JP3402757B2 - Secondary battery charging method and secondary battery charging device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging method and a charging device for a secondary battery, and more particularly to a charging method and a charging device for a secondary battery capable of reliably performing normal charging.

[0002]

2. Description of the Related Art Secondary batteries represented by nickel-hydrogen secondary batteries or nickel-cadmium secondary batteries are widely used as operating power sources for various equipment systems such as mobile phones and portable image pickup devices. Has been converted.
That is, this type of secondary battery can secure or store electric power by so-called charging operation, and drive (discharge) a load by using the secured or stored electric power as a power source.
Since it can be repeatedly operated, it is used as a semi-permanent power source by being incorporated into various equipment systems.

By the way, in any of the secondary batteries, charging and discharging are the main functions as described above, and from the viewpoint of safety, the charging end voltage (fully charged state) and the discharge end voltage are set. Each limit is set, and charging and discharging are performed at a voltage within this limit range. In the constant current charging of the secondary battery, the charging efficiency depends on the temperature (charging temperature) of the battery, and when the temperature is high (for example, about 45 ° C. or higher), the charging efficiency decreases with the increase of oxygen generation. As a result, the battery life (discharging action) is shortened. Therefore, when the temperature of the battery to be charged during charging exceeds about 45 ° C., the method of stopping the charging is adopted.

It is also known that the determination of the fully charged state (the end of charging) due to the change in the battery temperature is performed by using a negative potential difference of the charging voltage of the battery to be charged and a timer together. In other words, in a rechargeable battery that is being charged with a constant current, a more appropriate full charge state (end of charge) can be determined by grasping the tendency of the charging voltage to rapidly increase with the progress of charging in relation to a certain period of time. It is carried out.

FIGS. 5 and 6 are for explaining the principle of determining the end of charging by using a negative potential difference of the charging voltage and a timer together. That is, in the constant current charging of the secondary battery, the charging voltage (curve A) changes with the charging time, as shown in the general tendency in FIG. Then, shortly after the start of charging, the charging voltage shows a rapid change, and then the charging voltage shows a negative potential difference -ΔV ₁ , which confirms that the normal charging state has been entered.
With the progress of this normal charging, the charging voltage is constantly maintained, but exhibits a sharp change again. That is, when approaching the fully charged state, the negative potential difference in the charging voltage is -ΔV ₂
Indicates. FIG. 6 shows a sudden change state of the charging voltage at a time point close to the full charge state. And
At this point, the negative potential difference −ΔV ₂ of the charging voltage is grasped as a transition within a fixed time, and the charging is terminated.

[0006]

However, in the constant current charging of the secondary battery, when the method of using the negative potential difference detection and the timer together is adopted for the determination of the termination of charging, the following practical problems occur. There is. That is, when the battery to be charged approaches the fully charged state as the constant current charging progresses, as shown in FIGS. 5 and 6, a negative potential difference −ΔV ₂ is detected in the charging voltage. However, this negative potential difference -ΔV ₂ is comparatively small, and although the timer is also used, it is not possible to accurately detect and grasp the fully charged state (charging end), so it is practically normal charging. Can't do. This point will be described in more detail. The negative potential difference −ΔV ₂ in the charging voltage is detected by the potential difference −ΔV ₂
Since the change is relatively small and the change is gentle,
It is difficult to detect the fully charged state (end of charging) in a strict sense, and there is a possibility that charging may be terminated without reaching the fully charged state, or conversely, an overcharged state may occur. And, such discharge in a state of less than charging eventually leads to an over-discharged state, which leads to a shortened life of the battery, and the over-charged state causes damage or damage of the battery. To occur. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a secondary battery charging method and a charging device capable of easily and reliably achieving a fully charged state of a secondary battery. .

[0007]

A secondary battery charging method according to the present invention charges a secondary battery with a constant current, and a negative potential difference and a temperature change per unit time of a battery to be charged accompanying the progress of charging. (Temperature differential value) detects the fully charged state,
A method of charging a secondary battery in which charging is stopped or terminated, wherein a negative potential difference of the battery to be charged and a temperature differential value of the battery to be charged indicate after starting charging which is selected and set in advance.
Negative temperature difference and the first differential temperature value after the start of charging
Before upon reaching maintaining charge, which had been previously selected and set to
A full charge different from the first negative potential difference and the second negative potential difference and the first temperature differential value is shown.
It is characterized in that when the second temperature differential value is reached, the charging is stopped or terminated. Further, the secondary battery charging device according to the present invention, a voltage detection circuit for detecting the negative potential difference of the charging voltage by the constant current of the battery to be charged, per unit time accompanying the constant current charging of the battery to be charged. The temperature detection circuit that detects changes in the battery temperature (temperature differential value), the negative potential difference detected by the voltage detection circuit, and the temperature differential value detected by the temperature detection circuit are set in advance. and each compared with the temperature differential value, the
The detected negative potential difference and the detected temperature differential value are charged.
Shows the first negative potential difference after the start of charging and shows the start of charging.
When the first temperature differential value is reached, the state of charge is maintained and
Note that the detected negative potential difference and the detected temperature differential value are
A second negative potential indicating a full charge different from the first negative potential difference.
Indicates a full charge different from the potential difference and the first temperature differential value
And a charge control circuit that controls the charge switch when the second temperature differential value is obtained .
The present invention, in the constant current charging of the secondary battery, as shown in FIG. 1 and FIG.
Not only does the charging voltage of the battery to be charged exhibit a negative potential difference, but also the temperature change (temperature differential value) per charging unit time of the battery to be charged becomes large. From these negative potential difference and temperature differential value, constant current charging This is done by paying attention to the fact that the fully charged state can be accurately detected. That is,
As shown in the general tendency in FIG. 1, in constant current charging of a secondary battery, the charging voltage (curve A) and the battery temperature (curve B) change with the charging time. Shortly after the start of charging, the charging voltage and the battery temperature suddenly change, and then the charging voltage has a negative potential difference -ΔV1.
And the temperature differential value Δt1 at the battery temperature as well, confirming that the normal charging state has been entered. With the progress of this normal charging, the charging voltage is constantly maintained, and the battery temperature gradually rises, but exhibits a sharp change again. That is, when approaching the fully charged state, a negative potential difference -ΔV2 is shown at the charging voltage, and a relatively large temperature differential value Δt2 is shown at the battery temperature.
FIG. 2 shows a sudden change state of the charging voltage and the battery temperature at a time point close to the fully charged state. At this point, since the temperature differential value Δt2 is relatively large with respect to the negative potential difference −ΔV2 of the charging voltage, the fully charged state is obtained from the correlation between the negative potential difference −ΔV2 and the temperature differential value Δt2. By understanding the above, it becomes possible to easily and accurately stop charging at the point of full charge. In other words, it is possible to accurately detect the full charge state by adding the temperature differential value Δt2, whose change is more clearly understood than the negative potential difference of the charging voltage -ΔV2, and correlating the two for reference. It is what

In the present invention, as a power source for charging, a commercial AC power source converted into a direct current having an appropriate voltage is used. In addition, a power source such as a fuel cell is used. Alternatively, electric power generated from a gasoline engine or a diesel engine may be used.

[0009]

In the charging method according to the present invention, the negative potential difference of the charging voltage of the secondary battery and the charging temperature change rapidly just before the full charge state, and the negative potential difference and the temperature change thereof are utilized. In the form of charge voltage differential and temperature differential, and using constant charge voltage differential (negative potential difference) tendency and temperature differential value increasing tendency (or increasing slope) as a guide, continue or stop constant current charging ( End) is determined. That is, the full charge state can be detected and grasped with higher accuracy by using the negative potential difference and the temperature differential value together, and thus the life of the secondary battery can be extended.

Further, in the case of the charging device according to the present invention, the voltage detecting circuit for detecting the negative potential difference of the charging voltage, the temperature detecting circuit for detecting the temperature differential value, and the charging control circuit for controlling the charging switch, Each of the negative potential difference and the temperature differential value is detected and compared with the negative potential difference and the temperature differential value, which are preset and built-in reference values, to automatically continue charging or stop charging (end of charging). To be done. That is, the action and effect of the charging method according to the present invention can be automatically achieved without requiring a complicated operation.

[0011]

Embodiments of the present invention will be described below with reference to FIGS.

First of all, FIG. 3 is a block diagram showing an example of the main configuration of a charging device for a secondary battery according to the present invention, where 1 is a battery 2 to be charged, for example, a nickel-hydrogen battery, which is charged with a constant current. , A voltage detection circuit for detecting a negative potential difference of the charging voltage, 3 is a temperature detection circuit for detecting a change (temperature differential value) of the battery temperature per unit time accompanying the constant current charging of the battery 2 to be charged. is there. Here, the voltage detection circuit 1 is arranged on the charging input 4 side of the charged battery 2 for constant current charging,
The charging voltage of the to-be-charged battery 2 that is charged with a constant current is sequentially detected, and it has a function of detecting not only the charging voltage at the time of charging progress but also the negative potential difference in the fully charged state.

Further, the temperature detecting circuit 3 detects the temperature rise / temperature change of the battery 2 to be charged due to the progress of the constant current charging by the temperature detecting element 3a arranged close to the battery 2 to be charged, It also has the function of calculating and detecting the temperature differential value. Further, reference numeral 5 is connected to the voltage detection circuit 1 and the temperature detection circuit 3, and the negative potential difference detected by the voltage detection circuit 1 and the temperature differential value detected by the temperature detection circuit 3 are set in advance and stored as a negative value. The charge control circuit controls the opening and closing (on, off) of the charging switch 6 by comparing the potential difference and the temperature differential value with each other and determining whether or not they are in the range of the set value.

When a voltage abnormality is detected by the voltage detection circuit 1 and a temperature abnormality is detected by the temperature detection circuit 3, the charge control circuit 5 controls the charging switch 6 to stop the constant current charging, and The negative potential difference −ΔV ₂ of the charging voltage detected by the voltage detection circuit 1 and the temperature differential value Δt ₂ detected by the temperature detection circuit 3 are within a preset negative potential difference range. It functions to open / close / control the charging switch 6 by comparing whether or not it is within the temperature differential value range, determining whether to continue or stop the constant current charging.

Next, the charging operation of the secondary battery in the charging device will be described with reference to the flow chart of FIG.

First, while setting the range of the negative potential difference and the temperature differential value of the charging voltage of the charged battery 2 in the fully charged state, the charged battery 2 (for example, nickel-hydrogen battery) is set, and then The charging switch 6 is turned on to start constant current charging. In the constant current charging process (charging is in progress), the voltage detection circuit 1 and the temperature detection circuit 3 detect the charging voltage of the battery 2 to be charged and the temperature of the battery 2 to be charged, respectively. Then, in these detection operations, when the voltage abnormality is recognized, the charging switch 6 is turned off to stop the charging, but when the voltage abnormality is not recognized,
Further, by checking the presence or absence of temperature abnormality, when the temperature abnormality is recognized, the charging switch 6 is turned off to stop the charging, and when the temperature abnormality is not recognized, the charging is continued.

At the time when the constant current charging further progresses and the voltage detecting circuit 1 and the temperature detecting circuit 3 detect the negative potential difference of the charging voltage and the increased temperature differential value, respectively, these negative values are detected. The charge control circuit 5 compares and determines whether the potential difference and the temperature differential value are within the preset negative potential difference range or the temperature differential value range. Here, when the negative potential difference -ΔV ₂ exceeds the set value, it is compared / determined whether the temperature differential value Δt ₂ exceeds the set value range, and both are exceeded. If
Since the battery has reached the fully charged state, the charging switch 6 is turned off, and the constant current charging is completed. However, negative potential difference-△ V
_{When 2} does not exceed the set value, or when the negative potential difference -ΔV ₂ exceeds the set value, the temperature differential value Δt ₂
Does not exceed the set value range, the constant current charging operation is continued until the full charge state is reached.

Thus, with respect to the required battery 2 to be charged,
It is possible to always perform normal charging by removing the battery 2 to be charged, mounting a new battery 2 to be charged, if necessary, after performing charging in a fully charged state, and repeating the charging operation. .

Although the constant current charging for the nickel-hydrogen battery has been described above, the present invention is not limited to this example, and various modifications can be made without departing from the spirit of the present invention. For example, the target secondary battery can be similarly applied to the case of a nickel-cadmium secondary battery or the like to obtain the same effect.

[0020]

As can be seen from the above description of the embodiments and the like, according to the present invention, in carrying out the constant current charging of the secondary battery to be charged, the full charge accompanying the charging of the secondary battery to be charged is achieved. While using the negative potential difference of the charging voltage at the time close to the state (immediately before full charge) as one guide, on the other hand, the battery temperature change can be grasped in the form of temperature differential, and the increase of this temperature differential value can also be used as a standard. Then, a method of stopping (terminating) charging at a time point when both of these values reach a preset value (or at a time point when they exceed each other) is adopted. That is, the point of time when the secondary battery is fully charged (or charged closer to the full charge) is indicated by two factors. Therefore, it is possible to reliably avoid insufficient charging or overcharging of the battery to be charged, and it is possible to always perform normal constant current charging, so that the problems of insufficient charging (overdischarging) and overcharging are completely eliminated, The life of the secondary battery will be extended.

[Brief description of drawings]

FIG. 1 is a characteristic diagram schematically showing an example of a relationship between a charging elapsed time and a charging voltage and a battery temperature in constant current charging of a secondary battery.

FIG. 2 is a characteristic diagram schematically showing an example of a negative potential difference of a charging voltage and a battery temperature change (temperature differential value) in a fully charged state in constant current charging of a secondary battery.

FIG. 3 is a block diagram showing a configuration example of a charging device according to the present invention.

FIG. 4 is a flow chart for explaining an example of an embodiment of a constant current charging method for a secondary battery by the charging device according to the present invention.

FIG. 5 is a characteristic diagram schematically showing an example of the relationship between charging elapsed time and battery temperature in constant current charging of a secondary battery.

FIG. 6 is a characteristic diagram schematically showing an example of battery temperature change (temperature differential value) in a fully charged state in constant current charging of a secondary battery.

[Explanation of symbols]

1 ... Voltage detection circuit 2 ... Charged battery 3 ... Temperature detection circuit 3a ... Temperature detection element 4 ... Charge input 5 ... Charge control circuit 6 ... Charge switch

Front page continued (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02J ^7/ 00-7/12 H02J ⁷ /34-7/36

Claims (2)

(57) [Claims] 1. A fully charged state is detected by charging a secondary battery with a constant current and detecting the full charge state from the negative potential difference of the battery to be charged and the temperature change per unit time (temperature differential value) accompanying the progress of charging. A method of charging a secondary battery that is stopped or terminated, wherein a negative potential difference of the battery to be charged and a temperature differential value of the battery to be charged are a first negative value indicating after start of charging selected and set in advance.
To the first temperature differential value that indicates the potential difference of
Reached when maintaining the charge, said first preselected and set
A second negative potential difference indicating a full charge different from the negative potential difference of 1 and a second negative potential difference indicating a full charge different from the first temperature differential value
The method of charging a secondary battery, wherein the charging is stopped or terminated when the temperature differential value is reached. 2. A voltage detection circuit for detecting a negative potential difference of a charging voltage due to a constant current of a battery to be charged, and a change in battery temperature per unit time (temperature differential value) accompanying constant current charging of the battery to be charged. ), The negative potential difference detected by the voltage detection circuit and the temperature differential value detected by the temperature detection circuit are respectively compared with the preset negative potential difference and the temperature differential value which are built in. , Before
Note that the detected negative potential difference and the detected temperature differential value are
The first negative potential difference that indicates after the start of charging and after the start of charging
When it is the first temperature differential value shown, the state of charge is maintained,
The detected negative potential difference and the detected temperature differential value
Is a second negative indicating a full charge different from the first negative potential difference.
Full potential different from the potential difference of and the first temperature differential value
A charging device for a secondary battery, comprising: a charging control circuit for controlling a charging switch when the second temperature differential value shown is obtained .