JP3237229B2 - Secondary battery system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery system using an alkali metal as an active material for a negative electrode, and more particularly to a secondary battery system provided with a display device for a remaining charge / discharge cycle life of a secondary battery.

[0002]

2. Description of the Related Art In a secondary battery, when the battery life is exhausted by repeating charge and discharge, the battery needs to be replaced. If the replacement time instruction appears without a notice period, the power supply to the load side is stopped if it does not have a function such as automatic switching to a spare battery. When the size of the battery is increased, a large burden is imposed on the provision of the spare battery, and the effect when the power supply to the load is stopped is enormous. For this reason, predicting the remaining cycle life, that is, knowing the battery replacement time after a certain notice period in advance can prevent the power supply to the load side from being stopped and deal with the battery replacement systematically. It has a big meaning. Conventionally, to indicate the remaining time that can be used and the remaining capacity of a used battery, it is necessary to know the time of battery replacement for a primary battery and the time of charging for a secondary battery. Have been. For example, the amount of electricity discharged up to that point is integrated to calculate the difference from the initial capacity, or the battery voltage is measured and compared with a reference voltage as described in JP-A-59-75581. The remaining capacity can be indicated by a method or the like.

[0003] On the other hand, regarding the prediction of the remaining cycle life as to how many times repetitive charge / discharge is possible,
Little done due to technical difficulties. Regarding the open type lead storage battery, a method of detecting the specific gravity of the electrolytic solution or the position of the liquid surface of the electrolytic solution is well known as a method for instructing the battery replacement time. This method is possible only in an open-type lead-acid battery in which a large amount of free electrolyte is filled in a battery container. On the other hand, as for the display of the life of a sealed type lead-acid battery, a method of detecting the expansion of a grid current collector has been proposed, for example, as described in Japanese Patent Application Laid-Open No. Sho 60-30067. However, these methods are specific to lead-acid batteries.

Since it is difficult to predict the life of other battery systems, the number of charging times is measured as described in, for example, JP-A-4-87159 or JP-A-4-98769, and the difference from the nominal cycle life is measured. A method has been proposed for estimating the remaining cycle life from the data.

[0005]

SUMMARY OF THE INVENTION According to the present invention, in a secondary battery system, in order to predict the end of the life and contribute to the planned operation of the secondary battery, the operating data during use of the secondary battery group and the open It is an object of the present invention to provide a battery system having a display unit that collects circuit state data, estimates the remaining cycle life at that time, and notifies the number of times of charging until battery replacement or the date and time of battery replacement in advance based on the data. And Another object of the present invention is to provide a system for detecting a battery abnormality in advance and preventing an accident from occurring.

[0006]

In order to foresee the life of a secondary battery with a certain grace period before it becomes unusable, it is quantified using an index capable of detecting the cause of the battery life. Accordingly, it is necessary to estimate the period until the life is degraded or the number of times of charge and discharge. The causes of the life of a secondary battery can be roughly classified into two types: the case where the charging or discharging reaction does not proceed due to the deterioration of the electrode active material, and the case where the internal resistance of the battery increases due to the exhaustion of the electrolyte, and the voltage drop due to the internal resistance is large. In some cases, charging and discharging become impossible.

For the deterioration of the electrode active material, the rate of change of the discharge capacity of the secondary battery and the rate of change of the index obtained from the AC impedance of the battery can be used as the index. That is, the rate of change of the discharge capacity is the lower limit of the discharge guaranteed by the battery system by extrapolating the rate of change of each cycle of the discharge capacity by integrating the amount of electricity discharged between the charge and the next charge and calculating the discharge capacity. Estimate the number of times the capacity is reduced and display it as the remaining cycle life. If the secondary battery system is operated under a constant discharge amount condition, a change in the discharge capacity is not detected in principle, so it is particularly effective as another index, particularly in the case of a lithium secondary battery. The remaining cycle life can be extrapolated using the voltage at the end of discharge or the open circuit voltage after the end of discharge. As the voltage at the end of discharging, it is desirable to use a value obtained by subtracting the voltage drop due to the internal resistance of the battery. Hereinafter, a method of predicting the remaining cycle life using a change in the discharge capacity will be mainly described. However, a method of predicting the discharge end voltage can be implemented by a similar method.

In order to improve the accuracy of life prediction, it is effective to measure the AC impedance of the battery in an open circuit state after charging or discharging, in addition to extrapolation of the discharge capacity, and to add this as an index. . The measurement of the AC impedance is one of the causes of deterioration of the secondary battery described above.
This is effective for evaluating both the depletion of the electrolyte and the deterioration of the electrode active material. An index relating to electrolyte depletion can be obtained by measuring the AC impedance in a relatively high frequency region. On the other hand, regarding the deterioration of the electrode active material, an index can be obtained by measuring the AC impedance in a relatively low frequency region, expressing the complex number, and calculating the ratio between the imaginary part and the real part. Since the most suitable measurement frequency range differs depending on the type, size, shape, and the like of the battery, it is necessary to determine two optimum measurement frequency ranges for the target battery system in advance. As the low frequency region, for example, a frequency of 1 Hz or less can be used. The measured AC impedance is displayed as a complex number, and the ratio between the imaginary component (capacitive component) and the real component (resistance component) is calculated and used as one index. In the high frequency region, for example, the AC impedance is measured at a frequency of about 1 kHz, and the value of the resistance component is used as one index.

Usually, several batteries are used in a small battery pack, and in the case of a large battery, more batteries are connected in series so that a voltage of 100 V or 200 V can be obtained. When the batteries are connected in series, the unevenness of the characteristics between the individual batteries constituting the battery group may be increased and the characteristics of the battery group may be degraded. For example, a battery having a low capacity completes discharging first, lowering the discharge voltage of the battery group, and causing a reduction in capacity. Furthermore, in a battery using an alkali metal as a negative electrode active material, when a battery which has been discharged first is dragged by another battery and discharge is continued to cause over-discharge to inversion, the negative electrode active material is placed on the positive electrode. The substance alkali metal precipitates (reverse charging reaction), which may cause a serious accident. In order to avoid this, it is necessary to stop using the battery when the discharge voltage drops to 0 V in a specific battery in the battery pack.

In the case of a battery pack in which several batteries are connected in series, it is possible to measure the voltages of all the batteries.
However, in the case of a large battery that generates a voltage of about 100 V or 200 V, 30
From 70 to 70 batteries need to be connected in series. In this case, it is possible in principle to measure the voltage for all batteries, but it is simpler to measure the voltage for each battery group (module) in which unit cells are connected in series in several units. In this case, if an abnormality occurs, the module can be replaced in module units, and the battery replacement operation can be simplified.
When the voltage is measured for each module, for example, as shown in FIG. 5, when the capacity of one of the five battery modules connected in series is half of that of the other battery module, there is a step difference in the module voltage change during discharging. Occurs. This can be detected as an abnormality in the differential value of the module voltage with respect to the amount of discharged electricity. In this detection method, it is desirable to reduce the number of batteries connected in series as a module in order to avoid an error due to a small voltage change during discharging. For example, in the case of a lithium secondary battery, if a voltage change from around 2 V to 0 V corresponding to an overdischarge reaction occurs in one battery, 5
In this series, 2V / 15V = 0.133 change, 1
In the case of 0 series, the change becomes 2V / 30V = 0.0667, and the detection is easier in the case of 5 series.

In the case of a large battery group, the AC impedance of the battery is also measured for each module, and the abnormality alarm of the module detected by the change in the AC impedance and the discharge voltage is prioritized for estimating the life of the battery system. Is instructed to replace the failed module. Thus, it is possible to cope with an abnormal situation that occurs suddenly other than the normal cause of cycle life deterioration.

[0012]

When the operation of the secondary battery system to which the present invention is applied is started, the discharge capacity during the discharge period is integrated by a current detection device installed in series with the battery group and stored in a storage device. The service life is basically estimated by determining the coefficient of the discharge capacity for each cycle as a function of the number of cycles, and extrapolating the number of cycles to reach the minimum guaranteed discharge capacity of the target secondary battery system. Is done.

At this time, it should be noted that there are two patterns in the manner of change in the discharge capacity of the secondary battery for each repeated charge / discharge cycle, as shown in FIG. The first pattern is a case where the discharge capacity rapidly decreases after a certain discharge capacity has elapsed until the end of the cycle (Type I). The second pattern is a case where the discharge capacity decreases almost linearly as the charge / discharge cycle proceeds (Type II). The difference between these two is that the battery system is different, for example, a nickel-cadmium battery behaves like type I, and a lithium secondary battery behaves like type II in many cases. of course,
Even the same battery system behaves differently depending on the battery design or operating conditions. For example, if the discharge is repeated under a shallow discharge condition with respect to the design capacity, a lithium secondary battery which originally exhibits a type II behavior under a deep discharge condition will also have a type I capacity.
In some cases.

Based on this point, various studies have been made on a method of predicting the remaining cycle life by combining the values of the nominal cycle life, discharge capacity, discharge voltage, and AC impedance (two points of low frequency and high frequency) of the secondary battery. As a result, according to the pattern of change of the discharge capacity with the progress of the charge / discharge cycle shown in FIG. I found that I could raise. For type II batteries, the remaining cycle life can be predicted from the change in discharge capacity for each cycle. In order to more accurately predict the remaining cycle life, the extrapolation and the coefficients of the underlying equation are updated at regular intervals, for example, using the discharge capacity data of the last 100 cycles, and the prediction of the remaining cycle life is corrected. It is desirable. In the former case, the life is rarely conscious during the period when the discharge capacity is constant.

On the other hand, in the case of the type I battery, if it is confirmed that the battery is presently in the phase I area by comparing the discharge capacity of each cycle, the charge / discharge cycle number up to that point is subtracted from the nominal cycle life, or Alternatively, in a lithium secondary battery, F.I. O. M. Estimate the remaining cycle life using the above concept or extrapolate the voltage value at the end of discharge to predict the life. When the discharge capacity of each discharge cycle is compared and a decrease tendency is detected in the discharge capacity, it is determined that the phase has shifted to the phase II area, and the remaining cycle life is estimated by extrapolating the change of the discharge capacity for each cycle. I do. After the phase II of the type I battery, the life is predicted by the same method as the type II battery.
Along with the correction of the life expectancy based on the change in the discharge capacity at regular intervals, the AC impedance of each battery module is measured at two frequencies during the suspension of use, and the voltage change of each module is measured during the discharge. . Regarding the AC impedance, a deviation between modules is taken for each value on the low frequency side and the high frequency side. If a module having a significantly changed AC impedance is generated, an inspection or warning of module replacement is issued as phase III. With respect to the voltage change at the time of discharge, a differential value with respect to the discharge amount is calculated for each module, and when the set value is exceeded, an alarm for module replacement is issued.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 1 shows an outline of a case where a secondary battery system according to the present invention is applied to a power storage facility. AC bus 1 to switch 4
And load 2 and battery 3 via inverter / rectifier 5
Are connected in parallel. The voltage of the assembled battery 3 is measured by a voltage measuring device 7, and conditions are set so that the battery is discharged to a certain lower limit voltage during discharging. A timer 6 is attached to the switch 4 to set a charging time. The charging time is set, for example, to 8 hours from 11:00 pm in the night to 7:00 in the next morning. The current detector 11 is connected to the battery pack 3 in series. The current detector 11 is configured to detect the direction of the current. As a result, the change in the direction of the current is detected to detect charging and discharging, and the current flowing in the discharging direction from charging to the next charging is integrated by the integrator 13. At the same time, a pulse is sent to the counter 12 when the direction of the current changes from the discharging state to the charging state, and the pulse is integrated as the number of cycles increases. The integrated amount of electricity and the number of cycles are stored in the storage unit 14, and the integrated value of the amount of electricity discharged in the arithmetic unit 51 is determined as a function of the number of cycles, and a coefficient is determined. Is estimated, and the result is displayed on the display unit 52. The service life is indicated as follows. Immediately before 20 stored in the storage unit 14
The calculation unit 51 compares the discharge capacities of the batches, and the life is not displayed as long as no change is recognized. When a decrease in the discharge capacity for the last 20 times is observed, the calculation unit 5
The life value calculated in 1 is converted by a built-in calendar and displayed on a monthly basis as a battery replacement time. The estimation is repeated using the latest discharge capacity data every 100 cycles. When the remaining cycle life falls below 200 cycles, the battery replacement time is displayed in units of 10 days.

As shown in FIG. 2, the assembled battery 3 is a battery module 21 in which about five unit cells required to obtain a predetermined voltage are connected in series, and these are further connected in series. Construct a battery group.

An alternating current power supply 17 having an oscillation frequency of 1 kHz and 0.05 Hz and a signal analyzing unit 18 are provided, and are connected to a battery module 21 of an assembled battery via a wiring 24, a contact switching device 22 and a switch 25. After the discharge and charging are completed, the switch 23 is released from the load and the measurement unit, and then connected to the AC power supply 17 and the signal analysis unit 18 by the changeover switch 25 to measure the AC impedance at two frequencies. The measured AC impedance is sent to the storage / operation unit 53, and the AC impedance is compared between modules to calculate a deviation. If the deviation exceeds the set value, an alarm is issued to the alarm unit 55 to replace the module.

Similarly, the voltage measuring unit 16 is connected to the module via a wiring 24, a contact switching unit 22 and a switch 25.
Connect to The input of the voltage of each module during the discharging operation is sequentially switched by the contact switching device 22 and the voltage measurement unit 16 is switched.
To measure the voltage of each module. The module voltage is differentiated by the amount of discharged electricity in the arithmetic unit 54, and if the differentiated value is larger than the set value, an alarm is issued to the alarm unit 55 to replace the module.

Embodiment 2 FIG. 3 shows an outline of a case where the secondary battery system according to the present invention is applied to a power storage facility. AC bus 1 to switch 4
And the load 2 and the battery pack 3 are connected in parallel via the inverter / rectifier 5. This battery pack is set to stop discharging when a certain amount of electricity is discharged by the integrator 13 during discharging. A timer 6 is attached to the switch 4 to set a charging time. The charging time is set, for example, to 8 hours from 11:00 pm in the night to 7:00 in the next morning. The current detector 11 is connected to the battery pack 3 in series. The current detector 11 is configured to detect the direction of the current. As a result, a change in the direction of the current is detected to detect charging, discharging, and an open circuit state. The voltage immediately before the transition from the discharge to the open circuit state is measured by the voltage measuring device 7, the resistance loss is subtracted and stored in the storage unit 14, and the data is updated each time the transition from the discharge to the open circuit state. The data remaining in the storage unit 14 at the time of transition from the open circuit state to the next charge is stored as the discharge end voltage. At the same time, when the direction of the current changes from the discharging state to the charging state, a pulse is sent to the counter 12, the pulse is accumulated as the number of cycles increases, and stored in the storage unit 14 as the number of cycles. The calculation unit 51 determines a coefficient of the discharge end voltage as a function of the number of cycles, estimates the life until the discharge end voltage reaches a predetermined lower limit discharge end voltage by extrapolation, and displays the result on the display unit 52. The service life is indicated as follows. The calculation unit 51 compares the last 20 discharge end voltages stored in the storage unit 14, and does not display until no change is recognized. When a drop in the discharge end voltage for the last 20 times has been observed, the life value calculated by the arithmetic unit 51 is converted by a built-in calendar and displayed as a battery replacement time on a monthly basis. The estimation is repeated using the latest discharge end voltage capacity data every 100 cycles. When the remaining cycle life falls below 200 cycles, the battery replacement time is displayed in units of 10 days. Example 1 for alarm display at the time of abnormality
The procedure is performed in the same manner as described above.

Embodiment 3 FIG. 4 shows an outline of a case where the secondary battery system according to the present invention is applied to a lithium secondary battery pack. The current detection device 11 is connected in series to the five battery groups 15 connected in series, and the wiring 26 for voltage detection is drawn out from the bipolar terminals of each battery. The current detecting device 11 has a function of generating a pulse by reversing the direction of the current. The integration of the output from the current detection device 11 is started by a pulse when the current is inverted from the charging direction to the discharging direction, and the integration is continued by the integrator 13 until the current is inverted from the discharging direction to the charging direction. The integration result is stored in the storage unit 14. At the same time, the counter 12 is advanced by one pulse when the current is reversed from the discharging direction to the charging direction, and is stored in the storage unit 14 as the number of cycles. A coefficient is determined as a function of the number of cycles for the discharge capacity for each cycle integrated in the arithmetic unit 51, the number of cycles up to a preset lower limit capacity is estimated, and is displayed on the display unit 52 as the number of remaining cycles. .

The voltages of the five batteries are measured by the voltage detector 16. At this time, as shown in FIG. 4, only one voltage detection device may be provided via the contact switching device 22, or a voltage detection device may be provided for each battery. When one voltage detection device is used via the contact switching device, the input from the battery is switched at regular intervals. The voltage of each battery being discharged is sequentially measured, and the
When the value is lower than the set value as compared with the set value, a warning to stop use is issued on the display unit 55.

[0024]

According to the present invention, since the life of the secondary battery system can be predicted and the time for battery replacement can be known in advance, the secondary battery system can be operated systematically and secondary batteries can be used. Coordination with the load side can be enhanced. Further, according to the present invention, an abnormality in the secondary battery system can be detected in advance, and occurrence of an accident in the secondary battery system can be prevented.

[Brief description of the drawings]

FIG. 1 shows a configuration in which a secondary battery system according to the present invention is applied to a power storage facility.

FIG. 2 shows a configuration of a battery group in the secondary battery system according to the present invention.

FIG. 3 shows a configuration in a case where the secondary battery system according to the present invention is applied to a power storage facility.

FIG. 4 shows a configuration when the secondary battery system according to the present invention is applied to a lithium secondary battery pack.

FIG. 5 shows a state of a discharge voltage change in a 5-series lithium secondary battery.

FIG. 6 shows a state of a cycle change of a discharge capacity of a secondary battery.

[Explanation of symbols]

1 ... AC bus, 2 ... load, 3 ... assembled battery, 4, 23, 2
5 switch, 5 inverter / rectifier, 6 timer
7: voltage measuring device, 11: current detector, 12: counter, 13: accumulator, 14: storage unit, 15: battery group, 16
... voltage measuring section, 17 ... AC power supply, 18 ... signal analysis section, 2
DESCRIPTION OF SYMBOLS 1 ... Battery module, 22 ... Contact switching device, 24 ...
Wiring, 51, 54 arithmetic unit, 52 display unit, 53 storage unit / arithmetic unit, 55 alarm unit, 71 voltage change when a normal battery is connected, 72 half capacity of one battery , A change in the discharge capacity of the type I battery due to repeated charge / discharge, and a change in the discharge capacity of the type II battery due to repeated charge / discharge.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Katsunori Nishimura 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (72) Tatsuo Horiba 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Hitachi Research, Ltd. (56) References JP-A-4-98769 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 10/42-10/48 G01R 31/36

Claims (22)

(57) [Claims] 1. A collection comprising a plurality of secondary batteries connected in series.
Repeated charging and discharging over time in the combined secondary battery group
In the process of use, (1) extrapolate the discharge capacity at each discharge cycle or (2) extrapolate the voltage at the end of discharge at each discharge cycle, and charge and discharge from that point to the end of life
It is specially equipped with a function to estimate
Rechargeable battery system. 2. A collection comprising a plurality of secondary batteries connected in series.
In the combined secondary battery group, the battery group is divided into a plurality of battery modules.
Module and the AC impedance of the battery module
Measurement in the open circuit state, and the measurement connection between each battery module.
Battery module when the deviation exceeds the set value.
2. An alarm for exchanging files is issued.
Secondary battery system. 3. A collection comprising a plurality of secondary batteries connected in series.
In the combined secondary battery group, the battery group is divided into a plurality of battery modules.
Module and detects the discharge voltage of the battery module
The value obtained by differentiating the discharge voltage with respect to the amount of discharge electricity is the set value.
Alarm when the battery module is replaced.
3. The method according to claim 1 or 2, wherein
Next battery system. 4. At least one or more secondary batteries are provided.
Release during the charge cycle or discharge cycle of the secondary battery
Extrapolating the capacitance or the voltage at the end of discharge
Estimate the number of times charge / discharge is possible from the point
Rechargeable battery displaying the number of times the battery can be charged
system. 5. The secondary battery system according to claim 4, wherein
A secondary battery group including a plurality of the secondary batteries,
The secondary battery group is divided into a plurality of battery modules,
Open circuit state of the AC impedance of the above battery module
And measure the AC impedance between each battery module.
If the deviation exceeds a preset value, the battery
A display or warning of a joule replacement.
Next battery system . 6. The secondary battery system according to claim 4, wherein
In, the secondary battery group consisting of a plurality of the secondary batteries
The above secondary battery group is divided into a plurality of battery modules
The discharge voltage of the battery module is detected, and the
Differentiated value obtained by differentiating the discharged discharge voltage with respect to the amount of discharged electricity
Battery module when exceeds the preset value
Replacement battery system characterized by display of replacement or warning
Stem. 7. The discharge capacity according to claim 4,
Means that the voltage at the end of discharge is
A secondary battery system characterized by extrapolation. 8. The discharge capacity according to claim 4,
Means that the voltage at the end of discharging is
Externally for each battery module obtained by dividing the secondary battery group into
A secondary battery system characterized by being inserted. 9. The method according to claim 4, wherein
Connected to any of the above batteries or battery modules
The current from the battery or battery module or the battery or
A current detector for detecting a current to the battery module;
Connected to the current detector and detects the current detected by the current detector.
Integrator that calculates the integrated value of the flow
And a storage unit for storing the calculated integrated value,
Using the secondary battery to calculate the discharge capacity.
Pond system. 10. The method according to claim 4, wherein :
Connected to any of the above batteries or battery modules.
The current from the battery or battery module or the
Detects current and direction of current to battery or battery module
A current detector and the current detector connected to the current detector.
Calculate the quantity of electricity that is the integrated value of the current detected by the output unit
Connected to the integrator and the current detector, the direction of the current
When the counter changes, a counter that counts the number of cycles
The amount of electricity, which is the integrated value of the current integrated by the integrator ,
Stores the number of cycles accumulated by the above counter
A storage unit, and the integrated value of the electric quantity and the number of cycles
Using the function calculated from
A secondary battery system characterized by estimating the life. 11. The method according to claim 10, wherein the calculated relation is
The number is a function using the integrated value of the electric quantity as the number of cycles.
The coefficient of the above function is calculated, and the integrated value of the quantity of electricity is calculated.
Is extrapolated to the above function to reach the predetermined lower limit discharge capacity
Rechargeable battery characterized by estimating the life before
Stem. 12. The method according to claim 10 or 11, wherein
The function performed is at least one over a predetermined number of cycles.
A function represented by a function approximating one or more linear functions
A secondary battery system characterized in that: 13. The method according to claim 4, wherein :
Display unit that displays the result of calculation or estimation.
The display section indicates that the calculated discharge capacity has already been calculated and held.
The display is updated until there is a change compared to the discharge capacity
A secondary battery system characterized by not having a battery. 14. The method according to claim 4, wherein :
Display unit that displays the result of calculation or estimation.
The display section indicates that the calculated discharge capacity has already been calculated and held.
Calculated life if there is a change compared to the discharge capacity
Is displayed as the battery replacement time.
Pond system. 15. The method according to claim 4, wherein :
Connected to any of the above batteries or battery modules.
The discharge current from the battery or battery module or
Battery or battery module charging current or open circuit status
And a current detector for detecting the
The product for calculating the integrated value of the current detected by the current detector
And measure the voltage before discharging to open circuit.
Voltage measurement device and the integrated value integrated by the integrator
And storing the measured voltage by the voltage measuring device serial
And a voltage at the end of the discharge using the voltage.
A secondary battery system characterized by calculating: 16. The method according to claim 4, wherein
Connected to the battery or battery module, and
Discharge current from the battery module or the battery or battery module
Current detection to detect charging current to the module or open circuit status
Connected to the current detector and the current detector.
An integrator for calculating the integrated value of the output current;
Output device, and when the direction of the current changes, the cycle
A counter that counts the number of
Voltage measurement device for measuring the discharge end voltage before
Store the integrated value, the discharge end voltage, and the number of cycles.
A discharge section and the number of cycles.
Lower limit predetermined using the function calculated from
It is characterized by estimating the life until it reaches the voltage
Rechargeable battery system. 17. The method according to claim 16, wherein the calculated relation is
The number is a function of the discharge end voltage as the number of cycles.
Then, the coefficient of the function is calculated, and the discharge end voltage is increased.
Extrapolates to the above function to reach a predetermined lower limit discharge voltage
Battery system characterized by estimating the life of the battery
M 18. The method according to claim 16, wherein
The function performed is at least one over a predetermined number of cycles.
A function represented by a function approximating one or more linear functions
A secondary battery system characterized in that: 19. The method according to claim 4, wherein
Table showing the result of calculation or estimation in item 1.
Display unit, and the display unit indicates that the calculated discharge voltage is already
Compared to the calculated and held discharge voltage,
Battery system characterized by not updating the display
M 20. Any of claims 4 to 8 or 15 to 18
Table showing the result of calculation or estimation in item 1.
Display unit, and the display unit indicates that the calculated discharge voltage is already
If there is a change compared with the calculated and held discharge voltage,
Displaying the calculated life as battery replacement time
Secondary battery system. 21. The method according to claim 5, wherein at least two
AC power supply that generates an AC signal with
Measure the dance, express it as a complex number and analyze it to the real and imaginary parts
And a signal analysis unit for performing
AC input at at least two frequencies in open circuit
Impedance and measure the AC impedance between each module.
A secondary battery system characterized by comparing dances. 22. The battery according to claim 6, wherein each battery is in a discharging operation.
It has a voltage measuring unit for measuring the voltage of the module,
Measure the voltage of each battery module and calculate the
A secondary battery system characterized by differentiating.