battery is charged at a constant current at a specified current value, and after the closed circuit voltage of the secondary battery reaches a specified value, the closed circuit voltage of the battery is continuously maintained at the specified value. In the constant-voltage charging, the closed-circuit voltage of the secondary battery reaches a specified value by the constant-current charging, and the degree of deterioration of the battery is determined from the rate of change in current flowing through the battery after the charging method is switched to the constant-voltage charging. A method for detecting deterioration of a secondary battery, comprising estimating the deterioration. 5. A test secondary battery is charged at a predetermined current value,
After the voltage of the secondary battery reaches a predetermined value, in the constant-current constant-voltage charging in which charging is continuously performed to maintain the voltage of the battery at the predetermined voltage value, after the start of charging, the constant-current charging to the constant voltage. A secondary battery characterized by measuring a current value flowing through the test battery after switching to charging, and estimating a degree of deterioration of the secondary battery from a correlation between the current value and a battery capacity of the secondary battery. Deterioration detection method. 6. A charger provided with the deterioration detection function according to claim 1, 2, 3, 4, or 5.