JPH1092473A - Method and device for controlling charge of battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To charge a storage battery at high precision, so as to prevent overcharge, by controlling charging through a process of detecting that the change amount of the inner impedance per unit time in the charging last stage of the storage battery exceeds a specified value. SOLUTION: The inner impedance of a storage battery, the battery voltage, the battery temperature are changed around 140 minutes after charge is started, in particular, the inner impedance is suddenly changed. The change amount of the inner impedance per unit time is approximately half as large as the inner impedance in 140 minutes and larger than that of the battery voltage and the battery temperature. Therefore, control of charge by the detection of the change amount of the inner impedance per unit time is more reliable than that by the detection of the charge of the battery voltage and the battery temperature, the risk of overcharge is low, and charge can be controlled at high precision. When the change amount of the inner impedance exceeds 2.0MΩ/min., that is detected, charging is stopped, and the charging electric amount is 95% of the discharging amount, and overcharge can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for controlling charging of a storage battery.

[0002]

2. Description of the Related Art Conventionally, as a charge control method of a storage battery,
Temperature rise of storage battery per unit time during charging (ΔT / Δ
There is generally known a method of controlling charging by detecting t) or detecting a battery voltage (ΔV / Δt) increased per unit time.

[0003]

The conventional storage battery control system described above is susceptible to the environment and charging conditions, so that the temperature and battery voltage of the storage battery are not constantly changed, and the amount of change is small. For this reason, this method has a problem in that it is difficult to detect the end of charging of the storage battery, and the battery may be overcharged. The present invention solves the above disadvantages,
It is an object of the present invention to provide a storage battery charging control method and device that can control charging with higher accuracy and do not become overcharged.

[0004]

In order to solve the above-mentioned problems, the charge control method according to the present invention provides a method for controlling the internal impedance when the amount of change in internal impedance per unit time at the end of charging of a storage battery exceeds a specified value, or When the value exceeds a specified value, charging is controlled by detecting this. The charging is controlled by pausing the charging or by switching the constant current charging to a smaller constant current charging and thereafter continuing for a predetermined time, or by switching the constant current charging to the constant voltage charging and drooping the current, and thereafter, Is to continue for hours. The charging control device according to the present invention includes an impedance measuring device that measures the internal impedance of the storage battery being charged, and a storage battery whose internal impedance measured by the impedance measuring device or a variation per unit time of the internal impedance has a specified value. It is characterized in that a control unit is provided for detecting this when it is exceeded and controlling the charging circuit. The present invention makes use of the characteristic that the internal impedance of the storage battery during charging rises abruptly when gas is generated at the end of charging. According to this configuration, the end of charging is reliably detected and charging is controlled. .

[0005]

Next, an embodiment of the above-described charge control method of the present invention will be described in detail. While charging the sealed lead-acid battery in a completely discharged state with a constant current, an alternating current was passed through the lead-acid battery using an impedance measuring instrument, and the internal impedance of the battery being charged was measured by the AC impedance method. At this time, the battery voltage and the battery temperature were measured at the same time.
The result is shown in FIG. As is clear from FIG. 1, the change in the internal impedance of the storage battery is very small from the start of charging of the storage battery to the end of the charging and the generation of gas due to the electrolysis of water inside the storage battery. However, when gas starts to be generated and the battery voltage rises, the internal impedance of the storage battery rises sharply and then falls, so that a sharp internal impedance peak appears. The reason why the internal impedance rises rapidly is that, when charging proceeds and gas generation occurs due to electrolysis of water, the gas fills the pores of the active material of the electrode plate and prevents contact between the electrolyte and the active material. Therefore, it is considered that the internal impedance increases, and thereafter, the gas is discharged from the pores, and the contact area between the electrolyte and the active material increases, so that the internal impedance decreases. This increase in the internal impedance is clearly larger than the increase in the battery voltage and the battery temperature, and the internal impedance rapidly increases and decreases in a short time. For example, normal constant-current charging is performed, and when the internal impedance becomes larger than a specified value, this is detected. Pause the current,
After that, charge the battery regularly and make up for the shortage of charge.
Or, switch the constant current charging to a smaller constant current charging,
After that, the charging is continued for a predetermined time or after the constant current charging is switched to the constant voltage charging and the charging current is dropped,
The charging is controlled by continuing the charging for a certain period of time.
According to the method of the present invention, even if the storage battery has a small internal resistance, the end of charging of the storage battery can be detected with high accuracy by detecting this change, and the battery is not overcharged.

[0006]

【Example】

(Example 1) A monoblock type sealed lead-acid battery formed integrally with six cells is placed in a thermostat at 25 ° C, and a current of 26 A is used for 90 minutes (about 50% of the battery capacity).
15A after discharging and standing for 2 hours to stabilize the storage battery
The battery was charged at a constant current of 190 minutes (about 120% of the discharge capacity), and the internal impedance, battery voltage, and battery temperature of the storage battery at this time were measured. The impedance measuring device is, for example, a device for measuring the impedance by an AC impedance method by passing an AC current of 17.5 Hz and 0.1 A, and for example, a device manufactured by Yachiyo Electronics Co., Ltd. (hereinafter the same). As shown in FIG. 2, the internal impedance, the battery voltage, and the battery temperature of the storage battery all change around 140 minutes after the start of charging, but particularly the internal impedance changes rapidly. The internal impedance, battery voltage and battery temperature at the 140th minute before this change occurred, and each value when each value showed the maximum value and its time were measured. Table 1 below shows the measurement results.

[0007]

[Table 1]

As shown in Table 1 above, the amount of change in the internal impedance per unit time is about 0.5 times the internal impedance at 140 minutes, which is larger than that of the battery voltage and the battery temperature. Therefore, if the charge is controlled by detecting the amount of change in the internal impedance per unit time, the risk of overcharging is smaller and the risk of overcharging is smaller than that of controlling the charge by detecting the change in the battery voltage or the battery temperature, and with high accuracy Charge control can be performed. Then, when the change amount of the internal impedance per unit time exceeds 2.0 mΩ / min, this is detected and the charging is stopped, and the charged electricity amount is 95% of the discharged amount. Did not.

(Embodiment 2) Six cells having different degrees of deterioration
Three monoblock type sealed lead-acid batteries were prepared, each was discharged to 9.9 V with a current of 26 A, left for 2 hours, and then charged to 120% of the discharge capacity with a constant current of 15 A to reduce the internal impedance. The maximum value was measured. Table 2 below
Indicates the test results.

[0010]

[Table 2]

In the test cell-1, a similar test was conducted by changing the depth of discharge at a current of 26 A. The test results are shown in Table 3 below.

[0012]

[Table 3]

As can be seen from Tables 2 and 3, the internal impedance increases as the actual capacity of the storage battery decreases and as the depth of discharge decreases. Therefore, in the case of the storage battery used in this test, the internal impedance value during charging is slightly smaller than 8.2 mΩ based on the internal impedance value at a discharge depth of 100%.
When the value exceeded 0 mΩ, the charging was stopped by detecting the value, and the amount of electricity charged at this point was 97.3 of the discharge capacity.
%Met.

Example 3 A 6-cell monoblock type sealed lead-acid battery was placed in a thermostat at 25 ° C.
The battery was discharged at a current of A to 9.9 V, allowed to stand for 2 hours, and then charged at a constant current of 15 A while measuring the internal impedance. During charging, the internal impedance value of the storage battery is 7.0
When a value of mΩ or more is detected, the charging current is reduced to 4 A and
Charged for hours. FIG. 3 shows the internal impedance, battery voltage and charging current characteristics of the storage battery with respect to the charging time in this embodiment. Table 4 below shows the charging characteristics.

[0015]

[Table 4]

As is evident from FIG. 3 and Table 4 above,
When the set value of the internal impedance is detected to be 7.0 mΩ, the amount of charged electricity with respect to the discharge capacity is 96.8%. After the detection, the amount of charged electricity when the charging current is reduced to 4 A and charging is performed for 2 hours is 108. The battery was almost completely charged at 0.6%. When the charging is stopped after the detection, the battery is slightly undercharged. However, overcharging is prevented and the amount of liquid reduction is reduced to extend the life of the storage battery. The shortage of the charge amount is compensated for by performing equal charge periodically. In the charging characteristics shown in FIG. 3, the battery voltage rapidly changes around 4 hours as in the case of the internal impedance, but the maximum value is obtained when the battery voltage is 7.0 mΩ. If the charge control is not performed, the impedance has a larger value, so that the amount of change is much larger than the battery voltage.

FIG. 4 shows a block diagram of the charge control device of the present invention. In the figure, 1 is a charging circuit connected to a commercial power supply, 2 is the storage battery whose charging is controlled, 3 is an impedance measuring device, 4 is an operation, comparison and data recording unit, and 5 is an operation, comparison and data recording unit. An operation unit 4 inputs conditions and the like to 4, and a control signal and a charging circuit 1 for inputting the output of the arithmetic, comparison and data recording unit 4 for controlling the charging circuit 1.
Is a control output unit that outputs a start signal of the timer 7 that operates for a predetermined time. The impedance measuring device 3 includes, for example, a frequency generator and a power amplifying unit 8 for supplying an alternating current of 17.5 Hz and 0.1 A to the storage battery 2, a terminal voltage of the storage battery 2 by the AC current by an AC impedance method, and the AC voltage. An impedance calculator 9 for calculating the internal impedance of the storage battery 2 from the current is used. The calculation, comparison and data recording unit 4 is composed of, for example, a microcomputer, and the internal impedance of the storage battery 2 measured by the impedance measuring device 3 is sequentially input,
For example, 7.0 m preset in the memory by the operation unit 5
Compared with Ω, a control signal is output when it is exceeded. The control output unit 6 includes:
The charging circuit 1 is controlled at a constant current of 4 A by the control signal output from the calculation, comparison and data recording unit 4 and the timer 7 is started, and after a predetermined time, for example, 2 hours, the charging circuit 1 is turned off to charge. It is made to stop.

FIG. 5 shows an example of a flowchart of the operation of the charging control device. The charging circuit 1 is operated to perform constant current charging (step S1). Next, in step S2, measurement of the internal impedance of the storage battery 2 is started by the impedance measuring device 3 so that the internal impedance becomes a specified value, for example,
It is determined whether the value exceeds 7.0 mΩ. If the value exceeds the specified value, the current value is switched to a constant current charge having a smaller current value in step S1 in step S1.
If the internal impedance does not exceed the specified value in step S2, the process returns to step S1. If it is determined in step S4 that a predetermined time set by the timer 7, for example, 2 hours, has elapsed since the switching, the charging is stopped (step S5).
In this embodiment, after detecting the set value of the internal impedance, constant current charging was performed by reducing the current, but similarly, after detecting the set value of the internal impedance, the charging voltage was set arbitrarily. It is also possible to charge with a constant voltage. The flowchart at this time corresponds to step S in FIG.
3 is the same as FIG. 5 except that the constant current charging is replaced by the constant voltage charging.

Example 4 A 6-cell, monoblock type sealed lead-acid battery was placed in a thermostat at 25 ° C., discharged to 9.9 V with a current of 26 A, allowed to stand for 2 hours, and then the internal impedance of the battery was measured. Perform constant current charging with a current of 80 A while measuring, and set the internal impedance to 20.
When the voltage reached 0 mΩ, the set voltage was switched to constant current charging of 15.0 V, and charging was performed for a total of 1 hour. The test results are shown in FIG. 6 and Table 5 below. As is apparent from FIG. 6, a sharp rise in the internal impedance of the storage battery appeared around 47 minutes after the start of charging. As is clear from comparison with the voltage change and the temperature change at this time, the change in the internal impedance of the storage battery is larger. As is clear from Table 5, the amount of charged electricity with respect to the discharge capacity at the time of detection of the maximum value of the internal impedance of the storage battery is 90.6%, and the end-of-charge state of the storage battery can be reliably detected.

[0020]

[Table 5]

(Embodiment 5) Rated capacity 120 Ah, 1.2
V nickel-metal hydride storage battery in a 25 ° C. constant temperature bath.
The battery was discharged to 1.0 V at 33 CA and allowed to stand for 2 hours.
Two-stage constant current charging was performed at 0.05 CA for 4 hours.

FIG. 7 shows the internal impedance, battery voltage, battery internal pressure and battery temperature of the storage battery measured at this time.
As can be seen from this figure, a sharp rise in the internal impedance of the nickel-metal hydride storage battery appears at the end of charging as in the case of the lead storage battery. Since the amount of change in the internal impedance at this time is larger than the amount of change in the other battery voltage, battery internal pressure, and battery temperature, the end of charging can be detected with high accuracy, and charge control can be performed. In the charge control device shown in FIG.
The calculation, comparison, and data recording unit 4 includes the impedance measuring device 3
The control signal is output when the internal impedance measured in step 2 exceeds the specified value.If the control signal is output when the amount of change in internal impedance per unit time exceeds the specified value, The same charge control as in Example 3 can be performed. Further, in the configuration of the apparatus shown in FIG. 3, the charging circuit 1 can be turned off by a control signal output from the calculation, comparison and data recording unit 4 to suspend charging without using the timer 7.

[0023]

According to the storage battery charge control method of the present invention described above, the storage battery can be charged with high accuracy, and there is an effect that overcharging can be prevented.

[Brief description of the drawings]

FIG. 1 is a view showing an internal impedance, a battery voltage, and a battery temperature of a storage battery at the time of charging for explaining the storage battery charging method of the present invention.

FIG. 2 is a diagram showing an internal impedance, a battery voltage, and a battery temperature of a storage battery during charging according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating an internal impedance, a battery voltage, and a charging current of a storage battery during charging according to a second embodiment.

FIG. 4 is a block diagram of a charge control device according to the present invention.

FIG. 5 is a flowchart of an operation of the charge control device.

FIG. 6 is a diagram showing an internal impedance, a battery voltage, and a battery temperature of a storage battery during charging according to a fourth embodiment.

FIG. 7 is a diagram showing an internal impedance, a battery voltage, a battery temperature, and a battery voltage of a storage battery during charging according to a fifth embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Charging circuit 2 Storage battery 3 Impedance measuring device 4 Calculation, comparison, data recording part 6 Control output part

Claims (3)

[Claims] 1. A charge control method for a storage battery, comprising: detecting a change amount of an internal impedance per unit time at a final stage of charge of the storage battery when the change amount exceeds a specified value, and controlling the charge. 2. A method for controlling charging of a storage battery, wherein when the internal impedance of the storage battery at the end of charging exceeds a specified value, this is detected and charging is controlled. 3. An impedance measuring device for measuring an internal impedance of a storage battery during charging, and when an internal impedance of the storage battery measured by the impedance measuring device or an amount of change per unit time of the internal impedance exceeds a prescribed value. A storage battery charging control device comprising a control unit that detects this and controls a charging circuit.