JPH06124732A - Detection method and device for interelectrode shortcircuit of secondary battery - Google Patents

Abstract

PURPOSE:To enable the occurrence of interelectrode shortcircuit to be easily detected by stopping a discharge process after a battery is discharged up to over-discharge state, measuring self-recovery voltage upon stoppage of the process, and making judgement about the existence of the interelectrode shortcircuit on the basis of the voltage. CONSTITUTION:When a fully charged battery 1 as a measurement object is mounted on a detection device, a discharge start trigger signal is applied from a control circuit 3 to a discharge circuit 2, and a battery 1 is discharged at constant current. Then, while the discharge is continued, battery voltage is inputted to the control circuit 3, thereby causing a memory circuit 4 to save voltage at each point of the discharge process. Thereafter, the circuit 3 makes judgement as to whether voltage drops to level prior to the appearance of a pole change phenomenon due to over-discharge. As soon as voltage drops to the level, the operation of the circuit 2 is stopped, and a timer circuit 5 is triggered. Thereafter, the battery voltage is inputted to the circuit 3 whenever the predetermined time passes, and saved in the circuit 4. When the voltage is found as restored to the vicinity of the over-discharge, the battery is judged to be normal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a device for detecting a short circuit between electrodes of a secondary battery for detecting a short circuit between electrodes in a secondary battery such as a nickel-cadmum battery.

[0002]

2. Description of the Prior Art Two such as nickel-cadmum batteries.
It is known that when the secondary battery is charged and discharged a predetermined number of times or more, the battery capacity decreases due to the battery life.
However, the capacity of the battery may decrease even though the number of times the battery has been charged and discharged has not reached the predetermined number. It is considered that this is because a minute short circuit occurred between the electrodes due to a defective manufacturing process or generation of dendrite (needle-shaped crystal) such as zinc. Such a minute short circuit between the electrodes is conventionally detected by disassembling each cell of the battery and observing the electrode state of the cell with a microscope.

[0003]

However, the work of disassembling the cells of the battery requires a long time, is dangerous, and requires skilled work. In addition, to determine that a micro short has occurred, it is necessary to fully charge it once, leave it for a week or more, and then use the fact that the voltage drop is larger than that of a normal battery. It takes more than one week to judge.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method and apparatus for detecting a short circuit between electrodes of a secondary battery which can easily detect a minute short circuit of a secondary battery such as a nickel-cadmum battery.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a step of discharging a secondary battery to be measured until it is over-discharged, and when the secondary battery to be measured is over-discharged, the discharge is stopped and Measuring the self-recovery voltage of the secondary battery,
A method for detecting a short circuit between electrodes of a secondary battery, which comprises the step of determining whether or not a short circuit between electrodes has occurred based on the self-recovery voltage.

According to the present invention, a discharging means for discharging a secondary battery to be measured until it is over-discharged, and when the secondary battery to be measured is over-discharged, discharging is stopped, and the self-recovery of the secondary battery to be measured is carried out. An inter-electrode short-circuit detection device for a secondary battery, comprising a control circuit that measures a voltage and determines whether or not an inter-electrode short-circuit has occurred based on the self-recovery voltage.

[0007]

Function: The secondary battery to be measured is discharged until it is over-discharged, then the discharge is stopped, the self-recovery voltage of the secondary battery to be measured is measured, and the occurrence of a short circuit between electrodes based on this self-recovery voltage. Determine the presence or absence. This makes it possible to easily detect the occurrence of a short circuit between the electrodes.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. When the nickel-cadmium battery is fully charged and then discharged at a constant current, the voltage decreases with the passage of time. When this discharge is stopped at a specified voltage and no load is applied, the battery self-recovers to a predetermined voltage even if the battery has no capacity.

On the other hand, when the nickel-cadmum battery is fully charged, it is discharged at a constant current, over-discharged to below the specified voltage, and then no load is applied, the same self-recovery occurs. , A battery with a short circuit between electrodes has a lower self-recovery voltage than a normal battery, and
Self-recovery also takes time. From this, a micro short circuit between electrodes can be detected by over-discharging a fully-charged battery to below the specified voltage, then stopping the discharge, applying no load, and measuring the self-recovery voltage when self-recovering. .

That is, FIG. 2 shows the discharge characteristics of a nickel-cadmum battery. In FIG. 2, the horizontal axis represents time, and the vertical axis represents the terminal voltage of the battery when the fully charged battery is discharged at a constant current (for example, 1 A). In FIG. 2, when a fully charged battery is discharged with a constant current of, for example, 1 A, the voltage drops with time. That is, the voltage is V at time t ₁ immediately after discharge.
_{Is 1} . At time t ₂ , 80% of the battery capacity is discharged, and the voltage at that time is V ₂ . In this way, the battery capacity of 80
There is almost no voltage drop until% discharge. Time t
Discharge continues after ₂ and the remaining battery capacity is 10
The power supply voltage starts to drop rapidly when it reaches% -5%. V _th is a specified discharge voltage, which indicates a voltage at which over discharge occurs when the voltage drops. Specified voltage V _th
When the discharge is stopped and no load is applied at the time point t ₃ , the battery voltage self-recovers even if the battery has no capacity.

On the other hand, FIG. 3 shows the over-discharge characteristics of the nickel-cadmume battery. In FIG. 3, the voltage is V ₁₁ at time t ₁₁ immediately after discharge, and
80% of the battery capacity is discharged at ₁₂ , and the voltage at that time is V ₁₂
Becomes After the time point t ₁₂ , the discharge is continued until the remaining battery capacity reaches 10% to 5%, and the power supply voltage rapidly drops. At time t ₁₃ , the voltage reaches the specified discharge voltage V _th1 . If the discharge is continued after the specified discharge voltage V _th1 , the battery will be over-discharged. When the voltage drops to about 70% to 60% of the nominal voltage, that is, at time t ₁₄ when the voltage V _th2 before the occurrence of the reversal phenomenon occurs, the discharge is stopped and no load is applied, the battery self-recovers.
At this time, if the battery is normal, the recovery time is long, as shown by the alternate long and short dash line A1, but the battery is self-recovering. However, when a short circuit occurs between the electrodes, the self-recovery voltage is low as shown by the solid line A2, and it takes time for self-recovery.

FIG. 1 shows an embodiment of the present invention. In this embodiment, based on the principle described above, the battery is over-discharged, then the discharge is stopped, the self-recovery voltage is detected, and the short circuit between the electrodes is detected.

In FIG. 1, a battery 1 to be measured is subjected to constant current discharge by a discharge circuit 2. The measured value of the voltage of the measured battery 1 is supplied to the control circuit 3. In the control circuit 3,
The memory circuit 4, the timer circuit 5, and the display 6 are connected.
The operation of the discharge circuit 2 is controlled by the control circuit 3. The control circuit 3 inputs the measured voltage value of the battery 1 to be measured, compares the measured voltage values, and determines whether or not a short circuit between electrodes occurs. The result of this judgment is displayed on the display 6.

That is, the fully charged battery 1 to be measured is mounted. When the battery under test 1 is mounted, the control circuit 3 gives a discharge start trigger signal to the discharge circuit 2. The discharge circuit 2 is triggered by this trigger signal, and the measured battery 1 is discharged at a constant current. And the battery under test 1
While the battery is being discharged, the voltage of the battery under test 1 at this time is input to the control circuit 3, and the voltage of the battery at each time point is stored in the memory circuit 4.
Memorized in.

When discharging continues, the voltage of the battery under test 1 becomes
Gradually descend. The control circuit 3 detects whether or not the voltage of the battery 1 to be measured is discharged until it is over-discharged and is lowered to the voltage before the inversion phenomenon (voltage V _th2 in FIG. 3). When the voltage of the battery under test 1 reaches the voltage V _th2 , the operation of the discharge circuit 2 is stopped and the timer circuit 5 is triggered.

When it is detected by the timer circuit 5 that a predetermined time has elapsed, at that time (time t ₁₅ in FIG. 3).
The voltage of the battery 1 to be measured is input to the control circuit 3 and taken into the storage circuit 4. Then, when it is detected that the predetermined time has elapsed, the voltage of the battery under test 1 at that time (time point t ₁₆ in FIG. 3) is input to the control circuit 3 and taken into the memory circuit 4.

The control circuit 3 controls the times t ₁₅ and t after the overdischarge.
_Based on the voltage V ₁₅ and the voltage V _{16 at 16} and the voltage V ₁₂ at the time point t ₁₂ before over-discharging, it is determined whether a micro short circuit has occurred. That is, at times t ₁₅ and t after over-discharge
_If the voltage V ₁₅ and the voltage V _{16 at 16} have recovered to the vicinity of the voltage V ₁₂ at the time point t ₁₂ before overdischarge, it is determined that the battery is a normal battery. Voltage V at time t ₁₅ and t ₁₆ after over-discharge
_{If the} voltage ₁₅ and the voltage V ₁₆ do not reach the vicinity of the voltage V ₁₂ at the time t ₁₂ before the overdischarge, it is determined that the minute short circuit has occurred. The result of this judgment is displayed on the display 6.

In the above-described embodiment, the self-recovered voltage after over-discharging and the voltage before over-discharging are compared to determine a minute short circuit. However, after a predetermined time has passed after the normal over-discharging of the battery. It is also possible to measure the self-recovered voltage in advance, and compare the pre-measured value with the self-recovered detected voltage after a predetermined time from over-discharging to judge a minute short circuit.

It is also possible to measure the time required for the voltage to recover to a predetermined voltage after over-discharging and judge the minute short circuit from the length of the time.

Further, first, the self-recovery characteristic of the battery to be measured after stopping the discharge before the over-discharging (corresponding to the characteristic of FIG. 2) is obtained, and then the same battery is over-discharged. It is also possible to measure the self-recovery characteristics from (corresponding to the characteristics of FIG. 3) and compare them to judge a minute short circuit. It is considered that the micro short circuit can be detected most accurately when measured in this way.

[0021]

According to the present invention, the secondary battery to be measured is discharged until it is over-discharged, the discharge is stopped, and the self-recovery voltage of the secondary battery to be measured is measured. The occurrence of the inter-electrode short circuit can be easily detected by determining whether or not the inter-electrode short circuit has occurred.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a graph used to explain one embodiment of the present invention.

FIG. 3 is a graph used to explain one embodiment of the present invention.

[Explanation of symbols]

 1 Battery under test 2 Discharge circuit 3 Control circuit

Claims (2)

[Claims] 1. A step of discharging a secondary battery to be measured until it is over-discharged; when the secondary battery to be measured is over-discharged, discharging is stopped, and a self-recovery voltage of the secondary battery to be measured. And a step of determining whether or not an interelectrode short circuit has occurred based on the self-recovery voltage. 2. A discharging means for discharging a secondary battery to be measured until it is over-discharged, and when the secondary battery to be measured is over-discharged, discharging is stopped and a self-recovery voltage of the secondary battery to be measured. And a control circuit for determining whether or not an inter-electrode short circuit has occurred based on the self-recovery voltage, and an inter-electrode short circuit detection device for a secondary battery.