JPH10322917A - Method and apparatus for determining deterioration of secondary battery - Google Patents

Abstract

(57) [Summary] [Problem] When charging a secondary battery by intermittent charging,
It is an object of the present invention to provide a secondary battery deterioration determination method and device capable of determining the deterioration of the secondary battery without disconnecting the secondary battery from the load. A rechargeable battery is charged from a constant current circuit, and when a voltage of the rechargeable battery reaches a maximum threshold voltage, a charging switch is turned off to stop charging, and the rechargeable battery is discharged. Disconnect from the current circuit to open circuit state,
When the voltage of the secondary battery drops to the minimum threshold voltage due to self-discharge, charging of the secondary battery is started, and in the intermittent charging of the secondary battery that repeats the charging state and the open circuit state, the charging state After switching to the open circuit state from above, when the open circuit time until the voltage of the secondary battery decreases to the minimum threshold voltage reaches a predetermined threshold, it is determined that the secondary battery has deteriorated. It is.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an uninterruptible power supply, and relates to an apparatus using a secondary battery such as a nickel-cadmium battery, a nickel-metal hydride battery, and a lithium-ion battery as a backup power source. The present invention relates to a method and an apparatus for detecting deterioration due to a decrease.

[0002]

2. Description of the Related Art Conventionally, a secondary battery such as a nickel cadmium battery used as a backup power supply is subjected to trickle charging in which a minute current is always supplied to charge the battery.

However, in this trickle charging, a current always flows through the battery, so that the battery is overcharged for a long time, the electrolyte of the battery and the electrode plate are deteriorated, and the battery life is shortened. There is a problem that it becomes shorter. In order to extend the battery life, it is necessary to use a trickle charge battery that is not easily degraded by trickle charge.However, this trickle charge battery is more expensive than a cycle battery that is charged after all the charge has been discharged. There is a problem that it is expensive.

As a secondary battery having a higher energy density than a nickel cadmium battery, a nickel-metal hydride battery is known. However, this nickel-metal hydride battery has a problem that a trickle charging method cannot be adopted. .

In order to solve these problems, an inexpensive cycle battery may be used as a secondary battery, and the secondary battery may be charged intermittently.

In other words, the secondary battery is charged from the constant current circuit, and when the voltage of the secondary battery reaches the maximum threshold voltage, the charging switch is turned off to stop charging and the secondary battery is opened. When the voltage of the secondary battery drops to the minimum threshold voltage due to self-discharge, charging of the secondary battery is started, and intermittent charging of repeating the above-described charging state and the above-described open circuit state may be performed. Then, in this intermittent charging, to determine the deterioration of the secondary battery, the secondary battery is disconnected from the load, the secondary battery is actually discharged, and the capacity of the secondary battery is measured. Of the deterioration of the secondary battery or a method of determining the deterioration of the secondary battery by measuring the internal resistance of the secondary battery with the secondary battery disconnected from the load.

[0007]

However, in the above-mentioned conventional example, when the secondary battery is charged intermittently and the deterioration of the secondary battery is determined, it is necessary to disconnect the secondary battery from the load. Therefore, there is a problem that backup cannot be performed while the secondary battery is disconnected from the load.

The present invention provides a method and an apparatus for judging the deterioration of a secondary battery which can determine the deterioration of the secondary battery without disconnecting the secondary battery from a load when the secondary battery is charged by intermittent charging. It is intended to provide.

[0009]

According to the present invention, a secondary battery is charged from a constant current circuit, and when the voltage of the secondary battery reaches a maximum threshold voltage, the charging switch is turned off to stop charging. And disconnecting the secondary battery from the constant current circuit into an open circuit state, and when the voltage of the secondary battery drops to the minimum threshold voltage due to self-discharge, charging of the secondary battery is started; In the intermittent charging of the secondary battery that repeats the open circuit state and the above, the open circuit time is measured until the voltage of the secondary battery drops to the minimum threshold voltage after switching from the charging state to the open circuit state. Then, when the open circuit time reaches a predetermined threshold value, it is determined that the secondary battery has deteriorated.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a characteristic diagram for explaining the operation principle of the present invention, and is a characteristic diagram when measurement is performed using a nickel-metal hydride battery.

When a secondary battery such as a nickel-metal hydride battery is intermittently charged, a charge state and an open circuit state are repeated. That is, the secondary battery is charged from the constant current circuit, and when the voltage of the secondary battery reaches the maximum threshold voltage, the charging switch is turned off to stop charging, and the secondary battery is connected to the constant current circuit. When the voltage of the secondary battery drops to the minimum threshold voltage due to self-discharge, charging of the secondary battery is started, and the charging state and the open circuit state are repeated.

After switching from the charged state to the open circuit state, a time until the voltage of the secondary battery decreases to the minimum threshold voltage is defined as an open circuit time T. Is one cycle, and the capacity of the secondary battery is Q
FIG. 1 is a diagram showing the relationship between the open circuit time T and the capacity Q of the secondary battery, and the open circuit time T decreases as the capacity Q of the secondary battery decreases. Characteristic.

According to the present invention, by utilizing this characteristic, a threshold value Tf of the open circuit time corresponding to the threshold value Qq of the capacity when the secondary battery is deteriorated is determined in advance, and the open circuit time T is set in the process of intermittent charging. If the open circuit time T becomes equal to or less than the predetermined threshold value Tf, it is determined that the secondary battery is deteriorated.

FIG. 2 is a characteristic diagram for explaining the principle of the temperature dependence of the capacity Q of the secondary battery and the open circuit time T, which decrease with the deterioration of the secondary battery, according to the present invention. FIG. 6 is a characteristic diagram when measurement is performed using the following.

FIG. 2 shows that the relationship between the capacity Q of the secondary battery and the open circuit time T changes according to the temperature change of the secondary battery. Based on this characteristic, the temperature correction is performed by changing the value of the threshold value Tf of the duration corresponding to the capacity Qq for determining that the secondary battery is degraded with the temperature change.

According to the present invention, instead of stopping the charging operation and measuring the internal resistance as in the prior art, or performing an intermittent charging operation instead of actually discharging and making a deterioration judgment, This is to measure the deterioration of the secondary battery while maintaining the state where the secondary battery and its load are connected, and utilizes the phenomenon that the open circuit time T becomes shorter as the capacity decreases due to the deterioration of the secondary battery. Thus, the deterioration of the secondary battery is determined.

FIG. 3 is a diagram showing a secondary battery deterioration determination circuit DC1 according to one embodiment of the present invention.

The secondary battery deterioration determination circuit DC1 controls a secondary battery 1 such as a nickel-metal hydride battery or a lithium ion battery, a constant current circuit 2 for charging the secondary battery 1, and a charge state of the secondary battery 1. MOSFET3 as a charging switch
A reference voltage source 4, a Schmitt trigger circuit 8 for realizing a voltage determination circuit, a DC power supply 9, a current source 10, and an analog switch 11 for controlling charging and discharging of a capacitor 12.
A capacitor 12, a pulse rise detection circuit 13 for detecting the rise of a pulse output from the Schmitt trigger circuit 8, a discharge resistor R3, a comparator 15 for detecting the length of the open circuit time, and a reference voltage source 16. , An analog switch 17, and a reference voltage source 18.

Note that the AC power supply 31 is converted into a DC voltage by the DC power supply 9 and this DC voltage is applied to the load 33 during a non-power failure, and the secondary battery 1 is connected via the diode 32 in preparation for a power failure. It is connected to a load 33.

The Schmitt trigger circuit 8 has a comparator 5 and resistors R1 and R2. The minimum threshold voltage and the maximum threshold voltage are obtained by the voltage of the reference voltage source 4 and the values of the resistors R1 and R2. This is a circuit that outputs a pulse while the voltage Va of the secondary battery 1 changes from the minimum threshold voltage to the maximum threshold voltage.

When the pulse rising detection circuit 13 detects that the output pulse of the Schmitt trigger circuit 8 changes from “0” to “1”, the pulse rise detection circuit 13
Is a circuit that outputs a pulse having a time width Ta shorter than the width of the output pulse.

FIG. 4 is an operation explanatory diagram showing the operation of the analog switch 11 in the above embodiment.

The analog switch 11 has an input terminal K1,
A switch having K2 and terminals S0, S1, S2, and S3 and operating under the conditions shown in FIG. The output signal of the Schmitt trigger circuit 8 is applied to the input terminal K1,
The output signal of the pulse rise detection circuit 13 is applied to the input terminal K2. Note that the output signal of the pulse rise detection circuit 13 rises at substantially the same timing as the rise of the output signal of the Schmitt trigger circuit 8, and is a pulse whose pulse width is shorter than the pulse width of the output signal of the Schmitt trigger circuit 8.

That is, when the input terminals K1 = 0 and K2 = 0 in the analog switch 11 (when the output signal of the Schmitt trigger circuit 8 is "0"), the terminal S0 of the analog switch 11 is connected to the terminal S1. And the current from the current source 10 flows into the capacitor 12. When the input terminals K1 = 1 and K2 = 1 in the analog switch 11 (just after the output signal of the Schmitt trigger circuit 8 becomes "1"), the terminal S0 of the analog switch 11 is connected to the terminal S2. , The voltage Vd due to the charges charged in the capacitor 12 is transmitted to the non-inverting terminal of the comparator 15. When the input terminals K1 = 1 and K2 = 0 in the analog switch 11, the terminal S0 of the analog switch 11 is connected to the terminal S3, and the capacitor 1
2 is discharged in a short time through the resistor R3.

The analog switch 17 is a switch which is turned on when the output pulse of the pulse rise detection circuit 13 is "0" and turned off when the output pulse of the pulse rise detection circuit 13 is "1".

Next, the operation of the above embodiment will be described.

FIG. 5 is a diagram showing operation waveforms of each part in the above embodiment.

That is, in FIG. 5, the vertical axis indicates the voltage and the horizontal axis indicates the time, and FIG. 5 shows the terminal voltage Va of the secondary battery 1 and
The output pulse Vb of the Schmitt trigger circuit 8, the output pulse Vc of the pulse rise detection circuit 13, the output voltage Vd of the capacitor 12, the output signal Ve of the analog switch 11, the voltage value Vf of the reference voltage source 16, the comparator 15 shows the output voltage waveform Vg.

First, when the MOSFET 3 is on, that is, when the output signal Vb of the Schmitt trigger circuit 8 is at the ON signal level “1”, the secondary battery 1 is switched from the constant current circuit 2 to the secondary battery 1. Electric current flows into the secondary battery 1
Is charged. A maximum threshold voltage (charging stop voltage) V1 and a minimum threshold voltage (charging start voltage) V2 are determined according to the resistances R1, R2 and the value of the reference voltage source 4, and the voltage of the secondary battery 1 in the above-described charged state. When Va rises to the maximum threshold voltage (charging stop voltage) V1 of the Schmitt trigger circuit 8, the comparator 5 outputs an off signal "0".

When the comparator 5 outputs the off signal "0", the MOSFET 3 serving as a charging switch is turned off, the charging current flowing from the constant current circuit 2 to the secondary battery 1 is cut off, and the secondary battery 1 is opened. It becomes a circuit state. The secondary battery 1 that has entered the open circuit state has its stored capacity (charged charge) gradually decreased due to self-discharge, and as the capacity decreases, the open circuit voltage (switches from the charged state to the open circuit state). After that, the time until the voltage of the secondary battery 1 decreases to the minimum threshold voltage) decreases.

When the open circuit voltage drops to the minimum threshold voltage (charging start voltage) V2 of the Schmitt trigger circuit 8, the comparator 5 generates an ON signal "1". As a result, the charging switch 3 is turned on, the charging current flows from the constant current circuit 2 into the secondary battery 1, and charging is started. By repeating the open circuit state and the charging state, intermittent charging is performed, and the capacity of the secondary battery 1 is constantly maintained at a predetermined capacity or higher (the voltage Va of the secondary battery 1 is constantly maintained at a minimum threshold voltage or higher). ).

Here, at the time point t1 when the state changes from the charging state to the open circuit state, the output voltage level Vb of the Schmitt trigger circuit 8 changes from “1” to “0”, and the terminal voltage Va of the secondary battery 1 changes. Consider a period in which the value gradually decreases according to the self-discharge of the secondary battery 1 and the value of the terminal voltage Va of the secondary battery 1 decreases. In this case, the open circuit state continues until the value of the terminal voltage Va of the secondary battery 1 decreases to the minimum threshold voltage (charging start voltage) V2. In this open circuit state, the input terminal K1 of the analog switch 11
= Vb = 0, input terminal K2 = Vc = 0, and the terminal S0 of the analog switch 11 is connected to the terminal S1, as shown in FIG. Therefore, the capacitor 12 is connected to the constant current source 10 and the capacitor 12 is charged with a constant current, so that the voltage Vd of the capacitor 12 is changed as shown in FIG.
As shown in FIG. Assuming that the capacitance of the capacitor 12 is D, the open circuit time is T, and the current value of the constant current source 10 is I, the maximum value Vmax of the voltage value of the capacitor 12 is Vmax = D
× T × I.

Next, at time t2 shown in FIG. 5, the state shifts from the open circuit state to the state of charging the secondary battery 1, and the output voltage level Vb of the Schmitt trigger circuit 8 changes from "0" to "1". Then, in this charged state, a period in which the value of the terminal voltage Va of the secondary battery 1 sharply increases will be considered.

At the beginning of this period, the output voltage level Vb of the Schmitt trigger circuit 8 is "1" and the output voltage level Vc of the pulse rise detection circuit 13 is "1". Input terminal K1 = Vb = “1”, input terminal K2 = Vc = “1”
The analog switch 11 is, as shown in FIG.
Terminal S0 is connected to terminal S2.

Further, since the output signal of the pulse rise detection circuit 13 is "1", the analog switch 17 is turned off. Therefore, the value of the output signal Ve of the analog switch 11 is changed from the voltage Vi of the reference voltage source 18 by The output voltage of the capacitor 12 drops to Vd. Note that capacitor 1
The value larger than the maximum voltage value Vmax at which 2 is charged is
It is set as the voltage Vi of the reference voltage source 18.

The comparator 15 outputs the voltage Ve across the capacitor 12 output from the analog switch 11.
And the voltage Vf of the reference voltage source 16 are compared. here,
The voltage Vf of the reference voltage source 16 is determined by the following equation using the threshold value Tf of the open circuit time corresponding to the capacity Qq of the secondary battery 1 in which the secondary battery 1 is determined to be deteriorated. Vf = D × Tf × I Here, the capacitor 1 output from the analog switch 11
When the comparator 15 detects that the value of the voltage Ve across the terminal 2 is higher than the voltage Vf of the reference voltage source 16 (case 1 shown in FIG. 5), it is determined that the capacity of the secondary battery 1 is normal. It is determined, and the comparator 15 continuously outputs a signal “0” indicating that the capacity of the secondary battery 1 is normal.

Next, when the output voltage level Vb of the Schmitt trigger circuit 8 is "1" and the output voltage level Vc of the pulse rise detection circuit 13 is "0",
The input terminal K1 of the analog switch 11 is
The output voltage level Vb = “1” of the trigger circuit 8 is input, the output voltage level Vc = “0” of the pulse rise detection circuit 13 is input to the input terminal K2 of the analog switch 11, and the analog switch 11 As shown in FIG. 5, the terminal S0 is connected to the terminal S3, and the electric charge charged in the capacitor 12 is rapidly discharged through the resistor R3.
The output voltage Vd of the capacitor 12 is reset to zero.
The state of charge of the secondary battery 1 is determined by the terminal voltage V of the secondary battery 1.
When a reaches the maximum threshold voltage (charging stop voltage) V1, the operation is stopped, and the circuit returns to the open circuit state again.

By the way, at time t3 shown in FIG.
When the comparator 15 detects that the value of the voltage Ve across the capacitor 12 output by the analog switch 11 is lower than the voltage Vf of the reference voltage source 16 (case 2 shown in FIG. 5), the secondary battery 1 Is judged to be deteriorated, and the comparator 15 generates an abnormal signal “1”.

During the period in which the operation in the open circuit state and the operation in the charged state are repeated, the open circuit time T reflecting the deterioration state of the secondary battery 1 is monitored in the above-described manner. The deterioration of the battery 1 is determined.

FIG. 6 is a circuit diagram showing a deterioration determination circuit DC2 of the secondary battery 1 according to another embodiment of the present invention.

The deterioration determination circuit DC2 includes a secondary battery 1 such as a nickel hydrogen battery and a lithium ion battery, and a secondary battery 1
A constant current circuit 2, a charging switch for controlling the state of charge, a MOSFET 3, a reference voltage source 4, a Schmitt trigger circuit 8, a DC power supply 9, and a current source 10. , An analog switch 11,
A capacitor 12, a pulse rise detection circuit 13,
Discharge resistor R3, comparator 15, reference voltage source 1
6, an analog switch 17, a reference voltage source 18, a resistor R4, and a thermistor 20. The Schmitt trigger circuit 8 includes a comparator 5 and resistors R1 and R
And 2.

The deterioration judgment circuit DC2 is provided with a deterioration judgment circuit DC.
1 is basically the same circuit, except that a resistor R4 and a thermistor 20 are added, and the voltage Vf of the reference voltage source 16 is divided by the resistor R4 and the thermistor 20. The difference from the deterioration determination circuit DC1 is that the voltage is applied to the non-inverting terminal. The thermistor 20 is in contact with the secondary battery 1 and measures the operating temperature of the secondary battery 1.

That is, the deterioration determination circuit DC2 includes the resistor R
P1 is a connection point of the thermistor 4 and the thermistor 20. This connection point P1 is connected to the non-inverting terminal of the comparator 15, and the divided voltage Vf1 obtained by dividing the voltage Vf of the reference voltage source 16 by the resistor R4 and thermistor 20 Is generated at a connection point P1 between the resistor R4 and the thermistor 20. Therefore, the resistance value of the thermistor 20 changes according to the temperature change of the secondary battery 1. Therefore, the divided voltage Vf1 divided by the resistor R4 and the thermistor 20 causes the temperature change of the secondary battery 1 to change. It becomes the compensated voltage. In this manner, the temperature can be corrected for the open circuit time Tf at which the secondary battery 1 can be determined to be deteriorated.

That is, in the above embodiment, the rechargeable battery is charged from the constant current circuit, and when the voltage of the rechargeable battery reaches the maximum threshold voltage, the charging switch is turned off to stop the charging. The secondary battery is disconnected from the constant current circuit to open the circuit, and when the voltage of the secondary battery drops to the minimum threshold voltage due to self-discharge, charging of the secondary battery is started. In the intermittent charging device for a secondary battery that repeats a circuit state, after switching from the charging state to the open circuit state, an open circuit time is measured until the voltage of the secondary battery drops to the minimum threshold voltage. A secondary battery deterioration judging device comprising a circuit time measuring means and a deterioration judging means for judging that the secondary battery has deteriorated when the open circuit time reaches a predetermined threshold value. In this case, the open circuit time measuring unit is charged with a constant current after the voltage of the secondary battery reaches the minimum threshold voltage by self-discharge after switching from the charge state to the open circuit state. A device that measures the open circuit time based on the terminal voltage of the capacitor, and the deterioration determination unit is a unit that includes a temperature compensation unit that compensates for the operating temperature of the secondary battery. Device.

Further, in the above embodiment, if grasped as a method invention, the secondary battery is charged from the constant current circuit, and when the voltage of the secondary battery reaches the maximum threshold voltage, the charging switch is turned off. To stop charging and disconnect the secondary battery from the constant current circuit to open the circuit, and start charging the secondary battery when the voltage of the secondary battery drops to the minimum threshold voltage by self-discharge. Then, in the intermittent charging method of the secondary battery that repeats the charging state and the open circuit state, after switching from the charging state to the open circuit state, until the voltage of the secondary battery decreases to the minimum threshold voltage. And a deterioration determination step of determining that the secondary battery has deteriorated when the open circuit time has reached a predetermined threshold. It is the law. In this case, after switching from the charging state to the open circuit state, until the voltage of the secondary battery reaches the minimum threshold voltage by self-discharge, based on the terminal voltage of the capacitor charged with a constant current. The method is a method in which the open circuit time is measured, and the predetermined threshold value has a dependency on the operating temperature of the secondary battery.

In the above embodiment, the capacitor 12 is used as an open circuit time measuring means for measuring the open circuit time until the voltage of the secondary battery drops to the minimum threshold voltage after switching from the charging state to the open circuit state. Although the configuration for measuring the open circuit time is simple, other means such as a clock for measuring the open circuit time may be used instead of the capacitor 12.

[0047]

According to the present invention, during the intermittent charging of the secondary battery 1, during one cycle of the charging state and the open circuit state,
The open circuit time is T, the capacity Q of the secondary battery 1 and the secondary battery 1
Is prepared in advance to indicate the relationship with the open circuit time T when the battery is intermittently charged. When this happens, it is determined that the secondary battery 1 has deteriorated. Therefore, when charging the secondary battery by intermittent charging, it is possible to determine the deterioration of the secondary battery without disconnecting the secondary battery from the load. It works.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram for explaining the operation principle of the present invention, and is a characteristic diagram when measurement is performed using a nickel-metal hydride battery.

FIG. 2 is a characteristic diagram illustrating the principle of the temperature dependence of the capacity Q of the secondary battery and the open circuit time T that decrease with the deterioration of the secondary battery in the present invention. FIG. 6 is a characteristic diagram when measurement is performed by using the following method.

FIG. 3 is a diagram illustrating a deterioration determination circuit DC1 of a secondary battery according to an embodiment of the present invention.

FIG. 4 is an operation state diagram showing an operation of the analog switch 11 in the embodiment.

FIG. 5 is a diagram showing operation waveforms of respective parts in the embodiment.

FIG. 6 is a circuit diagram showing a secondary battery deterioration determination circuit DC2 according to another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Secondary battery, 2 ... Constant current circuit, 3 ... MOSF which is a charge switch for controlling a charge state
ET, 4: Reference voltage source, 5: Comparator 8: Schmitt trigger circuit for realizing a voltage judgment circuit, 9: DC power supply, 10: Current source, 11: Analog switch, 12: Capacitor, 13: Pulse rising detection circuit, Reference numeral 15: comparator, 16: reference voltage source, 17: analog switch, 18: reference voltage source, 20: thermistor, R0 to R4: resistor.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Seiichi Muroyama 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (6)

[Claims] A secondary battery is charged from a constant current circuit, and when a voltage of the secondary battery reaches a maximum threshold voltage, a charging switch is turned off to stop charging and the secondary battery is charged. Disconnect from the constant current circuit to open circuit state,
The intermittent charging method for a secondary battery, which starts charging the secondary battery when the voltage of the secondary battery drops to a minimum threshold voltage due to self-discharge and repeats the charging state and the open circuit state, An open circuit time measuring step of measuring an open circuit time until the voltage of the secondary battery decreases to the minimum threshold voltage after switching from the state to the open circuit state; and the open circuit time reaches a predetermined threshold. A deterioration determining step of determining that the secondary battery has been deteriorated when the above operation has been performed. 2. The battery according to claim 1, wherein the secondary battery is charged with a constant current after switching from the charging state to the open circuit state until the voltage of the secondary battery reaches the minimum threshold voltage by self-discharge. A method for determining deterioration of a secondary battery, wherein the open circuit time is measured based on a terminal voltage of a capacitor. 3. The method for determining deterioration of a secondary battery according to claim 1, wherein the predetermined threshold value has a dependency on the operating temperature of the secondary battery. 4. A secondary battery is charged from a constant current circuit, and when the voltage of the secondary battery reaches a maximum threshold voltage, a charging switch is turned off to stop charging, and the secondary battery is discharged. Disconnect from the constant current circuit to open circuit state,
An intermittent charging device for a secondary battery that starts charging the secondary battery when the voltage of the secondary battery drops to a minimum threshold voltage due to self-discharge and repeats the charging state and the open circuit state, Open circuit time measuring means for measuring an open circuit time until the voltage of the secondary battery drops to the minimum threshold voltage after switching from the state to the open circuit state; and the open circuit time reaches a predetermined threshold. And a deterioration determining means for determining that the secondary battery has deteriorated when the operation has been performed. 5. The open-circuit time measuring means according to claim 4, wherein the open-circuit time measuring means switches from the charged state to the open-circuit state until the voltage of the secondary battery reaches the minimum threshold voltage by self-discharge. And a means for measuring the open circuit time based on a terminal voltage of a capacitor charged with a constant current. 6. The secondary battery deterioration judging device according to claim 4, wherein said deterioration judging means is means having a temperature compensating means for compensating the operating temperature of said secondary battery. .