JPH0612549Y2 - Battery deterioration detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial application field" The present invention is applied to a sealed lead battery such as an uninterruptible power supply and relates to a battery deterioration detection circuit for detecting deterioration of the battery.

"Prior Art" In batteries containing electrolyte, the specific gravity of the electrolyte was measured to determine the deterioration of the battery. The sealed lead-acid battery cannot measure the specific gravity of the electrolyte, so the battery must be 2 to 3 CA.
A large amount of current (C is a value corresponding to the rated discharge capacity) is discharged for a short time, and deterioration is detected by the instantaneous voltage drop width of the battery voltage. With this method, a large current, for example, 24 Ah
Since the battery of No. 1 discharges 50 to 70 A, the discharge resistor and the discharge switch element are large, and the amount of heat generation is large, which is not practical.

Moreover, in the method of estimating the deterioration from the open circuit voltage of the battery, the terminal voltage of the deteriorated battery changes with time, and the deterioration detection accuracy cannot be obtained by the detection in a short time.

According to the present invention, when the voltage of the charging circuit becomes higher than a predetermined value, it is detected by the first voltage detector, and the detection output of the first voltage detector activates the repetitive timer circuit. The output of the repetition timer circuit drives the monostable multivibrator, the output of the monostable multivibrator drives a relay, and when the relay is driven, the relay contact disconnects the charging circuit from the battery. A discharge resistor is connected in parallel with the battery, and when the voltage of the discharge resistor becomes a predetermined value or less, it is detected by the second voltage detector, and a flip-flop is set by the detection output of the second voltage detector to set the battery. A deterioration signal is output.

That is, the charging circuit is disconnected from the battery after the battery is fully charged, and the battery is 1 / 20th through the discharging resistor.
It discharges with a minute current of about 0 CA. The degree of deterioration of the battery is judged from the fluctuation range of the battery voltage immediately after the charge is cut off. The battery voltage immediately after the charge is terminated decreases as the battery deteriorates. When the battery voltage becomes equal to or lower than a predetermined value immediately after the charge is cut off, the flip-flop is set and the battery deterioration signal is output.

"Embodiment" FIG. 1 shows an embodiment of the present invention. The charging circuit 11 is connected to the battery 14 through a relay contact 12 and a backflow prevention diode 13. The charging circuit 11 includes a first voltage detector 15
When the voltage of the charging circuit 11 exceeds a predetermined value V ₁ , the output of the first voltage detector 15 is inverted from the high level to the low level. The reversal drives the repetition timer circuit 16 composed of an astable multivibrator, and the monostable multivibrator 17 is driven at every rise of the output of the repetition timer circuit 16. The logical product of the output of the repetition timer circuit 16 and the output of the monostable multivibrator 17 is the gate 1
8 and the output of the gate 18 is fed to the base of the transistor 19. The collector of the transistor 19 is connected to one end of the charging circuit 11 through the relay 21, and the emitter is connected to the other end of the charging circuit 11. When the relay 21 is driven, the relay contact 12 turns off.

A discharge resistor 22 is connected across the battery. When the charging circuit 11 is disconnected from the battery 14 due to full charge, the resistance value of the discharging resistor 22 is 1 /
It is selected so that a minute current of about 200 CA flows through the discharge resistor 22. A second voltage detector 23 is connected across the discharge resistor 22. The output of the second voltage detector 23 is inverted from a low level to a high level when the battery voltage becomes a predetermined value V ₂ or less. The logical product of the output of the second voltage detector 23 and the output of the monostable multivibrator 17 is taken by the gate 24, and the output of the gate 24 is supplied to the set terminal S of the flip-flop 25. The output of the repetitive timer circuit 16 is supplied to the reset terminal R of the flip-flop 25 through the differentiating circuit 26. The output of the flip-flop 25 outputs a battery deterioration signal to the terminal 26.

As the voltage of the charging circuit 11 increases as shown in FIG. 2A, the voltage of the battery 14 also increases as shown in FIG. 2B. When the voltage of the charging circuit 11 reaches the predetermined value V ₁ , this is detected by the first voltage detector 15, and at that time point t ₁ , the repetitive timer circuit 16 starts oscillation as shown in FIG. 2C. The cycle of the repeat timer circuit 16 is set longer than the required charging time. The output of the repetition timer circuit 16 becomes a high level in the half cycle thereof, which drives the monostable multivibrator 17, and its output is obtained as shown in FIG. 2D. When this is driven, the monostable multivibrator 17 outputs a high level of about 1 minute only once. When the output of the timer circuit 16 and the output of the monostable multivibrator 17 are simultaneously at a high level, the relay 21 operates, the relay contact 12 is turned off, and the charging circuit 11 is disconnected from the battery 14.

Therefore, a minute current of about 1/200 CA flows from the battery 14 to the discharge resistor 22. In this case, as the battery deteriorates as shown in FIG. 3B, the battery voltage drops significantly. When the battery voltage drops below a predetermined value V ₂ , this is detected by the second voltage detector 23, and an output is generated from the gate 24 as shown in FIG. 2E, and this output sets the flip-flop 25, and FIG. As indicated by F, the battery deterioration signal is output. The flip-flop 25
Is reset at the rising edge of the output of the repeat timer circuit 16. When the battery discharge current is large, as shown in FIG. 3C, it is difficult to detect battery deterioration because the battery voltage sharply drops to a voltage close to the nominal voltage regardless of battery deterioration. When there is no discharge current, the voltage tends to decrease as shown in FIG. 3A, but it takes time until the voltage stabilizes.

When the battery voltage is equal to or higher than the predetermined value V ₂ and the monostable multivibrator 17 becomes low level, the relay 21 is restored and the charging is restarted. After that, the battery discharge is repeated every cycle of the repetition timer circuit 16, and the deterioration of the battery 14 is constantly monitored.

If the make contact of the relay 21 is connected in series with the discharge resistor 22, the discharge resistor 22 can be connected only during discharging and can be disconnected during charging.

[Advantage of Invention] According to this invention, deterioration of a battery is detected by discharging a minute current at a repetition cycle longer than the charging time. Here, since the current flowing to detect the deterioration is set to a very small current, the power loss required for each detection is extremely small. Then, the number of times of detection becomes relatively small by performing the detection of deterioration at each repeating cycle longer than the time required for charging. After all, since the power loss generated by the battery deterioration detection is small, a special radiator does not need this, and the entire battery deterioration detection circuit device can be downsized. Since the deterioration of the battery can be detected in advance with a few circuit components, it is possible to prevent serious troubles due to the deterioration of the battery, which cannot back up the uninterruptible power supply.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a time chart showing an example of its operation, and FIG. 3 is 24Ah1.
It is a figure which shows the battery voltage fluctuation characteristic at the time of stopping charge about four 2V batteries connected in series.

Claims (1)

[Scope of utility model registration request] 1. A first voltage detector for detecting where the voltage of a charging circuit becomes higher than a predetermined value, and a repetitive timer which oscillates in a repetitive cycle longer than a time required for charging which is activated by a detection output of the first voltage detector. Circuit, monostable multivibrator driven by the output of the repeat timer circuit, relay driven by the output of the monostable multivibrator, relay contact that disconnects the charging circuit from the battery when the relay operates, and parallel connection with the battery Discharge resistor that discharges the generated minute current, a second voltage detector that detects when the voltage of the discharge resistor becomes a predetermined value or less, and a battery deterioration signal that is set by the detection output of the second voltage detector. A battery deterioration detection circuit including a flip-flop for outputting.