JPH0973922A - Storage battery operating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a storage battery by controlling the discharge of the storage battery. SOLUTION: When a plurality of unit storage batteries are connected in series, then charge/discharge is performed, the terminal voltage of each unit storage battery is measured during discharge, and the difference between the maximum voltage and the minimum voltage is detected. When the difference value becomes larger than the prescribed voltage in previously determined discharge current, an alarm is given.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of operating a storage battery used as a drive source of an electric vehicle, and more particularly to a method of operating a storage battery for controlling discharge of the storage battery to protect the storage battery. Regarding

[0002]

2. Description of the Related Art Conventionally, as a general means adopted to control the discharge of a storage battery to protect the storage battery, the total voltage of the storage battery is measured and the total voltage reaches a predetermined value. Sometimes there is a way to stop the discharge.

[0003]

However, since this method does not measure the terminal voltage of each unit storage battery when a plurality of unit storage batteries are connected in series, it is often used to obtain a relatively high voltage. It is inevitable that, when the unit storage batteries of (1) are connected in series and discharged, the more deteriorated the storage batteries are, the more the deterioration progresses. A unit storage battery that has deteriorated in the series of storage batteries connected in series has a relatively high terminal voltage higher than the average charging voltage during charging even if the total charging voltage of the storage battery array is set appropriately. Since it is possible that a large amount of hydrogen gas will be generated at an early stage, it is an important issue to prevent an accident such as a flammable explosion from occurring due to this hydrogen gas. Came.

The present invention proposes a method which, when a plurality of unit storage batteries are connected in series and used, can detect (detect) before the variation in the deterioration of the characteristics of each unit storage battery becomes large. .

That is, in the operation method of the storage battery proposed in the present application, when the plurality of unit storage batteries are connected in series and the charging / discharging is repeated, the discharge characteristics of each unit storage battery vary over a predetermined range. It is an object of the present invention to prevent the occurrence of abnormal heat generation and other troubles during the charging operation after discharging by providing a mechanism for issuing an alarm when the battery is discharged.

[0006]

In order to achieve the above-mentioned object, the present invention measures the terminal voltage of each unit storage battery at the time of discharging when charging and discharging a plurality of unit storage batteries connected in series. Detects the difference between the highest voltage and the lowest voltage,
It is characterized in that when the value of the difference becomes larger than a predetermined voltage difference at a predetermined discharge current, an alarm is issued.

It is preferable that an alarm is issued when the difference between the maximum voltage and the minimum voltage becomes larger than the predetermined voltage difference a plurality of times.

Typical types of the storage batteries are, for example, lead storage batteries, nickel-cadmium storage batteries, nickel-hydrogen storage batteries and the like.

The unit storage battery may be one single-cell storage battery, or may be a set of two or more single-cell storage batteries. For example, in the case of a lead storage battery, a 2V single cell itself can be used as a unit storage battery, or a 12V storage battery obtained by converting six 2V single cell storage batteries into a monoblock battery case can be used as a unit storage battery.

Further, the larger the number of unit storage batteries connected in series, the larger the unit storage batteries. This is based on the fact that the greater the number of unit storage batteries forming the storage battery array, the greater the variation between the unit storage batteries as the storage batteries repeat charging and discharging.

[0011]

As for the charging method after discharging, the constant voltage charging method in which the total charging voltage is controlled so as to suppress extreme overcharging is more preferable than the constant current method in which the charging voltage is not controlled. The effect of can be expected more. This is because even if the charging voltage of the entire storage battery array is set to a value that suppresses extreme overcharging, the internal resistance of the storage battery increases because the storage battery whose characteristics have deteriorated among the constituent unit storage batteries. This is because the terminal voltage at the time of charging becomes high and electrolysis of water in the electrolytic solution occurs to generate hydrogen gas.
It is necessary to suppress the amount of hydrogen gas generated here as small as possible. In addition, the charging currents flowing in the series connected storage batteries are the same for all unit storage batteries, but among them, the unit storage batteries with a higher charging voltage naturally generate more heat, so that a significant rise in temperature is avoided. Absent. This heat generation may also cause deformation of the storage battery case or other problems.

As described above, when a plurality of unit storage batteries are connected in series and used, it is safe to appropriately detect a relatively deteriorated unit storage battery, issue an alarm, and suspend charging. This is important for the operation of various storage batteries.

Incidentally, the discharge current value is usually not constant,
Since the value often changes with time or the discharge ends in a short time, the value of this predetermined voltage difference is relatively high when the discharge current is small, and relatively low when the discharge current is large. It is desirable to do. In addition, the actual alarm is not limited to the case where the difference between the maximum value and the minimum value of the terminal voltage at the time of discharge exceeds a predetermined value once in a short time, but also a predetermined alarm during this short time. It can take the form that is emitted only when the value is exceeded multiple times. This is because it is often expected that the discharge characteristics will be restored when a slightly lighter discharge or a pause is entered after the deterioration of the discharge characteristics for a very short time.

[0014]

EXAMPLES Examples of the present invention will be described below.

Nominal voltage 12V, 20 hour rate rated capacity 5A
The sealed lead-acid storage battery of h was used as a unit storage battery, and a storage battery train having a nominal voltage of 240 V was configured by connecting 20 unit storage batteries in series. Using this battery array, a cycle life test was performed in which charging and discharging were repeated. Here, charging is
It was continuously discharged for 1 week at a constant voltage of 274.0V with a current limit of 1.0A, and continuously discharged at a constant current of 5.0A until the terminal voltage of the storage battery array became 200V. In addition, the environmental temperature of the test is approximately 20 to 30 ° C., and the nominal voltage is 12
The terminal voltage at the time of discharging the V unit storage battery was measured.

After the measurement, the state of change in the difference between the maximum value and the minimum value of the terminal voltages of the unit storage batteries at the time of the end of discharge, that is, the time when the total terminal voltage of the storage battery array reaches 200 V is changed by changing the number of discharges. The result of the investigation is shown in FIG.

FIG. 2 shows a change in temperature difference between the wall surface of the unit storage battery having the maximum terminal voltage during discharge and the unit storage battery having the minimum terminal voltage at the end of discharge.

As a result of the test, the relationship between the number of discharges and the change in the difference between the maximum value and the minimum value of the terminal voltage of the unit storage battery at the end of discharge is remarkable as the number of discharges progresses, as is clear from FIG. . At the same time, the temperature difference of the wall surface of the unit storage battery (near the central portion of the upper surface of the unit storage battery) corresponding to the measurement time point in FIG. 1 also becomes remarkable as the number of discharges progresses, as shown in FIG. I found it to match.

In the case of the embodiment of the present application, as is clear from the results of FIGS. 1 and 2, from the point where the voltage difference between the maximum terminal voltage and the minimum terminal voltage of the unit storage battery at the end of discharge exceeds 2 V, the unit storage battery Since the temperature difference becomes noticeable, if you stop using the storage battery array and replace it with a new one when you detect this voltage difference of 2V, you can prevent unexpected accidents due to deterioration of the storage battery. You can Note that the unexpected accident mentioned here is caused by the fact that the unit storage batteries constituting the storage battery array have a large variation in the degree of deterioration, and the unit storage batteries that are significantly deteriorated cause an abnormal temperature rise during discharging and charging. This refers to the deformation and other damage of the storage battery, and various types of extended accidents resulting from these.

[0020]

As described above, according to the operation method of the storage battery of the present invention, the terminal voltage of each unit storage battery is measured at the time of discharging, the difference between the highest voltage and the lowest voltage thereof is detected, and the value of the difference is detected. When is larger than a predetermined voltage difference in a predetermined discharge current, it is possible to protect the storage battery by accurately controlling the discharge of the storage battery only by issuing an alarm.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing the relationship between the number of discharges and the difference between the maximum terminal voltage and the minimum terminal voltage of a unit storage battery at the end of discharge in an example of the present invention.

FIG. 2 is a characteristic diagram showing a difference in temperature between the unit battery having the maximum discharge voltage and the minimum discharge voltage at the end of discharge among the unit batteries shown in FIG.

Claims (2)

[Claims] 1. When charging and discharging a plurality of unit storage batteries connected in series, the terminal voltage of each unit storage battery is measured at the time of discharge to detect the difference between the highest voltage and the lowest voltage, and the difference A method of operating a storage battery, wherein an alarm is issued when the value becomes larger than a predetermined voltage difference in a predetermined discharge current. 2. The method of operating a storage battery according to claim 1, wherein an alarm is issued when the difference between the maximum voltage and the minimum voltage becomes larger than the predetermined voltage difference a plurality of times.