JPH10174306A - Charging circuit for secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily charge an alkaline secondary battery to the fully charged state without over-charging the battery nor receiving any influence from the ambient temperature by controlling the charging current to the battery when it is detected that the terminal voltage of the voltage drops by a prescribed value from the maximum value while the battery is charged. SOLUTION: When the terminal voltage VB of a battery 1 is lower than a set value, the battery 1 is charged with a constant current and, when the terminal voltage VB rises and reaches the set value, the battery 1 is charged with a constant voltage so that the terminal voltage VB can be maintained at the set value. The battery l is connected with a -ΔV detecting circuit 4 which monitors the terminal voltage VB of the battery 1 and, when the voltage VB drops by a prescribed value (ΔV) from its peak value after reaching the peak value in the last stage of charging, generates a detecting signal. The output of the circuit is supplied to the control input terminal of a switching element 2 which is turned off when the circuit generates the detecting signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging circuit for a secondary battery, and more particularly to a charging circuit suitable for rapidly charging an alkaline secondary battery.

[0002]

2. Description of the Related Art Various methods have been considered as a rapid charging method for charging an alkaline secondary battery such as a nickel hydrogen storage battery or a nickel cadmium storage battery in a short time. For example, there is a-[Delta] V control method in which quick charging is controlled by utilizing a characteristic in which the terminal voltage of a battery reaches a peak at the end of charging and thereafter decreases. Specifically, this method stores the peak value of the terminal voltage of the battery at the end of charging, and stops the rapid charging when the terminal voltage decreases by a predetermined value (ΔV) from this peak.

On the other hand, as a rapid charging method for a lithium ion battery or a lead battery, charging is performed at a constant current in the initial stage of charging, and when the terminal voltage of the battery increases and reaches a set value, the current is reduced.
A constant current / constant voltage charging method is used in which the battery voltage does not exceed a set value, that is, charging is performed at a constant voltage.

[0004] However, if the charge control is performed by the -ΔV control method, a certain degree of overcharge is inevitably generated.
The temperature rises at the end of charging, shortening the battery life, and in particular, in the case of a nickel-metal hydride storage battery, the charging efficiency decreases.

[0005] Alkaline secondary batteries such as nickel-metal hydride storage batteries and nickel cadmium storage batteries have the characteristic that the terminal voltage decreases as the temperature increases. Therefore, when the alkaline secondary battery is charged by the constant current and constant voltage method, when the ambient temperature is high, the terminal voltage of the battery does not reach the set value, and even when the battery is fully charged, the rapid charging current continues to flow, resulting in overcharging May be.

Furthermore, if the set value of the terminal voltage in the constant current and constant voltage charging is set low in order to prevent such a situation, the terminal voltage reaches the set value before the battery is fully charged, and charging cannot be performed until the battery is fully charged. .

[0007]

As described above, in the conventional -.DELTA.V control method, when an alkaline secondary battery such as a nickel-metal hydride storage battery or a nickel cadmium storage battery is rapidly charged, overcharging occurs. The battery life is shortened, the battery life is shortened, the number of charge cycles is reduced, and especially in the case of nickel-metal hydride storage batteries, the charging efficiency is reduced. When the battery is charged at a high ambient temperature, the terminal voltage of the battery does not reach the set value, and even when the battery is fully charged, the rapid charging current continues to flow, which may result in overcharging. If the set value of the terminal voltage is set low, there is a problem that the terminal voltage reaches the set value before the battery is fully charged, so that charging cannot be performed until the battery is fully charged.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and provides a secondary battery which can be easily charged to a full charge without overcharging an alkaline secondary battery and without being affected by ambient temperature. It is an object of the present invention to provide a charging circuit.

[0009]

In order to solve the above-mentioned problems, a charging circuit for a secondary battery according to the present invention is a charging circuit for charging an alkaline secondary battery. A charging power source for charging the battery by a method, -ΔV detecting means for detecting a terminal voltage during charging of the secondary battery, and detecting that the terminal voltage has decreased by a predetermined value from a maximum value;
Charge control means for controlling a charging current to the secondary battery in accordance with a detection output signal of the V detection means.

[0010] Further, another charging circuit for a secondary battery according to the present invention is a charging circuit for charging an alkaline secondary battery, comprising: a charging power supply for charging the secondary battery by a constant current and constant voltage method; A temperature sensor for detecting the temperature of the secondary battery, temperature change detecting means for detecting that the temperature change of the secondary battery has reached a predetermined value based on an output signal of the temperature sensor, and Charge control means for controlling a charge current to the secondary battery according to the detection output signal.

Specifically, the temperature change detecting means includes: (a) when the output signal of the temperature sensor reaches a predetermined value, (b) the difference between the output signal at the start of charging of the temperature sensor and the output signal during charging. (C) when the change per unit time of the output signal of the temperature sensor during charging reaches a predetermined value, (d) the output signal of the temperature sensor and another temperature at which the ambient temperature is detected. A detection output signal is generated when the difference from the sensor output signal reaches a predetermined value.

Since the charging circuit of the secondary battery configured as described above normally performs charging by a constant current and constant voltage charging method, overcharging can be performed if the set value in the constant current and constant voltage charging is appropriately set. Since there is no charge, the number of charge / discharge cycles is increased and the temperature rise at the end of charging is small, so that charging efficiency is increased and more capacity can be taken out.

Further, based on the constant current / constant voltage charging method, a combination of the -.DELTA.V control method and the temperature change detection control method is used, when the terminal voltage of the secondary battery drops by a predetermined value from the maximum value, or By controlling the charging current when the temperature change of the battery reaches a predetermined value, overcharging can be performed even if the terminal voltage of the secondary battery does not reach the set value for constant current and constant voltage charging due to high ambient temperature. Can be prevented. Furthermore, since it is not necessary to lower the set value in the constant current and constant voltage charging, it is possible to reliably charge the battery until it is fully charged.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a circuit diagram showing a charging circuit for a secondary battery according to a first embodiment of the present invention. In FIG. 1, a battery 1 is an alkaline secondary battery such as a nickel-metal hydride storage battery or a nickel cadmium storage battery, and is connected to a charging power supply 3 via a charging control switch element 2. The charging power supply 3 is for charging the battery 1 in a constant current and constant voltage charging system.
When B is lower than the set value V1, the battery 1 is charged with the constant current I1, and when the terminal voltage VB rises and reaches the set value V1, the charging current is lowered from I1 to make the terminal voltage VB equal to the set value V1.
The battery 1 is charged at a constant voltage so as not to exceed 1, that is, to maintain the terminal voltage VB at V1.

The battery 1 is further connected to a -ΔV detection circuit 4. The −ΔV detection circuit 4 monitors the terminal voltage VB of the battery 1 and generates a detection output signal when VB reaches a peak at the end of charging and thereafter decreases by a predetermined value (ΔV) from the peak. The output of the -ΔV detection circuit 4 is given to the control input terminal of the switch element 2, and the switch element 2 is turned off when the -ΔV detection circuit 4 generates a detection output signal.

Next, the operation of the secondary battery charging circuit of the present embodiment will be described with reference to the timing chart of FIG. First,
When the charging is started, initially, the terminal voltage VB of the battery 1 is lower than the set value V1 in the constant current constant voltage charging of the charging power supply 3, so that the charging power supply 3 Charge 1.

As the charging proceeds, the terminal voltage VB of the battery 1 gradually increases as shown by the solid line in FIG. 2A, and the battery temperature T gradually increases as shown by the solid line in FIG. 2B. To rise.

At the end of charging, at time t = t1, battery 1
When the terminal voltage VB reaches the set value V1, the charging power supply 3 thereafter decreases the charging current I as shown by the solid line in FIG. 2C, so that VB = V1, that is, the terminal voltage VB Is charged to keep V1 constant.

Here, when the ambient temperature is high, the terminal voltage VB decreases as shown by the broken line in FIG.
Even at the end of charging, the set value V1 has not been reached, and therefore the charging power supply 3 tries to keep flowing the constant current I1 to the battery 1.
According to the present embodiment, in such a case, at t = t2, the −ΔV detection circuit 4 detects that the terminal voltage VB of the battery 1 has decreased from the peak value by ΔV1, and generates a detection output signal. , The switch element 2 is turned off, and charging is stopped. Therefore, the battery 1 is not overcharged.

The effect of this embodiment will be described in more detail. In the conventional-[Delta] control method, when charging an alkaline secondary battery, charging is first performed with a constant current, and as shown by the one-point line in FIG. Charging was controlled by catching the peak. That is, charging was stopped when the terminal voltage VB dropped from the peak value by ΔV2. In this case, as indicated by the broken line in FIG. 2B, the battery temperature T sharply increases.

On the other hand, in the present embodiment, a constant current and constant voltage charging system is basically used. When the terminal voltage VB of the battery 1 reaches the set value V1, the charging current is reduced from I1 and the terminal voltage VB Since the battery 1 is charged such that the voltage V1 is constant at V1, the rise in the battery temperature T is slight as shown by the solid line in FIG. Therefore, not only does the battery 1 not deteriorate, but also the charging efficiency depending on the battery temperature is good, so that the discharge capacity can be increased.

Further, even when the end of charging is reached due to the influence of the ambient temperature and the cycle, if VB <V1, charging is continued with the current I1, but in such a case, the detection output signal of the -.DELTA. Charging can be stopped. Therefore, overcharging does not occur. Further, by detecting the full charge by the combination of the -ΔV control method, there is no need to set the constant current / constant voltage charge set value V1 to a low value, so that the charge may be stopped before the full charge is reached. Not
It is possible to reliably charge the battery until it is fully charged.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention.
FIG. 4 is a circuit diagram showing a charging circuit for a secondary battery according to the embodiment. In FIG. 3, a battery 1 is an alkaline secondary battery such as a nickel-metal hydride storage battery or a nickel cadmium storage battery, and is connected to a charging power supply 3 via a switch element 2 serving as charging control means. The charging power supply 3 is for charging the battery 1 in a constant current / constant voltage charging method. Specifically, when the terminal voltage VB of the battery 1 is lower than the set value V1,
When the battery 1 is charged with the constant current I1 and the terminal voltage VB rises and reaches the set value V1, the charge current is lowered below I1 so that the terminal voltage VB does not exceed the set value V1, that is, the terminal voltage VB becomes V1. The battery 1 is charged at a constant voltage so as to be maintained at a constant voltage.

The thermistor 4 as a temperature sensor is installed in close contact with the battery 1 and converts the temperature of the battery 1 into an electric signal. The output of the thermistor 4 is input to the temperature detection circuit 5. The temperature detection circuit 5 monitors the output of the thermistor 4 and generates a detection output signal when the battery temperature during charging rises to a predetermined value. The output of the temperature detection circuit 5 is given to the control input terminal of the switch element 2, and the switch element 2 outputs -ΔV
When the detection circuit 4 generates a detection output signal, it is turned off.

Next, the operation of the charging circuit for a secondary battery according to the present embodiment will be described with reference to the waveform diagram of FIG. When the charging is started, initially, the terminal voltage VB of the battery 1 is lower than the set value V1 in the constant current constant voltage charging of the charging power supply 3, so that the charging power supply 3 Charge 1.

As the charging proceeds, the terminal voltage VB of the battery 1 gradually increases as shown by the solid line in FIG. 2A, and the temperature also gradually increases. At the end of charging, when the terminal voltage VB of the battery 1 reaches the set value V1 at t = t1, the charging power supply 3 thereafter decreases the charging current I as shown by the solid line in FIG. , VB = V1, that is, the battery 1 is charged such that the terminal voltage VB becomes constant at V1.

Here, when the ambient temperature is high, the terminal voltage VB decreases as shown by the broken line in FIG.
Even at the end of charging, the set value V1 has not been reached, and therefore the charging power supply 3 tries to keep flowing the constant current I1 to the battery 1.
In such a case, the battery temperature rises sharply as shown by the broken line in FIG. According to the present embodiment, when the battery temperature rises as described above, when the battery temperature reaches a predetermined value, the temperature detection circuit 5 generates a detection output signal, so that the switch element 2 is turned off and charging is stopped. You. Therefore, the battery 1 is not overcharged.

As described above, the same effects as those of the first embodiment can be obtained by the second embodiment. The present invention is not limited to the above embodiment, and can be implemented with various modifications as follows.

(1) In the second embodiment, the temperature detection circuit 5 generates a detection output signal when the battery temperature reaches a predetermined value, but the difference between the battery temperature at the start of charging and the temperature during charging is obtained. When the battery temperature reaches a predetermined value, when the change in battery temperature per unit time during charging reaches the predetermined value, a second thermistor for measuring the ambient temperature is provided, and the difference between the ambient temperature and the battery temperature reaches the predetermined value. At this point, a detection output signal may be generated.

(2) In the first embodiment, the constant current / constant voltage charging method and the -ΔV control method are combined, and in the second embodiment, the constant current / constant voltage charging method and the temperature change detection control method are combined. Alternatively, it may be combined with other charge control methods such as timer control and voltage control. In addition, the present invention can be variously modified and implemented without departing from the gist.

[0031]

As described above, in the charging circuit of the present invention, the -ΔV
Combining the control method or the temperature change detection control method,
When the terminal voltage of the secondary battery drops by a predetermined value from the maximum value,
Or, when the temperature change of the secondary battery reaches a predetermined value, the charging current is controlled, so that the terminal voltage of the secondary battery is set to constant current and constant voltage charging at the end of charging due to an increase in ambient temperature or the passage of cycles. Even when the value does not reach the value, overcharging can be prevented. Furthermore, since it is not necessary to lower the set value in the constant current and constant voltage charging, it is possible to reliably charge the battery until it is fully charged.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a charging circuit for a secondary battery according to an embodiment of the present invention.

FIG. 2 is a timing chart of a battery terminal voltage, a battery temperature, and a charging current for explaining the operation of the embodiment;

FIG. 3 is a block diagram showing a configuration of a charging circuit for a secondary battery according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Secondary battery 2 ... Switching element for charge control 3 ... Power supply for charging 4 ...-. DELTA.V detection circuit 5 ... Thermistor 6 ... Temperature detection circuit

Claims (6)

[Claims] 1. A charging circuit for charging an alkaline secondary battery, comprising: a charging power supply for charging the secondary battery by a constant current / constant voltage method; and a terminal voltage during charging of the secondary battery. -ΔV detecting means for detecting that the terminal voltage has decreased by a predetermined value from the maximum value; and charging control means for controlling a charging current to the secondary battery in accordance with a detection output signal of the -ΔV detecting means. A charging circuit for a secondary battery. 2. A charging circuit for charging an alkaline secondary battery, comprising: a charging power supply for charging the secondary battery by a constant current and constant voltage method; a temperature sensor for detecting a temperature of the secondary battery; Temperature change detection means for detecting that the temperature change of the secondary battery has reached a predetermined value based on the output signal of the temperature sensor; and charging the secondary battery in accordance with the detection output signal of the temperature change detection means A charging circuit for a secondary battery, comprising: charging control means for controlling current. 3. The secondary battery charging circuit according to claim 2, wherein said temperature change detecting means generates said detection output signal when an output signal of said temperature sensor reaches a predetermined value. 4. The temperature change detecting means generates the detection output signal when a difference between an output signal of the temperature sensor at the start of charging and an output signal of the temperature sensor during charging reaches a predetermined value. The charging circuit for a secondary battery according to claim 2. 5. The apparatus according to claim 2, wherein said temperature change detection means generates said detection output signal when a change per unit time of an output signal of said temperature sensor during charging reaches a predetermined value. A charging circuit for a secondary battery according to claim 1. 6. The temperature change detecting means generates the detection output signal when a difference between an output signal of the temperature sensor and an output signal of another temperature sensor for detecting an ambient temperature reaches a predetermined value. The charging circuit for a secondary battery according to claim 2, wherein: